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Home , Grepafloxacin, Nitrofurantoin, Sparfloxacin, Teixobactin

WEEK 27

OSPAP Programme

MPHM14 Antibacterial Chemotherapy

Slide 1 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Overview

• Agents targeting the cytoplasm – [Sulfonamides] – – • Agents targeting the – Chloramphenicol – Linezolid – Tetracyclines – Macrolides – Aminoglycosides • Agents targeting the nuclear material – – Fluoroquinolones • Updates and new developments • Clinical applications

Slide 2 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 The Bacterial Cell ( Prokaryotic )

SULPHONAMIDES TRIMETHOPRIM NITROFURANTOIN

http://whyfiles.org/126dna_forensic/images/dna.gif

Slide 3 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Agents acting in the cytoplasm

• Many common biochemical processes in cytoplasm of all cells • Rely on differences between prokaryotic and eukaryotic cells for selectivity – Agents targeting metabolic processes only found in provide selective antibacterials • Bacteria synthesise several vitamins, e.g. folic acid, not synthesized in mammalian cells – These processes are good targets for antibacterial agents • The sulfonamides are (like methotrexate) and interfere with the bacterial biosynthesis of folic acid • Trimethoprim is also an , targeting a different part of the folic acid biosynthetic pathway • Nitrofurantoin acts on several processes in the cytoplasm, some similar to mammalian processes, but… – Is prodrug and only activated efficiently in bacterial cells

Slide 4 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Antibacterials

• Sulfonamides were the first synthetic antibacterials used clinically • Bacteriostatic action • Sulfonamides are structural mimetics of para -aminobenzoic acid (PABA, essential metabolite) and compete for a key enzyme in the synthesis of folic acid • Folic acid is an essential metabolite for mammals (cannot be synthesised by mammalian cells), so this interference in folic acid synthesis is the basis of the selectivity of the sulfonamides • Sulfonamides are extremely rarely used now due to extensive resistance in both G+ve and G-ve bacteria – Alterations to the enzyme target, dihydropteroate synthase (DHPS) – to gene for DHPS resulting in poor sulfonamide binding • Only (as Co-trimoxazole) and in BNF

Slide 5 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Folic Acid Synthesis

PABA

Folic acid Dihydropteroic acid

NH 2 Sulfonamides resemble PABA and are mistakenly used instead, preventing synthesis of folic acid H2NO 2S

Slide 6 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK

27 NH2 OMe Trimethoprim N

H2N N OMe OMe

• Trimethoprim is an antifolate agent through dihydrofolate reductase (DHFR) inhibition; bacteriostatic • Used for UTIs (good renal as unchanged drug), acute and chronic (well distributed), pneumocystis pneumonia • Can be used as monotherapy or in combination (synergistic) with sulfamethoxazole (Co-trimoxazole) in ratio 5 : 1 – Similar gives best combination • Co-trimoxazole acts on two enzymes in the same biosynthetic sequence (sequential blocking ) • Doses of both drugs are lower than would be required if either used alone so side-effects (and possibly resistance) can be minimised

Slide 7 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Co-trimoxazole (Septrin)

NH2 CO2H OH OH

N HO2C N N OPP N N H Dihydropteroate H2N N N synthetase (DHPS) H2N N N

L-Glu O H CO H Sulfamethoxazole 2 OH N CH CH CO H H 2 2 2 Although reduction of DHF to THF also occurs N N N in mammalian cells, trimethoprim has about H

40,000x greater affinity for the bacterial H2N N N enzyme than the mammalian version – hence FOLIC ACID

the selectivity NADPH

O H CO H O H 2 NADP CO2H

OH N CH2CH2CO2H OH N CH CH CO H H H H 2 2 2 N N N N NADP NADPH N N H H Dihydrofolate reductase H2N N N H N N N H (DHFR) 2 H TETRAHYDROFOLIC ACID DIHYDROFOLIC ACID

Trimethoprim

Slide 8 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 UTIs • Although sulfonamides rarely used now, co-trimoxazole is sometimes still useful for urinary tract – Susceptibility should be established 1 st [culture / MS methods] • Also useful for: – Pneumonia due to Pneumocystis jirovecii (fungus, was called Pneumocystis carinii ) – Toxoplasmosis and nocardiasis • Co-trimoxazole associated with rare, serious ADRs, especially in elderly patients – Was replaced by or cephalexin, but less commonly used now due to resistance (amoxicillin) and increased risk of C. diff after use (cephalexin) • Nitrofurantoin more commonly used now – (Relatively) broad spectrum, bactericidal agent, particularly against E. coli , most Enterococci , Klebsiella sp., Staphylococci and Streptococci (But poor activity vs Proteus sp. and inactive vs sp.) – Rapid renal elimination after oral admin: low serum, high urinary concentration

Slide 9 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Nitrofurantoin MoA

• Activated by several bacterial enzymes to reactive nitrosyl radical • Reacts with cytoplasmic and other macromolecules • Inhibits: synthesis, aerobic (carbohydrate) energy metabolism, DNA synthesis, RNA synthesis, and synthesis • Resistance rare, even although introduced into clinic in 1952; resistance may be due to non-specific activity – resistance would require concurrent changes to many enzymes, proteins and pathways = unlikely • Although broad spectrum, rapid and efficient absorption from GI tract reduces risk to GI bacteria (low risk of C. diff resulting)

Nitrosyl radical

Slide 10 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 The Bacterial Cell ( Prokaryotic )

CHLORAMPHENICOL TETRACYCLINES MACROLIDES AMINOGLYCOSIDES LINEZOLID http://whyfiles.org/126dna_forensic/images/dna.gif

Slide 11 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Agents targeting protein synthesis via

Slide 12 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Transcription and translation

Transcription and translation describe the processes by which the genetic code on DNA is converted into proteins In bacteria, these Replication processes all take place in Translation the cytoplasm, making an DNA Transfer RNA (tRNA) – easy target for antibacterial agents Transcription Selectivity is possible, as bacterial ribosomes are Messenger RNA (mRNA) RIBOSOME (rRNA) different to mammalian ribosomes Protein http://highered.mcgraw- hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120077/micro06.swf::Protein%20Synthesis

Slide 13 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Transcription and translation - revision

TRANSCRIPTION • Genetic code on DNA template transcribed into messenger RNA by RNA polymerase • In bacteria, mRNA moves to ribosomes [ cf in eukaryotes, mRNA exits nucleus into cytoplasm] TRANSLATION • Ribosomes have two subunits: 30S and 50S in bacteria [70S] (40S and 60S in eukaryotic cells [80S]) • mRNA binds to small subunit of ribosome, followed by initiator: tRNA-methionine • Large ribosome subunit binds to small subunit. Large ribosome subunit has two binding sites, P and A in the peptidyl transferase centre (PTC) • Transfer RNAs carry amino acids to the ribosome site where mRNA binds (charged tRNA) • Only tRNA with codon of complementary sequence to that on mRNA can bind to ribosome Codon = 3 nucleotides (triplet), which codes for a specific amino acid • Ribosome moves along mRNA from 5′ to 3’: once peptide bond formed, non-acylated tRNA leaves P site and peptide-tRNA moves from the A to the P site A new charged tRNA-amino acid (as specified by the mRNA codon) enters A site • Peptide chain grows as amino acids added until stop codon reached, then leaves ribosome through protein exit tunnel

Slide 14 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Chloramphenicol (Chloromycetin, Cm)

• Originally obtained from Streptomyces venezuelae , now prepared synthetically HO H • Bacteriostatic with broad spectrum of activity; CH 2OH only R,R -isomer is active HN H O2N • Highly lipophilic and penetrates most tissues CHCl O 2 (crosses -brain barrier) • Active against Neisseria meningitidis , and (causes of meningitis) • Can be used in treatment of meningitis in patients with β-lactam allergies and drug of choice against typhoid fever • But…. severe toxicity possible, so only given systemically in life-threatening infections: benefit must outweigh risks • Side-effects after systemic admin include aplastic anaemia (bone marrow cannot replenish blood cells) – unpredictable and may occur weeks after treatment ceases • Commonly used topically in treatment of bacterial conjunctivitis

Slide 15 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Chloramphenicol: MoA & resistance

• Chloramphenicol binds to large ribosome subunit (50S) at the peptidyl transferase centre A site, preventing binding of the next charged tRNA • www.youtube.com/watch?v=0VINqUF-r5I • Binding involves 4 H-bonds from chloramphenicol to the ribosome and coordination to a Mg 2+ ion in the catalytic site • Selectivity arises due to differences between the conformations of bacterial and eukaryotic PTC • Chloramphenicol inhibits bacterial protein synthesis as it only binds to A site of bacterial ribosome • However, use of systemic chloramphenicol can lead to serious side effects due to inhibition of mammalian mitochondrial protein synthesis

Slide 16 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Resistance to chloramphenicol

• Resistance to chloramphenicol in is due to efflux pumps (via both chromosomal and plasmid transmission) • An RNA (cfr ) methylates a key part of the 23S subunit near to ‘fenicol’ binding site and blocks the binding • Resistance also arises due to chloramphenicol acetyltransferases (CAT) which acetylate chloramphenicol so that it no longer binds to the PTC A site. CAT genes are both plasmid (e.g. CatC in S. aureus ) and chromosome-derived (e.g. CatB3 in Salmonella typhimurium ) • Florfenicol does not contain 3-OH so is not acetylated. Cm-resistant strains in which resistance is due to CATs are susceptible to florfenicol

HO H CH 2F HN H MeO 2S CHCl Inactive O 2 Acetylated chloramphenicol Florfenicol

Slide 17 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Linezolid (Zyvox ®)

• First member of oxazolidinone agents O – Only example currently licensed N O • New synthetic class of antibacterials • Discovered in 1990s, approved in 2000 F N O • Active against G+ve bacteria, such as: Linezolid NHAc – MRSA – Community acquired and nosocomial pneumonia (caused by G+ve bacteria) – -resistant faecium (VRE) • Not active against G-ve bacteria • Bacteriostatic to Enterococci and Staphylococci; bactericidal to Streptococci • Time dependent, low PAE

Slide 18 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Mode of Action

• Also inhibits protein synthesis, but at different point to other agents • Binds to pocket formed by 8 RNA base residues, conserved across all bacterial 50S ribosomes • Causes slight change in conformation to rRNA, so tRNA units have reduced affinity to A site • Also inhibits formation of 70S unit by blocking interactions between 50S and 30S subunits • Selectivity for bacterial ribosomes, little inhibition of mammalian cytoplasmic protein synthesis • But side effects due to inhibition of mitochondrial protein synthesis linked to myelosuppression if extended period of use – Cf toxicity of systemic chloramphenicol – similar issue

Slide 19 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Resistance to Linezolid

• Resistance 1st noted in 1999 (before approved!) • Still relatively rare, probably due to restricted use of linezolid • In 2013, >98% Staph aureus sensitive to linezolid • Acquired resistance by 2 mechanisms: – in 23S rRNA unit at linezolid binding site – of 23S rRNA by methyltransferase (also causes resistance to chloramphenicol and clindamycin) • Both change the linezolid binding site and prevent its binding • G-ve bacteria have intrinsic resistance due to endogenous efflux pumps – Prevents sufficient linezolid getting into cells to have antibacterial effect

Slide 20 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Tetracyclines

Generic Name (Old) Trade Name X R1 R2 R3

Tetracycline (Achromycin / Sustamycin) H OH Me H

Demeclocycline (Declomycin) Cl OH H H

Oxytetracycline Oxymycin / (Terramycin) H OH Me OH

Chlortetracycline (Aureomycin); not licensed Cl OH Me H

Doxycycline Doxlar / Vibramycin H H Me OH

Minocycline Aknemin NMe 2 HHH

Lymecycline* Tetralysal H OH Me H (prodrug of tetracycline)

*Amide NH 2 (at RHS) is modified to NHCH 2NH(CH 2)4CH(NH 2)CO 2H

Slide 21 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 General Information • Broad spectrum agents against G-ve and G+ve bacteria and other organisms, e.g. chlamydiae, mycoplasmas, rickettsia • In general, tetracyclines considered bacteriostatic – But certain tetracyclines bactericidal against specific bacteria if used at appropriate concentration – Doxycycline with quinine can be used to treat/prevent malaria • Time dependent, but also active in concentration-dependent manner (PK-PD type III) – Concn dependent parameters give good clinical results (T at concn above MIC) • Strong PAE; t½ 7 – 17 hours • Well distributed throughout tissues and body fluids; variable protein binding • For most tetracyclines, dosing 1-2 daily is sufficient • Less commonly used now due to increased levels of resistance

Slide 22 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK pKa 9.4 27 HO Me NMe2 H H 7 OH pKa 3.3 6 5 4 Pharmacokinetics 8 3 2 9 11 1 NH2 10 12 Tetracycline OH OH O OH O O pKa 12.0 pKa 7.5

• The oral of tetracyclines varies according to the species – Doxycycline and minocycline have high oral bioavailability (>90%) – Lower oral bioavailability for other members (50 – 75%) – Lymecycline is more aqueous soluble: 5000x more than tetracycline, and is absorbed by active transport from GI tract, yet still only ca. 50% available – Absorption of most is affected by food (absorption decreased) – Any complexed to metal ions in GI tract are excreted in faeces – Non-absorbed tetracyclines can disrupt commensal bacteria and result in gastric disturbance

Slide 23 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Tigecycline

N-tButylglycine Minocycline • Developed recently to combat tetracycline resistance (FDA approved 2005) • First glycyltetracycline (based on minocycline, which is rarely used itself due to ADRs); others in development (e.g. omadacycline, in phase III CT) • Indicated for skin, soft tissue and intra-abdominal infections caused by MDR bacteria • Administered IV (why?) • Active against many G+ve and G-ve bacteria, including: – MRSA, VRE, Haemophilus influenzae, Neisseria , MDR Acinetobacter baumanii and tetracycline-resistant bacteria – Active at about 5 µg/mL – Inactive against Pseudomonas and Proteus species

Slide 24 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Tetracyclines

• Chlortetracycline discovered (in 1948) from Streptomyces aureofaciens • Tetracycline obtained either by hydrogenolysis of chlortetracycline or fermentation of S. alboniger in chlorine-free medium • Derive their name from tetracyclic ring system (octahydronaphthacene) • Dehydration in acid conditions at C5a-C6 leads to inactive anhydrotetracyclines (demeclocycline more stable than chlortetracycline) • Second generation tetracyclines, doxycycline and minocycline, and third generation, tigecycline, more stable to acid as no C6-OH to be protonated

(C6 = CHMe or CH 2) • Chelate polyvalent metal ions (Fe 3+, Ca 2+ and Mg 2+) so should never be given with dairy products, or co-administered with iron-rich antacids, and not given to children under twelve

Slide 25 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Dehydration under acid conditions:

Unstable to acid

More stable to acid

Much more stable to acid

Slide 26 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Tetracyclines

www.danderm-pdv.is.kkh.dk/moulages/ www.healthhype.com/wp-content/ images/pics/syphilis%20primary-8.jpg uploads/rosacea11.jpg

microbewiki.kenyon.edu/images/thumb/1/17 • Bacteriostatic /Congenital.jpg/300px-Congenital.jpg • Drugs of choice for infections (e.g. urethritis). Used to treat acne, and respiratory and genital infections, e.g. syphilis and chlamydia, and Lyme disease • Bind to the ribosome 30S subunit through H-bonds and Mg 2+ chelation, inhibits binding of the aminoacyl-tRNA and leads to termination of peptide chain growth • Poor affinity for eukaryotic ribosome = basis of selectivity • Resistance causing decreased use of these agents and arises due to: – tetracycline efflux systems, e.g. Neisseria gonorrhoeae (chromosomal transmission) and S.aureus (plasmid transmission) – ribosomal protection proteins, e.g. S. aureus (plasmid transmission) – enzymatic deactivation of tetracyclines, e.g. by TetX (anaerobic bacteria)

Slide 27 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Tetracycline binding to 30S rRNA

G1053 O Binding through H-bonds (to G1053, C1054,

O P H2N O O G1198, U1196, C1195, A965, G966) , O OH N C1054 aromatic stacking (with C1054), and magnesium ion chelation (phosphates of C1054, O O H G1197 and G1198 with Tet Os on C11 & C12) D O O O O P HO O C O O O Me P G1197 H Mg2+ O O B O

H O H O A Me2HN O P O O O G1198 G966 O O O P O O N H O H O O P U1196 HO O O HO OH

O O O OH A965 O C1195

Slide 28 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Resistance by Enzymatic Deactivation of Tetracyclines

HO Me H OH H NMe 2 HO Me H OH H NMe2 H H H H OH OH TetX

NH [O] 2 NH2

OH OH OH OH O OH O O OH O O O O

Oxytetracycline

Me H OH H NMe2 H OH

O Spontaneous decomposition to inactive products

NH2

OH OH OH O OH O O

Hemiketal

Slide 29 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Macrolides (e.g. Erythromycin) • Macrolide indicates large lactone (ester) O ring ; these also contain 2 Me Me sugar units – desosamine and cladinose 9

• Erythromycin [ R=H ] (14-membered ring) HO OR1 OH NMe first isolated from Saccharopolyspora Me 12 6 Me 2 2' Me 5 RO erythraea in 1952 by Eli Lilly O Me Et O O • Erythromycin is bacteriostatic with broad 1 3 antibacterial spectrum, similar to that of O O OMe so is alternative for - Me Me allergic patients OH O Erythromycin, 2' R = R = H • Eythromycin is mildly basic ( pKa 8) due 1 Me Clarithromycin, 2' R = H, R1 = Me to aminosugar group and usually administered as the HCl salt Others in the family: • • Prodrug esters, e.g. Erythromycin ethyl Clarithromycin [ R1 = Me] • succinate [ R=CO(CH ) CO Et ] Azithromycin 2 2 2 • Telithromycin See later (Erythroped), are used to mask taste of bitter drug

Slide 30 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Acid instability of Erythromycin • Acid instability of erythromycin overcome by use of enteric-coatings so that drug is only released in the higher pH (7-8) of the small intestine • Water insoluble dosage forms (e.g. stearate salt [CH 3(CH 2)16 CO 2H] also used to overcome this problem and bitter taste (insoluble salts: do not dissolve in saliva, so no taste)

H H O Me Me Me OH Me 9 Me Me 9 9 HO HO HO OH 12 OH 12 O O Me O Me Me OH NMe 6 NMe Me 12 6 Me NMe2 6 Me 2 2 HO Me HO Me HO Me O Me O Me O Me Et O O Et O O Et O O

1 1 -H2O 1 O O OMe O O OMe O O OMe Me Me Me Me Me Me OH OH OH O O O Me Me Me

Erythromycin A Erythromycin A 12,9-hemiacetal Anhydroerythromycin Inactive spiroketal form • The other macrolides, azithromycin, clarithromycin and telithromycin, are much more acid stable, e.g. azithromycin: 10% degraded after 20 minutes at pH2 (and 37 oC) vs 4 seconds for erythromycin Slide 31 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Azithromycin Me Me N 9 • Lactone ring extended by 1C HO HO OH • No ketone at C9 , so greater acid CH3 NMe2 stability Me 13 6 Me Me HO • ca 40% oral bioavailability and good O Me tissue distribution Et O O • t 70-90h ½ O O OMe • Less G+ve activity, but increased vs G- Me ve, incl. H. influenzae Me OH O Azithromycin Telithromycin Me • O New ketolide form – cladinose at C2 Me replaced by ketone and side arm at Me O 9 C11 N • N OMe Substituted OMe at C6 and O N 11 O NMe at C12, so greater acid stability 12 6 Me 2 Me • Oral bioavailability 57% Me HO O Me • Et O O t½ 10h • Similar activity spectrum N 1 3 O O to erythromycin, but Telithromycin active vs penicillin and erythromycin resistant S. pneumoniae Me

Slide 32 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Macrolides: PK-PD

• Bacteriostatic activity with low post- effect • Similar spectrum of activity to β-lactams, often substituted for penicillin if allergic – Active vs most G+ve bacteria (e.g. Staph and Strep ) and some G-ve – Also active against mycobacteria • Erythromycin and clarithromycin: time dependent, low PAE (Type II) – 2-4 times daily • Azithromycin: time (& concn) dependent with good PAE (Type III) – once daily dosing • Telithromycin: concentration dependent, PAE 0.5 - 4hrs (Type I) – once daily dosing • Macrolides have better oral bioavailability than expected, perhaps due to unknown active transport across GI tract? • Excellent tissue distribution means can be used for skin and soft tissue infections, but poor ability to cross BBB • Macrolides accumulate in phagocytes (e.g. macrophages): transported to site of bacterial infection and released – Concentrates amount of macrolide at site of infection – Effect particularly strong with azithromycin • Clarithromycin rapidly metabolised, but to active metabolite (R 1 = OH)

Slide 33 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Macrolides: mode of action

• Macrolides block exit of protein tunnel by binding to a high affinity site, leading to the arrest of protein elongation and the dissociation of shortened peptidyl-tRNAs from the ribosome • Main component of binding pocket is nucleotide 2058. In bacteria, this is adenine (A) and macrolides bind strongly to this nucleotide. In eukaryotic cells, this nucleotide is guanine (G) and is too bulky to allow favourable interactions with the 14-membered macrolides  selectivity • Desosamine sugar (formation of 3 hydrogen bonds

between C2′-OH and A2058 and A2509, NMe 2 and A2505), ring hydroxyls (hydrogen bonds between (M. Gaynor and A.S. Mankin, the 6, 11 and 12-OH and nucleotides), and lactone Frontiers in Med. Chem ., 2005, 2, 21) (hydrophobic interactions) play key roles in macrolide binding to this site

Slide 34 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Resistance to Macrolides

• Resistance arises due to modifications to the ribosome , increased expression of efflux pumps , and chemical inactivation of the macrolide 1. Inducible or constitutive erm (erythromycin ribosome methylase) gene gives rise to resistance in Streptococci In Streptococcus pneumoniae , ribosomal methylase dimethylates a single site, A2058 (on N-6), resulting in a decreased binding affinity for erythromycin due to the increased size of this nucleotide • i.e. change to target 2. In Campylobacter jejuni (cause of food poisoning), over-expression of macrolide efflux system causes resistance 3. Two different types of chemical inactivation can occur: • Phosphorylation or glycosylation of C2’-OH desosamine ring prevents H- bonding to rRNA • Enterobacteriaceae express esterase that hydrolyses lactone ring to give inactive acyclic product

Slide 35 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Aminoglycosides

• Aminoglycosides currently in UK clinical use: – Gentamicin – Neomycin – Tobramycin – Amikacin (semi-synthetic version) • Streptomycin (1 st in series) discovered in 1944 • Isolated from an actinomycete mould, Streptomyces griseus • First agent to cure pulmonary tuberculosis • Many other aminoglycosides from Streptomyces family – Neomycin from S. fradiae in 1949 – Kanamycin from S. kanamyceticus in 1957 – Tobramycin from S. tenebrarius in 1968 – Gentamicin, was isolated in 1963 from various species of Micromonospora bacteria, as a complex of several structurally-related agents

Slide 36 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 A note on names…..

• The end of the name of an aminoglycoside, -mycin or –micin, relates to the microorganism source of each agent: – Aminoglycosides from Streptomyces species given the ending –mycin – from a Micromonospora species have the ending –micin • Useful guide to the origin of an aminoglycoside, but…. – Not necessarily extended to naming of other microorganism-derived agents – Many examples of agents from Streptomyces species not named by same system, e.g. chloramphenicol, , , and . • Structurally, antibiotic aminoglycosides are glycosidic polycyclic structures, incorporating an aminocyclitol ring: – Streptamine, streptidine or 2-deoxystreptamine, • 2-Deoxystreptamine most commonly found in clinical aminoglycosides • Two or three aminosugar rings are usually linked to the aminocyclitol

Slide 37 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK NH2

O 27 HO OH HO H2N O NH Me H2N 2 H O N O Me O NH HO HO 2 Me OH OH O O O NH2 H2N NH2

Gentamycin O OH H2N H2N NH2 NH HO Neomycin B HN HO O OH O H HO N NH2 OH O OH CHO O NH HO H2N Me Streptomycin H N O 2 OH HO O OH HO O O HO OH NH2 NH O H2N 2 NHMe HO O Tobramycin HO NH2 HO H2N O O OH NH2 HO HO O

OH HO N O H Amikacin NH2

H2N

Slide 38 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Mode of Action • Rapid bactericidal action, concn dependent: almost independent of bacterial load if above MIC • Broad spectrum vs G-ve and G+ve • Very polar molecules – small amount enters cells • Initially bind (H-bonds) to 16S ds rRNA part of 30S subunit adjacent to A site • Causes slight conformation change to A site, resulting in mis-reading of tRNA and incorrect amino acids added to growing protein chain: produces ‘nonsense’ proteins • Alters function of bacterial membrane with loss of membrane semi- permeability, difficult to repair • Allows influx of large concentrations of aminoglycoside • Halts protein synthesis entirely: fatal to bacterial cells • Selective for bacterial cell protein synthesis, but not entirely even at low concns: at v high concns, eukaryotic protein synthesis also halted • Widespread use limited by ototoxicity and nephrotoxicity

Slide 39 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Resistance

1. Most common cause of resistance to aminoglycosides is due to R factor-mediated enzymes – These modify the aminoglycoside structure: • N-acetylation • O-phosphorylation • O-adenylation – Structural modifications prevent binding to rRNA 2. Resistance can also arise due to point mutations in rRNA A site – Due to specific single nucleotide residue changes – Aminoglycoside no longer binds effectively to rRNA 3. Resistance also due to decreased aminoglycoside uptake into bacterial cells – Due to decreased cell membrane permeability and/or increased efflux

Slide 40 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Amikacin • Amikacin is a successful example of synthetic modification to NH2 kanamycin A HO OH • Designed to reduce susceptibility to metabolism and avoid OH resistance O O H • L-Hydroxyaminobutyryl amide O N OH chain inhibits deactivation by adenylation and phosphorylation, even at remote positions OH O

• Enhanced potency and spectrum NH2 OH H2N O – Active against Pseudomonas aeruginosa resistant to other Amikacin H2N agents OH – Active against Mycobacterium OH tuberculosis

Slide 41 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 The Bacterial Cell ( Prokaryotic )

SULPHONAMIDES  TRIMETHOPRIM

β-LACTAMS VANCOMYCIN 

POLYMYXINS  QUINOLONES RIFAMYCINS CHLORAMPHENICOL TETRACYCLINES  MACROLIDES AMINOGLYCOSIDES LINEZOLID http://whyfiles.org/126dna_forensic/images/dna.gif

Slide 42 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 (Fluoro)Quinolone Antibacterials

• was discovered in 1962 during the synthesis and purification of chloroquine (anti-malarial). • Nalidixic acid and other first generation quinolones have weak anti- bacterial (bactericidal) activity • Early quinolones active against G-ve bacteria only, due to poor uptake by passive diffusion into G+ve bacteria (use porins for G-ve uptake) • Later generations more potent and broader spectrum, including vs G+ve bacteria, mostly due to the introduction of a fluorine at the 6- position and substituent at C5 (see slide 9) = ‘FQs’ • Now have 2nd , 3rd and 4th (5th ?) generation fluoroquinolones • Bactericidal effect • Concentration dependent with prolonged PAE

Slide 43 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Example (F-)quinolone antibacterials O O

CO2H F CO2H

Me N N N N

Et HN

Nalidixic acid (Ciproxin) (1st gen) active only against Gram -ve (2nd gen) active against both G+ve and G-ve Can be used for uncomplicated UTIs (not vs Streptococcus pneumoniae or E. faecalis) wide spectrum of uses (not pneumococcal pneumonia) O O F CO2H F CO2H

H N N N N OMe N O Me Me H NH H (Avelox) (4th gen) improved Gram +ve activity (Tavanic) Not active vs P. aeruginosa and MRSA (3rd gen) active against G+ve & G-ve Back-up for CAP & complicated SSTIs 2nd line for community-acquired pneumonia caused by resistant bacteria

Slide 44 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Pharmacokinetic considerations • All FQs have good oral bioavailability (despite their zwitterionic nature), probably due to lipophilic groups. Lower oral bioavailability for earlier generation FQs – Ciprofloxacin (1 st generation) bioavailability: 70% – Levofloxacin ( 3 rd generation) bioavailability: 99%

•  LogP app (at pH 7.0) -1.6 (ciprofloxacin) +2.5 (nalidixic acid), Levofloxacin logP app 2.1 • Concn-dependent antibacterials, require high serum concentrations for effective activity; PAE 2-6 hours • Dosing depends largely on t ½: longer half-life (& PAE) allows once daily admin – st t½ 3-5 hours for 1 generation fluoroquinolones – t½ longer for later generation fluoroquinolones, e.g. 7.4 hours for levofloxacin and 9.6 hours for moxifloxacin • 1st generation used in higher doses due to protein binding and weaker activity

Slide 45 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Applications • FQs active primarily against G-ve bacteria + some G+ve bacteria – e.g Ciprofloxacin: broad spec vs G-ve (+ many G+ve), partic Salmonella, Shigella, Campylobacter, Neisseria ; used for RTI, UTI, GIT + bone/joint infections. Not v active vs Strep. pneumoniae + (G+ve) • 1st (+ some 2 nd ) generation excreted mostly unchanged in , have been used to treat UTIs (eg nalidixic acid, ) – Used less commonly now, due to increased resistance • 3rd and 4th generation FQs reported to be significantly more lipophilic, better absorbed (90 -100%), and widely distributed after oral, ophthalmic or respiratory system delivery • Greater versatility for treating systemic infections: – Superior activity across a wider range of Gram positive bacteria – Improved volume of distribution and uptake into many cells – Enhanced lipophilicity enables, e.g. treatment of prostatic and respiratory infections and infections in the brain / CSF – NB Most staphylococci resistant to FQs: not active vs MRSA Slide 46 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Side effects

• Common side-effects include GI disturbance, rashes, fatigue, dizziness, visual disturbances • If used alongside NSAIDs, convulsions can occur • Other serious side effects: – Spontaneous tendon ruptures – Prolongation of the QT interval (eg moxifloxacin) • Probably through blocking of the hERG channel (Human cardiac potassium channel = human ether a-go-go channel) – These side effects can be chronic and severe; some fatalities • Long QT syndrome led to several FQs being withdrawn from market, eg – (4 th generation) in 1999 – (3 rd generation) in 2001

Slide 47 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Structural requirements for activity

• Hundreds of analogues synthesized and evaluated • FQ structure activity relationship well established • Fewer new analogues being made now (but still some research to improve efficiency, reduce side effects and try to evade resistance mechanisms)

Slide 48 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Metallic interactions

• Structure of FQ essential for binding to gyrase (the target), but also allows binding of other species • Rich O donor ligand area : quinolone carbonyl and carboxylic acid • Co-admin with metal-ion containing preparations n+ leads to significant reduction in oral absorption M • Chelates range of metal ions: O O 2+ 3+ 2+ 2+ 3+ F C – Mg , Al , Zn , Ca , or Fe O – No co-admin with metal-cation containing agents, e.g. N N antacid preparations, H2N iron supplements, milk

Slide 49 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Fluoroquinolone Targets

• Bactericidal • Targets: inhibition of bacterial DNA gyrase and topoisomerase IV • The right handed helical nature of DNA means that positive supercoils (knots) form ahead of replication sites when DNA strands act as templates for new strands • In order for DNA replication to proceed, these supercoils must be removed by the gyrase or topoisomerase IV relaxing the DNA chain. By catalysing the formation of negative supercoils, these enzymes remove the positive supercoils and give a tension free DNA double helix • DNA gyrase and topoisomerase IV relax bacterial DNA by cutting one of the strands, passing the other strand through the cut and then resealing the cut • Mammalian cells do not have DNA gyrase or topoisomerase IV (they do have topoisomerases I and II, but FQs do not bind to these enzymes); hence, these agents show selectivity for bacterial enzymes

Slide 50 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Resistance to fluoroquinolones (FQs)

• Resistance to the FQs arises through two major mechanisms: 1. Alterations in the target enzymes : DNA gyrase and /or topoisomerase IV – Alterations to the DNA gyrase occur via mutations in the quinolone-resistance determining region (QRDR) of the gyrA gene which encodes the two A subunits of the tetrameric enzyme (gyrB encodes the two B subunits) – Similar mutations have been described in topoisomerase IV • These alterations to the target enzymes result in decreased FQ binding 2. Decreased accumulation of the FQs in cells due to the impermeability of the membrane ( decreased uptake ) or the over-expression of efflux pumps – FQs cross the outer membrane via specific porins (G-ve; all quinolones) or diffusion through the phospholipid bilayer (G+ve; hydrophobic, newer generation FQs only) – Porins are protein channels which allow passive diffusion of a specific agent across the cell membrane

Slide 51 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Specific examples

• Outer membrane of P. aeruginosa has very low permeability to small hydrophobic molecules giving this bacterium intrinsic resistance to the quinolones • Its low permeability in part due to secretion of mucoid alginate biofilm – Gives rise to name: ‘blue-green pus bacteria’ • E. coli has three main porins and a decrease in the level of one of these (OmpF) is associated with an increase in resistance to the quinolones • Ps. aeruginosa (Gram negative) and S. aureus (Gram positive) exhibit well characterised efflux pumps for the quinolones

Slide 52 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Rifamycins • The rifamycins are antibiotics from Amycolatopsis mediterranei and include , and • Discovered in 1957; >100 semi-synthetic analogues made • Rifampicin is an effective semi-synthetic bactericidal agent • Others also in clinical use, e.g. rifabutin (long t½: once daily dosing) • Prolonged PAE: >65 hours

Added chemically

Slide 53 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Therapy / combination therapy

• Rifampicin is used to treat: – tuberculosis and leprosy (both mycobacterium infections) • Rifater; with isoniazid and pyrazinamide • Rifinah; with isoniazid – MRSA / staphylococcal endocarditis (in combination with another antibacterial, e.g. fusidic acid (active vs pen-resistant Enterococci) • Obtained from Fusidium coccineum : inhibits protein synthesis – Legionella pneumophila (Legionnaires’ disease) – Can be used as prophylactic therapy against meningococcal meningitis ( Neisseria meningitidis ) and Haemophilus influenzae

Slide 54 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Rifampicin MoA

• Inhibitor of bacterial DNA-dependent RNA polymerase • Prokaryotic RNA polymerase (RNAP) is a holoenzyme composed of the core enzyme and a σ factor (gives the polymerase specificity for a particular promoter region of DNA) • Rifampicin binds to a pocket in the β subunit of the complex α2ββ ′ω structure • Amino acid sequence of rifampicin binding site is conserved among bacterial RNAPs but not between bacterial and eukaryotic RNAPs (selectivity ) • Rifampicin blocks transcription once the RNA becomes 3 nucleotides long through both allosteric and steric effects

Slide 55 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 DNA-dependent RNA polymerase: RNAP

Slide 56 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Rifampicin resistance / interaction

• Mutations to target : Mycobacterium tuberculosis resistance to rifampicin (rifampin) due to mutations in rpoB gene which codes for the β subunit of RNAP, resulting in a decreased affinity for rifampicin • These mutations have no effect on growth rate of M. tuberculosis (naturally slow growing and can tolerate less active transcription) • Interaction : inducer of enzymes so can lead to increased metabolism of many drugs cleared through — this interaction leads to reduced efficacy of the oral contraceptives and restricts choice of anti-HIV drugs

Slide 57 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 New antibacterial agents • There is a huge global need for new antibacterial agents, yet few pharmaceutical companies are interested – In Dec 2015, only 39 antibacterials in clinical trials in USA • There are many hurdles to developing new antibacterials, e.g. – Costs >$2.5 bn to develop 1 prescription-only med to market – Approx. 20% success rate in phase I CT – high failure rate – Acute use: only 5-7 days dosing, not economic – High risk of resistance developing: loss of market • Recent FDA and EMA incentives to increase pharma interest • Most antibacterials in CT are new derivatives of existing classes (e.g. , tetracyclines/aminocyclines, FQs) – Useful as increased activity, fewer side effects and lower resistance • Not all bad news: some new classes of antibiotics – E.g. FabI inhibitors, Pleuromutilins, Teixobactin • However, little progress towards countering ESKAPE threat – Need new agents active against G-ve bacteria

Slide 58 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 New agents:

• New derivative = prodrug (active parent: ceftaroline) • Potent in vitro activity due to very high binding affinity for PBP • Active against wide range of pathogenic bacteria: – G+ve : MRSA, MSSA, Streptococcus pneumoniae (incl. pen resistant), Streptococcus pyogenes (incl. macrolide resistant), Enterococcus faecalis – G-ve : Haemophilus influenzae, Enterobacter cloacae, , Shigella species – Not active vs VRE • T½: 2-3h; PAE 1.5 -7h depending on bacterial species • Of particular use for CAP and SSTI due to excellent tissue distribution • Little development of resistance so far

Slide 59 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Ceftaroline fosamil SAR Pos charged pyridinium provides zwitterionic counter charge 1,2,4-thiadiazole ring enhances Oxime provides Me uptake into G-ve bacteria and β-lactamase stability increased affinity for PBP N OEt N N S H N H S HO O N N O P N H N HO S S O 1,3-diazole ring Phosphoramidate prodrug CO2 confers MRSA activity enhances aq solubility Hydrolysed in vivo to free amine ring system – inhibits PBP

Slide 60 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 New agent: Lefamulin • New semi-synthetic member of pleuromutilin class of antibiotics – Originally isolated in 1950 from mould Pleurotus mutilis – General structure solved in 1962 • Medicinal chemistry changes resulted in agents for veterinary use in 1979 (Tiamulin) and 1999 (Valnemulin) – Unable to balance oral bioavailability and side effects with efficacy for humans • Retapamulin developed as topical agent for humans (2007) • Recently, developed new derivatives with suitable PK for oral administration in humans – Lefamulin (BC-3781) best candidate – Others in development

Derivatised part: semi-synthetic RS = HO in parent General pleuromutilin structure

Slide 61 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 MoA / Resistance?

• Acts on ribosome to block protein synthesis • Unique MoA : binds to specific site on 23S RNA of 50S bacterial ribosome subunit – Inhibits ribosomal peptidyl transferase activity, and partially inhibits the binding of the initiator tRNA substrate to the ribosomal P-site • Novel mechanism compared to other agents acting on ribosome means no cross-resistance observed with macrolides, tetracyclines, aminoglycosides and linezolid – Also not seen with fluoroquinolones, trimethoprim-sulfamethoxazole, mupirocin and β-lactam agents • Lefamulin possesses potent in vitro activity against the most common pathogens associated with CAP: S. pneumoniae , H. influenzae , S. aureus , M. pneumoniae , L. pneumophila , and C. pneumoniae , including MDR strains

Slide 62 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Current status

• Strong in vitro data allowed progress to clinical trials • Phase II for cellulitis completed 2010: comparative to vancomycin (but no resistance) • Now in phase III clinical trials in US and EU for CAP – Started Sept 2015, ends Aug 2017 – Comparing efficacy and safety with moxifloxacin ( ± linezolid) • Phase III CT for skin and soft tissue infections (SSTI) planned – Successful phase II CT completed in 2011 • Not yet available in UK unless patients part of trial • Altho old class, has in vivo activity against both G+ve and G-ve bacteria with novel MoA

Slide 63 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 New class of antimicrobials ☺

• Teixobactin: Ling et al ., Nature, 2015 • 99% of bacteria are not able to be cultured in vitro but offer novel antibiotics • New β-proteobacteria species, Eleftheria terrae , cultured in situ using new technique • Novel depsipeptide isolated with time-dependent bactericidal activity • Very potent vs G+ve bacteria (at <1 μg/mL), including MRSA and VRE, C. diff, and Mycobacterium tuberculosis • Teixobactin inhibits cell wall synthesis by binding to lipid II (precursor of ) and lipid III (precursor of cell wall teichoic acid) • Attempts to create resistance so far failed • Good news, but….. not active against P. aeruginosa or K. pneumoniae ! – And not orally bioavailable (peptide) 

Slide 64 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 FabI inhibitors

• Fab = fatty acid biosynthesis, an essential pathway for growth in both G+ve and G-ve bacteria and Mycobacteria • Fab inhibitors target the fatty acid synthase II (Fas-II) pathway that consists of several enzymes catalysing essential steps in fatty acid biosynthesis • Key regulatory reactions are most targeted by researchers: elongation condensing enzymes (FabF and FabB) and enoyl-acyl carrier protein reductase (FabI) • Several existing antibacterials found to act on Fas-II pathway, e.g. isoniazid (FabI), cerulenin (FabF), thiolactomycin (FabB and FabF), triclosan (FabI) • New agents being developed, 3 currently in CT in USA – All targeted at aureus and MRSA (e.g. Debio 1452) – Little success currently in creating broad spectrum FabI inhibitors

Slide 65 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Choosing an antibacterial agent

• Many considerations to make, e.g. – How severe is the infection? Agent required to kill bacteria (bactericidal) or simply halt growth (bacteriostatic)? – Which bacteria are causing the infection? Which agent is active against that pathogen? What is the susceptibility profile to that agent? – Where is the site of the infection? Which agent has the correct distribution characteristics? – What dosing method and regimen are required for effective treatment? • Most effective treatment when use specific agent (not just class of agent) appropriate to: – Pathogenic bacteria – use narrow spectrum if possible (susceptibility?) – Site of infection – distribution of agent must be suitable to reach site – Pharmacokinetic requirements – dosage method / regimen

Slide 66 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Broad or narrow spectrum? • Some antibacterial agents are active against both Gram positive and Gram negative bacteria – β-Lactams (broad spectrum G-ve and many G+ve [except ]) – Tetracyclines (broad spec G-ve and some G+ve) – Chloramphenicol (broad spec vs both G+ve / G-ve; but severe side effects possible if systemic admin) – Macrolides (e.g. erythromycin: broad spec vs both G-ve / G+ve) – Aminoglycosides (G-ve and some G+ve) – Trimethoprim/sulfamethoxazole (G-ve and some G+ve) – Rifamycins (broad spec vs both G-ve and G+ve) • Other agents only active against one or other – Linezolid (G+ve only) – Daptomycin (G+ve only) – (G-ve only; except cocci and certain other G-ve bacteria) – Vancomycin (G+ve only; but severe side effects possible)

Slide 67 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Examples

• Community acquired pneumonia • Meningitis • C. diff infection • TB • Infective endocarditis • UTIs

Slide 68 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 CAP • Inflammation / swelling in the tissues of one or both lungs, usually result of bacterial infection • Annual UK presentation rate in community: 0.5%-1% – 5-12% of adults who present to GPs with symptoms of lower RTI are diagnosed with CAP – 22-42% of these are admitted to hospital (about 100,000 hospital admissions each year in England) • Mortality rate 5-14% [patient.co.uk (1 st Jan 2016)] • Common infective agents: – G+ve : Strept. pneumoniae (20-60% of bacterial CAP in adults; 15-40% in children) Staph. aureus (2% CAP; uncommon cause in healthy adults) – G–ve : Haemophilus influenzae (3-10% of CAP) • Agents causing atypical pneumonia: – , Chlamydophila pneumoniae (G-ve) and Legionella pneumophila (G-ve) [Cause up to 15% of CAP cases] • Treatment requirements: – Broad spec activity vs G-ve and G+ve – Good tissue distribution (so sufficient concentration reaches lungs)

Slide 69 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 CAP treatment

• Initial treatment: amoxicillin or doxycycline or clarithromycin • Amoxicillin: β-lactam antibiotic, bactericidal with good PAE, active vs G+ve (Strep and Staph) and some G-ve (H. influenzae , but not Ps. aeruginosa ), good distribution into different tissues, time dependent (T > MIC important), orally bioavailable • Doxycycline: tetracycline class, broad spectrum (G-ve and G+ve), bacteriostatic, time / concn dep, good PAE, well distributed throughout tissues, excellent oral bioavailability – With loading regimen, follows concn dep kinetics, i.e. large dose = better effect – Without loading regimen, follows time dep kinetics and takes several days to be effective • Clarithromycin: macrolide, bacteriostatic, low PAE, time dep, good oral bioavailability and tissue distribution, concentrated at site of infection, espec. lung, by accumulation in macrophages • New agents also active: ceftaroline fosamil and lefamulin

Slide 70 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 HAP / VAP

• Early onset (2-4 days after admission): same as for CAP • Assume community source prior to admission • Late onset (≥5 days after admission): • G+ve : MRSA (10-15% nosocomial pneumonia – common 5d after start of viral influenza) • G-ve : Ps. aeruginosa (PA; major cause of nosocomial pneumonia); Klebsiella pneumoniae (associated with recent use of potent antibiotics); Neisseria meningitidis (usually associated with meningitis and septicaemia, but can also cause pneumonia) • 1st line often pipericillin with (Tazosyn) – Active against Ps. aeruginosa – If severe, aminoglycoside added, or or FQ (e.g. ciprofloxacin) • If MRSA suspected: vancomycin (unless resistant)

Slide 71 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Meningitis-causing bacteria

• Can be bacterial or viral: bacterial usually most dangerous (about 50% mortality if untreated) • Most common causes: – Gram +ve : Streptococcus pneumoniae; Listeria monocytogenes – Gram –ve : Neisseria meningitidis ; Haemophilus influenzae type B (latter primarily in infants and children) • Severe and life threatening, rapid empirical Tx required • Usually 1st line: – Broad spectrum G+ve and G-ve bacteria – Admin IV for rapid action – High protein binding and low renal excretion give half-life of several hours – Paracellular uptake (due to leaky meninges) and specific transport into CSF – Low active transport out of CSF leads to accumulation during meningitis – Good PAE with G+ve bacteria and H. influenzae

Slide 72 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Bacterial meningitis

• Significantly affected by distribution of drug – Distribution of drug across BBB into CSF important – Must guarantee effective dose in CSF • In meningitis, BBB compromised, so get higher than usual drug concentrations in CSF • β-lactams (ionised), but reach about 5 – 20% of levels found in serum – 3rd generation cephalosporins (e.g. Ceftriaxone, ) have good BBB penetration and active against most bacteria causing meningitis (unless resistant) • Lipophilic drugs reach higher concentrations – Fluoroquinolones, rifampicin, chloramphenicol: 30 – 50% of serum concentrations (even under normal circumstances), but FQs rarely used due to resistance • For successful treatment of meningitis, require – Rapid action – Concentration in CSF of 10 – 30 times MBC

Slide 73 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Summary

• Bacteria and bacterial infections • Covered many classes of antibacterials • Range of targets • Selectivity • Mode of action • Mechanism(s) of resistance • Bactericidal vs bacteriostatic • Time dependent vs concentration dependent actions • Guidelines, especially for emergency care • New treatments, new agents, new classes • Resources GOOD LUCK!

Slide 74 of 75 OSPAPMPHM14 Antineoplastic Chemotherapy WEEK 27 Resources

• TARGET Toolkit: – http://www.rcgp.org.uk/targetantibiotics/ – Local guidelines: ‘basket of ten’ • Start Smart Then Focus: – www.gov.uk/government/uploads/system/uploads/attachment_data/f ile/215308/dh_131181.pdf – Being reviewed and updated in 2015 • Antimicrobial prescribing and stewardship competencies: – www.gov.uk/government/uploads/system/uploads/attachment_data/f ile/253094/ARHAIprescrcompetencies__2_.pdf – Being developed for implementation 2016 • Mnemonics: http://www.cram.com/flashcards/mnemonics- galore-958558

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