Chapter 17 Microbiology and Infectious Disease Devan Jaganath, MD, MPH, and Rebecca G. Same, MD See additional content on Expert Consult I. MICROBIOLOGY A. Collection of Specimens for Blood Culture 1. Preparation: To minimize contamination, clean venipuncture site with 70% isopropyl ethyl alcohol. Apply tincture of iodine or 10% povidone–iodine and allow skin to dry for at least 1 minute, or scrub site with 2% chlorhexidine for 30 seconds and allow skin to dry for 30 seconds. Clean blood culture bottle injection site with alcohol only. 2. Collection: Two sets of cultures from two different sites of equal blood volume should be obtained for each febrile episode, based on patient weight: <8 kg, 1–3 mL each; 8–13 kg, 4–5 mL; 14–25 kg, 10–15 mL each; >25 kg, 20–30 mL each.1 Peripheral sites preferred. If concern for central line infection, collect one from central access site, second from peripheral. B. Rapid Microbiologic Identification of Common Aerobic Bacteria (Fig. 17.1) and Anaerobic Bacteria (Fig. 17.2) C. Choosing Appropriate Antibiotic Based on Sensitivities 1. Minimum inhibitory concentration (MIC): Lowest concentration of an antimicrobial agent that prevents visible growth; MICs are unique to each agent, and there are standards to determine if susceptible, intermediate, or resistant. Antibiotic selection should generally be based on whether an agent is “susceptible” rather than the MIC. 2. See Tables 17.1 through 17.6 for spectrum of activity of commonly used antibiotics.2,3 Note: Antibiotic sensitivities can vary greatly with local resistance patterns. Follow published institutional guidelines and culture results for individual patients and infections. When possible, always use agent with narrowest spectrum of activity, particularly when organism susceptibilities are known. Downloaded for dr.Rahmat Dani Satria, M.Sc, Sp.PK ([email protected]) at Universitas443 Gadjah Mada from ClinicalKey.com by Elsevier on July 28, 2018. For personal use only. No other uses without permission. Copyright ©2018. Elsevier Inc. All rights reserved. 444 Part II Diagnostic and Therapeutic Information II. INFECTIOUS DISEASE A. Fever without Localizing Source: Evaluation and Management Guidelines4,5 1. Age <28 days: Hospitalize for full evaluation (Fig. 17.3). Owing to the greater risk of serious bacterial infections in young infants with fever, a conservative approach is warranted. 2. Age 29–90 days: Well-appearing infants who meet low-risk criteria can potentially be managed as outpatients if reliable follow-up and monitoring is ensured. 3. Age >90 days: The marked decline in invasive infections due to Haemophilus influenzae type b and Streptococcus pneumoniae, since introduction of conjugate vaccines, has reduced the likelihood of Gram stain Gram-negative bacteria Cocci BacilliCoccobacilli Neisseria Enteric Haemophilus Moraxella Kingella Curved Lactose Bordetella* or spiral fermenter Brucella*,† Francisella*,† Vibrio Campylobacter Ϫ Nonenteric ϩ Oxidase Escherichia coli Moraxella Enterobacter Kingella Citrobacter Pasteurella Ϫ ϩ Klebsiella Legionella* Eikenella Bartonella Salmonella Pseudomonas Shigella Aeromonas Proteus Burkholderia Serratia Citrobacter * Special media needed to Acinetobacter grow these organisms. Stenotrophomonas † Potential laboratory hazard—warn laboratory if these organisms are suspected. FIGURE 17.1 Algorithm demonstrating identification of aerobic bacteria. Downloaded for dr.Rahmat Dani Satria, M.Sc, Sp.PK ([email protected]) at Universitas Gadjah Mada from ClinicalKey.com by Elsevier on July 28, 2018. For personal use only. No other uses without permission. Copyright ©2018. Elsevier Inc. All rights reserved. Chapter 17 Microbiology and Infectious Disease 445 Gram-positive bacteria Bacilli Cocci Listeria Chains Clusters Bacillus spp. or pairs Corynebacteria Streptococci Staphylococci Coagulase test ϩ Quellung S. aureus Ϫ Ϫ ϩ S. epidermidis S. saprophyticus Hemolysis S. pneumoniae Micrococcus spp. ␤ Viridans streptococci ␣ Enterococci ␥ Group A streptococci (S. pyogenes) Group B streptococci (S. agalactiae) Group C streptococci Group G streptococci FIGURE 17.1, cont’d serious bacterial infection in a well-appearing child within this age group: a. If ill-appearing without source of infection identified, consider admission and empirical antimicrobial therapy. b. If source of infection identified,treat accordingly. c. If well-appearing and without foci of infection, many experts advocate urinalysis and urine culture as the only routine diagnostic test if 17 reliable follow-up and monitoring is ensured, including all females and uncircumcised males aged <2 years, all circumcised males aged <6 months, and all children with known genitourinary tract abnormalities. 4. Fever of unknown origin6,7 a. Generally defined as fever> 38.3°C for 2 or more weeks b. Often an unusual presentation of a common disease c. Broad differential, such as infectious (including deep-seated bone infections or abscesses), neoplasms, collagen vascular disease (i.e., juvenile idiopathic arthritis), drug fever, and Kawasaki syndrome Downloaded for dr.Rahmat Dani Satria, M.Sc, Sp.PK ([email protected]) at Universitas Gadjah Mada from ClinicalKey.com by Elsevier on July 28, 2018. For personal use only. No other uses without permission. Copyright ©2018. Elsevier Inc. All rights reserved. 446 Part II Diagnostic and Therapeutic Information Gram stain Gram-negative Bacilli Cocci Bacteroides spp. Veillonella Fusobacterium Gram-positive Bacilli Cocci Clostridium spp. Peptostreptococcus Propionibacterium Actinomyces Lactobacillus spp Listeria FIGURE 17.2 Algorithm demonstrating identification of anaerobic bacteria. d. Confirmation of feveris essential, thorough history of fever pattern, associated signs/symptoms, family history, ethnic/genetic background, environmental and animal exposures, and complete physical exam e. Labs and imaging will be guided by history and physical, and corresponding category of differential (i.e., infectious vs. oncologic vs. autoimmune/rheumatologic vs. immunodeficiency) B. Evaluation of Lymphadenopathy8 1. Etiology a. Reactive lymph nodes (LNs): Majority of lymphadenopathy b. Direct infection of LN: Suppurative lymphadenitis (typically due to Staphylococcus aureus or Streptococcus pyogenes) or indolent lymphadenitis (e.g., Bartonella henselae, atypical Mycobacterium) c. Malignancy: Can be observed with leukemia, and lymphoma Text continued on p. 452 Downloaded for dr.Rahmat Dani Satria, M.Sc, Sp.PK ([email protected]) at Universitas Gadjah Mada from ClinicalKey.com by Elsevier on July 28, 2018. For personal use only. No other uses without permission. Copyright ©2018. Elsevier Inc. All rights reserved. Gadjah Madafrom ClinicalKey.com byElsevier onJuly 28,2018.For personal useonly. Noother Downloaded fordr.RahmatDani Satria,M.Sc,Sp.PK ([email protected]) atUniversitas TABLE 17.1 uses without permission. Copyright ©2018. Elsevier Inc. All rights reserved. β-LACTAMS: INHIBIT CELL WALL SYNTHESIS Gram-Positive Organisms Gram-Negative Organisms Anaerobes Spirochetes PENICILLINS Natural penicillins (Pen G or Pen V) Streptococcus pyogenes, Neisseria meningitidis Oral anaerobes Borrelia Chapter 17 Streptococcus agalactiae, burgdorferi, Streptococcus pneumoniae Leptospira (with about 10%–20% interrogans, resistance depending on local Treponema epidemiology), Viridans pallidum Microbiology andInfectiousDisease streptococcus, Listeria monocytogenes, Corynebacterium diphtheriae Anti-Staphylococcus–resistant MSSA, CoNS (high levels of penicillins: Nafcillin, oxacillin, resistance) dicloxacillin Aminopenicillins: Amoxicillin, S. pyogenes, S. agalactiae, Non–β-lactamase–producing Escherichia Oral anaerobes B. burgdorferi, ampicillin S. pneumoniae, Viridans coli, other Gram-negative enterics, and L. interrogans, streptococcus, L. monocytogenes, non–β-lactamase–producing respiratory T. pallidum Enterococcus faecalis Gram-negatives such as Haemophilus influenzae Extended-spectrum Organisms covered by amoxicillin/ β-Lactamase–producing Gram-negative Oral and intestinal β-lactamase inhibitors without ampicillin plus MSSA intestinal (E. coli) and respiratory anaerobes pseudomonal activity: organisms (H. influenzae) Amoxicillin/clavulanic acid, ampicillin/sulbactam 447 Continued 17 Gadjah Madafrom ClinicalKey.com byElsevier onJuly 28,2018.For personal useonly. Noother Downloaded fordr.RahmatDani Satria,M.Sc,Sp.PK ([email protected]) atUniversitas 448 TABLE 17.1 uses without permission. Copyright ©2018. Elsevier Inc. All rights reserved. β-LACTAMS: INHIBIT CELL WALL SYNTHESIS—cont’d Gram-Positive Organisms Gram-Negative Organisms Anaerobes Spirochetes Part II Extended-spectrum E. faecalis, MSSA, S. pyogenes, E. coli and other Enterobacteriaceae and Oral and intestinal β-lactamase inhibitors with S. agalactiae enterics, Pseudomonas aeruginosa anaerobes pseudomonal activity: (percent susceptibility varies based on Diagnostic andTherapeuticInformation Piperacillin/tazobactam local epidemiology) CEPHALOSPORINS Do not cover LAME [Listeria, Atypicals such as Mycoplasma and Chlamydia, MRSA (except for ceftaroline), and Enterococci] First-generation: Cephalexin, MSSA, S. pyogenes, S. agalactiae Very good coverage of enteric cefazolin Gram-negative organisms (e.g., E. coli, Klebsiella) Second-generation: cefuroxime and Cefuroxime: same as β-Lactamase–producing Gram-negative Cephamycins have good oral the cephamycins (cefotetan and first-generation; cephamycins: organisms (E. coli, H. influenzae, anaerobic activity