Bacteroides Infections in Children

J. Med Microbiol. Vol. 43 ( 1995). 92-98 0 1995 The Pathological Society of Great Britain and Ireland

CLINICAL ANAEROBIC MICROB I0 LOGY

Bacteroides infections in children

1. BROOK

Department of Pediatrics, Georgetown University School of Medicine, Washington, DC, USA

Summary. From 1974 to 1990, 336 Bacteroides isolates were obtained from 312 specimens from 274 patients. They comprised 180 (54%) B. fragilis isolates, 55 (16%) B. thetaiotaomicron, 36 (1 1 %) B. culgatus, 34 (10 %) B. distasonis, 21 (6 %) B. ovatus and 10 (3 %) B. unzformis. Infections in 253 (92 Yo) patients were polymicrobial, but in 21 (8 ”0) children, a Bacteroides sp. was isolated in pure culture. Most Bhcteroides isolates were from peritoneal fluid (1 14)’ abscesses (1 lo), wound infections (20), blood cultures (10) and from patients with pneumonia (14) or chronic otitis media (8). Predisposing conditions were present in 145 (53 %) children ; these were previous surgery (46), trauma (28), malignancy (2 I), prematurity (19), immunodeficiency (18), steroid therapy (12) foreign body (lo), diabetes (9) and sickle cell disease (7). The micro-organisms isolated most commonly mixed with Bacteroides spp. were anaerobic cocci (221), Escherichia coli (122), Fusobacteriurn spp. (38) and Clostridium spp. (30). All patients received antimicrobial therapy in conjunction with surgical drainage or correction of pathology in 197 (72 Oh) cases. All but 12 (5O/O) patients recovered. These data illustrate the importance of Bacteroides spp. in infections in children.

Introduction have been published before in articles describing the role of anaerobic bacteria in various paediatric The species of Bacteroidaceae that occur with infections,’ but cases not previously presented are also greatest frequency in anaerobic infections in children, included and the unique nature of bacteroides as they do in adults, belong to the genus Bacteroides. infections in children is emphasised. These micro-organisms are resistant to penicillins by virtue of P-lactamase production and by other un- Patients and methods known mechanisms.’ They were formerly classified as five subspecies of B. .fragilis (ss. fragilis, ss. distasonis, Pa tients ss. oratus, ss. thetaiotaonzicron and ss. culgatus) and were reclassified in 1976 into distinct species on the The children included in this review were studied by basis of DNA homology studies,’ and then became the the author between June 1974 and June 1990. They only species remaining in the genus Bacteroides sensu were seen in the following hospitals: University of stricto in 1990.3 B. -fragilis is the anaerobe most California Medical Center, Los Angeles County Medi- frequently isolated from clinical infections. cal Center and Serra Memorial Hospital in Los Recognition of the role of Bacteroides spp. in Angeles, CA ; Children’s Hospital National Medical paediatric infection has become more important in Center and South-East Medical Center in Washington, recent years because of their increased resistance to DC ; and National Naval Medical Center in Bethesda, some commonly used antimicrobial agents that were MD. Records from the clinical microbiology lab- previously very effective against them,* e.g., clinda- oratory were reviewed to identify patients with mycin. cephalosporins, metronidazole and chloram- bacteroides infections. The available case histories of phenicol.4 all patients from whom Bacteroides spp. had been This retrospective review summarises my experience isolated were reviewed to ascertain the presence and of the isolation of Bacteroides spp. from infections in site of infection, associated micro-organisms, under- children during a period of 16 years. Some of the data lying disease processes, and possible predisposing or associated conditions. Receixed 31 Ma) 1994: revised version received 8 Feb. 1995; accepted 9 Feb. 1995. Microbiological exam in at ion Correspondence should be sent to Professor I. Brook, PO Box 70417. Chev) Chse. MD 20813-0412, USA. Only specimens that were properly collected without

92 BACTEROIDES INFECTIONS IN CHILDREN 93 contamination by the normal skin or mucosal surface Bacteroides isolates flora and submitted in transport media appropriate for anaerobic bacteriological investigation were accepted The 336 Bacteroides isolates comprised 180 (54 "/O) by the microbiology laboratories. These were B. fragilis, 55 (16 %) B. thetaiotaomicron, 36 (1 1 YO)B. specimens obtained during surgery or by aseptic needle vulgatus, 34 (10 YO)B. distasonis, 21 (6 YO)B. ovatus and or biopsy aspiration of abscesses or fluid from body 10 (3 YO)B. uniformis (tables I and 11). Infections were cavities. Lung aspirates were obtained by transtracheal polymicrobial in 253 (92 YO)patients, but in 21 (8 YO) aspiration or biopsy. Urine was collected by supra- children, Bacteroides spp. were isolated in pure culture pubic aspiration. When possible, pus and fluids were (table 111). collected and transported in syringes. Most specimens, There were 749 other bacterial isolates with the except blood, were submitted on a Port-A-Cul trans- Bacteroides spp. in the 290 specimens from mixed port swab or in liquid systems (BBL, Cockeysville, infection; 429 of these were anaerobes and 320 were MD, USA). However, precise records of the transport facultative or aerobic species. The number of isolates media used were not available. Blood was collected in the mixed cultures was 2-7 (average 2-6 isolates/ aseptically from patients suspected of having specimen, 1.5 anaerobes and 1.1 facultative or aerobic). bacteraemia and was inoculated (10 YOv/v) into one The micro-organisms isolated most commonly with bottle each of two commercially produced broth Bacteroides spp. were anaerobic cocci (21 1 isolates), media, both under vacuum and with CO, 5% in the Escherichia coli (122), Fusobacterium spp. (40) and atmosphere. The sources of blood-culture media Clostridium spp. (31). Most E. coli and Clostridium varied during the period of review. spp. were isolated with Bacteroides spp. from intra- Specimens were inoculated on to pre-reduced vit- abdominal infections, and skin and soft tissue amin K1-enriched Brucella Blood Agar (BBL), blood infections around the rectal area. Most pigmented agar with kanamycin (75 mg/L) and vancomycin Prevotella and Porphyromonas isolates were from head (7.5 mg/L), and blood agar with colistin sulphate and neck infections. (0.01 mg/L) and nalidixic acid (50 mg/L), and into Most Bacteroides isolates were from peritoneal fluid an enriched thioglycolate broth containing haemin specimens (1 14 isolates, 34 YO),abscesses (1 10, 33 YO), (5 mg/L) and vitamin K (0.1 mg/L). The cultures were wounds (29,9 YO),pneumonia (14,4 YO),blood cultures incubated in GasPak jars (BBL) and examined after 48 (1 3,4 %), decubitus ulcers (10, 3 %) and chronic otitis and 96 h6. Plates that showed any growth were held media (8, 2%). until the micro-organisms had been identified. All cultures that showed no growth were held for at least Types of infections 5 days. Micro-organisms were identified by the API anaerobic system (Analytab Products, Plainview, NY, Peritonitis. The 114 peritoneal isolates of Bac- USA). When complete identification was not possible teroides spp. were from 108 children and were mixed by this method, other carbohydrate tests (Scott with other bacteria, mostly Peptostreptococcus spp. Laboratories, Fiskeville, RI, USA) and gas-liquid (96 isolates) and E. coli (65), but also Fusobacterium chromatography6 were performed as needed to spp. (23), group D streptococci (1 9), Eubacterium spp. identify the organisms. The criteria for identification (17) and Clostridium spp. (14). In 79 of the children, were according to guidelines published previo~sly.~3' peritonitis was associated with a ruptured appendix, nine cases followed trauma, and 10 rupture of a viscus.

Abscesses. Of the 321 specimens from abscesses, 101 Results (32 O/O) yielded a growth of Bacteroides spp. (table 11). The most common abscesses from which the Patients Bacteroides spp. were isolated were abdominal (23 From a total of 1658 specimens examined for isolates), perirectal(14), pilonidal(l2) and subphrenic anaerobic bacteria, 336 Bacteroides strains were iso- (9). The most common other organisms in these lated from 312 (20%) specimens obtained from 274 abscesses were E. coli and Peptostreptococcus spp. patients. Clinical records were not available for review from another 18 patients; these were not included in Wound infections. The 29 isolates from wounds were the final analysis. Patients' ages ranged from one day from post-surgical infection of the abdomen (13 to 17.5 years (mean 7 years 9 months); 164 were male isolates), head and neck (six) and rectal area (five). In and 110 female. Predisposing or underlying conditions all cases, the Bacteroides isolates were mixed with were present in 145 (53%) of the patients. A single other bacteria-E. coli (eight isolates), enterococci underlying condition was noted in 120 cases, and two (four) and Staphylococcus aureus (four). The 10 conditions were recorded in 25 ; these conditions were isolates from decubitus ulcers were from ulcers of the previous surgery (46), trauma (28), malignancy (2 l), buttocks (four isolates), lower extremities (three) and prematurity (19), immunodeficiency (18), steroid head (three); all were mixed with other micro-organ- therapy (12), presence of a foreign body (lo), diabetes isms-Peptostreptococcus spp. (eight isolates), E. coli (9) and sickle cell disease (7). (four), S. aureus (three) and Clostridium spp. (two). 94 LBROOK

Table I. Bacteroides isolates from 3 12 specimens from 274 children

Number of specimens Number of Bacteroides isolates

Type of infection B. B. thetaiotaomicron uniformis

Peritoneal fluid 115 108 114 63 5 9 11 16 10 Abscess 321 101 2 110 61 11 13 6 19 Wounds 75 24 29 13 4 2 3 7 Decubitus ulcers 58 9 10 4 2 2 2 Omphalitis 25 6 7 4 1 2 Burn 180 5 5 4 1 Bites, human 18 1 1 1 Blood 334 13 12 13 10 1 2 Ear: mastoiditis 24 3 3 1 2 otitis. chronic 94 8 8 4 3 otitis, cholesteatoma 38 6 6 3 1 1 Pneumonia 80 13 3 14 4 3 7 Empyema 72 7 3 7 3 1 3 Sinusitis, chronic 45 1 1 1 Osteomyelitis 26 3 4 2 1 1 Conjunctivitis 148 1 1 1 1 Urinary tract infection 5 3 1 3 2 1 Total 1658 312 22 336 180 34 36 21 55 10

Table 11. Bacteroides isolates from 101 abscesses

Number of specimens Number of Bacteroides isolates

Abscess site with with B. B. B. B. B. Total Bacteroides B. fragilis Total thetaiota- fragilis distasonis vulgatus ovaturn SPP. alone omicron

Abdomen 33 23 25 14 3 2 6 Buttocks 15 8 10 4 2 1 3 Breast 14 1 1 1 Hand 25 2 -7 2 Fingers 20 3 3 2 1 3 Head 31 2 L 1 1 Intracranial 39 5 5 4 1 Liver 10 3 3 1 1 1 Lung 10 3 3 1 1 1 Pilonidal 25 12 12 5 2 1 2 2 Perirectal 28 14 2 14 8 2 2 2 Scalp 23 3 3 2 1 Subphrenic 14 9 13 6 2 2 3 Renal 10 6 7 5 1 1 Vuh OL aginal 6 3 3 2 1 Spleen 11 2 2 1 1 7 3 Trunk 17 i 6 2 Total 32 1 101 2 110 61 11 13 6 19

Seven isolates were from omphalitis and all were meningitis and one each with prematurity and isolated with other flora, mostly E. coli (four). Five necrotising enterocolitis, and leukaemia, empyema Bucteroides isolates were from burns around the rectal and rectal abscess. area (three) and lower extremities (two); all were mixed with Enterobacteriaceae or Pseudomonas aero- Other infections. Seventeen isolates were from qirmn. The single isolate of B. matus was from a bite chronic otitis media and its complications (mastoiditis wound and was mixed with Pstr. magnus and a- and cholesteatoma); all were mixed with other bac- haemoly tic s t reptococci. teria, the most common being Peptostreptococcus spp. (10 isolates) and pigmented Prevotella or Por- Bacteraen?ia. Of the 13 isolates from blood cultures, phyromonas spp. (seven). One isolate was from a 12 were in pure culture (table 111) and one was mixed maxillary sinus infection, in a mixed infection with two with E. coli in a patient with a ruptured appendix. The anaerobic cocci. Fourteen isolates were from aspir- single isolates were from two patients with immuno- ation pneumonia, of which three were in pure culture deficiency. three with perforated appendix, two with (table 111). The other 11 isolates were from mixed BACTEROIDES INFECTIONS IN CHILDREN 95

Table 111. Summary of 21 infected patients with pure cultures of Bacteroides

Patient no. Age Sex Diagnosis Culture site Culture results Therapy Outcome

1 2d M Pneumonia Tracheal aspirate, B. vulgatus Ampicillin & Died amniotic fluid gentamicin 2 Id M Pneumonia CSF, tracheal aspirate B. distasonis Ampicillin & Died gentamicin 3 2d M Pneumonia Tracheal aspirate, B. fragilis Ampicillin, Cured amniotic fluid clindamycin & gentamicin 4 7Y F Cystitis Urine B. fragilis Ticarcillin Cured 5 8Y M Abscess Abscess cavity B. thetaiotaomicron Clindamycin & Cured gentamicin 6 6Y F Conjunctivitis Conjunctival sac B. fragilis Clindamycin Cured 7 4Y F Empyema Empyema fluid B. distasonis Chloramphenico 1 Cured 8 5Y M Empyema Empyema fluid B. fragilis Metronidazole Cured 9 16 Y M Empyema Empyema fluid B. thetaiotaomicron Clindamycin Cured 10 21 d M Bacteraemia, meningitis CSF/blood B. fragilis Chloramphenicol Cured 11 23 d F Meningitis, bacteraemia CSF/blood B. fragilis Penicillin Died 12 6y9m M Bacteraemia, leukaemia, Blood/rectal abscess B. fragilis Carbenicillin & Died rectal abscess gentamicin 13 10 d M Bacteraemia, prematurity, Blood B. vulgatus Chloramphenicol Died NEC 14 5Y F Bacteraemia, perforated Blood B. fragilis Clindamycin & Cured appendix gentamicin 15 14 d F Bacteraemia, perforated Blood B. fragilis Metronidazole Cured appendix 16 12 d M Bacteraemia, perforated Blood B. fragilis Clindamycin Cured appendix 17 9y3m M Bacteraemia Blood B. fragilis Chloramphenicol Cured 18 7y6m F Bacteraemia, empyema Blood B. fragilis Clindam ycin Cured 19 8y10m F Bacteraemia Blood B. thetaiotaomicron Metronidazole Cured 20 13 Y M Bacteraemia, immune Blood B. fragilis Clindam ycin Cured deficiency 21 15 Y M Bacteraemia, immune Blood B. fragilis Metronidazole Cured deficiency

NEC, necrotising enterocolitis. infection with pigmented Prevotella or Porphyromonas in 18, a ureidopenicillin in 14, a penicillin in 38, spp. (five isolates), Peptostreptococcus spp. (four), cefazolin in 42 and co-trimoxazole in 11. Twelve Fusobacterium spp. (three) and Klebsiella pneumoniae patients (5%) died of their infections. The deaths (two). Seven isolates were from empyema, of which occurred in three patients with pneumonia (including three were in pure culture (table 111), all in patients cases nos. 1 and 2, table 111), three with bacteraemia with a primary intra-abdominal infection (one with a (nos. 11, 12 and 13, table 111), two with peritonitis, hepatic abscess) ; the other four isolates were from and one each with burns and splenic, hepatic and mixed infections with Peptostreptococcus spp. (four intracranial abscesses. isolates) and enterobacteria (one). Four osteomyelitis isolates were from three patients with mixed infections: one neonate with infection of Discussion the occipital bone after fetal monitoring, and two children with infection of the coccyx and occipital This retrospective review demonstrates the import- bone that complicated decubitus ulcers of the over- ance of Bacteroides spp. in various infections in lying skin. Of the three urinary isolates, one was in children. The 336 Bacteroides isolates were from 3 12 pure culture (table 111) in a girl with cystitis, and the (20%) of 1658 specimens submitted for culture for two others were mixed with E. coli and Pr. anaerobic bacteria. Bacteroides spp. are especially melaninogenica. The single Bacteroides isolate from the prevalent in abscesses (mostly abdominal, perirectal conjunctiva was from a 6-year-old girl without any and subphrenic), peritonitis, aspiration pneumonia predisposing condition (table 111). and bacteraemia. Because of its presence in the normal flora of the gastrointestinal tract, B. fragilis predominates in Treatment and outcome bacteraemia associated with intra-abdominal infec- Antimicrobial therapy was given to all patients, tions,*peritonitis and abscesses following rupture of a with surgical drainage or correction of pathology in viscus,' and subcutaneous abscesses or burns near the 187 (68 %). The antimicrobial agents administered anuslo Although Bacteroides spp. are not generally were aminoglycosides in 128 cases, clindamycin in 113, found in the normal oral flora, they can colonise metronidazole in 42, cefoxitin in 37, chloramphenicol the oral cavity of patients with poor oral hygiene or 96 I. BROOK of those who have received antimicrobial therapy, strains are more virulent than the non-capsulate especially with a p-lactam agent. Colonisation of the ~OI-IIIS.~~This increased virulence can be demonstrated oropharyngeal cavity can lead to the isolation of these by a higher rate of induction of bacteraemia, and a species from paediatric infections that originate in this greater enhancement of growth of other bacteria in area, such as aspiration pneumonia." lung abscesses," mixed infections.26 The emergence of capsule pro- chronic otitis media,13 brain abscesses,'' and sub- duction in polymicrobial infection may explain the cutaneous abscesses or burns near the oral cavity." predominance of B. fragilis in chronic infection. Bacteroides spp. can be isolated from infections in The relationship between the Bacteroides spp. and neonates. The newborn infant is at risk of developing the aerobic and facultative bacteria in intra-abdominal these infections when born to a mother with amnionitis infections has been shown to be ~ynergic.~~-~l or premature rupture of membranes, or through Altemeir,27Meleney et a1.,28Hite et al.,29 and Brook aspiration or contamination of wounds during passage et al.,30.31demonstrated such synergy in animal through the birth canal." B. -fragilis has been isolated models. Brook et al.30,31evaluated the synergic from neonates with aspiration pneumonia,16 potential between Bacteroides spp. and other aerobic bacteraemia," omphalitis," and subcutaneous and anaerobic bacteria inoculated subcutaneously into abscesses and occipital osteomyelitis following fetal mice; the synergic effects were determined by ob- monitoring. l9 serving abscess formation, animal rnortality3O and the The isolation rate of the different Bacteroides spp. number of organisms present in the The varies. In a recent survey in two military hospitals, B. bacteria tested included Fusobacterium spp., Pepto- fragilis accounted for 63 '/o of all Bacteroides isolates.2o streptococcus spp., S. aureus, P. aeruginosa, E. coli, B. thetaiotaomicron for 14%, B. idgatus and B. K. pneumoniae, Proteus mirabilis and enterococci. B. ocatus for 7 O/O each, and B. distasonis for 6 %. The fragilis significantly enhanced the virulence of most of highest frequency of isolation of B. fragilis compared the other organisms. The most virulent combinations to other Bacteroides spp. was in blood cultures (78 O/O were between P. aeruginosa or S. aureus and B. of all Bacteroides isolates), wounds (69 YO),abscesses fragilix3' Enhanced growth of all the aerobic or (65 YO)and abdominal infection (59 %). B. thetaiota- facultative species was found in most of these com- omicron was most frequently isolated from chest bination~.~~Several hypotheses have been proposed infections (35 %), infected cysts (22 %) and infected to explain this microbial synergy. It may be due to tumours (1 9 Oh). B. vulgams was mostly isolated from mutual protection from phagocytosis and intracellular obstetric and gynaecological infections (20 %) and B. killing,32 production of essential growth ovatus from biliary tract infections (18 YO). lowering of oxidation-reduction potentials in host Bacteroides spp. are generally isolated from mixed or any combination of these. infections with other aerobic and anaerobic bacteria, The Bacteroides spp. are generally resistant to forming a polymicrobial infection where the number penicillins, mainly through the production of p- of isolates varies from two to six.5qs The micro- lactamase. Other mechanisms of resistance to peni- organisms mixed with Bacteroides spp. in poly- cillin include alteration in the penetration of penicillins microbial infections vary and depend on the location into the microbial cell.35 The production of p- and circumstances leading to the infection. Most lactamase (mostly a cephalosporinase) enables the polymicrobial infections originate from the mucosal Bacteroides spp. to hydrolyse p-lactam antibiotics, flora adjacent to the infected site. Enterobacteria and including all first generation cephalo~porins.~The /?- Clostridium spp. predominate in mixed infections with lactamase produced by Bacteroides spp. can protect Bacteroides spp. in abdominal and rectal infections; not only the organisms producing the enzyme but also Prerotella and Porphyromonas spp. are common in other organisms in mixed infections. The presence of head and neck infections.'.* significant amounts of extracellular 13-lactamase in Although B. fragilis is the most common species abscess cavities or infected tissues may " shield" even found in clinical specimens, it is only a minor penicillin-susceptible bacteria from these drugs. In- Bacteroides spp. in faecal flora, comprising only 0.5 % vitro and in-vivo studies have demonstrated this of the cultivable bacteria in stool samples. The phenomenon of protection. When mixed with cultures pathogenicity of this species probably results from of B. fragilis, the resistance of group A p-haemolytic several virulence characters, including its ability to streptococci to penicillin increased 8500-f01d.~~ produce capsular material and the metabolite succinic Several animal studies have demonstrated the ability acid which protect against phagocytosis.21 Most of /I-lactamase to influence polymicrobial infections. Bacteroides strains are non-capsulate when they are Hackman and Wilkin~~~showed that penicillin- part of the normal gut flora. However, > 80% are resistant strains of B. fragilis, " B. " melaninogenicus capsulate when they are isolated from abscesses or and " B." oralis protected a penicillin-sensitive F. blo0d."2.~~The ability of B.fragilis to become capsulate necrophorum strain from penicillin therapy in mice. during an inflammatory process was demonstrated in Brook et al.3s demonstrated protection of Strepto- a subcutaneous abscess model in mice. Non-capsulate coccus pyogenes from penicillin by B. fragilis in a strains can become capsulate with the assistance of subcutaneous abscess model in mice. Brook3' also their aerobic counterparts,24 and these capsulate studied /I-lactamase activity in pus from 109 abscesses ; BACTEROIDES INFECTIONS IN CHILDREN 97

P-lactamase-producing organisms were isolated from ponents of the infe~tion.~'When such therapy is not 84 (77%) specimens, including all 28 isolates of B. given, the infection may persist and lead to com- fragilis. P-Lactamase activity was detected by the plications such as intra-abdominal absces~es.~~*~~Anti- nitrocefin method in 14 (56 %) of 25 pus samples from microbial therapies effective against mixed infections abscesses that harboured Bacteroides spp. are combinations of clindamycin, cefoxitin or metro- Almost all (> 99%) Bacteroides strains are sus- nidazole for the anaerobes plus an aminoglycoside, ceptible to metronidazole, imipenem and the com- cephalosporin or quinolone for the enterobacteria. bination of a penicillin and a 8-lactamase inhibit~r,~ Single agent therapy with cefoxitin, a penicillin plus and > 90 YOare generally susceptible to clindamycin, a p-lactamase inhibitor, or imipenem may also be cefoxitin and ti~arcillin.~However, as most infections effective. due to Bacteroides spp. are polymicrobial, therapy has to be directed also towards the other bacterial com- The laboratory assistance of the staff of the microbiology ponents of the infections. Management of mixed laboratories at the University of California Medical Center, Los infections caused by aerobic and anaerobic bacteria, Angeles County Medical Center and Serra Memorial Hospital in including Bacteroides spp., requires surgical correction Los Angeles, and Children's Hospital National Medical Center and South-East Medical Center in Washington, D.C., and the of pathology, drainage of pus and the administration Navy Hospital in Bethesda, MD, and the secretarial assistance of of antimicrobial agents effective against both com- Sarah Blaisdell are gratefully acknowledged.

References 18. Brook I. Bacteriology of neonatal omphalitis. JZnfect. 1982; 5: 127-1 3 1. 1. Olsson-Liljequist B, Dornbusch K, Nord CE. Characterization 19. Brook I. Osteomyelitis and bacteremia caused by Bacteroides of three different beta-lactamases from the Bacteroides fragilis : a complication of fetal monitoring. Clin Pediatr fragilis group. Antimicrob Agents Chemother 1980; 18: 1980; 19: 639-640. 220-225. 20. Brook I. Recovery of anaerobic bacteria from clinical specimens 2. Cat0 EP, Johnson JL. Reinstatement of species rank for in 12 years at two military hospitals. J Clin Microbioll988; Bacteroides fragilis, B. ovatus, B. distasonis, B. 26: 1181-1188. thetaiotaomicron, and B. uulgatus : designation of neotype 21. Rotstein OD, Pruett TL, Fiegel VD, Nelson RD, Simmons RL. strains for Bacteroides fragilis (Veillin and Zuber) Succinic acid, a metabolitic by-product of Bacteroides Castellani and Chalmers and Bacteroides thetaiotaomicron species inhibits polymorphonuclear leukocyte function. (Distaso) Castellani and Chalmers. Znt J Syst Bacteriol Infect Zmmun 1985; 48: 402-1108. 1976; 26: 230-237. 22. Brook I. Isolation of capsulate anaerobic bacteria from oro- 3. Shah HN, Collins DM. Preuotella, a new genus to include facial abscesses. J Med Microbiol 1986; 22: 171-174. Bacteroides melaninogenicus and related species formerly 23. Brook I, Myhal LA, Dorsey CH. Encapsulation and pilus classified in the genus Bacteroides. Znt J Syst Bacteriol formation of Bacteroides spp. in normal flora, abscesses 1990 ; 40 : 205-208. and blood. J Znfect 1992; 25: 251-257. 4. Cuchural GJ, Tally FP, Jacobus NV et al. Susceptibility of the 24. Brook I, Coolbaugh JC, Walker RI. Pathogenicity of piliated Bacteroidesfragilis group in the United States : analysis by and encapsulated Bacteroidesfragilis. Eur J Clin Microbiol site of isolation. Antimicrob Agents Chemother 1988; 32: 1984; 3: 207-209. 7 17-722. 25. Brook I, Walker RI. Significance of encapsulated Bacteroides 5. Brook I. Pediatric anaerobic infection: diagnosis and man- melaninogenicus and Bacteroides fragilis groups in mixed agement, 2nd edn. St Louis, C. V. Mosby Company. 1988. infections. Znfect Zmmun 1984; 44: 12-15. 6. Sutter VL, Citron DM, Edelstein MAC et al. Wadsworth 26. Brook I. Pathogenicity of capsulate and non-capsulate members anaerobic bacteriology manual, 4th edn. Belmont, CA, of Bacteroides fragilis and B. melaninogenicus groups in mixed infection with Escherichia coli and Streptococcus Star Publishing. 1985. pyogenes. J Med Microbiol 1988; 27: 191-198. 7. Lennette EH, Balows A, Hausler WJ, Shadomy HJ (eds). 27. Altemeier WA. The pathogenicity of the bacteria of appen- Manual of clinical microbiology, 4th edn. Washington, dicitis. An experimental study. Surgery 1942; 11 : 374378. DC, American Society for Microbiology. 1985. 28. Meleney FL, Olpp S, Harvey HD, Jern HZ. Peritonitis. 11. 8. Finegold SM. Anaerobic bacteria in human disease. New York, Synergism of bacteria commonly found in peritoneal Academic Press Inc. 1977. exudates. Arch Surg 1932; 25: 709-721. 9. Brook I. Bacterial studies of peritoneal cavity and postoperative 29. Hite KE, Locke M, Hesseltine HC. Synergism in experimental surgical wound drainage following perforated appendix in infections with nonsporulating anaerobic bacteria. J Infect children. Ann Surg 1980; 192: 208-212. Dis 1949; 84: 1-9. 10. Brook I, Finegold SM. Aerobic and anaerobic bacteriology 30. Brook I, Hunter V, Walker RI. Synergistic effect of Bacteroides, of cutaneous abscesses in children. Pediatrics 1981 ; 67: Clostridium, Fusobacterium, anaerobic cocci and aerobic 891-895. bacteria on mortality and induction of subcutaneous 11. Brook I, Finegold SM. Bacteriology of aspiration pneumonia abscesses in mice. J Infect Dis 1984; 149: 924-928. in children. Pediatrics 1980; 65: 1115-1 120. 31. Brook I. Enhancement of growth of aerobic and facultative 12. Brook I, Finegold SM. Bacteriology and therapy of lung abscess bacteria in mixed infections with Bacteroides species. Infect in children. J Pediatr 1979; 94: 10-12. Zmmun 1985; 50: 929-931. 13. Brook I. Chronic otitis media in children : microbiological 32. Tofte RW, Peterson PIC,Schemling, Bracke J, Kim Y, Quie PG. studies. Am J Dis Child 1980; 134: 564-566. Opsonization of four Bacteroides species : role of the 14. Brook I. Aerobic and anaerobic bacteriology of intracranial classical complement pathway and immunoglobulin. Infect abscesses. Pediatr Neurol 1992; 8: 210-214. Zmmun 1980; 27: 784-792. 15. Brook I, Barrett CT, Brinkman CR, Martin WJ, Finegold SM. 33. Lev M, Keudell KC, Milford AF. Succinate as a growth factor Aerobic and anaerobic bacterial flora of the maternal for Bacteroides melaninogenicus. J Bacteriol 1971 ; 108 : cervix and newborn gastric fluid and conjunctivae: a 175-178. prospective study. Pediatrics 1979; 63: 451-455. 34. Mergenhagen SE, Thonard JC, Scherp HW. Studies on syn- 16. Brook I, Martin WJ, Finegold SM. Neonatal pneumonia caused ergistic infections. I. Experimental infections with an- by members of the Bacteroidesfragilis group. Clin Pediatr aerobic streptococci. J Infect Dis 1958; 103: 334. 1980; 19: 541-544. 35. Neu HC. Contribution of beta-lactamases to bacterial resis- 17. Brook I, Controni G,Rodriguez WJ et al. Anaerobic bacteremia tance and mechanism to inhibit beta lactamases. Am J Med in children. Am J Dis Child 1980; 134: 1052-1056. 1985; 79 (Suppl. 58) : 2-12. 98 I.BROOK

36. Brook I, Yokum P. In vitro protection of Group A beta- 39. Brook I. Presence of beta-lactamase-producing bacteria and hemolytic streptococci from penicillin and cephalothin by beta-lactamase activity in abscesses. Am J Clin Pathol Bacteroidesfragilis. Chemotherapy 1983; 29: 18-23. 1986; 86: 97-101. 37. Hackman AS, Wilkins TD. In viuo protection of Fusobacterium 40. Solomkin JS, Meakins JL. A110 MD, Dellinger EP, Simmons necrophorum from penicillin by Bacteroides fragilis. RL. Antibiotics trials in intra-abdominal infections. A Antimicrob Agents Chemorher 1975 ; 7:698-703. clinical evaluation of study design and outcome reporting. 38. Brook I, Pazzaglia G, Coolbaugh JC, Walker RI et al. In-vitro Ann Surg 1984; 200: 29-39. protection of Group A beta-haemolytic streptococci from 41. Thadepalli H, Gorbach SL, Broido PW et al. Abdominal penicillin by beta-lactamase-producing Bacteroides species. trauma, anaerobes, and antibiotics. Surg Gynecol Obstet J Antimicrob Chemother 1983; 12: 599-606. 1973; 137: 270-276.