[Infections by anaerobes in children: frequency of isolation and antimicrobial resistance].

We studied the frequency of isolation and antimicrobial susceptibility of strict anaerobic bacteria isolated in a paediatric hospital. A total of 1,753 samples from purulent material and hemocultures were processed. One hundred and thirty strains were isolated from 95 children: 44 from 48 cases of peritonitis (91.7%), 2 from 8 brain abscesses (25%), 23 from 124 soft tissue abscesses (18.5%), 4 from 64 empyemas or lung abscesses (6.3%) and 22 from 1,509 hemocultures (1.5%). Mixed infection (anaerobic and aerobic bacteria) was detected in 38.5% of the cases; however, in peritonitis 81.3% of the cases showed mixed infection. The more frequently isolated bacteria were: Bacteroides (44.6%), Clostridium (19.2%), Fusobacterium (7.7%) and gram positive cocci (7.7%). Propionibacterium acnes was isolated in 15 specimens; however, most of them were considered as contamination. Bacteroides was isolated more frequently from patients with peritonitis (51.6%). The susceptibility to five antibiotics was tested in 124 strains using the method of serial dilutions in agar plates. The genus Bacteroides showed a high resistance to penicillin (73.1%), moderate to clindamycin (11.5%) and low to cefoxitin, chloramphenicol and metronidazole (6.8%, 2% and 5.8%). The rest of the anaerobic strains tested (other gram negatives and grampositives) were highly sensitive to all the antimicrobials tested, except for clindamycin (26.7% and 36.9% resistance, respectively). Cefoxitin, chloramphenicol and metronidazole had the lower CMI50 and CMI90 for the genus Bacteroides; and for the rest of the bacteria, penicillin had the highest activity (CMI90 less than 0.025). Since the frequency of isolation of anaerobic bacteria in children with severe infections, presumably originated from the digestive tract, paranasal sinus and middle ear is high, anaerobic cultures must be practiced in these patients. Empiric antimicrobial treatment should also be started. This treatment should be with penicillin when the probability of isolation of Bacteroides is low (infections in the face, neck, thorax and soft tissues) and with metronidazole in intraabdominal infections. Because of the severity and probable etiology of brain abscesses, treatment with penicillin and chloramphenicol or metronidazole is recommended in these cases.