Identification and antimicrobial resistance patterns of clinical isolates of Clostridium clostridioforme, Clostridium innocuum, and Clostridium ramosum compared with those of clinical isolates of Clostridium perfringens

Abstract

Clostridium ramosum, C. innocuum, and C. clostridioforme are frequently isolated from clinical specimens including blood. Because of Gram stain variability, a lack of spores, and atypical colonial morphology, identification of these species is often difficult. Three anaerobe identification kits were evaluated for their abilities to identify these species. For comparison, 11 strains of C. perfringens were evaluated in parallel. By using profile numbers and codebooks, the correct genus and species were identified, as follows: with the RapID ANA II kit, 100% (20 of 20) of C. ramosum isolates, 24% (5 of 21) of C. innocuum isolates, and 50% (10 of 20) of C. clostridioforme isolates; with the AnIDent kit, 60% (12 of 20) of C. ramosum isolates, 28% (6 of 21) of C. innocuum isolates, and 90% (18 of 20) of C. clostridioforme isolates; with the ATB32A kit, 70% (14 of 20) of C. ramosum isolates, 0% (0 of 21) of C. innocuum isolates, and 40% (8 of 20) of C. clostridioforme isolates. Profile numbers that overlapped several species were obtained as follows: with the RapID ANA II kit, 0% of C. ramosum isolates, 76% of C. innocuum isolates, and 40% of C. clostridioforme isolates; with the AnIDent kit 40% of C. ramosum isolates, 62% of C. innocuum isolates, and 5% of C. clostridioforme isolates; with the ATB32A kit, 15% of C. ramosum isolates, 52% of C. innocuum isolates, and 25% of C. clostridioforme isolates. One strain of C. innocuum was misidentified by the AnIDent kit, and the remainder yielded profile numbers that were not listed in the codebooks. The MICs of 11 antimicrobial agents including penicillin G, metronidazole, clindamycin, cefoxitin, cefotetan, imipenem, meropenem, amoxicillin-clavulanate, ampicillin-sulbactam, piperacillintazobactam, and vancomycin were determined by the agar dilution method. All C. perfringens strains were susceptible to all antimicrobial agents tested. Various levels of resistance to cefoxitin, cefotetan, and penicillin G were noted with C. ramosum, C. clostridioforme, and C. innocuum. In addition, resistance to clindamycin was noted with C. ramosum (5%) and C. innocuum (10%). Most strains of C. innocuum were only moderately susceptible to vancomycin (MIC at which 90% of strains are inhibited, 4 g/ml).

Clinical characteristics and outcomes of clostridial bacteraemia in cancer patients

“…However, this conclusion is limited by the small number of patients in this cohort who did not receive an active antibiotic during the first 48 h after bacteraemia had developed (15%). Most studies assessing the antibiotic susceptibility of Clostridia have shown that most species, except C. tertium , are susceptible to penicillin, metronidazole, carbapenems and vancomycin . This large number of active antibiotics is probably the reason that the large majority of patient in this cohort were treated empirically with an active antibiotic within 48 h of bacteraemia.…”

“…Within 48 h of clostridial bacteraemia 45 of 164 patients (27%) were treated with a penicillin (penicillin G, mezlocillin, ampicillin or piperacillin) or clindamycin and 139 (85%) were treated with at least one antimicrobial agent with in vitro activity against most Clostridia including penicillins, clindamycin, metronidazole, vancomycin or carbapenems . Among the 25 patients who were not treated with an active antibiotic within 48 h, eight were treated with one or more antibiotics that are not typically active in vitro against Clostridia (ceftazidime, gentamicin, levofloxacin, ciprofloxacin) during the first 48 h, six were not treated with antibiotics (two of whom chose comfort‐focused medical care only), and the remainder started active antibiotics more than 48 h after bacteraemia had developed.…”

Low frequency of endospore‐specific genes in subseafloor sedimentary metagenomes

“…The present analysis of 16 incomplete genomes of Class Erysipelotrichi revealed that they have up to 10 genes of the 23 genes. Indeed, Pelosinus fermentans in Negativicutes and Clostridium ramosum in Erysipelotrichi form endospores (Alexander et al ., ; Shelobolina et al ., ).…”

Low-Level Vancomycin Resistance in Clostridium innocuum

“…Few previous studies have reported Clostridium species to be intermediately resistant or even strongly resistant to vancomycin (1,7,13). In two of these studies (7,13), varied clostridial species were tested as one group of uniform organisms, i.e., C. innocuum was not distinguished from the other species.…”

“…Clostridium innocuum belongs to the normal intestinal flora of human infants and adults and is one of the species which have been reported to cause human infections, such as intra-abdominal sepsis, bacteremia, and endocarditis (5,9,12). However, its identification by commercial kits remains unsatisfactory and requires, therefore, the use of gasliquid chromatography and additional conventional tests (1). Clostridia are usually considered susceptible to vancomycin and teicoplanin (8).…”