Several species of anaerobic bacteria display variable Gram stain reactions which often make identification difficult. A simple, rapid method utilizing a 3% solution of potassium hydroxide to distinguish between gram-positive and gram-negative bacterial was tested on 213 strains of anaerobic bacteria representing 19 genera. The Gram stain reaction and KOH test results were compared with the antibiotic disk susceptibilities (vancomycin and colistin) the preliminary grouping of anaerobic bacteria. All three procedures were in agreement for the majority of strains examined. Some strains of clostridia, eubacteria, and bifidobacteria stained gram negative or gram variable; the KOH and antibiotic disk susceptibility tests correctly classified these strains as gram-positive. The KOH test incorrectly grouped some strains of Bacteroides sp., Fusobacterium sp., Leptotrichia buccalis, and Veillonella parvula, but all Gram stain results for these strains were consistent for gram-negative bacteria. The KOH test is a useful supplement to the Gram stain and antibiotic disk susceptibility testing for the initial classification of anaerobic bacteria.

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The in vitro activities of two new antimicrobial agents, apalcillin and cefpiramide (SM-1652), were evaluated against 324 strains of anaerobic bacteria. Apalcillin (a penicillin derivative) and cefpiramide (a semisynthetic cephalosporin) were compared with piperacillin, moxalactam, and cefoxitin. Organisms studied included the Bacteroides fragilis group, other Bacteroides species, fusobacteria, clostridia, nonsporeforming gram-positive rods, and anaerobic cocci. Piperacillin was found to be the most active overall, inhibiting 96% of the strains tested at its achievable level in serum (128 p.g/ml). Apalcillin was comparable in activity to piperacillin, inhibiting 93% of anaerobes tested at this concentration. The other antibiotics inhibited ca. 80% of the strains at 32 pLg/ml. In terms of activities against particular species, apalcillin was active against 75% of B. fragilis group strains and 97 to 100%o of all other anaerobes. Cefpiramide inhibited 37% of B. fragilis group strains at 32 Lg/ml and 68% at 64 pg/ml (a level that may be achievable with this drug). Cefpiramide inhibited 92% of all other anaerobes at 32 ,ug/ml and 95% at 64 ,g/ml. The clostridia other than Clostridium perfringens were the most resistant (84% inhibited at 32 ,ug/ml and 95% inhibited at 64 ,ug/ml).Many new beta-lactam antibiotics have been introduced in the last several years, many of which have limited activity against anaerobic bacteria (2, 3, 10, 13). Apalcillin is a naphthyridine derivative of ampicillin which has been reported to have levels of activity comparable to those of other broad-spectrum penicillin derivatives (e.g., azlocillin, mezlocillin, and piperacillin) against a wide range of organisms and particularly good activity against Pseudomonas aeruginosa (12). Cefpiramide (SM-1652) is a semisynthetic cephalosporin whose structure, antibacterial activity, and stability to P-lactamases have been described previously (4). Cefpiramide has been reported to have excellent activity against P. aeruginosa (4, 7, 9). The purpose of this study was to investigate the activities of these two new antimicrobial agents against a wide range of anaerobic bacteria, with particular attention to the Bacteroides fragilis group, which exhibits resistance to many of the newly developed antimicrobial agents. (Table 2). Apalcillin was moderately active against some of the B. fragilis group (MIC50 = 32 ,ug/ml), but 12 of the 37 strains of B. fragilis were resistant even at 256 ,ug/ml. Thus, 25% (18 of 74) of B. fragilis group strains were resistant to the highest concentration of antibiotic tested. Others (12) have also reported similar results. Other Bacteroides species were more susceptible to apalcillin; only 2 of 75 strains were resistant at 256 ,ugIml. B. oralis, B. bivius, B. capillosus, and B. melaninogenicus subsp. melaninogenicus were more resistant than the other non-B. fragilis group Bacteroides strains tested. All of the other anaerobes tested were susceptible to apalcillin at a concentration of 64 pug/ml or less. MATERIALS AND METHODSCe...

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An ampicilEn-sulbactakn combination was conipared with ampicillin alone, chloramphenicol, clindamycin, and metronidazoDe against 272 strains of anaerobic bacteria. Chloramphenicol and ampicillin-sulbactam were the most effective, inhibiting 98 to 99% of strains tested at breakpoint (16 pg/ml). The combination of sulbactam and ampicillin was much more effective than ampiciflin alone against Bacteroidesfragilis strains but did not differ substantially from ampicillin alone against Fusobactetium spp., gram-positive rods, and gram-positive cocci.,-Lactamase production is a major mechanism of resistance to P-lactam antibiotics among many anaerobes, and the prospect of comnbined treatment with a ,B-lactamase inhibitor and a P-lactamase-susceptible antibiotic is an attractive one.Various~-lactamase inhibitors, including sulbactam, clavulanic acid, and UK-38006 have been introduced and tested in vitro (2,6,12,14) and in clinical trials (11,13