Cumpylobucter grucilis (formerly Bucteroides grucilis) is an asaccharolytic, nitrate-positive, urease-negative organism that requires formate and fumarate or hydrogen as a growth additive and may pit agar media. Clinical isolates that were obtained primarily from appendiceal and peritoneal fluid specimens and initially were identified in our laboratory as B. grucilis were later found to include "unusual" strains that could be distinguished by biochemical and genetic criteria. These unusual C. gracilis strains were bile resistant, could not reduce tetrazolium chloride under aerobic conditions if formate and fumarate were added to the medium, and could grow in the presence of 2 or 6% oxygen if no blood was added to the medium. C. grucilis, other campylobacters, and the unusual strains produced distinctive dehydrogenase patterns when gels were incubated anaerobically. A cellular fatty acid analysis revealed that the cluster formed by the unusual organisms was distinct from the (separate) clusters formed by C. grucilis, Bucteroides ureolyticus, and other Cumpylobacter species. 16s rRNA sequence data indicated that these organisms are not related phylogenetically to either C. grucilis or other Campylobacter species; the most closely related taxa as determined by rRNA sequence analysis were unrelated aerobes (members of the genera Bordetellu, Alculigenes, Rhodocyclus, and Cornamonas). DNA homology data confirmed that these taxa are separate groups. Our data indicate that the unusual organisms are members of a new genus and new species, for which we propose the name Sutterellu wadsworthensis. The type strain of S. wadsworthensis is strain WAL 9799 (= ATCC 51579).

A total of 222 clinical isolates were used to test the accuracy of Sensititre dried microtitration trays for determining minimum inhibitory concentrations (MICs) of antimicrobial agents. In comparison with an agar dilution technique, 89.5% of all the pairs of results were within one doubling dilution. The 2,420 pairs of MIC results with finite values gave a corresponding figure of 86.8%. Exclusion of sulfisoxazole results, which demonstrated a significant interlaboratory variation in accuracy, raised this value to 89.1%. Very good differentiation of /1-lactamaseproducing strains of Staphylococcus aureus (24 of 24 giving an MIC 2 0.25 ,ug/ ml) and Haemophilus influenzae (3 of 3 giving an MIC 2 32 pug/ml) was obtained with the Sensititre system. This method also clearly distinguished erythromycinresistant S. aureus strains (7 of 7 giving an MIC > 32 ,ug/ml) from the susceptible strains (26 of 28 giving an MIC ' 0.5 pg/ml plus 1 strain at 1.0 ,ug/ml and 1 at 2.0 pg/ml). Sensititre offers an accurate and convenient method of detenmining MICs comparable to those obtained with the agar dilution procedure, with the advantage of an extended shelf life when stored at room temperature.The Kirby-Bauer disk diffusion method is widely used for antimicrobial susceptibility tests, but there are limitations to this method, mainly because of the sensitivity of the test to changes in operator technique and also in the subsequent interpretation of zone diameters. In recent years there has been a move towards a more quantitative method, namely, the measurement of an antimicrobial agent's miniimum inhibitory concentration (MIC). To date this type of susceptibility testing has relied on freshly prepared dilutions of antimicrobial agents in nutrient media or on frozen microtitration trays, either made in the hospital's laboratory (9) or, more recently, brought in from an outside supplier (3). The frozen systems have to be stored at -20°C to retain the potencies of the antimicrobial drugs, and at this temperature the trays have a relatively limited storage life. A microtitration system, Sensititre, is now commercially available; it consists of plates containing dried antibiotic which are stable for 12 months at ambient temperature (data are on file with the manufacturer).A previous study has demonstrated the good perfornance of Sensititre when compared with another broth microdilution procedure, and also the high reproducibility of results obtained in several laboratories (6). This report compares Sensititre with the agar dilution procedure for MIC determinations. Particular emphasis was put on selecting organisms known to be resistant to antimicrobial agents. MATERIALS AND METHODSSensititre plates were supplied by Seward Laboratory, UAC House, Blackfriars Road, London

The antimicrobial activity of temafloxacin for 328 anaerobic bacteria was determined and compared to that of cefotetan, cefoxitin, ciprofloxacin and metronidazole. The Wadsworth agar dilution technique using Brucella-lysed sheep blood agar was used throughout. At the recommended breakpoint concentration 4 mg/L, temafloxacin inhibited 60/62 (97%) of the isolates of Bacteroides fragilis and 82/87 (94%) of the isolates of other species of the B. fragilis group. Ninety-six percent of the 24 isolates of Peptostreptococcus, 97% of the 31 isolates of other Bacteroides species and 88% of 66 isolates of Fusobacterium species were also inhibited by 4 mg/L temafloxacin. Metronidazole (breakpoint 16 mg/L) had a broader spectrum of activity than temafloxacin (judged by the percentage of strains tested susceptible at the breakpoints employed) with the exception of non-sporing Gram-positive bacilli. The cephalosporins tested (breakpoint 32 mg/L) had a narrower spectrum of activity. Ciprofloxacin (breakpoint 2 mg/L) was the least effective agent against the majority of the anaerobes tested.

The antimicrobial activities of two new quinolones, CI-960 and PD 131628-2 were determined against 339 strains of anaerobic bacteria and compared to cefoxitin, imipenem and metronidazole. The NCCLS-approved Wadsworth agar dilution technique with Brucella-lysed blood agar was used throughout the study. Breakpoints of the new quinolones are 2 mg/L, and breakpoints for cefoxitin, imipenem and metronidazole are 32, 8 and 16 mg/L, respectively. CI-960 displayed excellent activity, inhibiting all strains tested at 1 mg/L. PD 131628-2 inhibited 94% of Bacteroides fragilis, 75% of other B. fragilis group isolates, 87% of Prevotella spp, 79% of the Fusobacterium mortiferum-varium group, 74% of non-sporing gram-positive bacilli, and 89-100% of Clostridium spp other than Clostridium difficile at 2 mg/L. None of the eight strains of C. difficile was inhibited at 2 mg/L although they were inhibited at 4 mg/L. PD 131628-2 inhibited all strains of other Bacteroides spp, Porphyromonas spp, and Fusobacterium nucleatum at < or = 1 mg/L.