Evaluation of the oxyrase OxyPlate anaerobe incubation system.

The Oxyrase OxyPlate anaerobe incubation system was evaluated for its ability to support the growth of clinically significant anaerobic bacteria previously identified by the Anaerobe Reference Laboratory at the Centers for Disease Control and Prevention. The results were compared with those obtained with conventional anaerobe blood agar plates incubated in an anaerobe chamber. We tested 251 anaerobic bacterial strains. Plates were read at 24, 48, and 72 h; growth was scored by a numerical coding system that combines the degree of growth and the colony size. Organisms (number of strains tested) used in this study were Actinomyces (32), Anaerobiospirillum (8), Bacteroides (39), Campylobacter (8), Clostridium (96), Fusobacterium (12), Leptotrichia (8), Mobiluncus (8), Peptostreptococcus (16), and Propionibacterium (24). At 24 h, 101 (40.2%) of the 251 strains tested showed better growth with the anaerobe chamber than with the OxyPlate system, 10 (4.1%) showed better growth with the OxyPlate system, and the remaining 140 (55. 8%) showed equal growth with both systems. At 48 h, 173 (68.9%) showed equal growth with both systems, while 78 (31.1%) showed better growth with the anaerobe chamber. At 72 h, 176 (70.1%) showed equal growth with both systems, while 75 (29.9%) showed better growth with the anaerobe chamber. The OxyPlate system performed well for the most commonly isolated anaerobes but was inadequate for some strains. These results indicate that the Oxyrase OxyPlate system was effective in creating an anaerobic atmosphere and supporting the growth of anaerobic bacteria within 72 h. OxyPlates would be a useful addition to the clinical microbiology laboratory lacking resources for traditional anaerobic culturing techniques.

Evaluation of the BBL Crystal Anaerobe identification system.

The BBL Crystal Anaerobe (ANR) identification system was evaluated, and the results were compared with those from conventional anaerobic methods. We tested 322 clinically significant anaerobic bacteria according to the manufacturer's instructions. The system identified correctly 286 of 322 (88.8%) of the anaerobic bacteria tested. Of these, 263 of 322 (81.7%) were identified correctly on initial testing and 49 were identified correctly only to the genus level; on repeat testing, 23 of 49 (46.9%) were identified correctly to both the genus and the species levels. A total of 26 (8.5%) were misidentified at the species level, and 10 (3.1%) were not identified. Performance characteristics for individual strains varied. The system correctly identified all tested strains of Campylobacter, Desulfomonas, Desulfovibrio, Leptotrichia, Mobiluncus, Peptostreptococcus, Porphyromonas, Provetella, Propionibacterium, Tisierella, and Veillonella and 36 of 37 (97.3%) Actinomyces strains, 42 of 46 (91.3%) B. fragilis group strains, 79 of 103 (76.7%) Clostridium strains, (however, the system failed to identify any of the 7 C. innocuum and 9 C. tetani strains tested), and 8 of 15 (53.3%) Bacteroides strains. This system was easy to use, did not involve the addition of reagents, and was faster than conventional anaerobic procedures. It would be a useful addition to the anaerobe laboratory of most hospitals.

Evaluation of AnaeroGen system for growth of anaerobic bacteria.

The Oxoid AnaeroGen system was compared with the BBL GasPak for the production of an anaerobic atmosphere and was evaluated for its ability to support the growth of 135 clinically significant anaerobic bacteria. An anaerobe chamber was used as the "gold standard" for supporting the growth of anaerobes. The AnaeroGen requires no catalyst, produces no hydrogen, requires no water, and reduces preparation time to a minimum. The water-activated BBL GasPak generates hydrogen. For 132 of the 135 strains tested, better initial growth at 48 h was noted for the jar methods than for the anaerobe chamber. At 72 h, 113 of the 135 strains showed equal growth, and at 7 days, only marginal differences in growth patterns were noted. The AnaeroGen never failed to reduce the anaerobic indicator, while the BBL GasPak occasionally failed to do so. The AnaeroGen performed at least as well as, and sometimes better than, the established methods. The AnaeroGen is a good alternative for use in anaerobic jars.

Use of Presumpto Plates to identify anaerobic bacteria.

Identification of anaerobic bacteria requires special media and growth conditions that contribute to a higher cost per identification than that for aerobic isolates. Newer rapid methods streamline the identification process, but confirmation to the species level is often difficult. The Presumpto Plate method for the identification of commonly encountered anaerobes consists of three quadrant plates, each containing four conventional media, that result in the generation of 21 test parameters: growth on Lombard-Dowell medium; production of indole, indole derivative, catalase, lecithinase, and lipase; proteolysis of milk, H2S, and esculin; growth on 20% bile; precipitate on bile; DNase, glucose, casein, starch, and gelatin hydrolysis; and fermentation of lactose, mannitol, and rhamnose. Identification charts were developed by using the results from 2,300 anaerobic isolates. Because conventional media were used, there was a high degree of agreement between the Presumpto Plate method and the reference method when testing commonly encountered anaerobes. The Presumpto Plate method is as accurate as commercially available enzyme systems for the identification of many anaerobic species but is less expensive to perform.

Evaluation of API An-IDENT and RapID ANA II systems for identification of Actinomyces species from clinical specimens.

We compared the accuracy of the An-IDENT system (bioMerieux Vitek, Inc., Hazelwood, Mo.) and the RapID ANA II system (Innovative Diagnostic Systems, Norcross, Ga.) with that of conventional biochemical tests for the identification of 85 strains of Actinomyces species. In our hands, the overall accuracy of the An-IDENT was 59% and that of the RapID ANA II was 24%. The error rate for the An-IDENT was 18% and that for the RapID ANA II was 38%. The results of this study suggest that although the An-IDENT was more accurate than the RapID ANA II (P < 0.005), neither system, in our hands, was able to identify Actinomyces species with an acceptable degree of accuracy. It is recommended that suspected Actinomyces isolates be identified by conventional testing.