Shelf life of prepared Bordet-Gengou and Regan-Lowe agar plates for isolation of Bordetella pertussis.

The shelf life of prepared agar plates used for the isolation of Bordetella pertussis was studied. They contained Bordet-Gengou agar, Bordet-Gengou agar with cephalexin, Regan-Lowe agar, Regan-Lowe agar with cephalexin, or Regan-Lowe agar with both cephalexin and amphotericin B. Plates stored were compared to freshly prepared control plates for up to a maximum of 18 weeks. They were inoculated with clinical isolates of Bordetella pertussis, either in pure culture, or mixed with a defined oropharyngeal flora. Bordet-Gengou agar plates may be used, with proper storage at 4 degrees C in airtight-sealed plastic bags, for up to 10 weeks, Regan-Lowe agar plates for up to 14 weeks. Field studies are needed to substantiate our findings.

Comparison of six media, including a semisolid agar, for the isolation of various Campylobacter species from stool specimens.

A recently described semisolid blood-free selective motility medium (SSM) (J. Goossens, L. Vlaes, I. Galand, C. Van den Borre, and J. P. Butzler, J. Clin. Microbiol. 27:1077-1080, 1989) was compared with two charcoal-based selective media (charcoal-based selective medium [CSM] and modified charcoal cefoperazone deoxycholate agar [CCDA]), two blood-based media (Skirrow medium [SKM] and CampyBAP), and a passive, 0.65-microns-pore-size cellulose acetate membrane filter technique for the recovery of campylobacters from stools of patients with diarrhea. A total of 1,980 specimens were tested, 161 of which were found to be positive for campylobacters. Campylobacter jejuni was isolated in 148 specimens (91.9%), C. coli was isolated in 27 (7.5%), and "C. upsaliensis" was isolated in 1 (0.6%). After 72 h of incubation with a single medium, the cumulative percentages of Campylobacter-positive specimens isolated on CSM, CCDA, SKM, and SSM were 87, 83, 80, and 72%, respectively. The filter method alone enabled us to recover 61% of all campylobacters. The "C. upsaliensis" strain was isolated by this method only. The highest isolation rates were observed when two media, including CSM, were combined. The combination of CSM and SSM yielded the highest rates (96%), but these were not statistically different from the rates observed with combinations of CSM and SKM (94%) or of CSM and the filter method (91%). Extending the incubation time from 48 to 72 h led to an increase in the isolation rate regardless of the medium used (P less than 0.001). CSM and CCDA were the most selective media. SKM and CampyBAP appeared to be the most inhibitory media for the isolation of C. coli.