A comparison of a new campylobacter selective medium (CAT) with membrane filtration for the isolation of thermophilic campylobacters including Campylobacter upsaliensis.

The newly developed CAT campylobacter selective medium employing the blood-free charcoal-based agar containing cefoperazone (8 mg l-1), amphotericin (10 mg l-1) and teicoplanin (4 mg l-1) was compared with the membrane filtration culture technique for isolation of Campylobacter spp. including Camp. upsaliensis. Nine hundred and fifty human, 275 dog and 65 cat faeces (in which modified CCDA medium was also compared) were tested. In addition, the recovery of Camp. upsaliensis from pure cultures and from spiked human faeces was examined after membrane filtration. A 50-fold reduction in recovery after filtration using the 0.65 micron filters and a 150-fold reduction using the 0.45 micron filters was found. Recovery of Camp. upsaliensis from spiked faeces was considerably improved using the CAT medium compared with filtration, especially with the lower concentration of organisms (approx. 10(4) cfu mL-1). Campylobacter upsaliensis was recovered from 91 specimens of animal faeces, with CCDA recovering 26 isolates (29%), CAT recovering 76 isolates (84%) and membrane filtration (0.65 microns) recovering 82 isolates (90%). CAT selective agar was found to be a suitable medium for the isolation of thermophilic campylobacters including Camp. upsaliensis from faecal samples.

Selective medium for thermophilic campylobacters including Campylobacter upsaliensis.

AIMS: To develop a selective supplement for the recovery of thermophilic Campylobacter spp, including Campylobacter upsaliensis from faeces, using campylobacter blood free selective agar base as the growth medium. METHODS: Minimum inhibitory concentrations (MICs) of cefoperazone and of teicoplanin were determined for 51 strains of C upsaliensis, 159 strains of other thermophilic Campylobacter spp, and for 66 Enterobacteriaceae (cefoperazone only). From these results a medium using campylobacter blood free selective agar base incorporating cefoperazone (8 mg/l), amphotericin (10 mg/l), and teicoplanin (4 mg/l)--CAT medium--was formulated and compared with the commercially available campylobacter blood free selective medium (modified CCDA) for isolation of Campylobacter spp from 7000 human faecal specimens. The two media were also compared for the recovery of C upsaliensis from 45 spiked human faeces. RESULTS: Isolation rates of Campylobacter spp other than C upsaliensis were similar for both media, but the CAT medium alone recovered four of the five strains of C upsaliensis from the faecal samples examined. From the spiked faeces specimens, recovery of C upsaliensis was increased by between 35% and over 200-fold on the CAT medium compared with the modified CCDA. CONCLUSIONS: CAT selective agar was a suitable alternative medium to modified CCDA for the growth of thermophilic Campylobacter spp, including C upsaliensis from faeces.

New rapid identification test for Clostridium difficile.

AIMS: A set of five tests were developed and tested for their ability to confirm the identity of C difficile colonies within 30 minutes. METHODS: The relevant substrates were incorporated into four filter paper squares attached to a plastic carrier (Diffstrip), five enzymes/products (prolyl aminopeptidase, galactosidase, leucine aminopeptidase, acid phosphatase and indole). The strips were inoculated, incubated for 20 minutes, and reagents added. RESULTS: 96.4% (212 of 220) strains of C difficile were immediately differentiated from 51 other Clostridium spp tested. The remaining 3.6% (eight of 220) of C difficile isolates produced a reaction pattern similar to some of the Clostridium sporogenes tested and required additional tests. None of the other Clostridium spp tested produced reaction patterns similar to C difficile. CONCLUSION: The Diffstrip allowed colonies of C difficile to be confirmed within 30 minutes for 96.4% of isolates, with less than 4% requiring any additional tests. No strains of C difficile were misidentified and no strains of other Clostridium spp tested were misidentified as C difficile.

Improved isolation of salmonellae from faeces using a semisolid Rappaport-Vassiliadis medium.

A modified semisolid Rappaport-Vassiliadis (MSRV) enrichment medium was evaluated as an alternative to Rappaport-Vassiliadis (RV) broth for culture of salmonellae from faeces. Faeces from 1544 subjects were cultured using MSRV medium, selective agars, and RV and selenite F enrichment broths. Of the 183 strains of Salmonella spp. isolated, 88% were recovered on MSRV medium, whilst only 59% were recovered using RV broth. When MSRV medium was combined with direct culture and selenite enrichment, 98.9% of salmonellae were recovered. The MSRV culture was found to be easy to read, and in most cases confirmation of organisms as Salmonella spp. could be made 24 hours after receipt of the faecal specimen.

New selective medium for isolating Clostridium difficile from faeces.

AIMS: To compare CCFA (cycloserine, cefoxitin fructose agar) with a new selective medium CDMN (containing cysteine hydrochloride, norfloxacin, and moxalactam) for the isolation of Clostridium difficile after direct faecal culture. METHODS: The minimum inhibitory concentration (MIC) of norfloxacin was determined for 64 strains of C difficile, 17 strains of other Clostridium sp, and 66 various isolates of faecal origin, together with MIC determinations of moxalactam against the 81 strains of Clostridium sp and 15 isolates of Bacteroides sp. Using C difficile agar base with 0.5 g/l of cysteine hydrochloride, norfloxacin and moxalactam were incorporated into the medium and compared with CCFA for the isolation of C difficile after direct faecal culture. RESULTS: Norfloxacin (12 mg/l) inhibited the growth of enterobacteriaceae and faecal streptococci; moxalactam (32 mg/l) inhibited the growth of most strains of Bacteroides sp tested, together with Clostridium sp other than C difficile. Using the antibiotics in combination (CDMN), the growth and colonial morphology of 64 strains of C difficile were unaffected. When CDMN medium was compared with CCFA for the isolation of C difficile from 832 faeces from inpatients with diarrhoea, the CDMN agar isolated 20% more strains and reduced the number of contaminating colonies by 30%. CONCLUSIONS: CDMN both improves the isolation rate of C difficile from faecal specimens and reduces the growth of other organisms compared with CCFA.

Two sources of contamination of a hydrotherapy pool by environmental organisms.

As a result of occasional water discolouration, the hydrotherapy pool of a large teaching hospital was monitored for free and combined chlorine, alkalinity, calcium hardness, total dissolved solids and cyanuric acid levels together with bacteriological analysis. The hose pipe supplying the pool and the dual water pumps were also examined as potential sources of bacterial contamination. The pool water yielded high counts of Pseudomonas vesicularis, Pseudomonas aeruginosa, and CDC Group IV C2, even in the presence of adequate levels of free chlorine. This was found to be due to high concentrations of cyanuric acid which resulted in a 'chlorine lock'. The source of the P. vesicularis and CDC Group IV C2 was found to be the pool hose and this problem was alleviated by flushing it with water each day before use. The source of the P. aeruginosa was the pool pumps, and was eradicated by regularly shock dosing them with 6-8 ppm of free chlorine.