- Volume 45, Issue 1, 1996

Of 28 isolates of Vibrio cholerae non-O1 (10 from diarrhoeal patients and 18 from environmental sources) examined for haemolytic activity and its correlation, if any, with enterotoxic activity, 24 showed haemolysis. The four non-haemolytic isolates showed haemolysis after consecutive passages through rabbit ileal loops (RILs). The titres of haemolytic activity were 4-64 HU/ml irrespective of their source. Eight (28.5%) of the non-O1 isolates caused fluid accumulation; six (25%) were haemolytic and two (50%) non-haemolytic. The remaining isolates showed enterotoxic activity after one-to-three consecutive passages through RILs irrespective of their haemolytic character and source. Environmental isolates caused significantly more fluid accumulation than the diarrhoeal isolates. All these isolates reverted to their original non-toxigenic character on repeated subculture or on storage in the laboratory, but continued to show haemolytic activity. The results of the present study indicate that V. cholerae non-O1 strains are potentially enterotoxigenic independent of their haemolytic character and source, and enterotoxin, not haemolysin, is the factor most likely to be responsible for their enterotoxic activity.

The naturally occurring plasmid pSTS7 from Staphylococcus epidermidis mediated resistance to tetracycline via a tetL gene and to kanamycin and neomycin via an aadD gene. Plasmid pSTS7 showed partial restriction map and sequence homology to the previously described tetracycline resistance plasmid pNS1981 from Bacillus subtilis and to the kanamycin/neomycin/bleomycin resistance plasmid pUB110 from S. aureus. Sequence analysis of the regions flanking the two resistance genes in pSTS7 led to the identification of a novel site for interplasmid recombination which could explain the derivation of pSTS7 from the incompatible pNS1981- and pUB110-like parental plasmids under tetracycline-selective pressure.

The efficiency of pulsed-field gel electrophoresis (PFGE), ribotyping and restriction enzyme analysis of the virulence plasmid (REAP) for typing and subtyping strains of Yersinia enterocolitica was compared. All three techniques gave concordant results, and the strains studied could be separated into three distinct clusters: (1) heterogeneous strains of biotype 1A and serotype O5 (1A/O5); (2) one 3/O3 strain and all 2/O9 strains; and (3) all 4/O3, 2/O5 and two 3/O3 strains. Within cluster 3, the 2/O5 and 3/O3 strains were related more closely to each other than to the 4/O3 isolates. With ribotyping, PFGE and phage-typing, the 4/O3 isolates were subdivided into two homogeneous groups, corresponding to strains of phage type IXb and strains of other phage types, respectively. Similarly, ribotyping and PFGE subdivided the 2/O9 strains into two conserved groups (I and II), but REAP gave a different subdivision and identified a new REAP pattern (P3). The three techniques confirmed the clear distinction between the heterogeneous group of non-pathogenic 1A/O5 strains and the well conserved group of pathogenic 2/O5 strains. Additional plasmids were identified in some 3/O3 strains. Combined, the results indicated that REAP (with EcoRI) and ribotyping (with EcoRV) are valuable alternatives to bioserotype determination, and PFGE is the most suitable technique for epidemiological tracing.

To assess prognostic indicators of a fatal outcome in patients with meningococcal disease, data from 562 patients with culture-proven meningococcal disease, reported in the Netherlands between 1 April 1989 and 30 April 1990, were collected prospectively by means of a questionnaire completed by the specialist in attendance. Analysis was done by the χ 2 test and multiple logistic regression. During the study period 43 patients (7.7%) died. The risk of a fatal outcome was increased in patients aged 0–5 months, 10–19 years, and ⩾ 50 years, in female patients and in patients presenting with coma, temperature ⩽ 38.0°, mean arterial pressure ⩽ 70 mmHg, white blood cell count ⩽ 10 × 109/L and platelet count ⩽ 100 × 109/L. Predisposing factors and duration of disease before admission were significantly associated with outcome, but these associations disappeared in the multivariate analysis. Race, the administration of antibiotics prior to admission, seizures and haemorrhagic skin lesions were not associated with outcome. In conclusion age, gender, coma, temperature, mean arterial pressure, white blood cell count and platelet count were independent prognostic indicators of the outcome of meningococcal disease. The assessment of these characteristics may be helpful for the identification of high risk patients, whose prognosis might be improved by prompt transfer to an intensive care unit.

A rapid immunoassay for the detection of specific PCR products is described in which a positive PCR amplification result is detected, usually in less than 5 min, by applying a few drops of the diluted PCR end-product to a small immunoassay sample device. The method was evaluated in comparison with conventional susceptibility tests and isoelectric focusing (IEF) for the detection of TEM-family β-lactamase genes in 477 Escherichia coli isolates from urine samples. Of 187 isolates identified as presumptive TEM β-lactamase producers by conventional methods, 185 generated a positive signal in the PCR immunoassay system. Two further signal-positive isolates were recognised when the PCR was repeated. In addition, one of the 276 ampicillin-susceptible isolates gave a positive signal in repeated PCR-immunoassay experiments despite being ampicillin susceptible and failing to give a TEM-type enzyme band in iso-electric focusing experiments.

One of five strains of Vibrio cholerae non-O1 isolated from environmental sources caused fluid accumulation in an initial rabbit ileal loop (RIL) test. The four strains that caused little or no accumulation of fluid gave a positive response after one-to-three consecutive passages through RILs. The amount of fluid produced increased after each passage. Filtrates of cultures of all five environmental isolates caused fluid accumulation similar to that produced by live cells. The enterotoxin showed a precipitin band with new cholera antitoxin and was neutralised completely by new cholera antitoxin diluted 1 in 32, indicating its close immunobiological relationship to the new cholera toxin. The present study indicates that V. cholerae non-O1 strains produce an enterotoxin that is similar to the new cholera toxin.

The relatedness of strains of a human intestinal spirochaete was investigated by comparison of electrophoretic protein profiles produced by Coomassie Blue staining of proteins separated by polyacrylamide gel electrophoresis (PAGE) of lysed organisms and by examination of autoradiographs following PAGE of lysed 35S-methionine-labelled organisms. A wide diversity of strains was revealed by both techniques but clustering of strains was different by the two methods. These findings support the view that the human intestinal spirochaetes comprise a group of bacteria of considerable heterogeneity.