Enterotoxigenic Escherichia coli (ETEC) were the most frequently identified enteric pathogens associated with diarrhoea in 0–5 year old Aboriginal children in tropical north-west Australia with an incidence similar to those from other tropical regions. Heat-stable toxin-producing (ST + ) strains were associated with diarrhoea throughout the year but heat-labile toxin-producing (LT + ) strains were more important in the monsoonal summer season. ST + strains were commonest in children with diarrhoea between 6 and 18 months of age while LT + strains were associated with diarrhoea in children aged 18–24 months. Verotoxigenic E. coli (VTEC) which produced VT1, but not VT2, and enteroadherent (EAF + ) E. coli were significant causes of diarrhoea, mainly in children below 18 months but without a seasonal pattern.

This study examines a series of phenotypic variants of Staphylococcus epidermidis that were generated from a pair of parent variants, isolated from valvular tissue of a patient with prosthetic valve endocarditis. The variants were initially classified by examining their colonial morphology on Congo red agar. In addition to differences in Congo red binding and colonial morphology, they differed in the expression of several surface components and enzymes. Despite these phenotypic differences, all variants had the same restriction endonuclease profile of plasmid DNA. Examination of a collection of clinical isolates demonstrated that phenotypic variation is a common property of S. epidermidis. The ability to express different combinations of surface components and enzymes could contribute to the virulence of S. epidermidis strains by enabling these organisms to colonize a range of diverse environments.

Sera from 50 patients with culture-proven Campylobacter gastroenteritis were examined for the presence of antibodies to Legionella pneumophila. Ten patients (20%) had a positive titre (≥16) as measured by indirect immunofluorescence. Antibodies were detected in only 1 of 36 acute sera but in 10 of 14 (71%) sera obtained more than 10 days after the onset of symptoms. All positive sera contained specific IgM antibodies but specific IgG or IgA could not be detected in any sample. No legionella antibodies could be detected in sera from 42 similar patients with salmonella gastroenteritis. These results were shown to be due to serological cross-reaction between L. pneumophila and Campylobacter.

High Staphylococcus hyicus colonization rates were found in vaginal samples of healthy breeding sows and in skin samples of their offspring. Twenty-two different phage types were identified among the 720 isolates of S. hyicus examined. Two to 13 different phage types were isolated per herd. Phage typing, as well as characterization of about 10% of the isolates by plasmid profiles and antibiogram patterns, showed that, several different clones of S. hyicus could be present simultaneously in vagina of gilts and also on skin of piglets. Generally isolates from the vagina of one animal were identical as regards to phage types, plasmid profiles, and antibiogram patterns during the entire investigation period. Isolates from the skin of piglets were of the same type as their mothers, indicating that vertical transmission had taken place. S. hyicus strains isolated from the skin of piglets within 24 h after birth were identical to strains isolated 3 weeks after birth from the same litter, indicating that the vaginal strains became part of a stable skin flora.

Non-secretors of ABO blood group antigens are over-represented among patients with meningococcal diseases. Lower levels of secretory IgA reported for non-secretors have been suggested to compromise mucosal defences. Total serum and salivary IgG, IgA and IgM and levels of these isotypes specific for Neisseria lactamica and five isolates of meningococci were determined by ELISA for 357 pupils and staff of a secondary school in which an outbreak of meningitis occurred. There were no differences in total or specific levels of serum IgG, IgA or IgM or salivary IgG or IgA of secretors compared with non-secretors. Non-secretors had significantly lower levels of salivary IgM (P=0·022) A similar pattern was observed for levels of IgM specific for N. lactamica and five meningococcal isolates. The significance of these results is discussed with reference to the role of secretory IgM in protection of mucosal surfaces in infants.

Commercially reared chickens were challenged with Salmonella enteritidis phage-type (PT) 4 by aerosol, or via the conjunctiva. Inhalation of 2·9 × 102 or 4·2 × 103 S. enteritidis resulted in the production of IgG antibodies to the lipopolysaccharide (LPS) of S. enteritidis PT4. When the aerosol inoculum was increased to 2·4 × 105 bacteria per bird the antibody produced were predominantly of the IgM-class. Chickens challenged with 103S. enteritidis PT4 via the conjunctiva mounted only a poor immune response. Increasing the challenge dose to 108 S. enteritidis resulted in the production of high-titre serum antibodies of both the IgG and IgM classes. Results from this study suggest that aerosols containing small numbers of S. enteritidis PT4 might be responsible for intraflock infection of poultry.

Between July 1987 and June 1989, 1054 urinary isolates of enterobacteria from Kaohsiung, Taiwan were studied for their trimethoprim resistance. Trimethoprim resistance was defined as MIC greater than 4 μg/ml and high-level resistance by MIC greater than 1000 μg/ml. The incidence of trimethoprim resistance increased from 33·6% in 1987 to 42·1% in 1989. Among the resistant strains studied, 90% were resistant to high levels of trimethoprim. An increase in the proportion of resistant strains (33·9–46·3%) exhibiting high-level non-transferable trimethoprim resistance was noted. The distribution of the dihydrofolate reductase (DHFR) genes by colony hybridization in 374 trimethoprim-resistant isolates revealed the presence of type I and type V DHFR genes in most of these isolates (45·4% and 10·4% respectively). Type I was predominant in Escherichia coli whereas type V was frequently seen in Enterobacter spp. None showed homology with the type II and type III DHFR probe DNA. In addition, transposon Tn7 was present in 7·8% of 374 trimethoprim-resistant enterobacteria.

The use of the polymerase chain reaction (PCR) for identifying serotypes of human and bovine rotaviruses was examined. In the identification of 115 human rotavirus samples in stools, results with PCR showed excellent agreement with results of serotyping by an enzyme-linked immunosorbent assay (ELISA) using serotype-specific monoclonal antibodies. Furthermore, the PCR showed a much higher sensitivity (93%) than the ELISA test (82·6%). The PCR method could also be applied for identifying the serotype of bovine rotaviruses.

A total of 598 isolates of Shigella species (24 S. dysenteriae, 254 S. flexneri, 30 S. boydii, 290 S. sonnei) submitted to the Ontario Public Health Laboratories in 1990 were tested for their susceptibility to 14 antimicrobial agents by the agar dilution method. Overall 79·6% of isolates were resistant to one or more antimicrobial agents and 52·0% were resistant to four or more. Trimethoprim resistance ranged from 26·7% among isolates of S. boydii to 39·4% among S. flexneri strains. The majority of the 224 TMP resistant isolates (88·8%) demonstrated high level resistance (MIC > 1000 mg/1) to trimethoprim. Resistance to cotrimoxazole increased from 3% in 1978 to between 26·7 and 37·6% in 1990. MICs for 90% of isolates (MIC90S) for ampicillin, ticarcillin and piperacillin were 128 to > 256 mg/1, > 256 for tetracycline and chloramphenicol, and > 2·0/38·0 for cotrimoxazole. These results from the Canadian Province of Ontario emphasize the need for prudent use of antimicrobial agents in the treatment of shigellosis.

Of 1171 isolates of Escherichia coli isolated from urine samples at the Public Health Laboratory, Toronto, Ontario, Canada, between May 1990 and December 1991, 120 (10·3%) were resistant to trimethoprim (TMP), cotrimoxazole (TMP/SMX), sulfamethoxazole (SMX) and other antimicrobial agents; 110 of the 120 isolates (91·7%) were resistant to four or more agents. The majority of resistant isolates (91·7%) exhibited high-level resistance (MIC > 1000 mg/L) to TMP. The MIC of TMP/SMX for all 120 isolates was > 2·0/38·0 mg/L and for SMX > 1024 mg/L. High-level resistances were also present among the β-lactam antimicrobials with MICs ranging from 16- > 256 mg/L. Forty-three of 120 TMP-resistant (35·8%) isolates conjugally transferred TMP-resistance to E. coli K-12. Co-transfer of several other resistances was observed. SMX cotransferred from 86% of the 43 donors and β-lactams together with SMX cotransferred from 70%. Nalidixic acid resistance was present among 22 (18·3%) of the 120 resistant isolates, however, nalidixic acid resistance was not transferred to E. coli K-12.

The influence of temperature on the behaviour of mixed bacterial contamination of the shell membrane of the hen's egg

The potential risk of bacterial dissemination due to the presence of cockroaches (Blattella germanica, Blattellidae) in low-income flats was investigated. Cockroaches can carry a great variety of bacterial species; we identified 30 different species from 52 different flats. Klebsiella oxycytoca, K. pneumoniae and Enterobacter cloacae were the most frequently found. Pathogenic and potentially pathogenic bacteria represented 54% of all the bacterial identifications. Bacteria were carried either on the cuticle or in the gut. Contamination through external contact is sufficient to insure bacterial diffusion. There was a very low level of overlap estimated by Pianka's index (a) between the bacterial flora of neighbouring blocks of flats, and (b) between bacterial flora of different flats in the same block.

Strains of different bacterial genera: Escherichia coli (7), Salmonella serotypes (7), Enteropathogenic E. coli O 157 (2), Aeromonas hydrophila (4), Yersinia enterocolytica (1), Pseudomonas fragi (5), and Listeria monocytogenes (5), inoculated onto the surface tissues of pieces of fresh beef were found to be susceptible to the lethal action of hot water. On average, more than 3 log10 (99·9%) of these organisms were destroyed when water at 80 °C was applied for 10 or 20 s. Therefore, a hot water decontamination cabinet would be effective for destroying in situ any viable cells of these bacteria which might be present on the surface tissues of fresh beef carcasses.

A new technique to study the prevalence of circulating antibodies directed against different morphological groups (‘morphotypes’) of bacteria in fresh faeces is presented. The technique combines quantitative indirect immunofluorescence with digital image analysis. Plasma antibody titres and patterns of IgA, IgG and IgM isotype against morphotypes of faecal bacteria were determined in ten healthy individuals.

A total of 439 individuals with diabetes mellitus were examined for carriage of yeasts by the oral rinse and palatal swab techniques. Eighteen genetic or environment variables were assessed for their contribution to carriage of yeasts. The factor contributing to palatal and oral carriage of yeasts among individuals with insulin dependent diabetes mellitus (IDDM) was age (P < 0·01). The factor contributing to palatal carriage of yeasts among individuals with non-insulin dependent diabetes mellitus (NIDDM) was poor glycaemic control (glycosuria P < 0·01); carriage in the oral cavity as a whole was influenced additionally by non-secretion of ABH blood group antigens (P < 0·05). Introduction of a denture altered the above risk factors. For individuals with IDDM, oral carriage was associated with the presence of retinopathy (P < 0·05); palatal carriage was influenced by poor glycaemic control (HbA1P < 0·01, plasma glucose levels P < 0·05) and age (P < 0·05). For those with NIDDM, palatal carriage was associated with continuous presence of the denture in the mouth (P < 0·01); oral carriage was associated with plasma glucose levels (P < 0·05).

Direct detection assays for Mycoplasma pneumoniae were established by PCR amplification of short sequences within the foot protein/adhesin (P1) gene and the 16S ribosomal RNA gene.

Specificity and sensitivity was excellent, no hybridization was observed with M. genitalium and other human Mycoplasma species. In nose and throat washings from subjects with respiratory infection a pattern of high counts (c.f.u./ml) of M. pneumoniae (deduced from the amount of amplified PCR product), and a positive antigen capture assay, was found in 83% of subjects with serological evidence of current infection with M. pneumoniae.

A small proportion of subjects with serological patterns suggesting infection in the more distant past had positive PCR assays. This was considered to represent either persistence of the organism from a previous infection or perhaps transient carriage during a reinfection, without substantial change in antibody response.

PCR-based assay of M. pneumoniae offers a powerful, rapid, and sensitive substitute for culture of the mycoplasma. Antigen capture, while less sensitive than PCR, offers the advantage that it is more often positive with samples from current infection and requires less stringent laboratory organization to contain false positive results. We conclude however that the laboratory diagnosis of a chosen clinical episode should not rest on the PCR or Ag-EIA assays alone, but must also include antibody assays to confirm whether infection is current or represents persistence from past exposure.

To examine the role of enteric adenoviruses (EAV) in an urban area of Buenos Aires (Argentina), we prospectively studied faecal samples from 49 families of newborns. These were monitored weekly for diarrhoea for 2 years.

A total of 180 samples from cases of diarrhoea and 766 samples obtained during diarrhoea-free periods were studied by dot-blot hybridization with an EAV-specific DNA probe. EAV were found in 6/180 (3·3%) cases of diarrhoea and 6/766 (0·8%) asymptomatic samples (P < 0·015). Incidence of EAV was 3·9 cases per 100 person-years in children < 60 months old. EAV-related diarrhoeas were slight and of short duration. In addition, 129 faeces from hospital out-patients, 1–30 months old, were also studied. EAV was identified in 7/129 cases (5·4%). These cases were 9·5 ±3·5 months old and the diarrhoea was mild or severe, of 3±1·5 days of duration.

We suggest that EAV are low-risk causes of diarrhoea under natural conditions, although a few children may develop more severe diarrhoea. The diagnosis of EAV needs to be considered in these patients.