A panel of 10 monoclonal antibodies was used to subgroup 326 strains of Legionella pneumophila serogroup 1. All but two strains could be classified into three major subgroups named after their representative strains Pontiac 1, Olda and Bellingham 1. Of the 50 isolates from patients, 44 representing 32 separate incidents were of the Pontiac subgroup. This subgroup was also found in 16 of 18 buildings epidomiologically associated with Legionnaires' Disease. In contrast, strains of the Olda subgroup predominated in buildings where no infections had occurred. In 9 of the 11 incidents where isolates were available from at least one patient as well as from the suspected environmental source, the monoclonal antibody reaction patterns of strains from patients were identical to those of one or more of their environmental counterparts.

The biochemical and biological properties of the flagella of Campylobacter jejuni have been investigated using two variants selected from a flagellate, motile clinical isolate (strain 81116): a flagellate, non-motile variant (SF-1) and an aflagellate variant (SF-2). Phenotypic and biochemical analysis of the strains and amino acid analysis of the isolated flagella suggest that the variants differed from the wild-type strain only in the absence of flagella and/or motility. The aflagellato variant poorly colonized the gastrointestinal tract of infant mice but the flagellate, non-motile variant colonized the mice as successfully as the wild-type strain.35S-labelled organisms were used to investigate the attachment of the variants to human epithelial cell monolayers in vitro. The flagellate, non-motile strain attached more efficiently to the cells than the wild-type strain or the aflagellate strain. Differences in attachment suggest that an adhesin is intimately associated with flagella of C jejuniand that active flagella mediate only a tenuous association with host cells. This adhesin attached most efficiently to cells of intestinal epithelial origin and was not specifically inhibited by various sugars.

Salmonella carriage in 5888 gulls sampled by cloacal lavage was found to be 7·8%. Marked geographical and seasonal differences in carriage rates were found. These differences appeared to be associated with human population density and seasonal differences in the reported incidence of human salmoncllosis. The maximum duration of salmonella excretion in 17 laboratory-maintained gulls was 4 days and the number of salmonellae excreted was never more than 170 per gram of faeces. On the basis of this study it is suggested that gulls are not important factors in the actiology of human salmonellosis.

The effect of hypochlorite concentration on Mycoplasma mycoides ssp. mycoides viability was tested under a variety of conditions. The experimental variables employed included chlorine-cell contact time, chlorine concentration, carrier system and organic loading. Initial populations of 106 c.f.u./ml were killed (no survivors in 1 ml) by hypoehlorite solution containing 25 p.p.m. available chlorine in 15 s in the absence of organic load and 50 p.p.m. available chlorine in 5 min in the presence of 1% protein. Higher concentrations of hypochlorite were required to disinfect a porous carrier system in the absence or presence of protein. The results are in contrast to previous reports that M. bovis is killed only by high hypochlorito concentrations.

Aztreonam, temocillin, gentamicin and tobramycin were studied for their effect on the human faecal flora in vitro and for their usefulness for selective decontamination (SD) of the gastrointestinal tract. The sensitivities of the obligately anaerobic flora and the Gram-negative facultatively anaerobic bacteria were determined and the ratio was expressed as SD factor. Tho high SD factor of the flora from most subjects for aztreonam and tobramycin indicates that the drugs are useful for SD in contrast to temocillin and gentamicin. Binding to and subsequent release of tobramycin from faeces are presumed to facilitate the maintenance of adequate concentrations in the intestine despite the discontinuous intake.

A series of 925 clinical isolates of klebsiella was examined by serological and biochemical typing. To perform serological typing (capsular swelling) 77 capsular antisera were prepared, tested against the type strains and grouped in 13 pools. With this serotyping method 80% of the cultures were typable and 63 distinct types could be recognized.

All strains were typable biochemically by means of the numerical coding system of the API-20E system supplemented by digits derived from 15 additional conventional biochemical tests. With the API-20E system 24 different biotypes could be distinguished whereas the combination of API-20E and the 15 additional tests produced 93 biotypes. Maximum discrimination of strains was achieved by the combination of serological and biochemical typing (256 bioserotypes). The reproducibility, typability and discriminating power of the biotyping system was not inferior to serotyping. For epidemiological purposes biotyping can replace serotyping of Klebsiella species, especially in laboratories less well equipped.

The numbers and serotypes of Clostridium perfringens present in the faeces of three groups of hospital patients and young healthy laboratory workers were examined in studies lasting between 10 and 13 weeks.

In one hospital some long-stay geriatric patients carried relatively high numbers of C. perfringens (> 107/g) most of the time and it was not unusual in any one week for the majority of these patients to carry the same serotype(s). However, the numbers of C. perfringens in the faeces of young long-stay patients in the same hospital were in the range of 103–104/g and carriage of common serotypes was not observed. These results were similar to the findings with the young laboratory workers.

This investigation indicates that two of the laboratory criteria often used in the investigation of C. perfringens food poisoning, i.e. faecal counts of ≥ 105C. perfringens/g and patients carrying the same serological type need to be interpreted with caution with suspected outbreaks involving some groups of geriatric long-stay hospital patients.

Over a two-year period 160 episodes of serious infection occurred in 139 infants admitted to a regional neonatal intensive-care unit. Eighty-seven (26%) of very low birth weight (VLBW) neonates and 52 (8%) of infants of birth weight > 1500 g were infected. The majority (84%) had bactcraemia alone. Though the clinical features of infection were not distinctive, in 94% of episodes the peripheral white blood cell or band counts were abnormal. Thirty-three (21%) of the infections occurred in infants under 48 h old and 15 of these followed prolonged rupture of membranes (>48h). All of the infections due to group B streptococci (5), Streptococcus viridans (2) and Haemophilus influenzae (3) occurred in this group. Coagulase-negativc staphylococci (CONS) accounted for 49% of the infections and there was a marked increase in incidence of such infections during the survey. Infections with CONS were not necessarily associated with parenteral nutrition, the presence of intra-arterial catheters or mechanical ventilation but the rise in incidence was coincident with change in skin disinfectant usage and the general use of a third-generation cephalosporin to which the CONS were resistant.

Although VLBW infants with meningitis were more likely to die than those of higher birthweight, the risk for those with bacteriacmia was the same in both groups. Infants with CONS sepsis were less likely to die than those with infections due to Gram-negative bacteria and the time from onset of infection to death was significantly longer for the former.

Vibrio parahaemolyticus was observed to overwinter in sediments and to be present in considerable numbers in sediments and Clithon retropictus (gastropod mollusc) during summer months at a brackish-water area along Hashizu Creek in Japan. The highest level of the organisms was 97·3 × 106 and 2·3 × 107/100 g in sediments and C. retropictus respectively.

Production of Kanagawa haemolysin was detected in approximately 12% and 20% of strains isolated from sediments and C. retropictus respectively at two stations in Hashizu Creek but were not detected at the other three stations. Two haemolysin-producing strains were isolated from water samples but none were isolated from Corbicula japonica (bivalve molluse). These findings suggest that haemolysin producers are preserved principally in sediments and some shellfish in the brackish-water areas with restricted salinity conditions.

A serological survey of free-ranging domestic pigs in the Central and Southern Regions of Malawi, together with laboratory data on confirmed cases of African swine fever (ASF) and data from interviews with pig owners, undertaken over a four-year period from 1981–4, has enabled the ASF enzootic area of Malawi to be identified. The area covers much of the western part of the Central Region and includes Mchinji district and parts of Kasungu, Ntchisi, Dowa and Lilongwe districts. Mortality is substantially less than 100% in outbreaks within the enzootic area but approaches 100% in outbreaks outside this area, as shown by both the serological investigation and the interview data.

Concentrations of air-borne bacteria and particles have been measured in turbulently ventilated operating theatres in full flow, half flow and zero flow conditions. Increased air-borne challenge produced by human activity and by mechanical cleaning procedures is demonstrated: die-away of this contamination is shown to be related to the ventilation rate. Ventilation can be reduced or turned off at night and during weekends, and cleaning can also be carried out, without increased risk of infection if full flow is restored one hour prior to preparation for surgery. Areas surrounding the theatres should remain at positive pressure with regard to the general hospital environment during low or no flow periods. The implementation of such energy-saving policies will substantially reduce theatre running costs without introducing infection hazards.

A total of 745 samples of chicken giblets was cultured to determine the relative efficiency of a commercially available Rappaport-Vassiliadis medium (RV-Oxoid). Experiments to determine the optimum inoculation ratio showed that 1:100 was superior to the other ratios tested. Comparison of RV-Oxoid with standard RV and RV-medium prepared using soya peptone (RV-soya) showed that after 24 h RV-soya was significantly better than RV-Oxoid (P < 0·05), although there was no significant difference between standard RV and RV-Oxoid. Furthermore, when the duration of incubation was extended to 48 h there was no significant difference between the three media (P > 0·25).

We conclude that RV-Oxoid is a satisfactory product for the isolation of salmoncllae from poultry, providing that it is inoculated at a ratio of 1:100 and is incubated for 48h. Its use can therefore be recommended to laboratories who wish to use a dehydrated medium.

A total of 193 sera were examined for antibody to Mycoplasma pneumoniae by three techniques – complement fixation (CF), haemagglutination (HA) and immunofluorescence (IF), the last method being used to assess IgM, IgG and IgA antibodies. The most reliable single test for diagnosis was HA, and the most useful combination of tests was HA with IF (IgM and IgG). The IgA IF was not found to be diagnostically helpful.

Two hundred and ninety-nine different strains of Escherichia coli, isolated from 172 patients with diarrhoea and 113 healthy subjects, were examined for enterotoxin, cytotoxin and haemolysin (Hly) production and for mannose-resistant haemagglutination (MRHA) and invasive properties. Three strains proved enterotoxigenic, none enteroinvasive; cytotoxin and Hly production was shown in 25 strains from patients and in 3 from controls. Ten strains produced the cytotoxic necrotizing factor (CNF), 6 released other factors which kill cell cultures. Hly production was shown in 21 strains, 9 of which were also positive for CNF. MRHA was detected in 26% of strains from diarrhoca compared with 14% of strains from healthy people. A strong association between toxin production and MRHA was demonstrated. Serotyping results showed that the strains exhibiting virulence traits mostly belonged to serogroups commonly involved in extra-intestinal infections. The possible role of strains of E. coli showing one or more virulence factors as opportunistic pathogens in diarrhoeal diseases is discussed.

The virulence of intracranially-inoculated mutant forum of an O18ac:K1:H7 ColV+ stain of Escherichia coli (designated MW) that lacked different combinations of its O and K antigens and CoIV, and of an E. coli K12 strain to which these characters had been transmitted was studied in mice, chickens, ducks and guinea-pigs.

The O18+ K1+Co1V+ form of MW was highly virulent for chickens and mice hut the corresponding form of K12 was only highly virulent for chickens; the O18-K1-ColV- froms of both strains were of low virulence for chickens and mice. K1 was more important than O18 or ColV in determining virulence for both animal species, Ducks and guinca-pigs resembled chickens, not mice, in their response to infection with the O18+K1+ColV+ from of K12.

Pathogenesis studies revealed than the virulence of the forms of MW and K12 was associated with their ability to proliferate in the central nervous system; only low numbers of organisms were found in the blood and spleen of inoculated animals.

The O18+K1+ColV+ form of K12 multiplied in mouse brian and in mouse blood in eitro; its multiplication in chicken blood was partinlly inhibited. Agglutinins to this and other forms of K12 were found in chicken serum but not in mouse serum. Large doses of mouse serum given to chickens and large doeses of checken serum given to mice did not alter the manner in which these animals responded to K12 O18+K1+ColV+ infection. Vaceination protected chickens and mice against lethal intraeranial infection with the O18+K1+ColV+ forms of K12 or MW; it produicted a much stronger immunity in mice against intrapertoneal challenge than against intraeranial challeage

As an estimate of their virulence, the ability of ovine, bovine, canine, feline and simian ureaplasma strains to cause mastitis in the ovine mammary gland was investigated. Five ovine ureaplasmas produced a clinical mastitis. Broth cultures of seven bovine ureaplasmas were unable to infect the ovine gland, but two of these strains plus one other were able to do so following passage through the bovine udder. One of two canine strains and a feline strain both caused mastitis, but the simian strain persisted at low titre for only 5 days post-inoculation in one of the two ewes tested.

A swabbing technique was compared with an excision and maceration technique for bacteriological sampling of pig carcass skin surfaces. Total viable counts at 37 °C obtained by swabbing were 46% of those obtained by maceration. At 21 °C, swabbing gave total viable counts which were 54% of the counts obtained from excision samples. Escherichia coli counts showed wide variation with both sampling methods. Neither method was more efficient than the other in recovering E. coli, although excision sampling gave generally higher counts. Both methods were equally effective at recovering salmonellac from carcass surfaces. There was no significant difference between the methods in recovering particular Salmonella serotypes.

Trimethoprim resistance was seen in 14·8% of 500 strains of salmonella, 43·1% of 153 strains ofshigella and 59% of 27 strains of Escherichia coli isolated from stools of patients with diarrhoea. Strains with a high level of trimethoprim resistance (MIC of ≥ 512 μg) were subjected to conjugal transfer. Trimethoprim resistance was plasmid-mediated in all of 42 strains of shigella and 12 strains of E. coli examined. However, 2 of the 47 strains of salmonella could not transfer their trimethoprim resistance either directly or by mobilization with the transfer factors X and Δ both at 37 and 25 °C overnight incubation.

We studied the effect of oral selective antibiotic decontamination (SD) on the faecal endotoxin content and microflora in individual C57BL mice. Suppression of the coliform count was associated with an initial rise in faecal endotoxin concentration from 0·1 to 3·1 mg/g wet faeces during the first week of SD, which fell to 0·04 mg/g during the second week of treatment. Cessation of SD resulted in an immediate sharp increase in coliform count followed by its decline and gradual recovery to pro-treatment counts. Faecal endotoxin levels followed a parallel course. SD did not effect significantly the counts of lactobacilli, baeteroides and enterococci.

It appears that the coliform population is responsible for the overall level of faecal endotoxin, and that during the initial period of SD endotoxin levels are elevated, an effect which may be mediated by antibiotic-enhanced release of endotoxin.

One contact plate and two homogenization methods have been compared for efficiency in assessing the bacterial contamination of fabrics with high or low, natural or artificial contamination. The contact plate method resulted in considerably lower counts than any of the homogenization methods, which closely resembled one another. One of these, utilizing a Stomacher 400®, was found to be more practical, and is therefore recommended for counting bacteria on fabrics.