In 1980, an outbreak of a mild illness involving twenty pupils and four adults in a boys' boarding school was identified serologically as psittacosis. Intensive epidemiological investigations did not uncover the source. It is suggested either that sources of chlamydia other than avian exist, which may produce a milder illness than the avian type, or that human-to-human spread of a mild form of chlamydiosis occurs.

The mechanisms whereby staphylococcal strains grown in plasma assume increased resistance to polymorph bactericidins were investigated. Observations reported here showed that cultural conditions could determine the path of conversion to resistance. Staphylococcal strains and mutants lacking either free coagulase or clumping factor or both all showed enhanced resistance after 10 h incubation in plasma proteins, thus giving no clear indication that these factors were involved in the interactions. In fact, prolonged incubation in bovine serum albumin (22 h) and ordinary broth medium (24 h) also resulted in increased resistance. A distinction between staphylococcal factors interacting specifically with plasma proteins and such non-specific conversions was obtained in two different ways. Stripping of a hypothetical surface protein by treatment with trypsin or 2 M potassium bromide rendered plasma- but not 24 h-broth organisms susceptible, indicating protein coating of plasma-grown organisms. Also free coagulase-positive strains and mutants incubated in plasma for 30 min were converted while those lacking both or possessing clumping factor alone were not. It therefore appears that one of the mechanisms of acquiring resistance involves a rapid interaction between staphylococcal-free coagulase and fibrinogen, resulting in the deposition of fibrin or fibrin derivatives on the bacterial surface.

In an inter-laboratory survey, the pour plate, surface spread, agar droplet and spiral plate methods were used in parallel with the surface drop method for enumeration of micro-organisms in foods. Good agreement was obtained between all surface methods of enumeration, but there was poor agreement between molten agar methods and the surface drop method.

A total of 1143 samples of food that were ready for consumption at the point of retail sale were examined. Eight types of food products were chosen: meat pasties, sausage rolls, real-cream slices, synthetic-cream slices, mayonnaise-based coleslaws, faggots, patés and continental sausages. The results of this survey suggest that the upper limit for an acceptable viable count should vary according to the food product. Salmonellae were not isolated on any occasion. Potentially harmful organisms were not isolated at levels expected to constitute a public health hazard.

Information concerning the nature of the product, the total viable count, the presence or absence of pathogenic, toxigenic or indicator organisms, the spectrum of the bacterial flora and the relative predominance of each organism must all be considered when assessing the microbiological acceptability of retail ‘ready to eat’ products.

A model for contact transfer of micro-organisms by hand has been extended to include representatives of bacterial species responsible for a majority of hospitalacquired infections. The ability of the organisms to transfer from contaminated fabrics to hands and from hands to sterile fabrics was measured, as was their ability to survive on the skin of the hands. There were differences between the species. Staphylococcus saprophyticus transferred well to the hand but not as well from hand to fabric as the other species; it survived well on skin. Pseudomonas aeruginosa, Klebsiella aerogenes and Serratia marcescens transferred moderately well overall and also survived on the skin. These results were in contrast to those obtained with a strain of Escherichia coli and one of Streptococcus pyogenes.

The contact transfer model was used to investigate the use of small volumes of alcohol in preventing transfer via the hands. An alcohol handrub of either 0·3 ml 80% ethanol or 0·3 ml 70% isopropanol gave reductions in transfer slightly less than that of a soap and water wash. Raising the volume, and consequently the contact time, to 0·5 ml 70% isopropanol gave a 14000-fold reduction in transfer, statistically indistinguishable from that of a thorough soap and water wash (9800-fold reduction).

The development of the normal intestinal microflora of the small intestine, caecum and large intestine of specific pathogen-free (SPF) chickens, was studied in the period from hatching to 84 days of age.

No bacteria were detected in any of the sites at hatchery (day 1), but by day 3 significant levels of faecal streptococci and coliforms were isolated from all sites. The flora of the small intestine was limited to faecal streptococci and coliforms for the first 40 days and then lactobacilli became established and dominated the flora.

A large variety of facultative and strictly anaerobic organisms colonized the caecum. Many of these species were transient and were only present for a limited period; after 40 days the flora stabilized to consist predominantly of faecal streptococci, Escherichia coli, Bacteroides spp. and Lactobacillus sp.

The flora of the large intestine was composed of organisms also present in the small intestine or the caecum.

These findings differ from previously published studies on conventionally reared chickens in that the number of species isolated and the population levels of organisms are much lower. This probably reflects the absence of continuous environmental challenge to the chickens because of the housing and feeding facilities in which the chickens were maintained.

An ‘in use’ test was developed to investigate effectiveness of disinfectant application and of detergent of hot water cleaning at kitchen, bathroom and toilet sites in the domestic environment. Detergent and hot water cleaning produced no observable reduction in microbial contamination. Single and daily application tests demonstrated that hypochlorite and phenolic disinfectants can be used to produce substantial reductions in bacterial contaminationin the home. Results indicate that maximum protection afforded by disinfection is relatively brief; 3–6 h after disinfection, contamination levels were only marginally less than those observed at pretreatment. Some suggestions are made for improvements in home hygiene.

Campylobacters were sought in swabs taken from work surfaces, sinks and floors of four kitchens–i.e. hospital, university, cook-freeze and commercial, processing frozen or fresh chickens. Each kitchen was visited on four occasions. In the large commercial kitchen environmental contamination was found on each visit, whereas campylobacters were isolated on six of the twelve visits to the other kitchens. The hands of operatives were contaminated with campylobacters on only two of the 45 swabs taken during processing. Cleaning with detergent and hot water (or steam) and drying appears to be sufficient to remove the organism from the environment.

Evidence of carriage of campylobacters by the birds was obtained on all 16 visits. In the three kitchens where only frozen birds were used the organism was isolated from 30% and 9·8% of swabs taken from the internal and external surfaces respectively, while 41 % of giblets and 22·2% of thawed juices yielded campylobacters. The external surface of 30 (88%) of 34 fresh birds grew campylobacters.

Faecal samples from 110 horses, 115 pigs, 111 sheep and 123 cows were examined for the presence of Aeromonas hydrophila, which was also sought in the available drinking water.

The overall faecal rate was 11·8%, but significantly more bovine than other samples were found to be positive. There was significant association between the isolation of A. hydrophila from all animal faeces and its presence in drinking water, but this was not found when individual animal groups were analysed separately. An enrichment technique increased the total number of isolates by 77·1 %. Strains of differing origins could not be differentiated by biotyping, although fermentation of sorbitol was associated with bovine isolates. There was a strong positive correlation between positive reactions for V–P, gluconate oxidase and haemolysis of rabbit erythrocytes, tests which had previously been shown to correlate with production of enterotoxin and cytotoxin. Biotypes giving positive reactions for these tests were most frequently isolated from cows, sheep and untreated water, and less frequently from pigs and horses. Most strains of A. hydrophila were resistant to amoxycillin, carbenicillin and cephradine, and sensitive to gentamicin, chloramphenicol and neomycin.

A prospective study identified 785 pregnant women who had been shown to possess complement fixing antibodies against cytomegalovirus (CMV) during a previous pregnancy. As these women were thus known to have been immune prior to their subsequent conception, their neonates were examined for evidence of congenital CMV infection. Specimens were obtained from 725(92%) of the neonatcs and congenital infection was found in only one (0·14%). The elder sister of the infected child was also shown, by retrospective testing of her stored cord serum for specific IgM antibodies, to have been infected in utero. Thus, one woman was identified who had delivered consecutive siblings congenitally infected with CMV. We conclude that some women have a propensity for intra-uterine transmission of CMV, despite being immune prior to conception, and speculate that such women may have acquired their infections perinatally.

In recent years widespread circulation of salmonella and shigella strains resistantto multiple antibiotics has become an international problem. Accordingly the bacterial sensitivity to a range of antibiotics has been assessed in vitro and recorded for the period 1979–83 for patients from the Al Qassimi Hospital. A total of 229 enteric pathogens from 148 children and 59 adult patients were isolated and studied. Most of the enterobacteria were sensitive to colistin, gentamicin, trimethoprim and chloramphenicol (Salmonella typhi approached 100% sensitivity). High rates of sensitivity were also found to ampicillin in S. typhi (96%) and other salmonella serotypes (85%), whilst only 57% of Shigella species and 14% of Escherichia coli were sensitive to this antibiotic. Low rates of sensitivity to sulphamethoxazole, streptomycin and tetracycline were found in shigella and E. coli (ranging from 7 to 14%). Approximately 50% of S. typhi and other salmonella serotypes were sensitive to sulphamethoxazole and streptomycin and 80% to tetracycline. Resistance to three or more antibiotics was very common in shigella and enteropathogenic strains of E. coli (74–85%), less common in non-typhoid salmonella (29%) and exceptional in S. typhi strains. In general, shigella and E. coli isolates showed a high rate of resistance to several antibiotics, whilst S. typhi and other salmonella serotypes retained their original sensitivity to most of the antibiotics used in clinical practice.

The levels of cytopathic enteroviruses at two wastewater-treatment works were monitored over a period of 9 months. The maximum level of virus at works 1 was 72500 p.f.u. l-1 and at Avorks 2,57500 p.f.u. l-1. Examination of process efficiency showed an overall reduction of 63% for works 1 and 26 % for works 2 when used without lagooning. When lagooning was employed at the second works, virus reduction was 97%. Individual treatment processes showed poor reduction of virus levels. Sedimentation and rapid sand filtration had no significant effect on levels whilst both percolating filtration and activated sludge showed some reduction. Only lagooning resulted in substantial reductions of virus levels.

Isolates from the intestinal Escherichia coli flora of 28 members of five families (including parents, children, and household pets) in Amherst, Massachusetts, and Rochester, New York, were characterized by the electrophoretic mobilities of 12 enzymes to estimate the extent of sharing of strains among associated and unassociated hosts. Among the 655 isolates examined, 60 different combinations of electromorphs (electrophoretic types or ETs), each representing a distinctive multilocus genotype, were identified, of which 85% were recovered from only a single individual. On average, 11 % of the ETs isolated from the same family were shared by two or more members; 4·9% of ETs were shared among members of unassociated families living in the same city; and only 2% were shared by families in different cities. All three ETs that were recovered from multiple hosts in the present study are widespread clones that have been isolated from many other host individuals in North America and Sweden.

The molecular epidemiology of rotavirus infections in Glasgow and the west of Scotland during 1981/82 and 1982/83 was investigated by electron microscopy, ELISA testing and RNA migration pattern analysis. In 1981/82, rotaviruses of both the ‘long’ and the ‘short’ electropherotype (in different variants) co-circulated from the onset throughout the winter peak of the outbreak. Approximately 80 % of the children were infected during the first year of life. No differences in incidence were found between sexes. In 1982/83 the isolated rotaviruses were almost exclusively of the ‘long’ electropherotype (in different variants) and 36% of the children were infected beyond the first year of life. Rotaviruses of the ‘long’ electropherotype serologically were of subgroup II and serotype 1 and those of the ‘short’ electropherotype of subgroup I and serotype 2.

Studies were carried out in South America to assess the effect of maternally derived antibody (MDA) on the responsiveness of calves to FMD vaccination. It was found that calves with MDA did not merely fail to respond to vaccination, but that their serum titres were depressed. This depression was proportional to the level of pre-existing MDA at the time of vaccination and following primary vaccination it persisted for a least 60 days. High MDA titres interfered with both primary and secondary responses. Animals with relatively low MDA titres were able to respond to vaccination, or at least to be sensitized so that on revaccination they showed a satisfactory response. The half-life of MDA was shown to be approximately 22 days, suggesting that under field conditions significant MDA titres are likely to persist for 4–5 months. A trial carried out in Brazil in which the primary course of two inoculations, 4 weeks apart, was initiated when the calves were 5–6 months of age, resulted in the reduction of FMD in the calf population from 11% to 0·9% over a 12-month period. The use of vaccination programmes of this type to lessen the incidence of FMD in young bovines is discussed.

A newly developed lectin neuraminidase test (LNT) and a panel of mouse monoclonal and post-infection ferret antibodies have been used to analyse antigenic drift in N1 neuraminidases of influenza A viruses isolated between 1933 and 1957 and also between 1977 and 1980. Significant antigenic differences were detected among the ‘early’ (1933–57) viruses since the NA of viruses isolated one year apart could be distinguished serologically. The NA ofthe ‘re-emerged’ virus A/USSR/92/77 (H1N1) was antigenically related but not identical to influenza A viruses isolated in 1949 (A/Paris/49 (H1N1), A/Geneva/49 (H1N1)) which thus predates the previously observed antigenic similarity of A/USSR/77 with A/FW/50 (H1N1) virus.

Three variables were included in a study to determine their effect on the incidence of Salmonella typhimurium in broilers challenged at four days of age. Variables included the presence or absence of a feed additive, avoparcin; the use of new or used litter and the initiating dose of salmonella. Cloacal swabs were taken from approximately 600 chicks at weekly intervals for 45 days. At 104, 106 and 108 c.f.u./chick there was a direct association of challenge dose and the incidence of positive chicks for the first several weeks. Chicks raised on used litter showed an appreciable reduction in susceptibility to salmonella when compared to control animals on fresh litter. As the birds approached slaughter age, the influence of litter hygiene and challenge dose diminished under the conditions of this study. Avoparcin in the diet at 10 p.p.m. had no enhancing effect on salmonella shedding at any time during the 45-day sampling period. The implications of competitive exclusion are discussed.

A cold-adapted influenza A virus, CR-37 (H1N1), derived from genetic reassortment between A/Ann Arbor/6/60 (H2N2) cold-adapted variant virus and A/California/10/78 (H1N1) wild-type virus, was tested in Japanese adult volunteers. The CR-37 live virus preparation induced only low-grade clinical reactionsin volunteers for the first 3–4 days after inoculation. Two vaccinees who did not show any antibody changes became febrile (over 38–0 °C). Skin tests using the vaccine preparation and uninfected allantoic fluid were performed, and indicated that one of these two vaccinees was positive for the CR-37 vaccine preparation. A high proportion of the vaccinees whose sera had a haemagglutination-inhibition (HI) antibody titre against thevaccine strain of ≤ 64 before inoculation, seroconverted in both HI and neuraminidase-inhibition (NA1) antibody titrations, and only a few seroconverted in the titration of antibody against type-specific internal antigens. The serological examinations against heterotypic H1N1 variants indicated that the cold-adapted live influenza virus vaccine could induce a broad spectrum of HI antibody reactivity and immunity of long duration.

A micro test for the detection of rubella IgG antibody by passive haemolysis in free solution (MIH) is presented. The technique is reproducible, sensitive, simple to perform and economical in the use of reagents. Identical results were obtained in all but one of 408 tests on serum specimens screened for rubella antibody at 15 i.u./ml by the MIH and haemagglutination inhibition (HI) techniques. The quantitative potential of the MIH test and the relative merits of the MIH, HI and radial haemolysis (RH) procedures for rubella screening are discussed.

The results of serotyping of 10953 salmonella isolates from humans over a 10-year period, 1973–82 at the Bacteriology Division, Institute for Medical Research, Malaysia are presented. A total of 104 serotypes from 22 ‘O’ groups were encountered; 95 isolates were considered untypable. The three most predominant serotypes, namely Salmonella typhi, S. typhimurium and S. weltevreden together accounted for 54·1% of all isolates whilst the 25 most frequent serotypes accounted for 93·6% of the total. Whilst the commoner serotypes occurred regularly throughout the study period, the rarer ones tended to appear only in one year, when they might be associated with an outbreak, and never again.

The pattern of serotypes, though quite similar to the one seen in neighbouring Singapore, is different from those experienced in other places such as Hong Kong, Jakarta, Bangladesh and Manchester.

Twenty-nine boys in a boarding school were present during a large outbreak of influenza A H1N1 in 1978 when 27 were infected, 21 with clinical influenza. These boys were bled annually and were still in school when another outbreak of influenza A H1N1 occurred in 1983. Twentythree of them were reinfected but only nine had symptoms. These results are compared with the experience of a similar group of boys in the early years of the influenza A H3N2 era.