Between February 1988 and March 1989 chicken carcases delivered to the kitchen of a long stay psycho–geriatric hospital were screened every week for salmonella contamination. While 214 of 477 (45▒) individual carcases carried one or more salmonella types, every single consignment examined contained affected carcases.

Simultaneously sewers draining the residential accommodation and excluding kitchen effluent, were also monitored. Thirty out of 79 (38▒) of Moore's swabs were positive for salmonella. There was a statistically significant association between the salmonella types isolated from chicken and those isolated from sewers the following week.

Following a change in kitchen policy to order only cooked chicken there was a significant reduction in the isolation of salmonella from the sewers.

It has long been known that the binding of antibodies to viruses can result in a loss of infectivity, or neutralization, but little is understood of the mechanism or mechanisms of this process. This is probably because neutralization is a multifactorial phenomenon depending upon the nature of the virus itself, the particular antigenic site involved, the isotype of immunoglobulin and the ratio of virus to immunoglobulin (see below). Thus not only is it likely that neutralization of one virus will differ from another but that changing the circumstances of neutralization can change the mechanism itself. To give coherence to the topic we are concentrating this review on one virus, influenza type A which is itself well studied and reasonably well understood [1–3]. Reviews of the older literature can be found in references 4 to 7.

In discussions of the origin of new infectious diseases, prominence is usually given to dramatic infections acquired from animals (Lassa fever, Marburg and Ebola viruses) or from the environment (legionellosis). But these infections do not spread from human to human, and their impact on mankind can never be catastrophic. If a new infectious agent is to pose a major threat to the human species, it will need to kill tens or hundreds of millions of people over a short period of time (a few years), before vaccines and antimicrobial agents can be developed or effective blocks to transmission established. The 1918 influenza pandemic (total deaths about 20 million) almost came into this world-shaking category, but many of the deaths were presumably due to secondary bacterial pneumonia and this was the pre-antibiotic era. A similar airborne pandemic occurring today could spread globally within weeks by air transport and would have a greater impact. Smallpox arose long before the world became one from an infectious disease point of view, and although it caused devastating epidemics it did not have the opportunity to develop into the ‘major threat’ category. A significant proportion of people recovered, less virulent strains of virus (variola minor) appeared, and an effective vaccine not only kept it under control in many continents but finally eliminated it from the world. The plague (Yersinia pestis) influenced the course of history in Asia and Europe [1] but oven in its respiratory form could not in those days be transferred rapidly from continent to continent.

Since 1987, the number of cases of salmonellosis caused by Salmonella enteritidis has considerably increased in Western Europe. Comparison of endemic animal strains isolated in Belgium from 1976–84 with strains isolated from 1987 on shows that the strains which cause the current epidemic have no features distinguishing them from the previously–isolated strains and that furthermore, they do not constitute a bacterial clone. They belong to 13 different lysotypes and in most cases remain sensitive to antibiotics. Nevertheless, the lysotype 33 which belongs to the phage type 4 [1] has increased significatively. It encompasses 37 % of the animal strains isolated in Belgium from 1987–9, but only 7% of the strains isolated from 1976–84.

It is worth noting that the endemic as well as the epidemic strains contain a virulence plasmid sharing sequence similarities with the FIB and FIIA plasmid replicons and with the VirA and VirB virulence regions of the S. typhimurium virulent plasmid: pIP1350.

Patients (454) referred for gastroscopy to the General Hospital of Athens were examined to determine (1) if non-secretors were over-represented among patients with ulcers and (2) is there was an association with ABO blood group or secretor status and carriage of Helicobacter pylori.

Compared with the local population, among patients with either gastric ulcer (51) or duodenal ulcer (96) there was a significant increase in the proportion of those who were blood group O (P < 0·025); however, there were no significant differences in the proportions of non-secretors. H. pylori was identified in 62 % of the 454 patients: 59·5 % of those without evidence of ulcers; 62·5 % of those with gastric ulcer; 88% of those with duodenal ulcer (P < 0·0005). These bacteria were cultured more often and in higher numbers from patients with duodenal ulcer (P < 0·025). There was no association between ABO blood group and prevalence of H. pylori. The prevalence of H. pylori among non-secretors with gastric ulcer (12·5%) was significantly lower than that for non-secretors with duodenal ulcer (100%) (P < 0·0005). This was not observed for secretors.

The efficacy of three proprietary glutaraldehyde disinfectants and their component bases was assessed using the duck hepatitis B virus (DHBV) model. Inactivation of infectivity of undiluted serum containing 106·8 ID50/ml DHBV was assessed after a mixture with an equal volume of disinfectant had stood at room temperature for 10 min. A dried spill of infectious serum was simulated using sterile filter paper disks, saturated with serum containing DHBV, dried and then exposed to test disinfectant for 10 min. Residual infectivity, and hence the reduction in virus titre, was determined by inoculation of dilutions of the treated samples into 1-day-old ducklings. A greater than 3 log10 reduction in virus titre could be demonstrated for the disinfectants as well as for some of their component bases. Disinfectant activity varied according to the method of viral presentation but a reduction of exposure time from 10 to 2·5 min did not diminish activity. The experimental protocol permits a comparative and quantitative assessment of the efficacy of both established and new disinfectants.

This investigation was to determine whether monoclonal antibodies (Mabs) could be used to differentiate coagulase-negative staphylococci (C-NS) at species and strain level. Mabs were produced to four Staphylococcus epidermidis strains, two S. haemolyticus strains, one S. saprophyticus strain and one S. warneri strain. A panel of nine antibodies was tested for species and strain specificity against five type strains and 65 clinical isolates of C-NS by enzyme-linked immunosorbent assay (ELISA). Species specificity was found with Mab D150 produced to one S. haemolyticus strain. Using Mab D150 and Mab D198 in conjunction, identification of 90% of S. haemolyticus isolates to species level was achieved. S. saprophyticus Mab K84 reacted with most other strains of C-NS tested but only three S. haemolyticus strains (16%). This finding provides further evidence that S. haemolyticus possesses different surface determinants to other C-NS which could form the basis of a typing scheme for S. haemolyticus using Mabs D150, D198 and K84.

In a household survey in the Faroe Islands, an isolated community with hyperendemic occurrence of meningococcal disease due to serogroup B 15, 1604 persons were examined for pharyngeal carriage of Neisseria meningitidis and N. lactamica. Two areas were chosen having experienced high (HIA), and two having experienced low incidences (LIA) of disease. Living in HIA compared with LIA was associated with higher risk of N. meningitidis B 15 carriage and lower risk of N. lactamica carriage, with odds ratios of 2·7 (95% confidence interval (CI) 1·4–5·1, P = 0·003) and 0·41 (95% CI 0·31–0·53, P < 0·0001), respectively. In HIA the risk of N. meningitidis carriage was much lower in non-carriers than carriers of N. lactamica, with an odds ratio of 0·19 (95% CI 0·08–0·47, P = 0·0003); in LIA this association (odds ratio 0·51, P = 0·05) was much weaker. Children 0–14 years had substantially higher risk of being carriers of N. meningitidis group B 15 if the mothers were so, with an odds ratio of 11 (95% CI 4–29, P < 0·0001).

Of 2210 salmonella isolates referred to the New Zealand Communicable Disease Centre for epidemiological surveillance during 1987, 147 (6·7%) were resistant to one or more of 10 antibiotics. Resistance to streptomycin was most common (4·5%). followed by sulphamethoxazole (3·4%), tetracycline (3·3%), ampicillin (1·5%). and kanamycin (1·4%). Resistance to cephalothin, chloramphenicol, gentamicin and trimethoprim occurred in less than 1 % of isolates. There was no resistance to norfloxacin. Isolates from human sources were significantly (P < 0·001) more resistant (10%) than those from other sources (3·2%). The majority of resistant isolates were resistant to more than one antibiotic, but multiresistance to five or more antibiotics occurred only among human isolates. Comparison of these results with data from earlier years shows that there has been little change in the incidence of resistance among salmonella in this country over the last 10 years. The prevalence of antibiotic resistance among salmonella in New Zealand is low relative to many other countries.

The distribution of Salmonella enteritidis phage types in Canada is described; 606 of 674 strains examined were of human origin. Typable strains of all sources, constituted 99·6% (671/674) of all strains examined, and were representative of 15 different phage types. Five phage types (8, 13, 4, 13a and 1) accounted for 92·4% of the total. Phage type 8 consistently showed the highest incidence in human (69·96%) and non-human (72·05%) sources and appeared to be the most common in North America. Phage type 4, the most prevalent in the UK, is infrequent in Canada (38/674). The distribution of phage types showed regional variation among infrequent phage types, whereas the common type, 8, was observed in different frequencies in all provinces. Examination of 29 outbreaks of S. enteritidis representing 254 isolates for humans revealed 5 different phage types, the highest number of outbreaks (11) were type 8. A study of these outbreaks and the animal-host-associations of the common phage types, 8 and 13, indicated that contaminated poultry appeared to be the most common source of human infection in Canada.

Isolates of Streptococcus pyogenes from vaginal swabs of children with vulvovaginitis received at Nottingham Public Health Laboratory during 1986–9 were studied. A total of 159 isolates was made during the 4 years, increasing from 17 in 1986 to 64 in 1989 and accounting for 11% of all vaginal swabs received from children. The numbers of throat swabs yielding S. pyogenes also showed an increase from 974 in 1986 to 1519 in 1989. A winter peak of isolates was noted for both vaginal swabs and throat swabs. A total of 98 strains from vaginal swabs were serotyped: 22 different types were identified, 61% of which were the common types M4, M6, R28 and M12. Erythromycin sensitivity was done on 89 strains; 84% were highly sensitive (MIC < 0·03 mg/1). There are no other reports of such large numbers in the literature; the reason for seeing this increase in Nottingham is unclear.

Pyrolysis mass spectrometry (PyMS) was used as a method of rapid inter-strain comparison of 19 isolates of coagulase-negative staphylococci from episodes of CAPD peritonitis. Thirteen isolates were from multiple, but distinct, episodes of peritonitis in 6 patients and the remaining 6 isolates were from 6 patients with single episodes. The results, expressed in terms of identity/non-identity of strains, were compared with those obtained using an established typing system comprising an extended antibiogram, determination of biotype and plasmid profile analysis. The PyMS results for inter-strain comparison were in agreement with the reference typing scheme results. PyMS can be used in this setting to rapidly obtain evidence that persistent infection is/is not likely to be due to the same organism, although it cannot be used for formal typing. The results by both methods showed that serial, apparently distinct, episodes of peritonitis over periods as long as 120 days may be due to the same strain of coagulase-negative staphylococcus. Clinically based distinctions between recurrence of infection (same strain) and re-infection (different strains) may not always be supported by the microbiological evidence.

Biotyping, slime production, antibiograms, extrachromosomal DNA banding and total DNA restriction analysis were used to characterize Staphylococcus epidermidis strains causing cerebrospinal fluid shunt infections in 11 patients. Infections considered to be community acquired and those acquired in the first 2 weeks of hospital admission were due to oxacillin-susceptible isolates. Multiply resistant strains were isolated from patients who were in hospital for more than 1 month before tube implantation. Slime was detected in staphylococci for 54% of cases, but its expression varied. Strains from different patients could be differentiated from one another by the extrachromosomal DNA bandings and total DNA restriction patterns, but isolates from the same patient were usually similar. During the period of external drainage, epidemiological markers were useful in differentiating persistence of infection from contamination or re-infection by a new strain.

Plasmids in five strains of Salmonella typhimurium resistant to ampicillin, chloramphenicol, gentamicin, neomycin/kanamycin, streptomycin, sulphonamides, tetracyclines and trimethoprim (ACGKSSuTTm), CGKSSuTTm, ACSSuT or CSSuT which had been isolated from poultry in the first 3 months of 1989 have been characterized and compared with plasmids in two strains of R-types ACGKSSuTTm and ASSuTTm isolated from two patients later in the year. With the exception of the human isolate of R-type ASSuTTm, all strains carried two non-conjugative plasmids, one coding for SSu and belonging to incompatibility group Q, and a second coding for multiple resistance and belonging to the FIme incompatibility group. The human isolate of R-type ASSuTTm did not carry the IncQ, SSu plasmid but like the poultry isolates, carried a non-conjugative FIme plasmid.

Restriction endonuclease digestion with the enzymes EcoR I, Pst I and Hind III demonstrated that the FIme plasmids from strains of different R-types showed a high degree of homology but exhibited numerous fragment size polymorphisms. The restriction digest fingerprint of plasmids in the human isolate of R-type ACGKSSuTTm was indistinguishable from a poultry isolate of the same R-type. Analysis of segregants of one of the poultry isolates of R-type ACGKSSuTTm demonstrated that resistance determinants could be rapidly lost from the FIme plasmid to give rise to a number of R-types and fingerprint patterns. Loss of tetracycline resistance from this plasmid appeared to be correlated with the integration of other plasmid-mediated resistances into the bacterial chromosome. Evidence is presented for the rapid loss of antimicrobial resistance determinants from a multiple resistance plasmid of the FIme incompatibility group in response to withdrawal of antibiotic selective pressure.

When Specific Pathogen–Free hens were infected with Salmonella enteritidis PT4 by direct administration into the crop, the age of the bird at infection was found to have an effect on both pathogenesis and antibody response. Birds at 20 weeks of age showed no adverse signs and developed high titres of antibodies of the IgM class, while those which were 1 year old at infection developed relatively little antibody arid had acute septicaemia, with 6 of 10 birds either dying or having to be humanely destroyed. The implication of these results for the control of salmonella infections in poultry is discussed.

A survey was conducted to estimate the prevalence of Salmonella enteritidis and other salmonellas among Canadian commercial egg producing flocks. Environmental (faecal and eggbelt) samples from 152 of 295 (52·9%) randomly selected flocks were contaminated with salmonellas. Thirty-five different salmonella serovars were isolated. Eggbelt samples were more often contaminated with salmonellas than faecal samples (25·7 v. 10·1 %). The most prevalent serovars were S. heidelberg, S. infantis, S. hadar, and S. schwarzengrund; they were isolated from samples of 59/295 (20%), 18/295 (6·1%), 17/295 (5·8%), and 15/295 (5·1%) flocks, respectively. Feed samples of 21/295 (7·2%) flocks were contaminated with salmonellas. Salmonella enteritidis was isolated from the environmental samples of 8/295 (2·7%) flocks. Salmonella enteritidis phage type (PT) 8 was isolated from 5 flocks, PT 13a from 2 flocks, and PT 13 from 1 flock.

The main aim of this study was to measure and explain geographic variations in the incidence of Legionnaires' disease in Scotland, particularly to help understand the source of non–outbreak infection.

Between 1978 and 1986 the overall mean annual incidence rate was 7·9 per million (range 3·1–20·2), and for non–outbreak, non-travel cases it was 5·6. There were geographical variations by health board, by city and within cities, e.g. the mean annual incidence rate per million for non–travel, non–outbreak disease was 1·2 in Tayside Health Board, 3·7 in Lanarkshire, 5·6 in Lothian and 14·4 in Greater Glasgow. In Greater Glasgow Health Board non–travel cases lived in and around the city centre and in some postcode sectors there, the mean annual incidence rate exceeded 100. Travel–related cases lived in peripheral areas.

These variations could not be explained by differences in access to and use of diagnostic services, surveillance, or host susceptibility (as reflected by socio–economic status and frequency of other respiratory disease). The explanation probably lay in environmental factors, though differences in agent virulence were not excluded.

The two main conclusions are, that non–outbreak cases were not truly sporadic, and that the spacetime variations in incidence support the hypothesis that cooling towers were an important source of infection for not–nravel, non-outbreak cases. If so such infection is potentially preventable.

Enterotoxigenic Escherichia coli (ETEC) from Burma, central Africa (Rwanda and Zaire) and Peru, were screened by enzyme-linked immunoassays for the colonization factor antigens (CFAs) and putative colonization factors (PCFs): CFA/I, CFA/II, which consists of three coli surface-associated (CS) antigens, CS1, CS2 and CS3, CFA/III, CFA/IV (CS4, CS5, CS6), CS7, PCFO9, PCFO159.H4, PCFO166, and CS17. The highest proportion of ETEC with identifiable colonization factors (71%) were found in the strains from Burma, which were mainly positive for CFA/I (38%), but strains producing CFA/II (4%), CFA/IV (11%), CS7 (10%), CS17 (4%), PCFO159.H4 (2%) and PCFO166 (2%) were also found. Sixty-nine percent of the ETEC from central Africa were positive for known colonization factors. While CFA/I positive strains were important (12%), a higher number of ETEC producing CFA/IV (33%) and CS17 (24%) were found. Fifty-two percent of the Peruvian strains produced identifiable colonization factors. The largest group of strains produced antigens of the CFA/IV complex (17%), while ETEC producing CFA/II (6%), CFA/III and CS6 (2%), CS7 (6%), PCFO9 (6%), PCFO166 (8%) and CS17 (7%) were also found. These surveys show that there is a considerable variation in the proportions and types of colonization factor found in different geographical areas. From 29 to 48% of the ETEC did not possess an identifiable colonization factor. These were particularly of the LT only producing type. These results have important implications for vaccine formulation.

The effect of some factors on the growth of Salmonella enteritidis phage type 4 in artificially contaminated shell eggs was investigated.

Salmonella enteritidis was found to be resistant to the antimicrobial properties of the albumen. Growth occurred on storage at 25 °C but not at 4 or 10 °C. The rate and extent of infection was influenced by the size of inoculum, the site of contamination relative to yolk movement, and the presence of iron in the inoculum.

The purpose of this study was to examine whether certain salmonella serovars, other than Typhi and Paratyphi, may have an increased ability to enter the human body fluids. The data are based on over 20000 salmonella isolated from humans during 1984–9, among them 436 from extra-intestinal (EI) sources. The mean percentage of EI salmonella isolated in Israel (excluding Typhi and Paratyphi), was 2·1 %. In three serovars: S. 9, 12:1, v:-, Virchow and Saintpaul, the percentage of blood isolations and of EI isolations in general, was high. Among the frequent serovars, ser. Infantis and Hadar had a much lower percentage of EI isolations.