Salmonella enterica Enteritidis in chickens serves as a reservoir for salmonellosis in humans and the structure of its lipopolysaccharide (LPS) has been used to assess invasiveness. Culture from chick spleens generated colonies with an unusual wrinkled morphology, and it is designated the lacy phenotype. To characterize the nature of the morphological change, three isogenic variants were compared. Only the lacy phenotype produced a temperature-dependent cell surface matrix composed of several proteins in association with LPS high molecular weight O-antigen.

Flagellin and a 35 kDa protein were identified as specific proteinaceous components of matrix. Both proteins cross-reacted with a monoclonal antibody previously determined to specifically detect the g-epitope of the Enteritidis monophasic flagella (H-antigen). These results suggest that O-antigen in association with protein contributes to cross-reactivity between molecules. The lacy phenotype was more organ invasive in 5-day-old chicks than isogenic variants producing low molecular weight O-antigen. However, it was no more efficient at contaminating eggs after oral inoculation of hens than a variant that completely lacked O-antigen, thus the lacy phenotype is classified as an intermediately invasive organism. The distinctive colonial phenotype of SE6-E21lacy was used to investigate environmental factors that decreased O/C ratios and contributed to attenuation. In so doing, it was found that growth in complement at 46°C caused matrix producing cells to hyperflagellate and migrate across agar surfaces. These results suggest that the structure of O-antigen might influence the secretion and/or the function of Enteritidis cell-surface proteins. The data also reveal a greater heterogeneity than has been assumed in the phenotype, and possibly the infectious behaviour, of Enteritidis.

Campylobacter jejuni serogroup reference strains and collections of sporadic and outbreak- associated isolates were examined for restriction fragment length polymorphisms (RFLPs), using C. jejuni random chromosomal and 16S rRNA gene probes. A collection of 48 Penner (HS) and 14 Lior (HL) serogroup reference strains, plus 10 clinical isolates, generated 35 RFLP and 26 ribotype patterns. In combination the two loci generated 48 distinct genotypes. Both probes were able to differentiate between certain random isolates of the same HS/HL serogroups but greater discrimination was obtained with RFLP than with ribotyping. Genotyping distinguished accurately between related and unrelated strains when applied to several outbreaks. Genotypic analysis of C. jejuni by restriction fragment length polymorphisms is a valuable technique for epidemiological typing. Chromosomal variation detected by the two unlinked probe loci provides some information about the genetic relationship between isolates.

From September 1991 until August 1993 an epidemiological study involving 20 Dutch broiler farms was conducted to identify risk factors and risk reducing measures for Campylobacter infections in broiler flocks. Campylobacter spp. were detected in 64 (57%) of the 112 broiler flocks and in 25 (63%) of the 40 broiler cycles examined. Univariate analysis of farm management data was performed followed by logistic regression analysis of selected risk and risk reducing factors. The presence of other farm animals, including pigs, cattle, sheep and fowl, other than broilers, was found to be independently associated with an increased risk of Campylobacter infections in broiler flocks (odds ratio (OR) = 1181; P = 0041). Further, the results indicate that application of specific hygiene measures during the rearing period, such as washing hands before tending the broiler flocks, the use of separate boots for each broiler house and the use of footbath disinfection when entering a broiler house, may significantly reduce the risk of Campylobacter infections in broiler flocks.

From February to July of 1994, 328 faecal samples from 32 herds were collected and verotoxin-producing Escherichia coli (VTEC) found on 84% of the farms. The proportion of animals infected varied from 0–63%. VTEC were recovered from 52 (20%) of 257 cows and from 16 (23%) of 71 calves. Although the VTEC belonged to 25 different serogroups, 7 (O8. O20, O22, O77, O113, O126 and O162) accounted for 46% of strains. Nearly 45% of the 83 bovine VTEC strains belonged to serogroups associated with haemorrhagic colitis and haemolytic uraernic syndrome in humans. However, only 2 (2%) of 83 VTEC strains isolated from cattle belonged to enterohaemorrhagic E. coli (EHEC) serotypes (O26:H11 and O157:H7), and only 8 (10%) were positive for the attaching and effacing E. coli (eae) gene sequence. Polymerase chain reaction (PCR) showed that 17 (20%) of VTEC strains carried VT1 genes. 43 (52%) possessed VT2 genes, and 23 (28%) carried both VT1 and VT2 genes. Characterization of VTEC isolates revelated a heterogeneous population in terms of serogroup and toxin type in the positive herds. This study confirms that healthy cattle are a reservoir of VTEC, but, the absence of eae genes in most bovine VTEC strains suggests that they may be less virulent for humans than eae-positive EHEC.

As part of the management of an outbreak of meningococcal infection, 119 school contacts of an index case were swabbed for nasopharyngeal carriage. In a cohort study, risk factors for Neisseria meningitidis carriage were ascertained by means of a questionnaire, completed by 114 (96%) of those swabbed.

Twenty five (21%) cultures were identified as ‘neisseria positive’; of which there were 18 (15%) Neisseria meningitidis isolates, 2 (2%) Neisseria lactamica isolates and 5 (4%) showed contaminants only. Two (2%) carriers were identified as harbouring the implicated outbreak strain. Single variable analysis identified six statistically significant risk factors for meningococcal carriage; increasing age, female sex, manual social class, personal smoking, regular attendance at a discotheque and rhinorrhoea. Multivariate analysis, using logistic regression modelling, found that of these six variables only age, sex and social class remained statistically significant when the other factors were controlled for. Nevertheless the role of smoking, social events and respiratory/viral infections in nasopharyngeal carriage, and other plausible mechanisms whereby age, sex and social class might exert their effect, could usefully be investigated further.

The ability to produce large quantities of bioflim on solid surfaces in vitro is believed to distinguish potentially pathogenic strains of Staphylococcus epidermidis from commensals. Bioflim consists of staphylococcal cells encased in a matrix of extracellular polysaccharide (also referred to as slime), firmly adherent to each other and to the underlying surface structure. The association of slime with colonization of catheter surfaces in vivo has been examined extensively. Less attention has been paid to the contribution of slime to infections that occur in the absence of an inserted device. In a mouse model of subcutaneous infection without an implanted device 10 S. epidermidis strains (5 slime-positive, 5 slime-negative) produced abscesses; thus a foreign body is not essential for the expression of virulence by S. epidermidis. Biofilm-positive strains produced significantly more abscesses, that persisted longer than biofilm-negative strains. In these chronic infections, large numbers of staphylococci were associated with macrophages and viable staphylococci were cultured from specimens of pus collected at autopsy. Thus slime or components of slime appear to delay the clearance of S. epidermidis from host tissues, possibly by interfering with intracellular killing mechanisms. However, differences in the capacity to produce abscesses, within both the slime-positive and slime-negative groups, indicate that other factors also contribute to the virulence of S. epidermidis.

Prevalence of brucella-specific antibodies was measured in 597 persons in high-risk occupations living in 10 regions of Lebanon using the standard agglutination test (SAT), anti-human globulin (Coombs') test (AHGT) and enzyme-linked immunosorbent assay (ELISA) for measuring immunoglobulin G (IgG), IgM and IgA. The study population consisted of butchers (54%) farmers (35%), laboratory technicians (8%), abbatoir workers (2%) and veterinarians (1%), with 82% males and 18% females. The overall seroprevalence based on SAT and AHGT titres of ≥ 80 was 1·7% and 15%, respectively, but seroprevalence varied by region from 0–5% in SAT and from 3·4–34% for AHGT. The overall seroprevalence based on ELISA IgG (OD≥0·6), IgM (OD≥0·6) and IgA (OD≥0·3) was 57, 61 and 26%, respectively. The highest seroprevalence was noted in Biqaa (34%), Kisrwan (24%), Shouf (21%), Sidon (16%) and Aley (12) regions. Nineteen percent of those surveyed reported symptoms that could be associated with brucellosis. We conclude that exposure to brucellosis is high among persons in high-risk occupations from all surveyed regions in Lebanon. Such findings should be used to design control measures especially now that the 17 years of civil strife is over.

Low-affinity penicillin-binding protein PBP-2a encoded by mecA is closely related to methicillin resistance in staphylococci, and expression of PBP-2a is controlled by regulator elements encoded by mecRl and mecI which are located adjacent to mecA on the chromosome. Deletion or mutation which occurred in mec regulator gene is considered to be associated with constitutive production of PBP-2a. The distribution of the mec regulator genes in 176 strains of Staphylococcus aureus and 33 strains of S. epidermidis isolated from a single hospital was studied by polymerase chain reaction amplification. Most clinical isolates of methicillin-resistant S. aureus (MRSA) (94.3 %) and S. epidermidis (MRSE) (83.9 %) possessed both mecI and mecR1 genes (type I), whereas no mec regulator genes were detected in mecA-negative isolates. In contrast, 7 MRSA and 5 MRSE isolates were found to have incomplete regulator genes, and they were classified into three groups; strains which lacked only mecI gene (type II), strains which lacked mecIand 3'-end of mecR1 gene (type III), and strains which lacked both regulator genes (type IV). Analysis of mecI gene from all the strains having mecI by restriction fragment length polymorphism after Mse I digestion indicated that three MRSA strains possessed one of the known point mutations identified previously. These findings indicated the predominance of a single type of MRSA possessing both mecI and mecR1 in the study period and also suggested a high genomic diversity in mec regulator region of staphylococci.

During March–April 1993, an estimated 403000 residents of the 5-county greater Milwaukee, Wisconsin area developed cryptosporidiosis after drinking contaminated municipal water. Although the number of cases dropped precipitously after the implicated water plant closed on 9 April, cases continued to occur. To investigate risk factors for post-outbreak cryptosporidiosis, 33 Milwaukee-area residents who had laboratory-confirmed Cryptosporidium infection with onset of diarrhoea between 1 May and 27 June 1993 were interviewed by telephone. Of these, 28(85%) had onset of diarrhoea during May, 12(36%) had watery diarrhoea during the outbreak, and 5 (15%) were HIV-infected. In a neighbourhood-matched case-control study, immunosuppression (matched odds ratio (MOR) not calculable, 95 % confidence interval (CI) 3·0, infinity) and having a child less than 5 years old in the household (MOR = 17·0, CI 2·0, 395·0) were independently associated with infection. When persons who had diarrhoea during the outbreak were excluded, immunosuppression remained significantly associated with illness (MOR not calculable, CI 1·6, infinity). Cryptosporidium transmission continued after this massive waterborne outbreak but decreased rapidly within 2 months.

A Register of HIV-infected persons who have had a negative antibody test within 3 years of their first antibody positive test (seroconverters) is being set up in the UK to monitor the distribution of times from HIV seroconversion to AIDS (the incubation period) and to death. It will also provide a national resource for use by those designing studies in this group of individuals. Clinicians caring for HIV-positive persons in Genito-Urinary Medicine, Infectious Disease and other departments throughout the UK were asked to participate by providing information on eligible subjects. Most laboratories undertaking HIV antibody testing were also contacted and asked to provide the name of the attending clinician for all seroconverters identified through the HIV laboratory reporting systems of the PHLS Communicable Disease Surveillance Centre (CDSC) and the Scottish Centre for Infection and Environmental Health (SCIEH) and for any other seroconverters known to them but not identified by CDSC or SCIEH. Data items sought for the Register include: sex, ethnic group, probable route of HIV transmission, annual CD4 counts, details of therapy and prophylaxis prescribed, AIDS-defining events and vital status. Follow up information is collected annually. Wherever possible, all seroconverters known to a clinic have been identified, whether currently alive or dead, either from clinic records or laboratory reporting or both. The objective is to establish and update a complete register of seroconverters on a long-term basis to provide reliable estimates of the incubation period on which future projections of AIDS cases in the UK can be made.

This paper uses meta-analysis of published data and a deterministic mathematical model of hepatitis B virus (HBV) transmission to describe the patterns of HBV infection in high endemicity areas. We describe the association between the prevalence of carriers and a simple measure of the rate of infection, the age at which half the population have been infected (A50), and assess the contribution of horizontal and perinatal transmission to this association. We found that the two main hyper-endemic areas of sub-Saharan Africa and east Asia have similar prevalences of carriers and values of A50, and that there is a negative nonlinear relationship between A50 and the prevalence of carriers in high endemicity areas (Spearman's Rank, P = 0·0086). We quantified the risk of perinatal transmission and the age-dependent rate of infection to allow a comparison between the main hyper-endemic areas. East Asia was found to have higher prevalences of HBeAg positive mothers and a greater risk of perinatal transmission from HBeAg positive mothers than sub-Saharan Africa, though the differences were not statistically significant. However, the two areas have similar magnitudes and age-dependent rates of horizontal transmission. Results of a simple compartmental model suggest that similar rates of horizontal transmission are sufficient to generate the similar patterns between A50 and the prevalences of carriers. Interrupting horizontal transmission by mass immunization is expected to have a significant, nonlinear impact on the rate of acquisition of new carriers.

To study the occurrence of hepatitis B virus (HBV) and hepatitis C virus (HCV) in patients with chronic liver disease (CLD) and hepatocellular carcinoma (HCC) in Pakistan, blood samples from 105 sequential patients with biopsy-proven CLD (n = 82) and HCC (n = 23) were tested for HBV and HCV markers. Of the 105, 87 (83%) had evidence of hepatitis B exposure, 58 (55%) were positive for hepatitis B surface antigen (HBsAg), 23 (22%) had hepatitis C antibodies and 25 (24%) had detectable HCV RNA. Significantly more patients with HCC had evidence of HBV exposure in the absence of HCV markers (49/82 vs. 20/23, odds ratio 4·49,95 % CI 1·17–25·16). The proportion of patients positive for HBsAg with no HCV markers was also significantly higher in the HCC group (34/82 vs. 18/23, odds ratio 5·08, 95% CI 1·59—18·96). There were more patients with only HCV markers in the CLD group than the HCC group but the difference was not statistically significant (19/82 vs. 1/23, odds ratio 6·63, 95% CI 0·93—288·01). A modified non-isotopic restriction fragment length polymorphism study on PCR products was used to investigate the epidemiology of HCV genotypes in Pakistan. Due to depletion of the initial samples, a second series of specimens collected one year afterwards was used. Fifteen out of 40 samples had amplifiable product and all were identified as type 3. A commercial serological typing method on the same samples also confirmed that type 3 was the predominant HCV genotype in Pakistan.

In a community hepatitis A outbreak in the Rochester, New York area, 64 of 79 (81 %) people with anti-hepatitis A 1gM-antibodies and onset of symptoms from 9 April–31 May 1994, recalled eating food obtained from a retail buyer's club. Eleven (65%) of 17 households with cases contained club members compared with 7 (21%) of 34 neighbourhood-matched control-households (matched odds ratio 8·5; 95% CI 1·7–41·6). Club employees who ate sugar-glazed baked goods were at fourfold increased risk for hepatitis. The source of infection was an 1gM- positive baker who contaminated baked goods while applying sugar glaze. Computer-generated purchase lists implicated 11–12 March and 21–24 March as the most likely dates when contamination occurred. This investigation demonstrates the importance of food workers adhering to established hygiene practices. Computer-generated commercial datasets can be useful in epidemiologic investigations.

The seroprevalence of human T-lymphotropic virus type I (HTLV-I), in relation to that of human immunodeficiency virus type 1 (HIV-1), was determined in a comparative unlinked anonymous antenatal and neonatal (for indirect measurement of maternal antibodies) serosurvey in the Gauteng region of South Africa, using dried blood spots (DBS) and modified particle agglutination assays. Samples were confirmed to be antibody positive by western blot. A total of 2582 DBS collected during 1993 and 1994 from subjects of African, European and coloured origin were tested. Ten were confirmed as positive for HTLV-I and 128 for HIV-1. No antibodies to HTLV-I or HIV-l were demonstrated in the 221 women of European and coloured origin who were screened. The HTLV-I seroprevalence rate in subjects of African origin appeared to increase from 0% in 1993 to 0·49% in 1994, while HIV-1 seroprevalence rates of 5·2% and 5·4% were recorded for 1993 and 1994 respectively. No significant differences in HTLV-I and HIV-1 seroprevalence rates were noted for the two areas investigated. These results indicate that HTLV-I should be included in infection control programs, and provide baseline data for monitoring the possible spread of HTLV-I in the heterosexual population in this region.

Isotype-specific antibody responses to foot-and-mouth disease virus (FMDV) were measured in the sera and upper respiratory tract secretions of vaccinated and susceptible cattle challenged with FMDV by direct contact or by intranasal inoculation. A comparison was made between cattle that eliminated FMDV and those that developed and maintained a persistent infection. Serological and mucosal antibody responses were detected in all animals after challenge. IgA and 1gM were detected before the development of IgG1 and IgG2 responses. 1gM was not detected in vaccinated cattle. Challenge with FMDV elicited a prolonged biphasic secretory antibody response in FMDV ‘carrier’ animals only. The response was detected as FMDVspecific IgA in both mucosal secretions and serum samples, which gained statistical significance (P < 0·05) by 5 weeks after challenge. This observation could represent the basis of a test to differentiate vaccinated and/or recovered convalescent cattle from FMDV ‘carriers’.

A survey of evidence of rodent hantavirus infection in County Down, Northern Ireland was carried out by using immunofluorescence to detect virus antigen and antibody. Antibodies to hantavirus (R22 strain of Seoul virus and Hantaan 76–118) were found in 11/51 (21·6%) brown rats (Rattus norvegicus), 1/31 (3·2%) field mice (Apodemus sylvaticus) and 17/59 (28·8%) house mice (Mus domesticus). Seven rodents had evidence of hantavirus antigen in lung tissues. Antibody positive animals were significantly more likely to be adults than juveniles (P = 0·04) but and there was no sex difference between antibody positive and negative animals. House mice were more likely to be antibody positive if captured inside farm outbuildings (P = 0·08). Attempts to culture virus from the rodent material were unsuccessful. This work demonstrates a substantial rodent reservoir for hantavirus in Northern Ireland.

A detailed analysis of equine (H3N8) influenza viruses isolated in Nigeria during early 1991 has been undertaken. Antigenic analysis and the complete nucleotide sequence of the HA gene of three Nigerian equine influenza viruses A/eq/Ibadan/4/91, A/eq/Ibadan/6/91 and A/eq/Ibadan/9/91 are presented and limited sequence analysis of each of the genes encoding the internal polypeptides of the virus has been carried out. These results establish that, despite the geographical location from which these viruses were isolated, two were similar to the viruses which were concurrently causing disease in Europe in 1989 and 1991 and were related to viruses that have been predominating in horses since 1985. The third was more closely related to viruses isolated from 1991 onward in Europe but also in other parts of the globe. A comparison of the nucleotide sequence of two of the viruses isolated in Nigeria (A/eq/Ibadan/4/91 and A/eq/Ibadan/6/91) with a European strain (A/eq/Suffolk/89) showed limited variation in the haemagglutinin gene which caused amino acid substitutions in one of the antigenic sites: this mutation resulted in the potential production of a new glycosylation site in antigenic site A. The other Nigerian virus (A/eq/Ibadan/9/91) showed only a single one amino acid change from another European strain (A/eq/Arundel/12369/91). The two distinct Nigerian viruses had several amino acid substitutions in the antigenic sites of the haemagglutinin glycoprotein.

A case control study of foal diarrhoea in the United Kingdom was carried out over a 3-year period. Clostridium perfringens was significantly associated with foal diarrhoea (Odds Ratio (OR) = 3·0), being isolated from 57% of 421 animals with diarrhoea but from only 27% of 223 healthy foals. Also, C. perfringens was significantly associated with fatal diarrhoea (OR = 4·5). About half of diarrhoea with a fatal outcome was attributable to this organism.

The other pathogens significantly associated with diarrhoea were rotavirus (OR = 5·6), Cryptosporidium spp. (OR = 3·2) and the nematode Strongyloides westeri, which was significant only when present in large numbers (> 2000 eggs/g of faeces: OR = 6·1). Salmonella spp. (OR = 14·2) and Cryptosporidium spp. (OR = 3·0) were the only other pathogens associated with fatal illness.

Overall, C. perfringens, rotavirus, and large numbers of Cryptosporidium spp. or S. westeri were isolated from 80% of foals with diarrhoea. Thermophilic Campylobacter spp., Yersinia enterocolitica, Escherichia coli and other parasites were not associated with diarrhoea. Carriage of C. perfringens, rotavirus and Cryptosporidium spp. was significantly greater in healthy foals in contact with cases of diarrhoea than in foals that were not in contact with diarrhoea (P < 0·05). There were no statistical interactions between any of the pathogens associated with diarrhoea although separate cases from one location often involved more than one pathogen.

A total of 32 Vibrio ordalii strains were studied for their plasmid content and shown to carry a plasmid of approximately 32 kb. This plasmid was subsequently subjected to restriction fragment length polymorphism (RFLP) studies. Using Hind III, three different restriction patterns were identified while BamHI cleaved the plasmid into a single linear fragment. The results suggest that the 32 kb plasmid is highly conserved but that some variation in restriction pattern occurs. The same set of strains was subjected to ribotyping. Using Mlu I, six different restriction patterns were demonstrated. Strains from the USA and Canada shared profiles with strains from Australia and Japan. Strains from Australia generated a single pattern whereas strains from North America were subdivided into three patterns, and the Japanese strains fell into five patterns. The results suggest that ribotyping in combination with RFLP studies of the pMJ101-like plasmid may be useful in epidemiological studies of V. ordalii.

Multilocus enzyme electrophoresis was used to examine the relatedness of 52 isolates of Clavibacter toxicus, the agent of annual ryegrass toxicity. These included 37 Western Australian (WA) field isolates sampled in 3 distinct locations over a 2-year period, and 15 isolates sampled from 6 different host plant species in 3 states in Australia over approximately 8 years. Seventeen reference strains for the related genera Curtobacterium, Rhodococcus and Arthrobacter were examined for comparison. The 69 isolates were divided into 29 electrophoretic types (ETs), separated by genetic distances of 0·06 to 0·81. The C. toxicus isolates fell into 12 ETs, 11 of which formed a tightly clustered group separated by a genetic distance of 0·23 or less. Thirty-one of the WA field isolates of C. toxicus fell into a single ET, and four into another ET. Clavibacter toxicus therefore formed a closely related group which was genetically distinct from the other plant pathogenic species, and a dominant widely disseminated strain of the species was identified in WA.