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BACKGROUND: Numerous residents of Shelby County, Alabama, were infected with Salmonella when a restaurant unknowingly served food tainted with the bacterium. Because of the similarity in symptoms caused by other gastrointestinal pathogens and the variability in time of presentation, an outbreak such as this could be confused with one of another pathogenic origin. The pathogen identified, Salmonella bredeney, is a particularly rare cause of food poisoning. It makes up only 0.1% of the Salmonella isolates identified by the Centers for Disease Control and Prevention (CDC) each year. METHODS: We analyzed patient presentations through chart review and combined this information with that obtained from the state laboratories in Montgomery and the Shelby County Health Department. RESULTS: Symptoms were mostly gastrointestinal and ranged greatly in severity. The total number of patients affected in this incident exceeded 170, making it the largest epidemic of its kind in the recent history of Alabama. CONCLUSIONS: The outbreak in Shelby County was caused by an exceedingly rare species of Salmonella. At this time, it is the only outbreak of S bredeney reported in MEDLINE-accessible literature since 1983.

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Pregnant ewes were infected in midpregnancy with three isolates of Chlamydia pecorum derived from the feces of healthy lambs from three different farms. Oral infection, alone or together with Fasciola hepatica, did not result in tissue invasion, since all placental and fecal samples were negative for chlamydiae. Intravenous infection resulted in placental infection in 16 of 18 ewes in that chlamydiae were cultured from placentas or vaginal swabs. Two ewes bore dead lambs after a shortened gestation time. The chlamydiae isolated were all C. pecorum. There were no significant differences between the weights of the lambs from the infected groups and those from uninfected control ewes. Most ewes showed no serological evidence of infection by the complement fixation test; therefore, it is unlikely that the enteric subtype of C. pecorum is responsible for the cross-reactions sometimes seen in flocks being tested for C. psittaci infection.

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Faeces samples were taken per rectum from sheep on 26 farms in England and Wales and examined for the presence of chlamydia by culture in McCoy cell monolayers. Thirteen of the farms were known to have had abortion outbreaks associated with Chlamydia psittaci (enzootic abortion) and 13 were free of this infection. The chlamydia isolated were characterized by cultural techniques. Chlamydia were isolated from the faeces of lambs on all 26 farms and the prevalence of infection varied form 5-50% on individual farms. There was no significant difference between the proportion of infected lambs on farms where enzootic abortion was present or absent. Lambs first showed infection when they were 3 months old and the prevalence rate of infection increased up to 9 months old. No chlamydia were isolated from the faeces of 316 adult ewes. The chlamydia were identified as enteric rather than abortion type and thus were C. pecorum rather than C. psittaci.

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Analysis of the genomic DNAs of chlamydial isolates from sheep, cattle, and pigs was performed by Southern blot hybridization and by restriction endonuclease (RE) profiling of DNA amplified by PCR. The hybridization probes were derived from whole genomic DNA, the major outer membrane protein (MOMP) gene, the 16S rRNA gene, and an avian Chlamydia psittaci isolate plasmid. The PCR analysis used targets in the MOMP gene, the 16S rRNA gene, and the 60-kDa cysteine-rich protein gene. Together, the results showed that although there was considerable heterogeneity in the DNA sequence in the MOMP gene region, all the isolates had the same underlying total genomic RE profiles and yielded identical RE profiles for the rRNA and 60-kDa-protein gene regions. Most of the isolates were found to hybridize with the plasmid probe. Comparison of the MOMP sequence of one of the isolates (P787) with that of a known Chlamydia pecorum strain together with the results of the RE analyses allowed the conclusion that the isolates should all be classified within this new species.

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Some isolates of Chlamydia pecorum from sheep feces failed to produce inclusions on passage in cycloheximide-treated monolayers, but chlamydiae could be recovered several weeks later. Chlamydia psittaci from sheep abortions did not show this phenomenon.

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Abortion and enteric isolates of Chlamydia psittaci from sheep differed in their growth in a fibroblastic cell culture derived from the small intestine of a lamb. Twenty abortion isolates, each from a different farm, produced large inclusions which could be passaged several times whereas 10 enteric isolates each from different farms (but from some of the farms of origin of the abortion isolates) produced sparse inclusions which could not be passaged. This appears to be a rapid method of distinguishing abortion and enteric isolates and may indicate different nutritional requirements or be related to the invasiveness of the isolates.

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Ewe placental and lamb intestinal isolates of Chlamydia psittaci recovered from flocks affected with ovine enzootic abortion were examined by inclusion morphology, indirect immunofluorescence (IIF) and immunoblot analysis. Chlamydiae recovered from the faeces of sheep from two flocks free of clinical disease were also examined. In cell culture ovine abortion (OA) and intestinal isolates were distinguishable by inclusion development and morphology. Similarly, in two-way IIF tests with one week mouse antisera isolates fell into two distinct groups: abortion or intestinal. Immunoblotting with convalescent sheep abortion antiserum identified 30 out of at least 40 silver staining polypeptides as antigenic both in OA and intestinal isolates. The serum produced a similar reaction pattern to the resolved proteins of each OA isolate, indicating a higher degree of antigenic conservation among these isolates. Considerable cross reactivity between the OA and intestinal isolates was identified, but the serum also showed apparent molecular weight differences between antigens of the two types in the 87-116 kDa, 38-44 kDa and 26-28 kDa regions. Furthermore, the immunoblotting analysis revealed heterogeneity among the intestinal isolates, particularly in antigens between 87-116 kDa and 38-44 kDa.

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