Comparisons of Salmonella conjugation and virulence gene hyperexpression mediated by rumen protozoa from domestic and exotic ruminants.

Recent studies have identified a phenomenon in which ciliated protozoa engulf Salmonella and the intra-protozoal environment hyperactivates virulence gene expression and provides a venue for conjugal transfer of antibiotic resistance plasmids. The former observation is relegated to Salmonella bearing the SGI1 multiresistance integron while the latter phenomenon appears to be a more generalized event for recipient Salmonella. Our previous studies have assessed virulence gene hyperexpression only with protozoa from the bovine rumen while conjugal transfer has been demonstrated in rumen protozoa from cattle and goats. The present study examined virulence gene hyperexpression for Salmonella exposed to rumen protozoa obtained from cattle, sheep, goats, or two African ruminants (giraffe and bongo). Conjugal transfer was also assessed in these protozoa using Salmonella as the recipient. Virulence gene hyperexpression was only observed following exposure to the rumen protozoa from cattle and sheep while elevated virulence was also observed in these animals. Conjugal transfer events were, however, observed in all protozoa evaluated. It therefore appears that the protozoa-based hypervirulence is not universal to all ruminants while conjugal transfer is more ubiquitous.

Fatal ulcerative colitis in a western lowland gorilla (Gorilla gorilla gorilla).

A captive western lowland gorilla (Gorilla gorilla gorilla) presented with watery diarrhoea that progressed to become profuse and haemorrhagic. Faecal analyses revealed Balantidium (B.) coli trophozoites and salmonella-like bacteria. Despite treatment the gorilla died on the 5th day after onset of symptoms. Post-mortem examination revealed a severe erosive-ulcerative superficial and deep colitis. Histological examination of post-mortem samples of the colon showed plentiful B. coli invading into the mucosa and submucosa, whilst PCR screening of bacterial DNA could not confirm any bacteria species which could be connected to the clinical picture. As B. coli is usually a non-pathogenic gut commensal, and as this animal previously showed evidence of non-symptomatic infection of B. coli, it is possible that the switch in pathogenicity was triggered by an acute bacterial infection. Despite successful treatment of the bacterial infection the secondary deep invasion of B. coli was not reversed, possibly because of the failure of the treatment regimen, and led to the death of the gorilla.

Experimental infection of Salmonella Enteritidis by the poultry red mite, Dermanyssus gallinae.

Dermanyssus gallinae is an important ectoparasite of laying hens in Europe and it is suspected of being a vector of pathogens. We carried out an in vitro study to evaluate the role of D. gallinae as a vector of Salmonella enterica subsp. enterica serotype Enteritidis. Two means of infecting the mite were tested: through the blood meal and after cuticular contact. Mites became carriers of Salmonella immediately after the infection with 29% and 53%, respectively, for oral route and cuticular contact. This percentage increased over time until it reached 95% (D7) and 80% (D14). The numerical identification of bacteria on the selective medium SM ID demonstrated the multiplication of Salmonella inside previously infected mites. In addition, transovarial passage as well as transstadial passage (from N1 to N2 stages) were demonstrated. Moreover, the observation of a negative effect of Salmonella on Dermanyssus oviposition was also observed. Finally, previously infected mites were able to contaminate the blood during the blood meal. Therefore, it appears that D. gallinae may act as a biological vector of S. Enteritidis under experimental conditions. It may represent a suitable environment for the development of Salmonella and could be an additional factor for the persistence of salmonellosis infection between successive flocks.

Acute toxoplasmosis in three wild arctic foxes (Alopex lagopus) from Svalbard; one with co-infections of Salmonella Enteritidis PT1 and Yersinia pseudotuberculosis serotype 2b.

Acute disseminated toxoplasmosis was diagnosed in three wild arctic foxes (Alopex lagopus) that were found dead in the same locality on Svalbard (Norway). The animals included one adult female and two 4-months-old pups. The adult fox was severely jaundiced. Necropsy revealed multifocal, acute, necrotizing hepatitis, acute interstitial pneumonia, and scattered foci of brain gliosis, often associated with Toxoplasma tachyzoites. One pup also had Toxoplasma-associated meningitis. In addition, the latter animal was infected with Yersinia pseudotuberculosis serotype 2b and Salmonella Enteritidis phage type 1 (PT1), which may have contributed to the severity of the Toxoplasma infection in this animal. The diagnosis of toxoplasmosis was confirmed by positive immunohistochemistry and detection of anti-Toxoplasma gondii antibodies in serum of all foxes. The animals were negative for Neospora caninum, canine distemper virus, canine adenovirus, and rabies virus on immunolabelling of tissue sections and smears.

Excretion in feces and mucosal persistence of Salmonella ser. Typhimurium in pigs subclinically infected with Oesophagostomum spp.

OBJECTIVE: To determine interactions between Oesophagostomum spp and Salmonella ser. Typhimurium in pigs. ANIMALS: 30 healthy 5- to 6-week-old pigs. PROCEDURE: Pigs were allotted to 3 groups (n = 10 pigs/group) and treated as follows: group A was given Oesophagostomum dentatum and O quadrispinulatum; group B was given O dentatum, O quadrispinulatum, and S Typhimurium; and group C was given S Typhimurium only. Pigs in groups A and B were trickle infected with Oesophagostomum spp 3 times weekly throughout the study. After 19 days, groups B and C were inoculated once with S Typhimurium. One pig from each group was euthanatized on the day of Salmonella exposure and 2 and 4 days after Salmonella exposure. The remaining pigs were euthanatized on days 16 and 17 after Salmonella exposure. RESULTS: Pigs with dual infections of nematodes and bacteria (group B) excreted significantly higher amounts of S Typhimurium in feces, compared with nematode-free pigs (group C). In addition, group-B pigs excreted S Typhimurium on more days than pigs in group C. Salmonella Typhimurium was detected in the cecum and colon in the majority of pigs in group B, whereas S Typhimurium was only detected in the colon in pigs in group C. Immunohistochemical examination detected S Typhimurium in 7 of 9 pigs in group B but only 2 of 9 pigs in group C. CONCLUSIONS AND CLINICAL RELEVANCE: Interactions between intestinal nematodes and bacteria may play an important role in the dynamics of S Typhimurium infections.

Fecal shedding of Giardia duodenalis, Cryptosporidium parvum, Salmonella organisms, and Escherichia coli O157:H7 from llamas in California.

OBJECTIVE: To evaluate fecal shedding of Giardia duodenalis, Cryptosporidium parvum, Salmonella organisms, and Escherichia coli O157:H7 from llamas in California with respect to host factors and management practices. ANIMALS: 354 llamas from 33 facilities. PROCEDURE: Fecal specimens were collected and examined for G. duodenalis and C. parvum by means of immunofluorescent microscopy. Salmonella organisms were cultured by placing feces into selenite enrichment broth followed by selective media. Escherichia coli O157:H7 was cultured by use of modified tryptocase soy broth followed by sorbitol MacConkey agar, with suspect colonies confirmed by means of immunofluorescent microscopy. RESULTS: 12 of 354 fecal specimens (3.4%) had G. duodenalis cysts. Younger llamas (crias) were more likely to be shedding cysts, compared with older llamas. Farm-level factors that increased the risk of shedding were large numbers of yearlings on the property (> 10), smaller pen sizes, large numbers of crias born during the previous year (> 10), and large pen or pasture populations (> 20). None of the 354 fecal specimens had C. parvum oocysts. Seventy-six (from 7 facilities) and 192 (from 22 facilities) llamas were tested for Salmonella organisms and E. coli O157:H7, respectively. All fecal specimens had negative results for these bacteria. CONCLUSIONS AND CLINICAL RELEVANCE: Shedding of G. duodenalis was primarily limited to crias 1 to 4 months old. Llamas from properties with large numbers of crias born in the previous year, resulting in large numbers of yearlings in the current year, were at greater risk of infection. In addition, housing llamas in smaller pens or pastures and managing llamas and crias in large groups also increased the risk of G. duodenalis shedding.

Effect of Eimeria tenella infection on Salmonella enteritidis infection in chickens.

The effect of Eimeria tenella infection on the Salmonella enteritidis infection in chickens was investigated in three experiments. Each experiment consisted of an uninfected control, birds infected with E. tenella, birds infected with S. enteritidis, and birds infected with a combination of E. tenella and S. enteritidis. A dose of 2 x 10(4) sporulated oocysts of E. tenella was given to each chicken. In Experiment 1, each chicken was infected with 10(5) cfu/d of S. enteritidis for 3 consecutive d starting 1 d after coccidia exposure and necropsied 4, 7, 10, and 14 d after coccidial infection. In Experiments 2 and 3, each bird was infected with 10(2) cfu/d and 10(1) cfu/d of S. enteritidis respectively, for 2 d beginning 4 d after coccidia exposure, and were killed 7, 10, and 14 d postinfection with E. tenella. Results showed that interaction between S. enteritidis and E. tenella was significant in Experiments 1 and 2, but not in Experiment 3, manifesting that the cecal Salmonella population were significantly increased by coccidial infection in birds killed 4, 10, or 14 d after coccidia exposure in Experiment 1 and in birds killed 14 d after coccidial infection in Experiment 2. The dose size of S. enteritidis was an important factor for the synergistic relationship between S. enteritidis and E. tenella. Frequency of recovery of S. enteritidis in liver and spleen was not increased by E. tenella infection.

Effects of infection with Eimeria tenella upon Salmonella typhimurium infection in the gnotobiotic chicks. Scanning electron microscopic study.

The gnotobiotic chicks infected with Eimeria tenella received an oral inoculation of Salmonella typhimurium 4 or 8 days after E. tenella infection. Chicks were necropsied one day after the salmonella infection. In the experiments 1 and 2, there were two groups; birds infected with S. typhimurium alone and birds infected with a combination of E. tenella and S. typhimurium. The number of S. typhimurium in the cecal contents was significantly greater in the concurrent infections than S. typhimurium infection alone. The S. typhimurium counts in the cecal wall of gnotobiotic chickens killed 5 days after E. tenella infection were significantly greater than those of chickens infected with S. typhimurium alone. In the experiment 3, the scanning electron microscopic study was made on damage of cecal mucosa. There were four groups; uninfected birds as control, birds infected with E. tenella, birds infected with S. typhimurium and birds infected with a combination of E. tenella and S. typhimurium. No damage was observed on the cecal mucosa of both the control and the S. typhimurium infection alone. The concurrent infections caused greater damage on the cecal mucosa than did the E. tenella infection alone.

Growth of Salmonella typhimurium in the caecum of gnotobiotic chickens with Eimeria tenella.

Gnotobiotic chickens infected with Eimeria tenella (5 X 10(4) oocysts per bird) received an oral inoculation of 100 Salmonella typhimurium two, four, six or eight days after coccidial infection at four days old. When S typhimurium was given two or four days after E tenella infection, S typhimurium counts in the caecal contents were similar to the counts in birds infected with S typhimurium alone. When S typhimurium was given six or eight days after E tenella infection, counts of the organism were significantly greater than with S typhimurium infection alone. There were no differences in the number of chickens positive for S typhimurium in the caecal contents, bile, liver and spleen between the two groups.