Campylobacteriosis is recognized as a leading bacterial cause of human gastro-enteritis in both developed and developing countries. Though it has been known for a long time that poultry is the main source of Campylobacter infection, recent studies have suggested that cattle and sheep are potential emerging sources for human infections. Cattle can contribute to human infections through several routes of transmission such as direct contact, environmental contamination, and ingestion of contaminated food and milk. C. jejuni and C. coli usually colonize cattle without showing clear symptoms. Iin the first study, we determined the prevalence, genotypic and phenotypic properties of these pathogens. Pulsed Field Gel Electrophoresis (PFGE) analysis showed that C. jejuni and C. coli isolates were genotypically diverse and certain genotypes were shared across two or more of the geographic locations. Further, MLST analysis demonstrated that the cattle associated C. jejuni strains harbored sequence types that were commonly shared in human cases and also showed varying invasion and intracellular survival capacity to human intestinal cells. Furthermore, many cattle associated Campylobacter isolates showed resistance to several antimicrobials including ciprofloxacin, erythromycin, and gentamicin. Conclusively, our results highlight the importance of cattle as an important reservoir of Campylobacter spp clinically important to human.
In the second study, we investigated the occurrence of the invasion associated marker (iam) in C. jejuni isolated from cattle in order to determine the contribution of this reservoir to human infections with invasive Campylobacter. Additionally, we assessed iam’s contribution to the colonization of multiple hosts by characterizing the potential of iam-containing cattle isolates for chicken colonization and human intestinal cell invasion. Simultaneous RAPD typing and iam-specific PCR analysis of cattle and human-associated C. jejuni isolates showed that the prevalence of iam in cattle C. jejuni is relatively lower as compared to isolates occurring in humans and chickens.
In the third study, we determined the prevalence, genotypic, and phenotypic properties of Campylobacter that were isolated from paired fecal samples of dairy cattle and starlings (Sturnus vulgaris) in Northeastern Ohio. Our results showed that the prevalence of C. jejuni in birds was significantly (P<0.01) higher than that in dairy cattle. Further, PFGE analysis showed that C. jejuni were mostly genetically diverse and host restricted. Our results highlight starlings as potential reservoirs for C. jejuni and may play important role in the epidemiology of clinically important C. jejuni in dairy cattle population.
In the last study, we determined the genotypic and phenotypic properties of ovine and bovine abortion associated Campylobacter isolates which were acquired from the diagnostic laboratories of the Ohio Department of Agriculture (ODA). Further analyses included invasion and intracellular survival potentials in human INT407 cells, along with in-vivo experiment in pregnant ewes. PFGE analysis showed that the fingerprints of ovine and bovine abortion C. jejuni were identical. Furthermore, by MLST analysis, ovine and bovine abortion isolates were classified as (Sequence Type) ST-8 which belonged to Clonal Complex (CC) ST-21 which is also commonly found in humans. Additionally, the ovine and bovine abortion associated C. jejuni strains showed varying invasion and intracellular survival capacity to human intestinal INT407 cells; however, one isolate showed a significantly higher invasion potential compared to other strains (P<0.01) which matched that of C. jejuni 81-1176, a hyper-invasive strain. Furthermore, the ovine and bovine abortion associated Campylobacter isolates showed resistance to several antimicrobials including ciprofloxacin, erythromycin, and gentamicin. Abortion-like symptoms and pathological lesions including suppurative necrotizing placentitis, suppurative and necrotic endometritis, along with occasional lymphadenitis and hepatitis were detected in pregnant ewes after inoculation with the abortion-associated C. jejuni strains. Taken together, our results showed that these C. jejuni isolates are capable of causing abortion in sheep, which indicated that the virulence characters of abortion inducing C. jejuni can be better studied in a natural host, sheep. Since this clone of C. jejuni share genotypic similarities with clones that exist in human population, it may have zoonotic potential. (Abstract shortened by UMI.)