AN INVESTIGATION ON PERSISTENCY OF SALMONELLA PARATYPHI B VARIANT JAVA IN EXPERIMENTALLY INFECTED BACKYARD CHICKEN

Abstract

Salmonella is by far the most widely distributed food-borne zoonotic pathogen. There are >2500 serovars of Salmonella enterica. All motile serovars are zoonotic, and poultry harbors a good number of them including Salmonella Paratyphi B variant Java (S. Java). Recently, isolates belonging to this serovar have been isolated from human non-typhoidal clinical cases of gastroenteritis in Bangladesh. Their source of origin in Bangladesh was unknown, but poultry could be a putative source, because reports in literature indicate that poultry could be its reservoir. But information on its persistency in infected/colonized backyard chickens is absent and this information is important to know because rural people in Bangladesh are closely associated with backyard chickens. Most motile serovars are generally colonized in poultry without causing any clinical disease, but can be shed from them to the environment causing a public health hazard. To explore the persistency of S. Java of human non-typhoidal case origin in backyard chickens and its potential to cause clinical disease 27 backyard chickens were infected orally at the rate of 1 ml per bird containingn106 CFU (Colony Forming Unit) and observed for 30 days post infection (DPI). The shedding of S. Java in faeces was screened using novobiocin-added Modified Semisolid Rappaport Vassiliadis (MSRV) medium and Brilliant Green Agar (BGA) by seeing spreading turbid growth on MSRV and bright red colonies on BGA. Persistency of the organism in different internal organs was investigated by taking inoculums of them from four sacrificed birds, and all dead birds.

Fecal samples from the infected chickens were collected by sterile swabs and then immediately immersed into test tubes containing peptone water and incubated for 24 hours at 37ºC. Following incubation, the broth cultures were inoculated onto MSRVP medium which was further incubated for 24 hours at 42ºC. Irrespective of shedding nature – continuous or intermittent, the last day at which fecal sample from a bird was diagnosed positive with S. Java, was considered its total period of shedding. S. Java shedding probability from the infected chickens was 67% (95%CI 44-82%) on DPI 2, 38% (95% CI 19-56%) on DPI 7, 17% (95% CI 5-34%) on DPI 16 and 4% (95% CI is 0.3-18%) on DPI 30. The survival probability of chickens was 82% (95% CI 61-92%) on DPI2; 63% (95% CI 42-78%) on DPI 8, 52% (95% CI 32-69%) on DPI 11 and 48% (95% CI 29-65%) on DPI 30. Of the infected chickens, 6 developed granulomatous lesions into lungs.