Comparison of recombinant and synthetic listeriolysin- O peptide- based indirect ELISA vis-à-vis cultural isolation for detection of listeriosis in caprine and ovine species.

The present study evaluated the comparative serodiagnostic efficacy of recombinant listeriolysin-O (rLLO) and synthetic LLO- 2 peptide-based indirect ELISA vis-à-vis cultural isolation using samples (n = 1326; blood, sera, vaginal swabs, and rectal swabs) collected from caprines (n = 350) and ovines (n = 50) having reproductive and/or nervous system disorders and/or healthy animals. On screening the test sera by rLLO- based ELISA, the antibodies against LLO (ALLO) were observed in 17.71% of the caprines and 2% of the ovines, respectively, while synthetic LLO-2- based ELISA revealed ALLO in 6.86% of caprines and not in ovines. Moreover, the adsorption of positive test sera with streptolysin-O (SLO) resulted in a significant reduction (7.43%; p < 0.05) in the seropositivity with rLLO- based ELISA, whereas LLO-2- based ELISA revealed marginal reduction (4.29%; p > 0.05) in the seropositivity. Overall, the seropositivity with LLO-2 synthetic peptide revealed comparatively less cross-reactivity in comparison to rLLO. The cultural isolation yielded five pathogenic L. monocytogenes isolates and three non-pathogenic Listeria spp. from caprine samples; however, Listeria spp. could not be recovered from any of the ovine samples. Further, on comparing seropositivity with the isolation study results, it was found that two out of the five animals from which pathogenic L. monocytogenes isolated were also found seropositive in both the ELISAs even after adsorption with SLO. Interestingly, rLLO- based ELISA detected antibodies against unadsorbed caprine sera even in those samples from which non-pathogenic Listeria spp. were isolated, whereas antibodies were not detected in LLO-2 peptide-based ELISA. In conclusion, it could be inferred that the synthetic LLO-2 peptide serves as a non- cross-reactive, ideal diagnostic antigen in serodiagnosis of capro-ovine listeriosis.

Development of the Com1 synthetic peptide-based Latex Agglutination Test (LAT) and its comparative evaluation with commercial indirect-ELISA for sero-screening of coxiellosis in cattle.

A novel Com1 synthetic peptide-based latex agglutination test (LAT) was developed and evaluated against commercial ELISA kit for sero-screening of coxiellosis in cattle. The developed test is economical, has field applicability and can serve as an important rapid tool for sero-screening of coxiellosis in cattle.

Virulence Potential, Biofilm Formation, and Antibiotic Susceptibility of Listeria monocytogenes Isolated from Cattle Housed in a Particular Gaushala (Cattle Shelter) and Organized Farm.

OBJECTIVES: The occurrence of Listeria monocytogenes was studied by using cultural and serological methods in cattle housed in a particular gaushala (cattle shelter) and organized dairy farm. MATERIALS AND METHODS: A total of 1201 samples from cattle comprising blood (n = 207), milk (n = 203), vaginal swabs (n = 210), and serum (n = 207) from an organized farm (n = 210) and blood (n = 100), milk (n = 74), vaginal swabs (n = 100), and serum (n = 100) from a gaushala (n = 100) were collected and analyzed for L. monocytogenes. All samples excluding serum were analyzed for isolation and identification of L. monocytogenes, while the serum samples were screened for seropositivity. The isolates were further subjected to assess their virulence potential (in vitro and in vivo), biofilm formation ability, and antibiotic susceptibility patterns. RESULTS: Four L. monocytogenes strains were isolated from the cattle; three (0.48%) from the organized farm and one (0.36%) from the gaushala. On serological screening of cattle from the organized dairy farm, 16.42% were found to be positive for antibodies against listeriolysin O, while cattle from the gaushala revealed 36% seropositivity. Furthermore, on characterization of the isolates for their pathogenic potential and biofilm-forming ability, all were found to be pathogenic by both in vitro and in vivo assays and were weak to moderate biofilm formers. The minimum inhibition concentration (MIC) of recovered isolates revealed resistance for ampicillin by two L. monocytogenes isolates (MIC >256 µg/mL), whereas three L. monocytogenes isolates were intermediately resistant (MIC >4 µg/mL) and one resistant against amoxicillin (MIC >8 µg/mL). However, all four isolates were susceptible to gentamicin, cotrimoxazole, and erythromycin. CONCLUSIONS: Isolation of virulent and antibiotic-resistant strains of L. monocytogenes warrants the need for epidemiological surveillance, antimicrobial susceptibility, and implementation of control measures to combat the occurrence of L. monocytogenes infection in animals as well as humans.