Outer membrane vesicles as nanovaccine candidates against pathogenic Leptospira in experimental Guinea pig model.

Leptospira interrogans serovar Hardjo is a long slender bacterium of size 0.1-0.3 µm × 5-50 µm. It is one of the major causes of bovine leptospirosis and is of economical importance because of the reproductive failure, still birth, abortion, and reduced productivity in cattle. It is also a zoonotic disease-causing infection in humans characterized by headaches, fever, chills, sweats and myalgia, lethargy, aching joints, pulmonary haemorrhages, and death in severe cases. Control of the disease involves antibiotic therapy, management and vaccination, of which immunization is the cheapest and effective means of disease prevention. The present study was developed to isolate and characterize the outer membrane vesicles of Leptospira interrogans serovar Hardjo and to evaluate their vaccine potential in guinea pig model. The OMVs were isolated from the culture by sonication and ultracentrifugation. In transmission electron microscopy, the isolated OMVs appeared as small spherical structures of 50-200 nm size. In Western blot and indirect ELISA, antibodies specific to OMVs were observed as indicative of a good humoral immune response elicited by L. interrogans serovar Hardjo OMV. The OMV-based Leptospira vaccine was able to prevent kidney lesions and renal colonization compared to the control and bacterin vaccinated group as proven by histopathology and PCR.

Isolation and characterization of bacteriophage Ib_pec2 against shigatoxigenic Escherichia coli.

This study was aimed to isolate and characterize bacteriophage against drug-resistant, shigatoxigenic Escherichia coli (STEC), one of the zoonotic, food-borne organisms associated with ruminants, mainly cattle. STEC were isolated (n = 35) from neonatal calves, dairy workers, and the surrounding environment and their antimicrobial resistance pattern was studied. Out of the 35 isolates tested, 17 isolates were found to be multidrug resistant to important antibiotics like ampicillin, amoxicillin-clavulanate, ciprofloxacin, streptomycin, and tetracycline. Bacteriophage namely Ib_pec2 was isolated against one of the STEC isolates and its morphology, genetic and proteomic characterization was done. Morphological analysis by TEM revealed bacteriophages belonging to myoviridae family. The genetic characterization of g23 gene revealed that the bacteriophage belonged to Tequatrovirus of myoviridae family. Proteomic analysis was able to identify five proteins identical to Tequatrovirus of myoviridae family. One-step growth curve experiment revealed a latency period of 40 min and a burst size of 893 pfu/bacteria. Temperature and pH ranging from 40°C to 50°C, pH 6-8, respectively. Phage could able to lyse majority of the STEC isolates. STEC are commensal organisms in the gastrointestinal tract of ruminants but are pathogenic in humans. Bacteriophages can be used as alternatives to antibiotics to control bacterial growth in ruminants and prevent its further spillage in the environment.