Deepthi Vijay

Antimicrobial effects of Lactobacillus plantarum and Lactobacillus acidophilus against multidrug-resistant enteroaggregative Escherichia coli

The in vitro and in vivo antimicrobial effects of Lactobacillus plantarum and Lactobacillus acidophilus were evaluated individually and synergistically against multidrug-resistant enteroaggregative Escherichia coli (MDR-EAEC). In vitro evaluation of each probiotic strain when co-cultured with MDR-EAEC isolates revealed a reduction in MDR-EAEC counts (eosin-methylene blue agar) in a dose- and time-dependent manner: probiotics at a dose rate of 10(10) CFU inhibited MDR-EAEC isolates at 72 h post-inoculation (PI), whereas at lower concentrations (10(8) and 10(9) CFU) MDR-EAEC isolates were inhibited at 96 h PI. The synergistic antimicrobial effect of both probiotic strains (each at 10(10) CFU) was highly significant (P < 0.01) and inhibited the growth of MDR-EAEC isolates at 24 h PI. For in vivo evaluation, weaned mice were fed orally with 10(7) CFU of MDR-EAEC. At Day 3 post-infection, treated mice were fed orally with the probiotic strains (each at 10(10) CFU). Compared with the control, post-treatment a significant (P < 0.01) reduction in MDR-EAEC counts was observed in faeces by Day 2 and in intestinal tissues of treated mice by Days 3 and 4 as evidenced by plate count (mean 2.71 log and 2.27 log, respectively) and real-time PCR (mean 1.62 log and 1.57 log, respectively) methods. Histopathologically, comparatively mild changes were observed in the ileum and colon from Days 3 to 5 post-treatment with probiotics; however, from Day 6 the changes were regenerative or normal. These observations suggest that these probiotic strains can serve as alternative therapeutics against MDR-EAEC-associated infections in humans and animals.

Genetic diversity, virulence potential and antimicrobial susceptibility of Listeria monocytogenes recovered from different sources in India

Listeria monocytogenes isolates (n = 36) recovered from human and animal clinical cases and foods from different geographical regions of India were characterized using multiplex PCR-based serotyping, pulsed field gel electrophoresis (PFGE), in vitro and in vivo pathogenicity tests and antibiogram profiling. Multiplex PCR-based serotyping distributed L. monocytogenes isolates into 3 serogroups, of which 91.67% belonged to 4b, 4d, 4e serogroup, followed by 5.56% to 1/2a, 3a and 2.78% to 1/2b, 3b serogroups. PFGE analysis using ApaI and AscI restriction enzymes revealed 17 pulsotypes among 36 L. monocytogenes isolates with 6 major clusters having similar fingerprint profile within their cluster and 11 unique fingerprint profiles. Interestingly, PFGE analysis inferred that foods of animal origin could be a significant source of infection for spread of listeriosis among human populations. Furthermore, on comparison of in vitro and in vivo pathogenicity tests, an overall good correlation was observed between hemolytic titer assay and chick embryo inoculation test as most of the isolates with a hemolytic titer of ≥ 16 were found to be lethal to chick embryo. All the isolates were found to be susceptible to tested antimicrobials except for one animal isolate which showed resistance towards co-trimoxazole.

Genetic diversity and antibiogram profile of diarrhoeagenic Escherichia coli pathotypes isolated from human, animal, foods and associated environmental sources

Introduction Infectious diarrhoea particularly due to pathogenic bacteria is a major health problem in developing countries, including India. Despite significant reports of diarrhoeagenic Escherichia coli (DEC) pathotypes around the globe, studies which address genetic relatedness, antibiogram profile and their correlation with respect to their isolation from different sources are sparse. The present study determines isolation and identification of DEC pathotypes from different sources, their genetic characterisation, antibiogram profile and their correlation if any. Materials and methods A total of 336 samples comprising diarrhoeic stool samples from infants (n=103), young animal (n=106), foods (n=68) and associated environmental sources (n=59) were collected from Bareilly region of India. All the samples were screened by using standard microbiological methods for the detection of E. coli. The identified E. coli were then confirmed as DEC pathotypes using polymerase chain reaction–based assays. Those DEC pathotypes identified as Enteroaggregative E. coli (EAEC) were further confirmed using HEp-2 adherence assay. All the isolated DEC pathotypes were studied for their genetic diversity using pulsed-field gel electrophoresis (PFGE), and antimicrobial susceptibility testing was performed by using disc diffusion method as per Clinical Laboratory Standards Institute guidelines. Results and discussion Of the four DEC pathotypes investigated, EAEC was found to be the predominant pathogen with an isolation rate of 16.5% from infants, 17.9% from young animals, 16.2% from foods and 3.4% from the associated environmental sources. These EAEC isolates, on further characterisation, revealed predominance of ‘atypical’ EAEC, with an isolation rate of 10.7% from infants, 15.1% from young animals, 16.2% from foods, and 3.4% from the associated environmental sources. On PFGE analysis, discrimination was evident within DEC pathotypes as 52 unique pulsotypes were observed for 59 recovered DEC pathotypes. However, a few EAEC isolates were found to be clonal (clusters A, B, C, D, F, G, and H) irrespective of their source of isolation, suggests sharing and/or circulation among different sources. Further, a high antibiotic resistance pattern was observed among isolated DEC pathotypes as almost 86.4% of isolates were found to be resistant against ≥3 tested drugs.

Isolation, Genotyping and Antibiogram Profile of Clostridium perfringens Isolates Recovered from Freshwater Fish and Fish Products from Kolkata Region

1Division of Veterinary Public Health, ICAR-Indian Veterinary Research Institute, Izatnagar-243122, India. 2Veterinary Public Health Laboratory, ICAR-Indian Veterinary Research Institute, Belgachia road, Kolkata 700 037, India. 3Department of Veterinary Public Health, College of Veterinary and Animal Sciences, Mannuthy, Kerala 680 651, India. 4Division of Livestock Products Technology, ICAR-Indian Veterinary Research Institute,Izatnagar-243122, India. 5Division of Pathology, ICAR-Indian Veterinary Research Institute, Izatnagar 243 122, India.