Presence & mobility of antimicrobial resistance in Gram-negative bacteria from environmental samples in coastal Karnataka, India

To understand antimicrobial resistance (AMR) patterns and mechanisms of horizontal gene transfer in human-associated environments is essential to AMR surveillance. Gram-negative bacteria (1122 isolates) from food-animal environments were characterized for antimicrobial susceptibility and AMR genes. Seventy five per cent of the isolates (837 of 1122) were resistant to at least one of the antibiotics tested. Resistance to more than three groups of antimicrobials (multidrug resistance) was observed in 43 isolates with most often encountered (12 of 43) resistance to ?-lactams, tetracycline, quinolones and nitrofurantoin. The profile of frequently reported plasmid-mediated resistance gene in these isolates was determined. The mobility of these elements as plasmids or phages was examined. The blaCTX-M gene was present in the plasmid of 61 per cent and packed in induced phage fractions in 72 per cent of the isolates and blaTEMin 69 per cent phage fractions compared to 15 per cent presence in the plasmid.

Molecular prophage typing of Staphylococcus aureus isolates from bovine mastitis

Staphylococcus aureus is one of the major pathogens causing bovine mastitis and foodborne diseases associated with dairy products. To determine the genetic relationships between human and bovine or bovine isolates of S. aureus, various molecular methods have been used. Previously we developed an rpoB sequence typing (RSTing) method for molecular differentiation of S. aureus isolates and identification of RpoB-related antibiotic resistance. In this study, we performed spa typing and RSTing with 84 isolates from mastitic cows (22 farms, 72 cows, and 84 udders) and developed a molecular prophage typing (mPPTing) method for molecular epidemiological analysis of bovine mastitis. To compare the results, human isolates from patients (n = 14) and GenBank (n = 166) were used for real and in silico RSTing and mPPTing, respectively. Based on the results, RST10-2 and RST4-1 were the most common rpoB sequence types (RSTs) in cows and humans, respectively, and most isolates from cows and humans clearly differed. Antibiotic resistance-related RSTs were not detected in the cow isolates. A single dominant prophage type and gradual evolution through prophage acquisition were apparent in most of the tested farms. Thus, RSTing and mPPTing are informative, simple, and economic methods for molecular epidemiological analysis of S. aureus infections.

The structure characteristics of prophages of foodborne Enterococcus hirae R17 and their interaction relationships with host bacterium / 中国食品卫生杂志

Objective This study was to understand the structure characteristics of prophages in the genome of Enterococcus hirae R17,and also to analyze their interaction relationships with the host bacterium.Methods The gene distribution and gene encoding characteristics of prophages in the genome of Enterococcus hirae R17 were identified using the PHAST software.The virulence gene,antimicrobial resistance genes,and environmental resistance genes in the prophages were also analyzed.Results Three prophages were found on the chromosome of Enterococcus hirae,including two incomplete prophage elements (Prophage-1 and Prophage-2) and one complete prophage (Prophage-3).Some function genes of bacteria were found in the sequence of three prophages,including nucleotide transportation and metabolism related genes.One incomplete prophage carrying erythromycin-and bacitracin-resistance genes was identified in the plasmid,which suggested that prophage induced gene horizontal transfer caused erythromycin-and bacitracin-resistance of Enterococcus hirae R17.Conclusion This study laid a solid foundation for the diversity analysis of prophages of Enterococcus hirae.Prophages played an important role in promotion of antimicrobial resistance of enterococci.Scientists should pay more attention to the spread of antimicrobial resistance and pathogenicity induced by prophages.

Study on the integration site and arrangement of SfII and SfX prophages in Shigella flexneri serotype 2b strains / 中华流行病学杂志

Objective To study the integration site and arrangement of SfII and SfX prophages in Shigella flexneri serotype 2b strains. Methods A series of primers were designed based on potential integration site of SfII and SfX prophages in Shigella flexneri serotype 2b strains, and PCR were performed for 50 serotype 2b strains to amplify special genes located in host and prophages. PCR products were sequenced to identify integration sites and arrangement of SfII and SfX. Results In all the serotype 2b strains, prophage SfII and SfX were adjacent to each other, and integrated into the thrW tRNA gene of the host, which were located between genes proA and yaiC of host. Prophage SfX was located immediately upstream of prophage SfII in all the detected 50 serotype 2b strains exception for strain 51251. Conclusion This was the first report on the integration site and arrangement of serotype-converting prophages SfII and SfX in Shigella flexneri 2b strains.

Prophages / 微生物学通报

It is common in bacterial genomes of the integration of prophages. As an important participant of the vital movement of their hosts, prophages affect closely the biological properties of the hosts. Therefore, if we want to comprehend a bacterial genome fully, it is essential to recognize and understand accurately prophages in it. This article is a compendious review about the classification, distribution, identification, evolution of prophages and the interaction with their hosts.