Use of multiple‐locus variable‐number of tandem repeats analysis (MLVA) to investigate genetic diversity of Salmonella enterica subsp. enterica serovar Typhimurium isolates from human, food, and veterinary sources

Abstract

Salmonella enterica subspecies enterica serovar Typhimurium is the most common zoonotic pathogen in Bulgaria. To allow efficient outbreak investigations and surveillance in the food chain, accurate and discriminatory methods for typing are needed. This study evaluated the use of multiple‐locus variable‐number of tandem repeats analysis (MLVA) and compared results with antimicrobial resistance (AMR) determinations for 100 S. Typhimurium strains isolated in Bulgaria during 2008–2012 (50 veterinary/food and 50 human isolates). Results showed that isolates were divided into 80 and 34 groups using MLVA and AMR, respectively. Simpson's index of diversity was determined to 0.994 ± 0.003 and 0.945 ± 0.012. The most frequently encountered MLVA profiles were 3‐11‐9‐NA‐211 (n = 5); 3‐12‐9‐NA‐211 (n = 3); 3‐12‐11‐21‐311 (n = 3); 3‐17‐10‐NA‐311 (n = 3); 2‐20‐9‐7‐212 (n = 3); and 2‐23‐NA‐NA‐111 (n = 3). No clustering of isolates related to susceptibility/resistance to antimicrobials, source of isolation, or year of isolation was observed. Some MLVA types were found in both human and veterinary/food isolates, indicating a possible route of transmission. A majority (83%) of the isolates were found to be resistant against at least one antimicrobial and 44% against ≥4 antimicrobials. Further studies are needed to verify MLVA usefulness over a longer period of time and with more isolates, including outbreak strains.

Antimicrobial susceptibility and MLVA analysis of S. Typhimurium strains isolated from human and poultry samples in Tunisia

“…On the other hand, STTR10 and ST8 locus were absent in many strains (46.6% and 48.8%, respectively). Our results were in concordance with results obtained by other authors, as it has been described how STTR10 is the locus with the highest percentage of absence, but also ST8 has been shown to be absent in many strains [33,37]. In our study, 33.3% of S. Typhimurium isolates were dominated by 7 frequent MLVA profiles.…”

“…In this work, some identical MLVA types were found in both human and poultry isolates, indicating a possible route of transmission [37]. The study of the most frequent alleles obtained from the isolates of the different origins and the higher discriminatory index (DI), showed that ST6 was the loci with highest discriminatory index, and it may be of potential use for source attribution.…”

“…However, the resistance to nalidixic acid was higher among poultry isolates, this can be explained by the wide utility of quinolones in veterinary practice [33,37]. It is known that the increase of nalidixic acid resistance, in some way, may reflect the emergence of fluoroquinolone resistance [38].…”

Antibiotic Resistance in Salmonella Typhimurium Isolates Recovered From the Food Chain Through National Antimicrobial Resistance Monitoring System Between 1996 and 2016

“…Typhimurium isolates obtained from humans than from non-human isolates. The ACSSuT is the typical resistance pattern factors of the DT104 (Adhikari et al, 2010; Mateva et al, 2018). The MDR S .…”

In vitro efficacy and pharmacodynamic profiles of four polyether ionophores against methicillin‐resistant Staphylococcus spp.

“…The differences in antimicrobial usage in humans and animals have resulted in different susceptibility profiles being observed in isolates of the same species depending on the host (Mateva et al., 2018; McManus et al., 2015). This was not found to occur for any of the ionophores tested against a range of MRSA isolates of human and veterinary origin.…”