Characteristics of Quinolone Resistance in Salmonella spp. Isolates from the Food Chain in Brazil

Abstract

Salmonella spp. is an important zoonotic pathogen related to foodborne diseases. Despite that quinolones/fluoroquinolones are considered a relevant therapeutic strategy against resistant isolates, the increase in antimicrobial resistance is an additional difficulty in controlling bacterial infections caused by Salmonella spp. Thus, the acquisition of resistance to quinolones in Salmonella spp. is worrisome to the scientific community along with the possibility of transmission of resistance through plasmids. This study investigated the prevalence of plasmid-mediated quinolone resistance (PMQR) in Salmonella spp. and its association with fluoroquinolone susceptibility in Brazil. We evaluated 129 isolates, 39 originated from food of animal sources, and 14 from environmental samples and including 9 from animals and 67 from humans, which were referred to the National Reference Laboratory of Enteric Diseases (NRLEB/IOC/RJ) between 2009 and 2013. These samples showed a profile of resistance for the tested quinolones/fluoroquinolones. A total of 33 serotypes were identified; S. Typhimurium (63) was the most prevalent followed by S. Enteritidis (25). The disk diffusion test showed 48.8% resistance to enrofloxacin, 42.6% to ciprofloxacin, 39.53% to ofloxacin, and 30.2% to levofloxacin. According to the broth microdilution test, the resistance percentages were: 96.1% to nalidixic acid, 64.3% to enrofloxacin, 56.6% to ciprofloxacin, 34.1% to ofloxacin, and 30.2% to levofloxacin. Qnr genes were found in 15 isolates (8 qnrS, 6 qnrB, and 1 qnrD), and the aac(6′)-Ib gene in 23. The integron gene was detected in 67 isolates with the variable region between ±600 and 1000 bp. The increased detection of PMQR in Salmonella spp. is a serious problem in Public Health and must constantly be monitored. Pulsed-field gel electrophoresis was performed to evaluated clonal profile among the most prevalent serovars resistant to different classes of quinolones. A total of 33 pulsotypes of S. Typhimurium were identified with a low percentage of genetic similarity (≤65%). This result demonstrates the presence of high diversity in the resistant clones evaluated in this study.

Molecular Survey of Quinolone Resistance in Salmonella spp. Isolated From Poultry Products in Karaj, Iran

“…3 On the other hand, in the last 60 years, the increase of antimicrobial resistance has resulted in many difficulties in controlling the infections caused by Salmonella spp. 9 Therefore, the current study aimed to determine the frequency of Salmonella serotypes contamination in poultry products and qnr genes in Salmonella contaminated samples in Karaj, Iran.…”

“…2 High frequency of Salmonella contamination in some of the above-mentioned surveys could be due to the common source of contamination, namely, the epizootic outbreak of salmonellosis at sampling time in the farms, as well as the high sensitivity of molecular techniques compared to culture-based methods. In addition, Pirbul et al evaluated 129 isolates including those originated from the food of the animal sources (n = 39), environmental sources (14), as well as those from animals (9), and humans (67), namely, qnrS 53.33% (8/15), qnrB 40% (6/15), and qnrD 6.66%, (1/15). 9 A total of 90 samples including 60 raw chicken meat (i.e., drumstick = 20, breast = 24, and liver = 16) and 30 egg samples were collected for the purpose of the study.…”

“…In addition, Pirbul et al evaluated 129 isolates including those originated from the food of the animal sources (n = 39), environmental sources (14), as well as those from animals (9), and humans (67), namely, qnrS 53.33% (8/15), qnrB 40% (6/15), and qnrD 6.66%, (1/15). 9 A total of 90 samples including 60 raw chicken meat (i.e., drumstick = 20, breast = 24, and liver = 16) and 30 egg samples were collected for the purpose of the study. None of the 30 egg yolk samples demonstrated bacterial growth in the culture media.…”

“…However, the situation changed with the discovery of a variety of determinants related to the plasmidmediated quinolone resistance (PMQR). 5,9 Currently, three mechanisms are recognized as PMQRs. The qnr genes with five different qnr families each with different numbers of alleles "(i.e., qnrA1-7, qnrS1-4, qnrB1-31, qnrC, and qnrD)", "a modified aminoglycoside acetyltransferase gene (aac(6′)-1b-cr)", and a specific quinolone efflux pump (qepA) and multidrug resistance pumps including oqxAB.…”

“…However, the ability to highlight pre-existing resistance mechanisms such as chromosomal mutations in the target regions of the quinolones that still allow the selection of resistant mutants to quinolone concentrations (therapeutic doses) emphasize the importance of studying these genes. 9 Infections resulting from resistant strains may compromise treatment outcomes thus result in increased morbidity and mortality. 13 Therefore, to protect the public health, continuous monitoring and surveillance systems are necessary in order to prevent the spread of PMQR genes among Salmonella spp.…”