Background:The development of antimicrobial resistance in bacteria is a serious public health issue worldwide. Salmonella spp. is considered a leader cause of gastrointestinal disease in animals and humans, and poultry products have been reported as an important reservoir of the bacterium. S. Heidelberg became lately one of the most prevalent serovars found in several countries. However, hardly any information is available about the epidemiology and the resistance profile of it. Therefore, the objective of this study was to determine the antibiotic resistance profile of S. Heidelberg (SH) and to compare to S. Enteritidis (SE) and S. Typhimurium (ST) isolated from the Southern part of Brazil. Materials, Methods & Results:A total of 162 Salmonella isolates of poultry origin serotyped as SH (54), SE (54), and ST (54) were submitted to the disk-diffusion test with disks containing 10 antibiotics of 7 different classes, routinely used in veterinary and human medicine such as: enrofloxacin, ciprofloxacin, norfloxacin, gentamicin, ceftiofur, ceftriaxone, nalidixic acid, tetracycline, sulfamethoxazole-trimethoprim, and chloramphenicol. In addition, the Multi-drug Resistance Pattern (MDRP) and the Multiple-Drug Resistance Index (MDRI) were determined. The Chi-square (χ 2 ) test with 1% of significance level was used to statistically evaluate the results. All isolates were susceptible to norfloxacin, enrofloxacin, and ciprofloxacin. The majority of the isolates were resistant to the quinolone class (68%), more specifically to nalidixic acid, which is considered a synthetic quinolone, followed by penicillin (47%) and cephalosporin (16%). Overall, SH isolates showed higher resistance compared to ST and SE (18,16.5, and 9.6%, respectively). SH isolated from field samples, mainly drag swabs, showed higher resistance levels (24.2%) than those isolated from slaughterhouses (5.6%). SH showed the highest percentage of resistance to ceftiofur (31.5%), ceftriaxone (9.3%), and tetracycline (64.8%) in comparison to the other two serotypes. Most of the SH isolates were resistant to at least two (66.7%), three or more antibiotics (33.3%). A different scenario was observed for ST and SE, where 25.9 and 9.3% were susceptible to at least one drug, respectively. The most common pattern of resistance (MDRP) was C (gentamicin -nalidixic acid -tetracycline) for 14 SH isolates, and A (ceftiofur -nalidixic acid -tetracycline) for 12 SH isolates. MDRI indicated that 22.8% of all isolates were multidrug resistant. SH was the isolate with the largest variety of resistance patterns compared to ST and SE, where 11.7% of the isolates were resistant to more than three antibiotics. In addition, SH showed the greatest MDRI (0.25) ranging from 0.2 to 0.5. Discussion: SH was resistant to almost all antibiotics tested and showed multi-drug resistant profile, therefores, it showed a potential for horizontal transmission of resistance genes. Additionally, SH showed a higher resistance profile for ceftiofur, an important antibiotic used in poultry, w...
Bacteria of the genus Salmonella may infect humans and domestic animals, causing a serious public health problem worldwide. Nowadays, Salmonella enterica serovar Heidelberg (SH) is among the top three serovars isolated from people with salmonellosis and it is present in the poultry production chain. Moreover, it seems to be more invasive than other serotypes that cause enteritis. The overall status of the antimicrobial resistant of Brazilian strains of SH is still unknow. The bacterium may use similar mechanisms of resistance to antibotics, as well as disinfectants such as the efflux system and enzymatic degradation of chemical compounds. Thus, the objective of this study was to identify the Minimal Inhibitory Concentration (MIC) for ceftiofur of SH isolated from different materials of poultry origin, as well as to verify the relation between antibiotic resistance and disinfectant resistance. In addition, the screening efflux system was performed, using ethidium bromide to determine the presence of this mechanism of resistance. MIC results indicated high levels of SH resistance to ceftiofur, indicating the need for alternative drugs to treat salmonellosis. The concentration of ceftiofur needed to eliminate SH resistant isolates were 32 times higher than the therapeutic dose. Regarding disinfectants, most of the disinfectants tested were efficient to eliminate SH, however one isolate was resistant to glutaraldehyde-quaternary ammonia. All isolates were negatives in the screening efflux system, which suggest a different mechanism of resistance. It is possible to conclude that SH shows a real threat to poultry production, and caution should be taken when choosing the right antibiotic and disinfectant against this serovar.
Salmonellosis is a disease caused by a bacterium Salmonella, a gram negative bacilli found in many environments, responsible for signifi cant economic losses in poultry, and of great impact on public health. Among more than 2500 serovars, S. Heidelberg seems to be more invasive causing disease of greater severity than other serovars. The objective of this study was to investigate, through real-time PCR (qPCR), differences in the expression of a virulent gene (invA) and an antibiotic resistance gene (blaCTXM-2) of S. Heidelberg isolated from poultry meat (slaughterhouses) and drag swabs (fi eld). Even though all isolates showed the presence of the invA gene, there were differences in the expression among the isolates, where isolates from the fi eld showed greater expression of invA compared to samples isolated from meat products. On the other hand, isolates from the slaughterhouses showed greater expression of the blaCTX-M2 than those isolated from fi eld samples.
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