Perfil de resistência a antimicrobianos e avaliação da presença de grupos clonais em isolados de Salmonella Bredeney de linfonodos submandibulares de suínos e matéria-prima para fabricação de embutidos / Antimicrobial resistance profile and assessment of clonal groups in Salmonella Bredeney isolated from pig submandibular lymph nodes and minced meat for sausage production

ABSTRACT

Background: Salmonella is an important agent of the foodborne disease and can be vehiculated by products of animal origin. In recent years, the risk that pathogenic bacteria resistant to antimicrobial enter the food production chain and be transmitted to consumer is a growing concern. Salmonella Bredeney is one of the most prevalent serovar isolated from lymph nodes of slaughter pigs, and the contamination of pork with this serovar has been reported. Therefore, the purpose of this study was to determine the resistance profile and clonality of Salmonella Bredeney isolates from submandibular lymph nodes and minced meat originated from common slaughter pig batches. Materials, Methods & Results: Fifty three isolates of Salmonella enterica serovar Bredeney from submandibular lymph nodes (n = 14) and minced meat used for fresh sausage production (n = 39) originated from five slaughter batch were evaluated. Antimicrobial resistance was determined by the agar disk diffusion tests using disks with the following antimicrobials nalidixic acid (Na, 30 µg), ciprofloxacin (Cip, 5 µg), gentamicin (Cn, 10 µg), sulphonamide (S3, 300 µg) and tetracycline (Te, 30µg). Later on, isolates that presented the most common resistance profile were submitted to Xba I macrorestrition and analyzed by pulsed-field gel electrophoresis (PFGE). Among the S. Bredeney isolates, 40 (75.5%) were resistant to at least one of the tested antimicrobials. Resistance against tetracycline was the most frequent (32 isolates, 61.5%), followed by resistance to sulphonamide (n = 21, 39.6%), gentamicin (n = 5, 9.4%) and nalidixic acid (n = 3, 5.6%). All strains were susceptible to ciprofloxacin. The profile resistance to tetracycline-sulphonamide (TeS3) was detected in 16 isolates from minced meat and two isolated from lymph nodes. PFGE analysis of these isolates showed six different pulsotypes. The pulsotypeA1 was the most frequent among the isolates, and pulsotype A2 was present in isolates from submandibular lymph nodes and minced meat originated from a common slaughter batch. Discussion: The analyzed isolated of Salmonella Bredeney showed lower multiresistance frequency when compared with previous reports. Resistance to tetracycline and sulphonamide were the most prevalent in line with other studies conducted with porcine Salmonella isolates. Overall, the resistance pattern TeS3 was the most common among the isolates, and was present in 16 isolates from minced meat and in two isolates from submandibular lymph nodes. This pattern is possibly related to the frequent prophylactic and therapeutic use of these antimicrobials in pigs. Strains presenting the resistance pattern TeS3 showed a high diversity of XbaI-pulsotypes. Nonetheless, it was possible to identify a common pulsotype between strains from lymph nodes and minced meat. Fresh pork sausage is not submitted to a thermal treatment step in its manufacturing process. Moreover, the survival of Salmonella strains at the refrigeration temperatures used during the shelf life of fresh pork sausages has been reported. In spite of the fact that pork sausages are mainly consumed after cooking, the hazard of cross-contamination during preparation and the insufficient thermal treatment leading to Salmonella-transmission to consumers, still remains. It leads to the conclusion that resistant Salmonella strains originated from slaughter pig can be present in pork products consumed by the population.(AU)