Antimicrobial Susceptibility and Biofilm Production by Salmonella sp. Strains Isolated from Frozen Poultry Carcasses

ABSTRACT The objectives of this study were to evaluate the antimicrobial resistance and the biofilm-producing ability of Salmonella sp. strains isolated from frozen poultry carcasses. Antimicrobial susceptibility was tested by the disk-diffusion method. Biofilm-producing ability was determined in 96-well polystyrene microplates stained with crystal violet at 1%. Out of the 22 strains tested, all were multiresistant, that is, resistant to more than three antimicrobial classes, and 72.7% were able to form biofilms. The highest resistance rates obtained were against sulfonamides, tetracycline, and quinolones. On the other hand, 100% of the strains were sensitive to chloramphenicol. According to the rate of biofilm formation, 3 (13.6%) and 13 (59.1%) strains were classified as moderate and weak biofilm-producers, respectively, and 27.3% did not form biofilms. Biofilms increase the tolerance of microorganisms to stress, reducing their sensitivity to disinfectants and antimicrobials; favor equipment corrosion; and act as substrates for the adhesion of bacteria with lower biofilm-producing capacity. The results of the present study stress the importance of cleaning procedures in food processing plants and highlight the public health risks related to the emergence of multiresistant strains.

摘要 本研究旨在评估从冷冻家禽胴体中分离的沙门氏菌（Salmonella sp.）菌株的抗菌耐药性及其生物膜形成能力。采用纸片扩散法（disk-diffusion method）开展抗菌药敏试验。生物膜形成能力通过1%结晶紫（crystal violet）染色的96孔聚苯乙烯微孔板（96-well polystyrene microplates）进行检测。受试的22株菌株全部为多重耐药（multiresistant）菌株，即对三类及以上抗菌药物类别存在耐药性，其中72.7%的菌株可形成生物膜。本研究检出的最高耐药率对应药物为磺胺类（sulfonamides）、四环素（tetracycline）及喹诺酮类（quinolones）；与之相对，所有受试菌株均对氯霉素（chloramphenicol）敏感。根据生物膜形成率，3株（13.6%）、13株（59.1%）菌株分别被归类为中等强度生物膜形成菌与弱生物膜形成菌，剩余27.3%的菌株无法形成生物膜。生物膜可提升微生物的应激耐受能力，降低其对消毒剂与抗菌药物的敏感性，加剧设备腐蚀，并可作为底物供生物膜形成能力较弱的细菌黏附。本研究结果强调了食品加工厂清洁流程的重要性，并凸显了多重耐药菌株出现所带来的公共卫生风险。