Faculty of Veterinary Medicine, Hawassa University, Hawassa, Ethiopia.
School of Animal and Range Sciences, Hawassa University, Hawassa, Ethiopia.
BMC Microbiol. 2022 Mar 31;22(1):84. doi: 10.1186/s12866-022-02504-2.
Salmonella is one of the foodborne pathogens affecting public health around the globe. A cross-sectional bacteriological study was conducted from December 2019 to November 2020. This study aimed to isolate, molecularly detect and determine antibiotic susceptibility patterns of Salmonella from raw cows' milk collected from dairy farms and households in Hawassa, Arsi Negele, and Dale districts.
A total of 384 raw milk samples were collected using a simple random sampling technique. Standard bacteriological and biochemical tests were used to isolate Salmonella. The positive samples were further confirmed by the molecular test. Kirby-Bauer disk diffusion method was used for antimicrobial susceptibility testing of Salmonella.
Using bacteriological and biochemical detection tests, Salmonella was isolated from 10.42% (N = 40) of the total sample. However, in molecular detection, only 32 of the 40 isolates were confirmed to be Salmonella using PCR test. The prevalence was 8.54, 12.69, and 10.46% in Hawassa, Dale, and Arsi Negele districts, respectively. Bacteriological prevalence did not vary significantly between the districts (P > 0.05). Likewise, no significant (P > 0.05) variation was observed in the Salmonella isolation rate between households (12.5%) and farms (8.33%) as well as between dry (8.85%) and wet (11.98%) seasons. Based on herd size, the isolation rate of Salmonella was significantly higher (P < 0.05) in large-scale farms (19.51%) than in small (5.1%) or medium (5.6%) scale dairy farms. The result of the antibiotic susceptibility test showed that Salmonella isolates were 100% resistant to ampicillin, while they were 100% sensitive to ciprofloxacin. Multi-drug resistance (MDR) was demonstrated in all isolates.
This study showed that Salmonella is widespread in the raw milk samples and developing MDR, which may be of public health concern in the study area. It is therefore important that dairy farmers and raw milk sellers in the study area take serious measures to avoid contamination of the milk with Salmonella spp. In addition, the active commitment of the animal health departments in the respective districts to sensitizing dairy farmers and the sensible use of antibiotics at the farm level can help to reduce the antibiotic resistance of Salmonella spp.
沙门氏菌是影响全球公共健康的食源性致病菌之一。本横断面细菌学研究于 2019 年 12 月至 2020 年 11 月进行。本研究旨在从豪萨、阿尔西内格尔和戴尔地区的奶牛场和家庭采集的生牛乳中分离、分子检测并确定沙门氏菌的抗生素药敏模式。
采用简单随机抽样技术采集了 384 份生牛乳样本。采用标准的细菌学和生化试验分离沙门氏菌。阳性样本通过分子试验进一步确认。采用 Kirby-Bauer 纸片扩散法进行沙门氏菌的药敏试验。
通过细菌学和生化检测试验，从 10.42%（N=40）的总样本中分离出沙门氏菌。然而，在分子检测中，只有 40 个分离株中的 32 个通过 PCR 试验确认为沙门氏菌。豪萨、戴尔和阿尔西内格尔地区的流行率分别为 8.54%、12.69%和 10.46%。各区之间的细菌学流行率无显著差异（P>0.05）。同样，家庭（12.5%）和农场（8.33%）之间以及干季（8.85%）和湿季（11.98%）之间的沙门氏菌分离率也没有显著差异（P>0.05）。根据畜群规模，沙门氏菌的分离率在大型农场（19.51%）显著高于小型（5.1%）或中型（5.6%）规模的奶牛场（P<0.05）。抗生素药敏试验结果显示，沙门氏菌分离株对氨苄西林的耐药率为 100%，对环丙沙星的耐药率为 100%。所有分离株均表现出多药耐药性（MDR）。
本研究表明，沙门氏菌广泛存在于生牛乳样本中，并表现出多药耐药性，这可能引起研究地区的公共卫生关注。因此，研究地区的奶牛场和生牛乳销售者应采取认真措施避免牛奶受到沙门氏菌污染。此外，各地区动物卫生部门积极致力于提高奶牛场主的意识，并在农场层面合理使用抗生素，有助于降低沙门氏菌的抗生素耐药性。
