Center for Meat Safety & Quality, Department of Animal Sciences, Colorado State University, Fort Collins, CO 80523-1171, USA.
Food Microbiol. 2013 Dec;36(2):260-6. doi: 10.1016/j.fm.2013.06.005. Epub 2013 Jun 19.
This study compared lactic acid resistance of individual strains of wild-type and rifampicin-resistant non-O157 Shiga toxin-producing Escherichia coli (STEC) and of susceptible and multidrug-resistant (MDR) and/or MDR with acquired ampC gene (MDR-AmpC) Salmonella against E. coli O157:H7. After inoculation of sterile 10% beef homogenate, lactic acid was added to a target concentration of 5%. Before acid addition (control), after acid addition (within 2 s, i.e. time-0), and 2, 4, 6 and 8 min after addition of acid, aliquots were removed, neutralized, and analyzed for survivors. Of wild-type and of rifampicin-resistant non-O157 STEC strains, irrespective of serogroup, 85.7% (30 out of 35 strains) and 82.9% (29 out of 35 strains), respectively, reached the detection limit within 0-6 min. Of Salmonella strains, 87.9% (29 out of 33 isolates) reached the detection limit within 0-4 min, irrespective of antibiotic resistance phenotype. Analysis of non-log-linear microbial survivor curves indicated that non-O157 STEC serogroups and MDR and susceptible Salmonella strains required less time for 4D-reduction compared to E. coli O157:H7. Overall, for nearly all strains and time intervals, individual strains of wild-type and rifampicin-resistant non-O157 STEC and Salmonella were less (P < 0.05) acid tolerant than E. coli O157:H7.
本研究比较了野生型和利福平耐药非-O157 产志贺毒素大肠杆菌（STEC）以及敏感和多药耐药（MDR）和/或获得性 AmpC 基因（MDR-AmpC）沙门氏菌的乳酸耐受力，与 E. coli O157:H7 相比。在无菌 10%牛肉匀浆接种后，将乳酸添加到目标浓度为 5%。在添加酸之前（对照）、添加酸后（2 秒内，即时间 0）以及添加酸后 2、4、6 和 8 分钟时，取出等分试样，中和并分析存活者。野生型和利福平耐药非-O157 STEC 菌株，无论血清型如何，分别有 85.7%（30/35 株）和 82.9%（29/35 株）在 0-6 分钟内达到检测限。对于沙门氏菌菌株，87.9%（29/33 株）在 0-4 分钟内达到检测限，无论抗生素耐药表型如何。非对数线性微生物存活曲线分析表明，与 E. coli O157:H7 相比，非-O157 STEC 血清型和 MDR 和敏感沙门氏菌菌株需要更少的时间进行 4D 减少。总体而言，对于几乎所有菌株和时间间隔，野生型和利福平耐药非-O157 STEC 和沙门氏菌的单个菌株比 E. coli O157:H7 更不耐酸（P<0.05）。
