Levent Gizem, Schlochtermeier Ashlynn, Vinasco Javier, Jennings Jenny, Richeson John, Ives Samuel E, Norman Keri N, Lawhon Sara D, Loneragan Guy H, Scott H Morgan
Department of Veterinary Pathobiology, Texas A&M University, College Station, TX 77845, USA.
School of Veterinary Medicine, Texas Tech University, Amarillo, TX 79106, USA.
Microorganisms. 2022 Oct 20;10(10):2071. doi: 10.3390/microorganisms10102071.
Extended-spectrum-β-lactamase (ESBL) and AmpC-lactamase-producing Enterobacteriaceae are serious public health threats. Due to an increasing number of reports of ESBL and AmpC producing Escherichia coli in agricultural settings, it is critical to understand the relationship between the use of two of the highest priority critically important human antibiotics (e.g., third generation cephalosporins [3GC] and macrolides) in food animals and their potential contribution to the selection of ESBL/AmpC E. coli. The objective of our randomized controlled feedlot trial was to measure the effects of ceftiofur crystalline-free acid and tulathromycin on 3GC resistant fecal E. coli populations in cattle before and at various time points after treatment up to and including at slaughter. Multi-level mixed-effects linear regression showed no effect of ceftiofur and tulathromycin on 3GC E. coli CFU counts at slaughter (Day 99); however, a significant (p < 0.05) population shift was observed from susceptible to 3GC resistant E. coli immediately after ceftiofur administration (Day 7). Among 799 fecal samples screened using selective media, 17.7% were ESBL/AmpC E. coli positive, which were further tested for phenotypic antibiotic susceptibility. The majority of the isolates from these plates were multidrug-resistant (94.3%) and expressed either AmpC (78.1%) or ESBL (28.1%) phenotype. A subset of isolates was whole-genome sequenced (n = 20) and identified to harbor chromosomal and/or plasmidal bla genes such as CMY-2, CTX-M, and TEM. Our findings show a time-dependent selection of antibiotics on 3GC-resistant E. coli. High prevalence of multidrug-resistant ESBL/AmpC E. coli found in cattle feces highlights the importance of prudent use of antibiotics in livestock.
产超广谱β-内酰胺酶（ESBL）和AmpCβ-内酰胺酶的肠杆菌科细菌对公众健康构成严重威胁。由于农业环境中产ESBL和AmpC的大肠杆菌报告数量不断增加，了解食用动物中两种最重要的人类关键抗生素（如第三代头孢菌素[3GC]和大环内酯类）的使用与它们对ESBL/AmpC大肠杆菌选择的潜在贡献之间的关系至关重要。我们的随机对照饲养场试验的目的是测量头孢噻呋晶体游离酸和泰拉霉素在治疗前以及治疗后直至包括屠宰在内的不同时间点对牛粪便中3GC耐药大肠杆菌菌群的影响。多级混合效应线性回归显示，头孢噻呋和泰拉霉素对屠宰时（第99天）的3GC大肠杆菌菌落形成单位计数没有影响；然而，在头孢噻呋给药后立即（第7天）观察到从敏感大肠杆菌到3GC耐药大肠杆菌的显著（p<0.05）菌群转变。在使用选择性培养基筛选的799份粪便样本中，17.7%的样本ESBL/AmpC大肠杆菌呈阳性，对其进一步进行表型抗生素敏感性测试。这些平板上的大多数分离株具有多重耐药性（94.3%），并表现出AmpC（78.1%）或ESBL（28.1%）表型。对一部分分离株进行了全基因组测序（n=20），并鉴定出其携带染色体和/或质粒bla基因，如CMY-2、CTX-M和TEM。我们的研究结果表明抗生素对3GC耐药大肠杆菌具有时间依赖性选择作用。在牛粪中发现的多重耐药ESBL/AmpC大肠杆菌的高流行率凸显了在牲畜中谨慎使用抗生素的重要性。
