We investigated the characteristics and persistence of Escherichia coli resistant to third-generation cephalosporins (3GCs) by early administration of ceftiofur or gentamicin and to analyze the impact of 3GC use in hatcheries. We studied 10 ceftiofur-treated flocks (CTFs) and 10 gentamicin-treated flocks (GTFs) of layers. Fecal samples were collected at 1, 2, 4, 8, 18, and 30 weeks of age for all flocks. Among the 446 E. coli isolates, 58 (29.0%) of 200 isolates in CTFs were identified as 3GC-resistant E. coli and 28 (11.4%) of 246 isolates in GTFs were identified as 3GC-resistant E. coli. The presence of 3GC-resistant E. coli isolates at 1, 2, and 4 weeks was significantly higher in CTFs than in GTFs (p < 0.05). Moreover, the rate of resistance to 3GCs gradually decreased from 83.3% at 1 week of age to 4.4% at 30 weeks of age in CTFs. Of the 86 3GC-resistant E. coli isolates, 32 isolates had β-lactamase-encoding gene: bla_CTX-M-14 (ten isolates), bla_CTX-M-15 (three isolates), bla_CMY-2 (five isolates), and bla_TEM-1 (twenty-five isolates) genes. Plasmid replicon typing revealed that bla_CTX-M-14, bla_CTX-M-15, bla_CMY-2, and bla_TEM-1 were located on F, F and FIB, I1 and K, and I1 and FII, respectively. Furthermore, 18 isolates carried class 1 integrons, with four different gene cassettes. These results revealed that ceftiofur used in hatcheries can lead to an increase in the number of 3GC-resistant E. coli with many characteristics. A voluntary ban must be imposed on the use of 3GCs for 1-day-old chicks in poultry industry.

我们通过对头孢噻呋或庆大霉素的早期给药研究了对第三代头孢菌素（3GC）耐药的大肠杆菌的特征和持久性，并分析了在孵化场中使用3GC的影响。我们研究了10头孢噻呋处理的羊群（CTF）和10庆大霉素处理的羊群（GTF）。在1、2、4、8、18和30周龄时收集所有鸡群的粪便样本。在446株大肠杆菌中，CTF中200株分离株中有58（29.0％）被鉴定为3GC耐药性大肠杆菌，在GTF中246株中28（11.4％）被鉴定为3GC耐药性大肠杆菌。在1、2和4周时，对3GC耐药的大肠杆菌分离物在CTF中的存在明显高于在GTF中（p  ＜0.05）。此外，CTF对3GC的耐药率从1周龄的83.3％逐渐降低到30周龄的4.4％。在86株抗3GC的大肠杆菌中，有32种具有β-内酰胺酶编码基因：bla _CTX-M-14（十株），bla _CTX-M-15（三株），bla _CMY-2（五株） ）和bla _TEM-1（25个分离株）基因。质粒复制子分型显示bla _CTX-M-14，bla _CTX-M-15，bla _CMY-2和bla _TEM-1分别位于F，F和FIB，I1和K以及I1和FII上。此外，带有四个不同基因盒的18个分离株带有1类整合素。这些结果表明，用于孵化场的头孢噻呋可导致具有许多特征的对3GC耐药的大肠杆菌的数量增加。必须对家禽业中的1日龄雏鸡强制禁止使用3GC。