Zhou Yu, Zhu Xuhui, Hou Hongyan, Lu Yanfang, Yu Jing, Mao Lie, Mao Liyan, Sun Ziyong
Department of Laboratory Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, No. 1095 Jiefang Road, Wuhan, 430030, China.
BMC Infect Dis. 2018 Feb 1;18(1):63. doi: 10.1186/s12879-017-2936-1.
Diarrhea is the leading infectious cause of childhood morbidity and mortality. Among bacterial agents, diarrheagenic Escherichia coli (DEC) is the major causal agent of childhood diarrhea in developing countries, particularly in children under the age of 5 years. Here, we performed a hospital-based prospective study to explore the pathotype distribution, epidemiological characteristics and antibiotic resistance patterns of DEC from < 5-year-old diarrheal children.
Between August 2015 and September 2016, 684 stool samples were collected from children (< 5 years old) with acute diarrhea. All samples were cultured and identified by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) and biochemical tests. PCR was used for subtyping, and enteropathogenic E. coli (EPEC) isolates were identified simultaneously with serology. Furthermore, antimicrobial sensitivity tests and sequencing of antibiotic resistance-related genes were conducted.
DEC strains were identified in 7.9% of the 684 stool samples. Among them, the most commonly detected pathotype was EPEC (50.0% of DEC), of which 77.8% were classified as atypical EPEC (aEPEC). Age and seasonal distribution revealed that DEC tended to infect younger children and to occur in summer/autumn periods. Multidrug-resistant DEC isolates were 66.7%; resistance rates to ampicillin, co-trimoxazole, cefazolin, cefuroxime, cefotaxime, and ciprofloxacin were ≥ 50%. Among 5 carbapenem-resistant DEC, 60.0% were positive for carbapenemase genes (2 blaNDM-1 and 1 blaKPC-2). Among 30 cephalosporin-resistant DEC, 93.3% were positive for extended-spectrum β-lactamase (ESBL) genes, with blaTEM-1 and blaCTX-M-55 being the most common types. However, no gyrA or gyrB genes were detected in 16 quinolone-resistant isolates. Notably, aEPEC, which has not received much attention before, also exhibited high rates of drug resistance (81.0%, 66.7%, and 14.3% for ampicillin, co-trimoxazole , and carbapenem resistance, respectively).
EPEC was the most frequent DEC pathotype in acute diarrheal children, with aEPEC emerging as a dominant diarrheal agent in central China. Most DEC strains were multidrug-resistant, making even ciprofloxacin unsuitable for empiric treatment against DEC infection. Among carbapenem-resistant DEC strains, those harboring blaNDM-1 and blaKPC-2 were the main causal agents. blaTEM-1 and blaCTX-M-55 were the major genetic determinants associated with high levels of cephalosporin resistance.
腹泻是儿童发病和死亡的主要感染性原因。在细菌病原体中，致泻性大肠杆菌（DEC）是发展中国家儿童腹泻的主要病因，尤其是5岁以下儿童。在此，我们进行了一项基于医院的前瞻性研究，以探讨5岁以下腹泻儿童中DEC的致病型分布、流行病学特征和抗生素耐药模式。
2015年8月至2016年9月期间，收集了684例急性腹泻儿童（<5岁）的粪便样本。所有样本均通过基质辅助激光解吸电离飞行时间质谱（MALDI-TOF MS）和生化试验进行培养和鉴定。采用PCR进行亚型分析，同时通过血清学鉴定肠致病性大肠杆菌（EPEC）分离株。此外，还进行了抗菌药敏试验和抗生素耐药相关基因的测序。
在684份粪便样本中，7.9%鉴定出DEC菌株。其中，最常检测到的致病型是EPEC（占DEC的50.0%），其中77.8%被归类为非典型EPEC（aEPEC）。年龄和季节分布显示，DEC倾向于感染年幼儿童，并在夏季/秋季出现。多重耐药的DEC分离株占66.7%；对氨苄西林、复方新诺明、头孢唑林、头孢呋辛、头孢噻肟和环丙沙星的耐药率≥50%。在5株耐碳青霉烯类DEC中，60.0%的碳青霉烯酶基因呈阳性（2株blaNDM-1和1株blaKPC-2）。在30株耐头孢菌素类DEC中，93.3%的超广谱β-内酰胺酶（ESBL）基因呈阳性，blaTEM-1和blaCTX-M-55是最常见的类型。然而，在16株喹诺酮耐药分离株中未检测到gyrA或gyrB基因。值得注意的是，以前未受到太多关注的aEPEC也表现出较高的耐药率（氨苄西林、复方新诺明和碳青霉烯类耐药率分别为81.0%、66.7%和14.3%）。
EPEC是急性腹泻儿童中最常见的DEC致病型，aEPEC成为中国中部地区主要的腹泻病原体。大多数DEC菌株具有多重耐药性，使得环丙沙星甚至也不适用于经验性治疗DEC感染。在耐碳青霉烯类DEC菌株中，携带blaNDM-1和blaKPC-2的菌株是主要病因。blaTEM-1和blaCTX-M-55是与高水平头孢菌素耐药相关的主要遗传决定因素。
