Al-Marri Theeb, Al-Marri Abdulla, Al-Zanbaqi Reham, Ajmi Ahmad Al, Fayez Mahmoud
Al Ahsa Veterinary Diagnostic Laboratory, Ministry of Environment, Water and Agriculture, Al-Ahsa 31982, Saudi Arabia.
Veterinary Diagnostic Laboratory, Department of Animal Resources, Doha, Qatar.
Vet World. 2021 Nov;14(11):2869-2877. doi: 10.14202/vetworld.2021.2869-2877. Epub 2021 Nov 10.
Backyard chicken flocks have traditionally been regarded as an essential food source in developed countries; however, they may act as reservoirs and spread various zoonotic bacterial pathogens. This study was designed to investigate the prevalence, phenotypic resistance, biofilm formation (BF), and pathotypes of isolates from backyard poultry farms.
Cloacal swabs (n=150) and internal organs (n=150) were collected from 30 backyard chicken flocks; 20 of them were experiencing systemic infection, and the other ten were apparently healthy. Samples were bacteriologically examined for isolation. Isolates were identified biochemically by the VITEK 2 COMPACT system (BioMérieux, France). For molecular identification, was amplified and sequenced. Ten antimicrobials were selected for antimicrobial susceptibility testing. The minimum inhibitory concentration for each antimicrobial was determined. The extended-spectrum β-lactamase activity in isolates was investigated using cephalosporin/clavulanate combination disks. The ability of isolates for BF was determined by the microtiter plate method. Thirteen virulence genes linked to different pathotypes and two serotype-related genes were investigated by real-time polymerase chain reaction.
Eighty-six strains were isolated from 30 backyard chicken flocks. The isolates were biochemically identified to the species level. Genetically, sequences of the A gene showed >98% identity with in the National Center for Biological Information database. The frequency of isolation from diseased flocks was significantly higher (p<0.05) than apparently healthy flocks; 63.9% of the isolates were recovered from cloacal swabs and 36.04% were recovered from internal organs. isolates showed high resistance to ampicillin (AMP; 75.6%), gentamicin (39.5%), and tetracycline (29.1%). However, none of the isolates were resistant to imipenem. A variable drug resistance profile for isolates was reported. Twenty-one (24.4%) isolates were sensitive to all ten antimicrobials. Seven (8.1%) isolates were resistant only to AMP, and 28 (32.6%) were resistant to two antimicrobials, whereas the remaining 30 (34.9%) isolates showed multidrug resistance (MDR). Of the 86 isolates, 8 (9.3%) were confirmed as extended-spectrum β-lactamase (ESBL)-producing by the combination disk diffusion method. All ESBL isolates were MDR with an MDR index of 0.5-0.6. Fifty-seven (66.3%) isolates were capable of forming biofilms; 22 (25.6%) of them were strong biofilm producers, 24 (27.9%) moderate producers, and 11 (12.8%) weak producers. A statistically significant pairwise correlation was obtained for MDR versus BF (r=0.512) and MDR index versus BF (r=0.556). Based on virulence gene profiles, five pathotypes were identified, including enteropathogenic (39.5%), avian pathogenic (32.53%), enterohemorrhagic (EHEC; 9.3%), enterotoxigenic (ETEC; 5.8%), and enteroaggregative (EAEC; 1.2%). The lower frequency of EAEC and ETEC was statistically significant than other pathotypes. Three isolates were identified as O157 based on the detection of the gene.
This study reported a high prevalence of MDR, suggesting the misuse of antimicrobials in backyard chicken farms. The emergence of ESBL and EHEC isolates in backyard chickens is a public health concern. Furthermore, the backyard flocks environment may harbor different pathogenic bacteria that may enhance the persistence of infection and the transmission to in-contact humans. Regular monitoring for the occurrence of MDR and the zoonotic pathotypes among in backyard chicken flocks is recommended, as these bacteria can transmit to humans through food products or contaminated environments.
在发达国家，后院鸡群传统上被视为重要的食物来源；然而，它们可能成为各种人畜共患细菌病原体的宿主并传播这些病原体。本研究旨在调查来自后院家禽养殖场的分离株的流行情况、表型耐药性、生物膜形成（BF）及致病型。
从30个后院鸡群中采集泄殖腔拭子（n = 150）和内脏器官（n = 150）；其中20个鸡群正在经历全身感染，另外10个鸡群表面健康。对样本进行细菌学检查以进行分离。通过VITEK 2 COMPACT系统（法国生物梅里埃公司）对分离株进行生化鉴定。为进行分子鉴定，扩增并测序。选择10种抗菌药物进行抗菌药敏试验。确定每种抗菌药物的最低抑菌浓度。使用头孢菌素/克拉维酸组合纸片研究分离株中的超广谱β-内酰胺酶活性。通过微量滴定板法测定分离株形成BF的能力。通过实时聚合酶链反应研究与不同致病型相关的13个毒力基因和2个血清型相关基因。
从30个后院鸡群中分离出86株菌株。将分离株生化鉴定到种水平。在基因方面，A基因序列与美国国立生物技术信息中心数据库中的序列显示出> 98%的同一性。患病鸡群的分离频率显著高于（p < 0.05）表面健康鸡群；63.9%的分离株从泄殖腔拭子中分离得到，36.04%从内脏器官中分离得到。分离株对氨苄西林（AMP；75.6%）、庆大霉素（39.5%）和四环素（29.1%）表现出高耐药性。然而，没有分离株对亚胺培南耐药。报告了分离株的可变耐药谱。21株（24.4%）分离株对所有10种抗菌药物敏感。7株（8.1%）分离株仅对AMP耐药，28株（32.6%）对两种抗菌药物耐药，而其余30株（34.9%）分离株表现出多重耐药（MDR）。在86株分离株中，通过组合纸片扩散法确认8株（9.3%）为产超广谱β-内酰胺酶（ESBL）的菌株。所有ESBL分离株均为MDR，MDR指数为0.5 - 0.6。57株（66.3%）分离株能够形成生物膜；其中22株（25.6%）为强生物膜形成菌，24株（27.9%）为中度形成菌，11株（12.8%）为弱形成菌。MDR与BF（r = 0.512）以及MDR指数与BF（r = 0.556）之间获得了具有统计学意义的成对相关性。基于毒力基因谱，鉴定出5种致病型，包括肠致病性大肠杆菌（39.5%）、禽致病性大肠杆菌（32.53%）、肠出血性大肠杆菌（EHEC；9.3%）、产肠毒素性大肠杆菌（ETEC；5.8%）和肠聚集性大肠杆菌（EAEC；1.2%）。EAEC和ETEC的较低频率在统计学上显著低于其他致病型。基于基因的检测，3株分离株被鉴定为O157。
本研究报告了MDR的高流行率，表明后院养鸡场存在抗菌药物的滥用情况。后院鸡中ESBL和EHEC分离株的出现是一个公共卫生问题。此外，后院鸡群环境可能携带不同的病原菌，这可能增强感染的持续性并传播给接触的人类。建议定期监测后院鸡群中大肠杆菌的MDR和人畜共患病致病型的发生情况，因为这些细菌可通过食品或受污染环境传播给人类。
