Muktan Bijaya, Thapa Shrestha Upendra, Dhungel Binod, Mishra Bagish Chandra, Shrestha Nabaraj, Adhikari Nabaraj, Banjara Megha Raj, Adhikari Bipin, Rijal Komal Raj, Ghimire Prakash
Central Department of Microbiology, Tribhuvan University, Kirtipur, Kathmandu, Nepal.
Kantipur Hospital Pvt. Ltd., Tinkune, Kathmandu, Nepal.
Gut Pathog. 2020 Sep 17;12:44. doi: 10.1186/s13099-020-00382-5. eCollection 2020.
Plasmid-mediated resistance to the last-resort drugs: carbapenems and colistin is an emerging public health threat. The studies on the prevalence and co-expression of resistant genes among livestock and human pathogens are rare in Nepal. This is the first study in Nepal exploring the prevalence and co-existence of colistin resistance gene, -1 along with carbapenemase resistance gene, -48 in isolated from poultry and clinical specimens.
A total of 240 rectal swabs from chickens of five different poultry farms of Kathmandu valley and 705 mid-stream urine samples from human subjects attending Kantipur Hospital, Kathmandu were collected between August, 2018 and March, 2019. Rectal swabs and urine specimens were cultured. isolated from the specimens were screened for antimicrobial susceptibility testing (AST) using disk diffusion method'. Minimum inhibitory concentration (MIC) of colistin was determined by agar dilution method using 0.5 µg/ml to 32 µg/ml. The isolates were first screened for - followed by screening for - genes using conventional Polymerase chain reaction (PCR).
Of the total samples analyzed, was isolated from 31.7% (76/240) of poultry and 7.9% (56/705) of clinical specimens. In AST, 80% (61/76) of from poultry and 79% (44/56) from clinical specimens were MDR. The phenotypic prevalence of colistin resistance in poultry specimens were 31.6% (24/76) and clinical specimens were 21.4% (12/56). In PCR assay, 27.6% (21/76) of poultry and 19.6% (11/56) of clinical isolates had colistin resistant - gene. MICs value of isolates ranged from 4 to 32 (µg/ml) in both clinical and poultry isolates. Prevalence of co-existing carbapenem resistance gene, -48, among colistin resistant -1 positive isolates was 38% (8/21) in poultry specimens and 18.2% (2/11) in clinical specimens.
The high prevalence of colistin and carbapenem resistant genes, and their co-existence in plasmid DNA of isolates in this study suggests the possible spread to other animal, human and environmental pathogens. Molecular methods in addition to the conventional diagnostics in laboratories can help in early diagnosis, effective management and control of their potential transmission.
质粒介导的对最后手段药物（碳青霉烯类和黏菌素）的耐药性是一种新出现的公共卫生威胁。在尼泊尔，关于家畜和人类病原体中耐药基因的流行情况及共表达的研究很少。这是尼泊尔第一项探索从家禽和临床标本中分离出的大肠埃希菌中黏菌素耐药基因mcr - 1与碳青霉烯酶耐药基因bla - NDM - 48的流行情况及共存情况的研究。
在2018年8月至2019年3月期间，从加德满都谷地五个不同家禽养殖场的鸡身上采集了240份直肠拭子，并从加德满都康德布尔医院就诊的人类受试者中采集了705份中段尿样本。对直肠拭子和尿液标本进行培养。使用纸片扩散法对从标本中分离出的菌株进行抗菌药物敏感性试验（AST）。使用琼脂稀释法，在0.5 μg/ml至32 μg/ml范围内测定黏菌素的最低抑菌浓度（MIC）。首先使用常规聚合酶链反应（PCR）对分离的菌株进行mcr - 1基因筛选，随后筛选bla - NDM - 48基因。
在分析的所有样本中，大肠埃希菌分别从31.7%（76/240）的家禽和7.9%（56/705）的临床标本中分离得到。在AST中，来自家禽的大肠埃希菌80%（61/76）和来自临床标本的79%（44/56）为多重耐药。家禽标本中黏菌素耐药的表型流行率为31.6%（24/76），临床标本中为21.4%（12/56）。在PCR检测中，27.6%（21/76）的家禽分离株和19.6%（11/56）的临床分离株具有黏菌素耐药mcr - 1基因。临床和家禽分离株中大肠埃希菌的MIC值范围为4至32（μg/ml）。在黏菌素耐药mcr - 1阳性分离株中，共存的碳青霉烯耐药基因bla - NDM - 48在家禽标本中的流行率为38%（8/21），在临床标本中为18.2%（2/11）。
本研究中大肠埃希菌分离株中黏菌素和碳青霉烯耐药基因的高流行率及其在质粒DNA中的共存表明，它们可能传播到其他动物、人类和环境病原体。实验室中除了常规诊断方法外，分子方法有助于早期诊断、有效管理和控制它们的潜在传播。
