Santhosh Kogaluru Shivakumaraswamy, Deekshit Vijaya Kumar, Venugopal Moleyuru Nagarajappa, Karunasagar Iddya, Karunasagar Indrani
1 Department of Fisheries Microbiology, Karnataka Veterinary, Animal and Fisheries Sciences University , College of Fisheries, Mangalore, India .
2 UNESCO MIRCEN for Marine Biotechnology, Nitte University Center for Science Education and Research, University Enclave , Medical Sciences Complex, Deralakatte, Mangalore, India .
Microb Drug Resist. 2017 Dec;23(8):994-1001. doi: 10.1089/mdr.2016.0142. Epub 2017 Apr 26.
Fluoroquinolone resistance in bacteria is usually associated with mutations in the topoisomerase regions. We report a novel point mutation in fluoroquinolone-resistant Escherichia coli strains. E. coli isolated from the environment in and around Mangalore, India, were examined for their antimicrobial resistance profile to 12 antibiotics and for the antibiotic resistance genes by polymerase chain reaction. Of the 67 E. coli isolated, 24 (35.8%) were sensitive to all antibiotics and 43 (64.2%) showed resistance to at least one of the 12 antibiotics used in the study. One isolate (EC10) was resistant to nine of the 12 antibiotics used. Resistance to nalidixic acid was the most common (34.32%), followed by nitrofurantoin (26.86%), tetracycline (22.38%), ampicillin (20.89%), cotrimoxazole (13.43%), ciprofloxacin (11.94%), gentamicin (10.44%), piperacillin/tazobactam (7.46%), chloramphenicol (7.46%), and cefotaxime (4.47%). Least resistance was observed for meropenem (1.49%) and none of the isolates showed resistance to imipenem. All the isolates harbored resistance genes corresponding to their antimicrobial resistance. Few quinolone-resistant isolates carried single point mutation (ser83Leu) and some had double point mutation (Ser83Leu and Asp87Asn) in gyrA. A third novel point mutation was also observed at position 50 with the change in the amino acid from tyrosine to cysteine (Tyr50Cys) in gyrA region. The study throws light on a novel point mutation in fluoroquinolone-resistant isolates. While the study helps to understand the risk and occurrence of antibiotic resistance among gram-negative bacteria from the environment, the alarming rate of antibiotic-resistant bacteria is a cause of concern in addressing infections.
细菌对氟喹诺酮类药物的耐药性通常与拓扑异构酶区域的突变有关。我们报告了氟喹诺酮耐药大肠杆菌菌株中的一种新型点突变。对从印度芒格洛尔及其周边环境中分离出的大肠杆菌进行了检测，分析它们对12种抗生素的耐药谱，并通过聚合酶链反应检测抗生素耐药基因。在分离出的67株大肠杆菌中，24株（35.8%）对所有抗生素敏感，43株（64.2%）对研究中使用的12种抗生素中的至少一种表现出耐药性。其中一株分离株（EC10）对所使用的12种抗生素中的9种耐药。对萘啶酸的耐药最为常见（34.32%），其次是呋喃妥因（26.86%）、四环素（22.38%）、氨苄西林（20.89%）、复方新诺明（13.43%）、环丙沙星（11.94%）、庆大霉素（10.44%）、哌拉西林/他唑巴坦（7.46%）、氯霉素（7.46%）和头孢噻肟（4.47%）。美罗培南的耐药率最低（1.49%），且所有分离株对亚胺培南均无耐药性。所有分离株都携带与其抗菌耐药性相对应的耐药基因。少数喹诺酮耐药分离株在gyrA基因中存在单点突变（ser83Leu），一些存在双点突变（Ser83Leu和Asp87Asn）。在gyrA区域的第50位还观察到第三个新型点突变，氨基酸由酪氨酸变为半胱氨酸（Tyr50Cys）。该研究揭示了氟喹诺酮耐药分离株中的一种新型点突变。虽然该研究有助于了解环境中革兰氏阴性菌抗生素耐药性的风险和发生情况，但抗生素耐药菌的惊人比例仍是应对感染时令人担忧的问题。
