Bhaskar Maanasa, Dinoop K P, Mandal Jharna
Department of Microbiology, JIPMER, Puducherry, India.
J Health Popul Nutr. 2015 Dec 1;33:26. doi: 10.1186/s41043-015-0036-7.
Aeromonas species can cause a wide spectrum of illnesses varying from intestinal to extra intestinal and vary in their susceptibility to different antibiotics. The current study was undertaken to characterize the third generation cephalosporin-resistant strains of Aeromonas spp. which were isolated from stool specimens.
Out of a total of 2780 stool samples, 29 Aeromonas spp. were identified, out of which, 9 were resistant to ceftriaxone by the Kirby-Bauer antibiotic testing method. These strains were subjected to minimum inhibitory concentration (MIC) determination by agar dilution for ceftriaxone. Phenotypic and genotypic testing of AmpC beta-lactamase and extended spectrum beta-lactamase (ESBL) were performed. Gene transfer was carried out to demonstrate transmissibility of these genetic elements by conjugation experiments.
Out of the 29 strains, 9 showed MIC of ≥4 μg/ml. Seven out of 9 showed presence of blaCTX-M, while 2 more strains showed the presence of inducible AmpC beta-lactamase and presence of MOX gene. Gene transfer experiments showed that these elements were transmissible to recipient (Escherichia coli J53 strain) in the presence of ceftriaxone.
Dissemination of these resistance determinants like plasmids is pivotal in the spread of these resistance genes into the aquatic environment into organisms like Aeromonas. This may further limit the future use of antibiotics for the treatment of diarrhoeal diseases. Hence, detection and antibiotic susceptibility testing of Aeromonas spp. should be performed when isolated from stool samples.
气单胞菌属可引起从肠道到肠道外的广泛疾病，且对不同抗生素的敏感性各异。本研究旨在对从粪便标本中分离出的第三代头孢菌素耐药气单胞菌菌株进行特征分析。
在总共2780份粪便样本中，鉴定出29株气单胞菌属，其中9株通过 Kirby-Bauer 抗生素检测方法对头孢曲松耐药。采用琼脂稀释法对这些菌株进行头孢曲松的最低抑菌浓度（MIC）测定。对 AmpC β-内酰胺酶和超广谱β-内酰胺酶（ESBL）进行表型和基因型检测。通过接合实验进行基因转移，以证明这些遗传元件的可传播性。
在29株菌株中，9株的 MIC≥4 μg/ml。9株中有7株显示 blaCTX-M 存在，另外2株显示存在诱导型 AmpC β-内酰胺酶和 MOX 基因。基因转移实验表明，在头孢曲松存在的情况下，这些元件可转移至受体（大肠杆菌J53菌株）。
这些耐药决定因素如质粒的传播对于这些耐药基因传播到水生环境中的气单胞菌等生物体至关重要。这可能进一步限制未来抗生素用于治疗腹泻疾病。因此，从粪便样本中分离出气单胞菌属时，应进行检测和抗生素敏感性测试。
