Pragasam Agila Kumari, Anandan Shalini, John James, Neeravi Ayyanraj, Narasimman Vignesh, Muthuirulandi Sethuvel Dhiviya Prabaa, Elangovan Divyaa, Veeraraghavan Balaji
Department of Clinical Microbiology, Christian Medical College and Hospital, Vellore, Tamil Nadu, India.
Indian J Med Microbiol. 2019 Apr-Jun;37(2):198-202. doi: 10.4103/ijmm.IJMM_19_300.
Non-typhoidal Salmonella (NTS) infection is a serious public health problem globally. Although NTS infections are self-limited, antimicrobial therapy is recommended for severe infections and immunocompromised patients. Antimicrobial resistance (AMR) in these pathogens further limits its therapeutic options. Here, we report an incidence of ceftriaxone resistance in NTS over the past 9 years in a southern Indian region.
Molecular mechanisms of resistance in ceftriaxone-resistant NTS have been tested by both phenotypic and molecular methods. Minimum inhibitory concentration was determined by the E-test and broth microdilution method. AMR gene markers of β-lactamases such as AmpCs (bla, bla, bla, bla, bla and bla) and extended-spectrum β-lactamases (ESBLs) (bla, bla, bla, bla, blabla, bla, bla and bla) were screened. The presence of IncH12 and IncI1 plasmid was also analysed.
The study reports a 5% prevalence of ceftriaxone resistance in NTS. The most common serogroup was Salmonella Group B followed by Salmonella Group E and Salmonella group C1/C2. The occurrence of bla, bla, bla and bla genes was observed in 54%, 54%, 48% and 3% of the isolates, respectively. Interestingly, few isolates carried dual resistance genes (ESBLs and AmpCs). IncH12 and IncI1 plasmid was identified in isolates carrying ESBL and AmpC genes, respectively.
This study shows that ceftriaxone resistance is mainly mediated by β-lactamases such as ESBL and AmpC. As the incidence of ceftriaxone resistance is rising gradually over the years, it is imperative to monitor the AMR in this species.
非伤寒沙门氏菌（NTS）感染是全球严重的公共卫生问题。尽管NTS感染通常为自限性，但对于严重感染和免疫功能低下的患者，仍建议进行抗菌治疗。这些病原体中的抗菌药物耐药性（AMR）进一步限制了其治疗选择。在此，我们报告了印度南部一个地区过去9年中NTS对头孢曲松耐药的发生率。
通过表型和分子方法检测了对头孢曲松耐药的NTS的耐药分子机制。采用E-test和肉汤微量稀释法测定最低抑菌浓度。筛选了β-内酰胺酶的AMR基因标记，如AmpCs（bla、bla、bla、bla、bla和bla）和超广谱β-内酰胺酶（ESBLs）（bla、bla、bla、bla、blabla、bla、bla和bla）。还分析了IncH12和IncI1质粒的存在情况。
该研究报告NTS对头孢曲松的耐药率为5%。最常见的血清群是B群沙门氏菌，其次是E群沙门氏菌和C1/C2群沙门氏菌。分别在54%、54%、48%和3%的分离株中观察到bla、bla、bla和bla基因的出现。有趣的是，少数分离株携带双重耐药基因（ESBLs和AmpCs）。分别在携带ESBL和AmpC基因的分离株中鉴定出IncH12和IncI1质粒。
本研究表明，头孢曲松耐药主要由ESBL和AmpC等β-内酰胺酶介导。由于多年来头孢曲松耐药的发生率逐渐上升，因此监测该菌种的AMR势在必行。
