National Salmonella & Escherichia Centre, Central Research Institute, Kasauli, India.
Indian J Med Res. 2017 Jul;146(Supplement):S9-S14. doi: 10.4103/ijmr.IJMR_979_15.
BACKGROUND & OBJECTIVES: Typhoid fever is a major cause of morbidity and mortality in the developing countries including India. Resistance to multiple antimicrobial agents is an emerging global problem that has serious impact on the treatment of disease. There are many factors associated with the emergence of resistance. Most important of them is the acquisition and further transmission and spread of resistance markers among various bacterial species. Therefore, we conducted this study to characterize the resistance plasmids in terms of their transferability and stability among Salmonella enterica serovar Typhi.
Six multidrug-resistant S. Typhi isolates were evaluated for the stability and transfer of resistance markers. The resistance plasmids were also checked for the presence of RepHI1A replicon.
All resistance markers were found to be transferred to the recipient through conjugation and transformation, except for nalidixic acid. None of the resistance plasmid was found to harbour RepHI1A replicon and therefore, did not belong to incompatibility group IncHI1. Resistance markers were found to be highly stable in all the isolates during serial passages and storage as stab cultures at different temperatures for different time periods.
INTERPRETATION & CONCLUSIONS: Resistance markers for chloramphenicol, ampicillin, streptomycin and trimethoprim were transferred through conjugation as well as transformation whereas that for nalidixic acid was not transferred in any of the isolates. Markers for chloramphenicol and streptomycin resistance were found to be most stable during various storage conditions. Presence of small-sized non-IncHI1 resistance plasmids is a matter of concern due to their capability to exist inside the host, thereby increasing the possibility of their transmission and spread among S. Typhi and other bacterial species.
伤寒是包括印度在内的发展中国家发病率和死亡率的主要原因。对多种抗菌药物的耐药性是一个新兴的全球问题，对疾病的治疗有严重影响。有许多因素与耐药性的出现有关。其中最重要的是耐药标记物在各种细菌之间的获得以及进一步的传播和扩散。因此，我们进行了这项研究，以确定伤寒沙门氏菌血清型中的耐药质粒在可转移性和稳定性方面的特征。
评估了 6 株多药耐药性伤寒沙门氏菌分离株的耐药标记物稳定性和转移能力。还检查了耐药质粒是否存在 RepHI1A 复制子。
除了萘啶酸外，所有的耐药标记物都通过接合和转化转移到了受体菌中。没有发现任何耐药质粒携带 RepHI1A 复制子，因此不属于不相容群 IncHI1。在不同温度下的连续传代和储存作为稳定培养物的过程中，所有分离株中的耐药标记物都被发现高度稳定。
氯霉素、氨苄西林、链霉素和甲氧苄啶的耐药标记物通过接合和转化均可转移，而萘啶酸的耐药标记物在任何分离株中均未转移。在各种储存条件下，氯霉素和链霉素耐药标记物最稳定。由于小尺寸的非 IncHI1 耐药质粒能够存在于宿主内，从而增加了它们在伤寒沙门氏菌和其他细菌之间传播和扩散的可能性，因此它们的存在令人担忧。
