Department of Genetic Engineering and Biotechnology, East West University, Dhaka, Bangladesh.
Laboratory of Gut-Brain Signaling, Laboratory Sciences and Services Division, icddr,b, Dhaka, Bangladesh.
Microbiol Spectr. 2022 Aug 31;10(4):e0074122. doi: 10.1128/spectrum.00741-22. Epub 2022 Jul 25.
is the second leading cause of diarrheal deaths worldwide. Azithromycin (AZM) is a potential treatment option for infection; however, the recent emergence of AZM resistance in threatens the current treatment strategy. Therefore, we conducted a comprehensive whole genome-based approach to identify the mechanism(s) of AZM resistance in . We performed antimicrobial susceptibility tests, polymerase chain reaction (PCR), Sanger (amplicon) sequencing, and whole genome-based bioinformatics approaches to conduct the study. Fifty-seven (38%) of the isolates examined were AZM resistant; Shigella sonnei exhibited the highest rate of resistance against AZM (80%). PCR amplification for 15 macrolide resistance genes (MRGs) followed by whole-genome analysis of 13 representative isolates identified two AZM-modifying genes, (A) (in all isolates resistant to AZM) and (E) (in 2 AZM-resistant isolates), as well as one 23S rRNA-methylating gene, (B) (41% of AZM-resistant isolates) and one efflux pump mediator gene, (E) [in the same two isolates that harbored the (E) gene]. This is the first report of (E) and (E) genes in . Moreover, we found that an IncFII-type plasmid predominates and can possess all four MRGs. We also detected two plasmid-borne resistance gene clusters: IS-(A)-(A)-(R)(A)-IS, which is linked to global dissemination of MRGs, and (E)-(E)-IS-IS, which is reported for the first time in . In conclusion, this study demonstrates that MRGs in association with pathogenic IS family insertion sequences generate resistance gene clusters that propagate through horizontal gene transfer (HGT) in . can frequently transform into a superbug due to uncontrolled and rogue administration of antibiotics and the emergence of HGT of antimicrobial resistance factors. The advent of AZM resistance in has become a serious concern in the treatment of shigellosis. However, there is an obvious scarcity of clinical data and research on genetic mechanisms that induce AZM resistance in , particularly in low- and middle-income countries. Therefore, this study is an approach to raise the alarm for the next lifeline. We show that two key MRGs [(A) and (B)] and the newly identified MRGs [(E) and (E)], with their origination in plasmid-borne pathogenic islands, are fundamental mechanisms of AZM resistance in in Bangladesh. Overall, this study predicts an abrupt decrease in the effectiveness of AZM against in the very near future and suggests prompt focus on seeking a more effective treatment alternative to AZM for shigellosis.
是全球导致腹泻死亡的第二大原因。阿奇霉素（AZM）是治疗 感染的潜在治疗选择；然而，最近在 中出现的 AZM 耐药性威胁到当前的治疗策略。因此，我们采用了一种全面的基于全基因组的方法来确定 中 AZM 耐药的机制。我们进行了抗菌药物敏感性测试、聚合酶链反应（PCR）、Sanger（扩增子）测序和基于全基因组的生物信息学方法来进行研究。在检查的 57 株 （38%）中，有 株对 AZM 耐药；志贺氏菌属 sonnei 对 AZM 的耐药率最高（80%）。随后对 15 个大环内酯类耐药基因（MRGs）进行 PCR 扩增，并对 13 株具有代表性的 株进行全基因组分析，鉴定出两种 AZM 修饰基因（A）（在所有对 AZM 耐药的 株中）和（E）（在 2 株对 AZM 耐药的 株中），以及一种 23S rRNA 甲基化基因（B）（在 41%对 AZM 耐药的 株中）和一种外排泵介质基因（E）[在携带（E）基因的相同 2 株 株中]。这是首次在 中报道（E）和（E）基因。此外，我们发现 IncFII 型质粒占主导地位，并且可以拥有所有四个 MRGs。我们还检测到两个质粒携带的耐药基因簇：IS-（A）-（A）-（R）（A）-IS，这与全球传播的 MRGs 有关，以及（E）-（E）-IS-IS，这是首次在 中报道的。总之，本研究表明，与致病性 IS 家族插入序列相关的 MRGs 产生了耐药基因簇，通过水平基因转移（HGT）在 中传播。 由于抗生素的不受控制和滥用以及抗菌药物耐药性因素的 HGT 的出现，它可能经常变成超级细菌。在治疗志贺氏菌病方面， 中 AZM 耐药性的出现已成为一个严重的问题。然而，在 中诱导 AZM 耐药的遗传机制的临床数据和研究明显匮乏，特别是在中低收入国家。因此，本研究旨在发出警报。我们表明，两种关键的 MRGs[（A）和（B）]和新发现的 MRGs[（E）和（E）]，以及它们起源于质粒携带的致病岛，是孟加拉国 中 AZM 耐药的基本机制。总体而言，本研究预测 AZM 对 的疗效将在不久的将来急剧下降，并建议立即关注寻找更有效的 AZM 替代方案来治疗志贺氏菌病。
