Department of Microbiology, Assam University, Silchar, Assam, India.
Department of Microbiology, Institute of Medical Sciences, Banaras Hindu University, Varanasi, India.
Indian J Med Res. 2024 Jun;159(6):644-652. doi: 10.25259/IJMR_1915_22.
Background & objectives OXA-232 is a five amino acid substitution variant of OXA-48 and is reported in carbapenem-resistant Klebsiella pneumoniae (CRKP), which is associated with nosocomial infections among immunocompromised patients in the intensive care unit. This study aimed to characterise blaOXA-232 in CRKP of clinical origin and investigate its transcriptional response against sub-inhibitory levels of carbapenems. Methods CRKP was isolated from blood (pathogens) and stool cultures (colonisers) of neonates and was characterized for blaOXA-232. Co-existing resistance determinants were investigated in blaOXA-232 positive isolates, followed by horizontal gene transferability assay and PCR-based replicon typing (PBRT). Cloning of blaOXA-232 was performed, and expression of blaOXA-232 in the isolates and their clones under sub-inhibitory concentrations of carbapenems was checked via RT-PCR. Mobile genetic elements associated with blaOXA-232 were investigated, followed by DNA fingerprinting through enterobacterial repetitive intergenic consensus (ERIC) PCR. Results blaOXA-232 with co-carriage of extended-spectrum beta-lactamases (ESBLs), sulphonamides and quinolones were identified in seven CRPK isolates recovered from blood samples of neonates. Transformation and cloning of blaOXA-232 was successful. The sub-inhibitory concentration of carbapenems induces elevated expression of this resistant determinant. ISEcp1 was associated with blaOXA-232 in the upstream region within two haplotypes of CRKP isolates of clinical origin. Interpretation & conclusions Selective carbapenem pressure resulted in higher expression of this gene, which could account for treatment failure. With frequent reports of occurrence among clinical isolates, monitoring and further investigation of this novel variant are necessary to understand its transmission dynamics and to thwart its further dissemination.
背景与目的 OXA-232 是 OXA-48 的五个氨基酸取代变体，存在于耐碳青霉烯类肺炎克雷伯菌（CRKP）中，与重症监护病房免疫功能低下患者的医院获得性感染有关。本研究旨在对临床来源的 CRKP 中的 blaOXA-232 进行特征描述，并研究其对亚抑菌浓度碳青霉烯类药物的转录反应。
方法 从新生儿血液（病原体）和粪便培养物（定植菌）中分离出 CRKP，对 blaOXA-232 进行鉴定。在 blaOXA-232 阳性分离株中检测共存的耐药决定因子，随后进行水平基因转移能力测定和基于 PCR 的复制子分型（PBRT）。克隆 blaOXA-232，通过 RT-PCR 检查亚抑菌浓度碳青霉烯类药物对分离株及其克隆的 blaOXA-232 表达。研究与 blaOXA-232 相关的移动遗传元件，随后通过肠杆菌重复基因间一致性（ERIC）PCR 进行 DNA 指纹图谱分析。
结果 在从新生儿血液样本中分离出的 7 株 CRPK 中发现了 blaOXA-232 与扩展谱β-内酰胺酶（ESBLs）、磺胺类药物和喹诺酮类药物共同携带。blaOXA-232 的转化和克隆成功。亚抑菌浓度的碳青霉烯类药物诱导该耐药决定因子的表达升高。ISEcp1 与 blaOXA-232 上游区域位于两个临床来源的 CRKP 分离株的两个单倍型中。
结论与解释 选择性碳青霉烯类药物压力导致该基因表达升高，这可能导致治疗失败。鉴于该新型变体在临床分离株中频繁出现，有必要对其进行监测和进一步研究，以了解其传播动态并阻止其进一步传播。
