背景:在越来越多的产生碳青霉烯酶的肠杆菌科(CPE)分离物中发现了OXA-48样碳青霉烯酶,它们正在传播到几个国家。尽管这种oxacillinase导致对碳青霉烯类抗生素的耐药性较弱,但不影响广谱头孢菌素活性,当它们与其他抵抗机制相关时,对这些抗生素的耐药水平可能明显更高。这种对碳青霉烯类和头孢菌素的耐药性较弱,在缺乏其他抗性机制的情况下,可能会使OXA-48样的分离株在实验室常规中未被发现。此外,缺乏针对这种酶的特异性筛选测试使这些分离物的检测复杂化。该报告表征了在我们实验室中检测到的第一批OXA-48样CPE分离株。
方法:这项研究是在国家研究所进行的,利马-秘鲁,2021年3月至12月。作为常规微生物学研究的一部分,检测到OXA-48样CPE分离株,和临床数据是通过查看病历获得的。自动化微生物系统通过稀释方法提供细菌鉴定和抗微生物剂敏感性曲线。此外,柱层析测试用于检测碳青霉烯酶酶,包括OXA-48-like.最后,通过聚合酶链反应PCR扩增blaOXA-48样酶进行OXA-48样酶的分子鉴定。
结果:分离出7株OXA-48样CPE菌株。值得注意的是,在所有情况下,自动化系统发布的厄他培南的最低抑制浓度(MIC)≥1ug/mL,哌拉西林/他唑巴坦的MIC>64/4ug/mL.此外,发现对亚胺培南和美罗培南的耐药类别(2/7),任何这些碳青霉烯类的至少一个不确定类别(5/7),和其他丝氨酸β-内酰胺酶如超广谱β-内酰胺酶(3/7)和AmpC(3/7)。免疫层析研究证实了OXA-48样酶在所有分离物中的存在,而A班和B班被排除在外。最后,多重PCR,对于可以回收的五个分离株,显示碳青霉烯酶OXA-48样的扩增,而其他卡巴酶均未扩增A类或B类碳青霉烯酶基因。
结论:我们确认在我们的癌症中心出现了OXA-48样CPE分离株,并强调需要对这些菌株实施监测和检测措施,控制他们的传播。我们发现了用于检测OXA-48样CPE的实用且廉价的方法:(1)在不存在A类和B类碳青霉烯酶的情况下,在抗菌谱中发现了对厄他培南和哌拉西林/他唑巴坦的耐药性,用于筛选和(2)免疫层析研究,用于确认。
BACKGROUND: OXA-48-like carbapenemases have been found in a growing and varied number of carbapenemase-producing Enterobacteriaceae (CPE) isolates, and they are spreading to several countries. Although this oxacillinase leads to weak resistance to carbapenems without affecting broad-spectrum cephalosporin activity, when they are associated with other resistance mechanisms, the level of resistance to these antibiotics may be significantly higher. This weak resistance against carbapenems and cephalosporins, along with the absence of other resistance mechanisms, could render OXA-48-like harboring isolates undetected in the laboratory routine. In addition, the lack of a specific screening test for this enzyme complicates the detection of these isolates. This report characterizes the first isolates of OXA-48-like CPE detected in our laboratory.
METHODS: The study was carried out at the Instituto Nacional de Enfermedades Neoplasicas, Lima - Peru, between March and December 2021. OXA-48-like CPE isolates were detected as part of the routine microbiological study, and clinical data were obtained by reviewing medical records. The automated microbiological system provides the bacterial identification and antimicrobial susceptibility profile by the dilution method. Additionally, the column chromatography test is used to detect carbapenemase enzymes, including OXA-48-like. Finally, the molecular identification of the OXA-48-like enzyme was carried out by Polymerase Chain Reaction PCR amplification for the blaOXA-48-like.
RESULTS: Seven OXA-48-like CPE strains were isolated. Notably, in all cases, the automated system issued a minimum inhibitory concentration (MIC) of ≥1 ug/mL for ertapenem and a MIC of >64/4 ug/mL for piperacillin/tazobactam. In addition, resistance category to imipenem and meropenem was found (2/7), at least one indeterminate category for any of these carbapenems (5/7), and other serine β-lactamases such as Extended-spectrum beta-lactamases (3/7) and AmpC (3/7). The immunochromatographic study confirmed the presence of the OXA-48-like enzyme in all isolates, while class A and class B were ruled out for them. Finally, the multiplex PCR, for the five isolates that could be recovered, showed amplification for carbapenemase OXA-48-like, while none of the other carpabemases was amplified for class A or class B carbapenemase genes.
CONCLUSIONS: We confirm the emergence of OXA-48-like CPE isolates in our cancer center and highlight the need to implement surveillance and detection measures of these strains, for controlling their dissemination. We found practical and inexpensive methodologies for the detection of OXA-48-like CPE: (1) the finding of resistance to ertapenem and piperacillin/tazobactam in the antibiogram in the absence of class A and B carbapenemases, for screening and (2) immunochromatographic study, for confirmation.