淋病奈瑟菌产β-内酰胺酶质粒，blaTEM-1 编码的截断 24 kDa TEM-1 青霉素酶中存在独特的 6 bp 缺失，该酶对氨苄西林缓慢水解。

A β-lactamase-producing plasmid from Neisseria gonorrhoeae carrying a unique 6 bp deletion in blaTEM-1 encoding a truncated 24 kDa TEM-1 penicillinase that hydrolyses ampicillin slowly.

机构信息

Department of Biochemistry, Microbiology and Immunology, 2D01 Health Science Building, 107 Wiggins Road, University of Saskatchewan, Saskatoon, SK, Canada.

Vaccine and Infectious Disease Organization-International Vaccine Centre, University of Saskatchewan, 120 Veterinary Road, Saskatoon, SK, Canada.

出版信息

J Antimicrob Chemother. 2019 Oct 1;74(10):2904-2912. doi: 10.1093/jac/dkz306.

DOI:10.1093/jac/dkz306

PMID:31335939

Abstract

BACKGROUND

Seven structurally related β-lactamase-producing plasmids have been characterized in penicillinase-producing Neisseria gonorrhoeae (PPNG) isolates. We characterized a variant (i.e. pJRD20, Canada type) of the Africa-type (pJD5) plasmid isolated from N. gonorrhoeae strain 8903.

OBJECTIVES

To compare the DNA sequence of pJRD20 with that of pJD5 and pJD4 (Asia-type) and their TEM-1 β-lactamases.

METHODS

N. gonorrhoeae 8903 was identified as part of the Gonococcal Antimicrobial Surveillance Program in Canada. β-Lactamase production was assessed using nitrocefin. MICs were determined by agar dilution and Etest methods (CLSI). The DNA sequences of pJRD20, pJD5 and pJD4 were assembled and annotated. The structure of TEM-1 and its penicillin-binding properties were determined by in silico molecular modelling and docking. TEM-1 proteins were characterized by western blot, mass spectrometry and ampicillin hydrolysis assays.

RESULTS

N. gonorrhoeae 8903 exhibited intermediate susceptibility to penicillin with slow β-lactamase activity (i.e. 35 min to hydrolyse nitrocefin). Except for a novel 6 bp deletion starting at the G of the ATG start codon of blaTEM-1, the DNA sequence of pJRD20 was identical to that of pJD5. The TEM-1 β-lactamase produced by pJRD20 is 24 kDa and hydrolyses ampicillin only after several hours.

CONCLUSIONS

This unusual PPNG isolate might have been characterized as a non-PPNG owing to its low MIC of penicillin and its very slow hydrolysis of nitrocefin. Given the unusual nature of its TEM-1 β-lactamase, laboratories might consider extending the duration of nitrocefin hydrolysis assays.

摘要

背景

已鉴定出在产青霉素酶淋病奈瑟菌（PPNG）分离株中存在 7 种结构相关的β-内酰胺酶产生质粒。我们对从淋病奈瑟菌菌株 8903 中分离出的非洲型（pJD5）质粒的变体（即 pJRD20，加拿大型）进行了特征描述。

目的

比较 pJRD20 与 pJD5 和 pJD4（亚洲型）及其 TEM-1β-内酰胺酶的 DNA 序列。

方法

加拿大淋球菌抗菌监测计划将淋病奈瑟菌 8903 鉴定为该计划的一部分。使用硝噻吩评估β-内酰胺酶的产生。通过琼脂稀释和 Etest 方法（CLSI）测定 MIC。组装和注释了 pJRD20、pJD5 和 pJD4 的 DNA 序列。通过计算机分子建模和对接确定了 TEM-1 的结构及其与青霉素的结合特性。通过 Western blot、质谱和氨苄西林水解测定对 TEM-1 蛋白进行了表征。

结果

淋病奈瑟菌 8903 对青霉素表现出中介敏感性，β-内酰胺酶活性较慢（即 35 分钟水解硝噻吩）。除 blaTEM-1 的 ATG 起始密码子的 G 处起始的新的 6bp 缺失外，pJRD20 的 DNA 序列与 pJD5 完全相同。pJRD20 产生的 TEM-1β-内酰胺酶为 24kDa，仅在数小时后才水解氨苄西林。