Hays Constantin, Lienhard Reto, Auzou Michel, Barraud Olivier, Guérin François, Ploy Marie-Cécile, Cattoir Vincent
CHU de Caen, Service de Microbiologie, Caen, France.
ADMED Microbiologie, La Chaux-de-Fonds, Switzerland.
J Antimicrob Chemother. 2014 Aug;69(8):2056-60. doi: 10.1093/jac/dku099. Epub 2014 Apr 7.
Actinobaculum schaalii is a Gram-positive bacillus increasingly reported as a causative agent of urinary tract infections as well as invasive infections, mainly in the elderly and patients with underlying urological conditions. Since little is known about the molecular basis of antimicrobial resistance in A. schaalii, the aim of this study was to investigate resistance to macrolides, lincosamides and streptogramins (MLS) in this emerging pathogen.
A total of 32 A. schaalii clinical isolates from France and Switzerland were studied. MICs of erythromycin, spiramycin, lincomycin, clindamycin and quinupristin/dalfopristin were determined by the agar dilution method. Resistance genes erm(A), erm(B), erm(C), erm(F), erm(G), erm(X), msr(A) and mef(A) were screened by PCR. The genetic environment was determined by random cloning and PCR mapping.
Out of 32 isolates tested, 21 were highly resistant to erythromycin, spiramycin, lincomycin and clindamycin (MICs >256 mg/L), whereas 11 exhibited low MICs (MICs < 0.12 mg/L). On the other hand, quinupristin/dalfopristin remained active against all the isolates. An inducible MLSB resistance phenotype was noted in all cases. The erm(X) gene was detected among all resistant strains, whereas none was detected in susceptible strains. Analysis of genetic support and environment revealed that erm(X) was probably part of the chromosome of A. schaalii.
This study is the first molecular characterization of MLS resistance in A. schaalii. In all cases, it was due to the presence of erm(X), a methylase gene previously identified in other clinically relevant Gram-positive bacilli.
Schaali放线杆菌是一种革兰氏阳性杆菌，越来越多地被报道为尿路感染以及侵袭性感染的病原体，主要发生在老年人和有潜在泌尿系统疾病的患者中。由于对Schaali放线杆菌耐药性的分子基础了解甚少，本研究的目的是调查这种新兴病原体对大环内酯类、林可酰胺类和链阳菌素（MLS）的耐药性。
对来自法国和瑞士的32株Schaali放线杆菌临床分离株进行了研究。采用琼脂稀释法测定红霉素、螺旋霉素、林可霉素、克林霉素和奎奴普丁/达福普汀的最低抑菌浓度（MIC）。通过PCR筛选耐药基因erm(A)、erm(B)、erm(C)、erm(F)、erm(G)、erm(X)、msr(A)和mef(A)。通过随机克隆和PCR定位确定基因环境。
在测试的32株分离株中，21株对红霉素、螺旋霉素、林可霉素和克林霉素高度耐药（MIC>256mg/L），而11株的MIC较低（MIC<0.12mg/L）。另一方面，奎奴普丁/达福普汀对所有分离株均保持活性。在所有病例中均观察到诱导型MLSB耐药表型。在所有耐药菌株中均检测到erm(X)基因，而在敏感菌株中未检测到。对基因支持和环境的分析表明，erm(X)可能是Schaali放线杆菌染色体的一部分。
本研究是对Schaali放线杆菌MLS耐药性的首次分子特征分析。在所有病例中，这是由于erm(X)的存在，erm(X)是一种先前在其他临床相关革兰氏阳性杆菌中鉴定出的甲基化酶基因。
