Université de Carthage, Faculté des Sciences de Bizerte, 7021 Zarzouna, Tunisia; Service des Laboratoires, Centre national de greffe de moelle osseuse, 1006 Tunis, Tunisia; Université de Tunis El Manar, Faculté de médecine de Tunis, UR 12ES02, 1007 Tunis, Tunisia.
Université de Carthage, Faculté des Sciences de Bizerte, 7021 Zarzouna, Tunisia; Service des Laboratoires, Centre national de greffe de moelle osseuse, 1006 Tunis, Tunisia; Université de Tunis El Manar, Faculté de médecine de Tunis, UR 12ES02, 1007 Tunis, Tunisia.
Int J Antimicrob Agents. 2018 Dec;52(6):893-897. doi: 10.1016/j.ijantimicag.2018.04.015. Epub 2018 Apr 24.
Macrolide-resistant Streptococcus pneumoniae isolates have increased considerably in the last decade, with important geographical variations in involved phenotypes and genotypes. The aim of this study was to investigate phenotypes, genotypes, serotypes and genetic relatedness of macrolide-resistant S. pneumoniae isolated from immunocompromised patients in Tunisia.
Antibiotic susceptibility was determined by disk diffusion, and MICs of erythromycin and clindamycin were determined for macrolide-resistant isolates by Etest. Macrolide-resistant isolates were analysed by PCR for ermB, mefA, tetM, tetO and Int-Tn1545. Serotyping was done by multiplex PCR and the Quellung reaction. Multilocus sequence typing (MLST) was performed for molecular typing.
Macrolide resistance was observed in 41 (69.5%) of 59 isolates. Of the 41 isolates, 37 (90.2%) had a macrolide-lincosamide-streptogramin B (MLS) resistance phenotype, with a predominance of high-level inducible MLS phenotype, and harboured the ermB gene. All isolates with high-level inducible MLS phenotype were highly resistant to erythromycin and clindamycin. Four isolates (9.8%) had a macrolide (M) resistance phenotype and harboured the mefA gene. Erythromycin-resistant isolates were multidrug-resistant (MDR) in 97.5% of cases and extensively drug-resistant in 12.2%. The isolates belonged essentially to four serotypes (19F, 23F, 14 and 6B). They were mainly assigned to three sequence types (ST81, ST2918 and ST386). Also, 65.9% of the isolates were grouped in three clonal complexes (CC81, CC838 and CC386).
These data indicate a high prevalence of Tn1545 transposon and of three MDR international clones contributing to the high frequency of multidrug resistance among S. pneumoniae isolates in our centre.
过去十年中，耐大环内酯肺炎链球菌分离株的数量显著增加，涉及的表型和基因型在地理上存在重要差异。本研究旨在研究突尼斯免疫功能低下患者分离的耐大环内酯肺炎链球菌的表型、基因型、血清型和遗传相关性。
采用纸片扩散法测定抗生素敏感性，Etest 法测定红霉素和克林霉素的 MIC 值。采用 PCR 法分析 ermB、mefA、tetM、tetO 和 Int-Tn1545 对大环内酯类耐药分离株进行分析。采用多重 PCR 和 Quellung 反应进行血清型分析。采用多位点序列分型（MLST）进行分子分型。
59 株分离株中，41 株（69.5%）对大环内酯类耐药。41 株分离株中，37 株（90.2%）表现出大环内酯-林可酰胺-链阳菌素 B（MLSB）耐药表型，以高水平诱导 MLS 表型为主，携带 ermB 基因。所有高水平诱导 MLS 表型的分离株对红霉素和克林霉素均高度耐药。4 株（9.8%）分离株表现出大环内酯（M）耐药表型，携带 mefA 基因。红霉素耐药分离株 97.5%为多药耐药（MDR），12.2%为广泛耐药。分离株主要属于 4 种血清型（19F、23F、14 和 6B）。它们主要分为 3 种序列型（ST81、ST2918 和 ST386）。此外，65.9%的分离株分为 3 个克隆复合体（CC81、CC838 和 CC386）。
这些数据表明 Tn1545 转座子和三种 MDR 国际克隆的高流行率导致了我们中心肺炎链球菌分离株中 MDR 的高频率。
