Anis Raddaoui1, Farah Ben Tanfous2, Yosra Chebbi3, Wafa Achour3, Rekaya Baaboura3, Assia Benhassen3. 1. 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. Electronic address: anis.raddaoui@yahoo.fr. 2. 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. 3. 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.
Abstract
OBJECTIVES: 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. METHODS: 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. RESULTS: Macrolide resistance was observed in 41 (69.5%) of 59 isolates. Of the 41 isolates, 37 (90.2%) had a macrolide-lincosamide-streptogramin B (MLSB) resistance phenotype, with a predominance of high-level inducible MLSB phenotype, and harboured the ermB gene. All isolates with high-level inducible MLSB 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). CONCLUSIONS: 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.
OBJECTIVES: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. METHODS: 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. RESULTS:Macrolide resistance was observed in 41 (69.5%) of 59 isolates. Of the 41 isolates, 37 (90.2%) had a macrolide-lincosamide-streptogramin B (MLSB) resistance phenotype, with a predominance of high-level inducible MLSB phenotype, and harboured the ermB gene. All isolates with high-level inducible MLSB 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). CONCLUSIONS: 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.
Authors: Richael O Mills; Mohammed R Abdullah; Samuel A Akwetey; Dorcas C Sappor; Gustavo Gámez; Sven Hammerschmidt Journal: Microorganisms Date: 2022-02-19