Determination of Capsular Serotypes, Antibiotic Susceptibility Pattern, and Molecular Mechanism of Erythromycin Resistance among Clinical Isolates of Group B Streptococcus in Isfahan, Iran

Abstract

Background: Documented streptococcal resistance to erythromycin has recently been raised. The aim of this study is to identify the molecular mechanism of erythromycin resistance among group B Streptococcus (GBS) strains and to correlate with the clinical origin of strains. Materials and Methods: A total number of 134 colonizing ( n = 36), invasive ( n = 36), noninvasive ( n = 46), and asymptomatic ( n = 16) GBS isolates were characterized by the detection of dltS gene, capsular serotyping, antibiotic susceptibility profiles using disc diffusion method, and screening of the ermB , ermTR , and mefA resistance genes. Results: The distribution of capsular serotypes was as follow: serotype III (24.6%), Ia (21.6%), V (17.9%), Ib (14.9%), II (8.9%), IV (8.9%), VI (1.5%), and VII (1.5%). From 134 GBS isolates, 51 (38%) isolates were resistant to erythromycin. The constitutive macrolide lincosamide streptogrmin B (MLSB) was the most common resistance phenotype (62.7%), followed by inducible MLSB (27.4%) and M phenotype (9.8%). Erythromycin resistance rate was higher among asymptomatic GBS strains (13/16, 81.2%). Serotype III was the most prevalent type among resistant isolates (41.1%). The ermB gene highly distributed among resistant strains (64.7%), followed by ermTR (21.5%) and mefA (9.8%). The ermB gene was related to constitutive MLSB phenotype (84.3%, P < 0.05) and serotypes III (61.9%), Ib (87.5%), and V (83.3%). All M phenotype strains harbored mefA gene and were in association with serotype Ia (90%). Conclusion: The current study suggests that ribosomal modification with erm genes is the main mechanism of erythromycin resistance. Because of relatively high prevalence of erythromycin resistance, double disc test highly recommended for GBS disease treatment and intrapartum prophylaxis among penicillin intolerant patients in our region.

Knowledge, Attitude, and Practice (KAP) Survey on the Management of Multidrug-Resistant Gram-Negative Infections With Innovative Antibiotics: Focus on Ceftazidime–Avibactam

“…A similar study conducted by Dasgupta et al (2015) in a tertiary care center in India revealed that pneumonia, ventilator-associated pneumonia, urinary tract infection, and bloodstream infections were the most common nosocomial infections in the clinical setting [ 18 ]. Studies have reported that the respiratory system, urinary system, and blood are the most common locations of nosocomial infections in ICUs [ 19 ].…”

Antibiotic Susceptibility Pattern of Nosocomial and Community-Acquired Pseudomonas aeruginosa in Isfahan: A Prospective Multicenter Study

“…Resistance of the organism to many available antibiotics is a worldwide health concern, especially in nosocomial infections that accompany increased mortality and high economic and social costs (5,6).…”