Molecular Characterization and Distribution of Class 1 Integron-Bearing Methicillin Resistant Staphylococcus aureus Strains in Burn Patients, Tehran, Iran

Abstract

Background: Methicillin resistant Staphylococcus aureus (MRSA) is an increasingly common hospital pathogen in burn patients, which is known to cause over 50% of burn related deaths. One of the serious threats associated with clinical isolates of MRSA is multi-drug resistance, which is associated with integrons. Objectives: The aim of this study was to determine the distribution and molecular types of MRSA in burn patients and their carriage of integrons. Methods: During a 7-month period, 106 MRSA isolates were collected from burn wounds of patients admitted to a referral burn hospital in Tehran. Antimicrobial susceptibility testing (AST) was performed for 12 antimicrobial agents. Polymerase chain reaction (PCR) was used to detect nucA, mecA, pvl and tsst-1 genes, and class 1 and 2 integrons. Multiplex PCR technique was used to determine the Staphylococcal cassette chromosome mec (SCCmec) types of MRSA strains. All isolates were genotyped by staphylococcal protein A (spa) typing. Results: AST showed the lowest rate of resistance to quinupristin-dalfopristin (19.8%), mupirocin (31.3%), and rifampicin (37.7%). All isolates were susceptible to vancomycin, teicoplanin, and linezolid. Multi-drug resistance was observed in 97% of isolates. The most SCCmec type was SCCmec type III (98.1%) while only 2 (1.9%) MRSA isolates harbored SCCmec type IV. SCCmec types I, II, and V were not detected. The study revealed the presence of class 1 integron in 58 (54.7%) isolates and class 2 integron in 3.8% of isolates. Six different spa types of t030 (66%), t037 (14.2%), t065 (9.4%), t1358 (4.7%), t937 (3.8%), and t084 (1.9%) were identified amongst the isolates. Conclusions: The study revealed a high prevalence of multi-drug resistance (MDR), class 1 integron, SCCmec type III, and spa type t030 amongst MRSA associated with burn wounds in an Iranian hospital. The existence of SCCmec type III in burn patients emphasizes the nosocomial origin of these strains.

Molecular Analysis and Integron Carriage of Mupirocin-Resistant Staphylococcus aureus Strains Isolated from Burn Wound Infections, Tehran, Iran

“…Our results imply that 21.8% of the tested isolates belonged to t790, the second most common spa type detected, which is in line with previous studies conducted in Iran (10,12). It is remarkable that in the present experiment, all the t790 isolates exhibited LLMUPR phenotype and carried integron class 1.…”

“…In 2007, Xu et al in China reported 53% of S. auerus strains isolated from environment and surgical patients were integron-positive (27). The findings of a study carried out in Iran on 106 MRSA isolates isolated from burn wound infections also showed that the majority of the isolates harbored integron class 1 (54.7%) (12), while class 2 integron was presented in 3.8% of the isolates. It is worth mentioning that the current findings are contrary to the findings of Guney from Turkey (17).…”

“…were interpreted after overnight incubation at 37°C according to the CLSI guidelines (11). Isolates with positive phenotypic results for MRSA screening were subjected to PCR assay in order to detect the mecA gene, as described elsewhere (12). As instructed by the CLSI (11), isolates were susceptible to clindamycin; nonetheless, they were resistant to erythromycin which showed the flattening of the clindamycin zone towards erythromycin (D zones) were considered as inducible macrolide, lincosamide, and streptogramin B (iMLS B ) phenotypes.…”

Distribution of Genes Encoding Toxin, Adhesion, and Antibacterial Resistance Among Various SCCmec Types of Methicillin-Resistant Staphylococcus aureus Isolated From Intensive Care Unit, Tehran, Iran

“…In the current study, pvl genes were detected in 21.5% of the tested isolates. Previous studies reported the prevalence of 2% to 35% of pvl genes among MRSA strains (7,23). Regarding the frequency of the exfoliative toxins, the results revealed that eta was more common (9.5%) than what was reported in Colombia (3%) (41) and the previous study in Iran (2), while it was lower than the rate reported in Turkey (19.2%) (42).…”

“…These 2 MRSA groups can be distinguished by some of their virulence factors and also epidemiologic, phenotypic, and genotypic characteristics (1,5,6). Methicillin-resistant S. aureus strains demonstrate a wide pattern of resistance to β-lactams and other therapeutic options such as macrolides, lincosamides, and aminoglycosides (7). Resistance to aminoglycosides is mediated by aminoglycoside-modifying enzymes (AMEs) such as aminoglycoside acetyl transferases (AACs), aminoglycoside phosphotransferases (APHs), and aminoglycoside nucleotidyl transferases (ANTs) (8,9).…”