Multiple-Locus Variable Number of Tandem Repeats Fingerprinting (MLVF) and Virulence Factor Analysis of Methicillin Resistant Staphylococcus aureus SCCmec type III

Abstract

Methicillin resistant Staphylococcus aureus (MRSA), particularly strains with type III staphylococcal cassette chromosome mec (SCCmec), represent a serious human pathogen in Tehran, Iran. The disease-causing capability depends on their ability to produce a wide variety of virulent factors. The prevalence of exotoxin genes and multiple-locus variable number of tandem repeats fingerprinting (MLVF) profile among MRSA isolates, from patients in Tehran, was evaluated by PCR and Multiplex-PCR. The MLVF typing of 144 MRSA isolates with type III SCCmec produced 5 different MLVF types. Generally, 97.2% (140/144) of all the isolates were positive for at least one of the tested exotoxin genes. The most prevalent genes were hld, found in 87.5% (126/144) of the isolates followed by lukE-lukD and hla found in 72.9% (105/144) and 70.1% (101/144) of the isolates, respectively. The tst gene, belonging to MLVF types I, IV and V, was found among three of the isolates from blood and wound samples. The sea gene was detected in 58.3% (84/144) of the isolates and the sed and see genes were found in one isolate with MLVF type V. The coexistence of genes was observed in the 87.5% (126/144) of the isolates. The rate of coexistence of hld with lukE-lukD, hla with lukE-lukD and sea with lukE-lukD were 66.7% (96/144), 44.4% (64/144) and 44.4% (64/144), respectively. The present study demonstrated that MRSA strains with type III SCCmec show different MLVF patterns and exotoxin profiles.

Antibiotic Resistance Patterns and Virulence Determinants of Different SCCmec and Pulsotypes of Staphylococcus Aureus Isolated from a Major Hospital in Ilam, Iran

“…Accordingly, rigorous regulations and policies should be adopted for sanitation or disinfection programs. Proper indoor air ventilation is also needed and minimal antibiotic therapy should be administered among patients [ 6 , 7 , 18 , 44 ].…”

“…Further confirmations were obtained through the use of molecular methods including PCR of nucA and spa genes. Isolates that were gram-positive, catalase-positive, coagulase-positive, and DNase-positive and also the ones that carried spa and mec A genes were entered into the study [ 6 , 7 ].…”

“…Antimicrobial susceptibility patterns were determined by the agar disk diffusion methods according to CLSI guidelines [ 8 ]. The tested antibiotics included gentamicin (10μg), erythromycin (15μg), clindamycin (2μg), doxycycline (30μg), minocycline (30μg), ciprofloxacin (5μg), trimethoprim-sulfamethoxazole (5μg), rifampin (5μg), quinupristin-dalfopristin (15μg), and linezolid (30μg) [ 6 - 8 ].…”

“…The sensitivity and resistance to methicillin were investigated using cefoxitin (30µg) disk. All MRSAs were further identified by agar dilution of oxacillin according to CLSI guidelines and then confirmed by mecA gene detection using PCR after DNA extraction by phenol chloroform based on the past reports [ 6 - 8 ]. Minimum inhibitory concentration (MIC) of vancomycin was also determined by micro-broth dilution.…”

“…Minimum inhibitory concentration (MIC) of vancomycin was also determined by micro-broth dilution. S. aureus ATCC25923 and ATCC 29213 were used as the internal control as well [ 6 , 7 ].…”