Background and objective: METHICILLIN-resistant Staphylococcus aureus (MRSA) has a great potential to acquire RESISTANCE to antimicrobial agents, which made treating of infections much more challenging. The aim of this study was to determine the daptomycin RESISTANCE of MRSA strains isolated from catheterized patients with urinary tract infection (UTI) in Tehran during 3 years. Materials and methods: A total of 419 S. aureus strains isolated from patients were identified using specific primers. MRSA strains were also detected using cefoxitin disk and specific primers for mecA gene; and minimum inhibitory concentration (MIC) of oxacillin was also determined. Moreover, the presence of different types of SCCmec and ccr types were also showed. All MRSA strains were also tested for susceptibility to daptomycin by disk diffusion method. Results: One hundred and eight cefoxitin resistant and mecA positive S. aureus strains were detected among isolates in which 97% harbored SCCmec type III and were positive for type 3 ccr. On the other hand, SCCmec type IVa and type 2 ccr were also detected in 3% of MRSA strains. Moreover, among MRSA strains 56% showed RESISTANCE to ≥ 256 μ g/ml oxacillin and using disk diffusion method, 86% of MRSA strains were also resistant to daptomycin. Conclusion: The results of this revealed that daptomycin is not a drug of choice for treatment of patients with UTI in this hospital.

Background: Staphylococcus aureus is associated with different infections ranging from skin and soft tissue infections to endocarditis and fatal pneumonia. S. aureus is still the most common bacterial species isolated from inpatient specimens and the second most common from outpatient specimens. Today, METHICILLIN resistant S. aureus (MRSA) isolates are present in the hospitals of most countries and are often resistant to several antibiotics.Objectives: This study was conducted from 2007 to 2011 to detect prevalence and antibiotic RESISTANCE patterns among MRSA and METHICILLIN sensitive S. aureus (MSSA) isolated from hospitals in Tehran, Iran.Materials and Methods: Totally 726 isolates of S. aureus were collected from three referral hospitals in Tehran. All isolates were identified at the species level by standard biochemical tests. Susceptibility to eighteen antibiotics was determined by disc diffusion method. Then oxacillin and vancomycin minimum inhibitory concentration (MIC) of resistant isolates was also determined using Etest. mecA gene was detected using specific primers.Results: A total of 216 (30%) strains were found to be MRSA isolates. The highest antibiotic RESISTANCE was to penicillin, clindamycin, tobramycin and tetracycline respectively. Ninety three and 61% of MRSA and MSSA isolates were multidrug resistant (MDR) respectively. However, no strain was resistant to vancomycin, synercid, linezolid and chloramphenicol. Sixty nine percent of MRSA isolates showed high level of RESISTANCE to oxacillin (MIC³256 mg/mL). mecA gene was detected among all MRSA isolates.Conclusions: Although the frequency of MRSA isolates in the current study was low, RESISTANCE to other antibiotics was high and most of the isolates were found to be MDR. Regular surveillance of hospital-associated infections and monitoring of their antibiotic sensitivity patterns are required to reduce MRSA prevalence. High frequency of MDR isolates of S. aureus could be considered as an urgent warning for public health.

Background & Aims: Staphylococcus aureus is one of the most common pathogens in nosocomial infections. Vancomycin is the most important therapeutic drug of choice for treatment of infections caused by METHICILLIN-resistant Staphylococcus aureus (MRSA) strains. Therefore, vancomycin-resistant Staphylococcus aureus (VRSA) or vancomycin-intermediate Staphylococcus aureus (VISA) strains are warnings for the medical community. The aim of this study was to evaluate the prevalence of vancomycin RESISTANCE in METHICILLIN-resistant Staphylococcus aureus isolated from the nose of patients hospitalized in Imam Reza Hospital, Kermanshah, Iran.Methods: In the present study, 85 strains of METHICILLIN-resistant Staphylococcus aureus were isolated from patients in Imam Reza Hospital and evaluated for vancomycin RESISTANCE with microdilution test, Epsilometer test (E-test), and polymerase chain reaction (PCR).Results: None of the strains were completely resistant to vancomycin; however, 39 strains (45.9%) were diagnosed as hetero-VRSA (hVISA) strains.Conclusion: VISA and VRSA strains were not observed in this study which is a promising finding in the treatment of clinical infections due to Staphylococcus aureus in our society. However, in our study, the prevalence of hVISA strain was 45.9%, which is perhaps a sign of the appearance of more resistant strains (VISA and VRSA) in our country in the future.

Background and Objectives: Macrolide, lincosamide and streptogramin B (MLSB) antimicrobial agents are widely used in the treatment of staphylococcal infection. Clindamycin is the medicine of choice for some staphylococcal infections, particularly skin and soft tissues infections. Erythromycin and clindamycin are two distinct classes of antimicrobial agents which inhibit protein synthesis in bacterial cells. Inducible RESISTANCE to clindamycin is not diagnosed using conventional antibiotic susceptibility testing and most of the physicians do not prescribe clindamycin in cases where isolates show RESISTANCE to erythromycin. However, not all of the erythromycin resistant strains are resistant to clindamycin. To detect co-RESISTANCE to both antibiotics, the inducible test should be performed to determine the potency of clindamycin for treatment. The aim of this study was to detect inducible clindamycin resistant isolates of METHICILLIN resistant isolates of Staphylococcus aureus and coagulase negative staphylococci.Material and Methods: The inducible test was performed by disk diffusion, placing an erythromycin disk adjacent to a clindamycin disk on Muller Hinton agar plate. If the isolates were resistant to erythromycin and this RESISTANCE was induced to clindamycin an inhibitiom zone shaped like the letter D was produced.  In this study all METHICILLIN RESISTANCE Staphylococcus aureus and coagulase negative staphylococci were tested for induced RESISTANCE.Results: Of 128 isolates of Staphylococci, 6 were D and 1 was D+.Conclusion: The inducible test correctly identified the inducible RESISTANCE to clindamycin caused by erythromycin. The RESISTANCE to clindamycin was not induced by erythromycin in the majority of isolates of staphylococci in our collection of isolates. We recommend the test routinely be used for correct determination of RESISTANCE to clindamycin.

Background: Coagulase-negative staphylococci (CNS) are a common cause of nosocomial infections. In recent years, an increase in the incidence of METHICILLIN-resistant coagulase-negative staphylococci (MRCNS) has led to the severity of the disease.Objectives: The aim of this study was to isolate and identify MRCNS strains by oxacillin disk agar diffusion, oxacillin agar screening, and polymerase chain reaction (PCR) and to evaluate their antibacterial RESISTANCE patterns.Patients and Methods: Totally, 122 CNS isolates were collected from the clinical specimens of four hospitals in Iran. Susceptibility testing was performed by disk agar diffusion against 15 antimicrobial agents. Then, disk agar diffusion, agar screening, and PCR were applied to determine susceptibility to oxacillin.Results: Out of the 122 isolates, 92 isolates were found to be MRCNS by PCR. The sensitivities and specificities of disk agar diffusion and agar screening were 89.2% and 69% and 93.8% and 96.3%, respectively. Also, 93 CNS isolates were resistant to METHICILLIN according to disk agar diffusion.Discussion: Our results indicated that agar screening was superior to oxacillin disk agar diffusion. A comparison between the antibiotic sensitivity patterns of the MRCNS and the METHICILLIN-Susceptible Coagulase-Negative Staphylococci (MSCNS) showed that the MRCNS were predominantly multiple-drug resistant isolates as the simultaneous RESISTANCE rate to 4 or more antibiotics in the MRCNS and MSCNS was 93% and 56%, respectively.

Introduction: The newly-launched strain of the Staphylococcus aureus, METHICILLIN-resistant S. aureus, is considered the most emerging bacterium in-hospital infections globally. Objectives: The current research focused on the prevalence and virulence features of METHICILLIN-resistant S. aureus (MRSA) bacteria recovered from urinary tract infections (UTIs) cases. Patients and Methods: A total of 710 urine specimens were taken from hospitalized patients who suffered from UTIs. S. aureus was recovered from urine specimens using the microbial culture. S. aureus antimicrobial susceptibility was assessed toward oxacillin and cefoxitin antimicrobial disk to determine the MRSA strains. The polymerase chain reaction (PCR) assessed the distribution of antimicrobial RESISTANCE encoding genes. S. aureus antimicrobial RESISTANCE was evaluated by disk diffusion. Results: Fifty-five out of 710 (7. 7%) urine specimens were positive for the MRSA bacteria. The uppermost antibiotic RESISTANCE was obtained against penicillin (100%), ceftaroline (100%), gentamicin (87. 2%), erythromycin (76. 3%), and ciprofloxacin (69. 0%). BlaZ (100%) and tetK (85. 4%) had the higher frequency amid examined antimicrobial RESISTANCE-encoding genes. Conclusion: The high prevalence of MRSA isolates harboring antimicrobial RESISTANCE-encoding genes in the UTIs suggests that diseases caused by them need more expansion healthcare monitoring with essential demand for novel antimicrobials.

In this study, the presence of METHICILLIN-resistant gene (mecA) and antibiotic RESISTANCE pattern were investigated in coagulase positive staphylococci (Staphylococcus aureus and Staphylococcus pseudintermedius) isolated from referred dogs to Veterinary Hospital of Ahvaz. Nasal swabs were collected from 143 dogs referred to Veterinary Hospital of Ahvaz and were cultured in mannitol salt agar (MSA) and blood agar. Coagulase-positive staphylococci were identified by routine identification methods. From 67 coagulase-positive staphylococci (13 isolates Staphylococcus aureus and 54 isolates Staphylococcus pseudintermedius) and by using specific primers for the METHICILLIN-resistant gene (mecA), 28 (41.79%) isolates possessed themecA gene. The presence of this gene was showed in 7 Staphylococcus aureus(25%) and 21 Staphylococcus pseudintermedius (75%) isolates. Among isolates carrying METHICILLIN RESISTANCE gene (mecA), maximum RESISTANCE was to ampicillin (92.85%) and then to penicillin (57.14%), cloxacillin (42.58%), oxacillin (35.71%), tetracycline (32.14%), ceftazidime (25%), erythromycin and azithromycin (21.42%), gentamicin and Ceftizoxime (14.28%), METHICILLINe, norfloxacin, meropenem, and cotrimoxazole (10.71%). No RESISTANCE was observed to vancomycin, chloramphenicol, rifampin, and nitrofurantoin in these isolates. Among isolates without METHICILLIN RESISTANCE gene (mecA), highest RESISTANCE was to ampicillin (84.61%) and then to penicillin (48.71%), tetracycline (23.07%), oxacillin (20.51%), gentamicin (7.69%), chloramphenicol, erythromycin, azithromycin, cotrimoxazole (5.12%) and ceftazidime (2.54%) respectively. No RESISTANCE was observed to oxacillin, meropenem, vancomycin, ceftizoxime, rifampin, METHICILLINe and nitrofurantoin. Identification and monitoring of METHICILLIN-resistant staphylococci and determination of their antibiotic susceptibility pattern are essential for successful treatment and preventing the spread of antibiotic-resistant strains. These studies have also led to awareness and promote effective practices to prevent the spread of resistant strains.