Mohammad Reza Nafisi, Huriyeh Kalhor, Behzad Zamanzad, Ali Karimi, Efat Farokhi, Majid Validi,
Volume 11, Issue 2 (6-2008)
Abstract
Introduction: Methicillin resistant staphylococcus aureus strains are the most important agents of nosocomial infections. The conventional antibiotic susceptibility methods such as disk diffusion are not suitable for detection of these strains due to their heteroresistancy. Therefore, in this study, agar screen and duplex-PCR were compared in determination of methicillin resistant Staphylococcus aureus (MRSA) strains isolated from nose of personnel in Hajar hospital of Shahre-kord, 2007. Materials and Methods: In this experimental study a total of 204 nasal swabs from personnel of Hajar hospital over a period of 6 months were collected. The specimens were cultured on mannitol salt agar for primary isolation and identification of Staphylococcus aureus strains and their susceptibility pattern to oxacillin was assessed using agar screen method. Finally, using duplex PCR, the isolates were tested for the presence of mecA gene. Results were compared and sensitivity and specificity of the method was determined. Results: In this study, 23 of the 52 (44%) Staphylococcus aureus isolates were resistant to oxacillin using agar screen method. However, mecA gene was detected in 27 of the 52 strains (52%). Our results showed that the sensitivity and specificity of agar screen method in determination of MRSA strains were 81.5% and 96%, respectively comparing with PCR. Conclusion: Oxacillin agar screen, comparing PCR, is an inexpensive, applied and phenotypical method with low false positive and suitable for screening of MRSA. However, due to its relatively high false negative results is not appropriate for screening of MRSA strains isolated from hospital-employed nasal carriers.
Hamed Tahmasebi, Sanaz Dehbashi, Mohammad Reza Arabestani,
Volume 21, Issue 7 (2-2019)
Abstract
Background and Aim: Gene mutation in Staphylococcus aureus is one of the most important causes of antibiotic-resistant strains. The High Resolution Melting Curve (HRM) analysis of DNA method can detect these mutations very high quality. The purpose of this study was to evaluate the role of clinical sample type in the occurrence of nucleotide mutations in the mecA gene of S. aureus by HRM method.
Materials and Methods: In this experimental study, 43 clinical isolates of S. aureus were used. To detect possible mutations, isolates with mecA gene were replicated and sequenced. Then, analysis was performed using StepOne Software v2.3 and HRM v3.0.1 software. Sequencing results were used as gold-standard.
Ethical Considerations: This study with research ethics code IR.UMSHA.REC.1396.637 has been approved by research ethics committee at Hamadan University of Medical Sciences.
Findings: Of 43 clinical isolates of S. aureus, 11 isolates (25.58%) had mecA gene and 32 isolates (47.41%) lacked the mecA gene. According to different clinical samples, 3 isolates (27.27%) were resistant to methicillin from blood samples, 2 isolates (18.18%) from urine specimens, 2 isolates (18.18%) from wound samples, 2 isolates (18.18%) of the catheter samples, 1 isolate (9.09%) of the abscess and 1 isolate (9.09%) were separated from the nose swab. In the meanwhile, isolates from the wound and urine had the highest mutation in the adenine amino acid as A → T, A → G, A → C, and
A → X. Isolates taken from blood have mutations in Guanine amino acid as
G → A.
Conclusion: There was a significant relationship between type of mutation and type of clinical specimen in methicillin-resistant Staphylococcus aureus isolates.
