Phenotypic characterization of nosocomial isolates of Staphylococcus aureus with reference to MRSA

Abstract

Background: Apart from being a major cause of mortality, nosocomial infections due to Staphylococcus aureus have been imposing a burden on patients, hospitals and health care systems. The present study was designed to determine the prevalence of methicillin resistant S. aureus (MRSA) among nosocomial isolates along with their phenotypic characterization. Methodology: MRSA and methicillin sensitive S. aureus (MSSA) were determined by performing four different tests viz: disc diffusion, oxacillin screen agar test, MRSA latex agglutination test, and MIC of oxacillin by E test. Results: Of the 149 S. aureus nosocomial isolates, 44.9% were MRSA, which included 82.1% of homogeneous MRSA and 17.9% of heterogeneous MRSA. Association of MRSA infection was found to be significantly higher in skin and lower respiratory tract infections. Of the MRSA isolates, 65 were multiresistant oxacillin resistant Staphylococcus aureus (MORSA) and 2 were nonmultiresistant oxacillin resistant Staphylococcus aureus (NORSA). D tests performed on 136 isolates showed that Inducible macrolide-lincosamide-streptogramin B (MLS B ) and constitutive MLS B resistance were found to be associated with MRSA. On the contrary, susceptibility to both erythromycin and clindamycin was found to be associated with MSSA. However, MS B (macrolide-streptogramin B) resistance was not found associated either with MRSA or MSSA. Furthermore, both inducible and constitutive MLS B were found to be associated with only homogenous MRSA. Conclusion: D tests may be made mandatory in all S. aureus isolates as inducible MLS B resistance cannot be detected in routine susceptibility test unless erythromycin and clindamycin are placed 15-26 mm apart.

Changing Trends in Resistance Pattern of Methicillin Resistant Staphylococcus aureus

“…This finding was similar to a that of a study which was done in Northern India, where out of 115 MRSA, 73% strains had shown multi-resistance [24]. Among other reports, Shrestha et al, had reported 97% MORSA [23]. However, their sample size was less (65 out of 67 strains).…”

“…MRSA strains with three or more non-beta lactam drug resistances have been described as multi-resistant oxacillin resistant S. aureus (MORSA) and they have been correlated with treatment failure [23]. We found that 79% MRSA isolates were multi drug resistant.…”

A Sea Hare L-Amino Acid Oxidase to Fight Multiple Antibiotic-Resistant Staphylococcus Aureus

“…Resistance to erythromycin, sulfamethoxazole-trimethoprim and clindamycin reached 58%, 43% and 28%, respectively. Particularly among the MRSA, the prevalence of resistant to those antibiotics was very elevate (87%, 83% and 60%, respectively) in comparison to the rates reported in previous studies [20][21][22]. Nowadays, it is common to see such resistance profiles, especially against clindamycin, due to haphazard use of these antibiotics [22].…”

“…Other studies have also reported high prevalence of MRSA in clinical samples [20][21][22]. Nowadays, vancomycin is used as drug of choice for treating MRSA, but the emergence of vancomycin intermediate-sensitive S. aureus (VISA) and vancomycin-resistant S. aureus (VRSA) has limited even this therapeutic route [2].…”

Untitled

“…Other studies have also reported high prevalence of MRSA in clinical samples [20][21][22]. Nowadays, vancomycin is used as drug of choice for treating MRSA, but the emergence of vancomycin intermediate-sensitive S. aureus (VISA) and vancomycin-resistant S. aureus (VRSA) has limited even this therapeutic route [2].…”