Evaluation of vancomycin MIC creep in methicillin-resistant Staphylococcus aureus infections—a systematic review and meta-analysis

Methicillin resistant Staphylococcus aureus (MRSA) has evolved as a serious threat to public health. It has capability to cause infections not only in health care settings but also in community. Due to the multidrug resistance shown by MRSA, there are limited treatment options for the infections caused by this superbug. Vancomycin is used as the drug of choice for the treatment of infections caused by MRSA. Different studies from all around the world have documented the emergence of strains of S. aureus those are intermediate sensitive or resistant to vancomycin. And recently, there have been reports of reduced susceptibility of MRSA to vancomycin, from Nepal also. So the main purpose of this study was to determine the minimum inhibitory concentration (MIC) of vancomycin to methicillin resistant S. aureus isolated from different clinical specimens. Total 125 strains of S. aureus isolated from different clinical samples at KIST Medical College and Teaching Hospital, Lalitpur, Nepal from Nov 2012 to June 2013, were subjected to MRSA detection by cefoxitin disc diffusion method. The minimum inhibitory concentrations of vancomycin to confirmed MRSA strains were determined by agar dilution method. Yellow colored colonies in mannitol salt agar, which were gram positive cocci, catalase positive and coagulase positive were confirmed to be S. aureus. Among, total 125 S. aureus strains isolated; 47(37.6%) were MRSA. Minimum inhibitory concentrations of vancomycin to the strains of MRSA ranged from 0.125 μg/ml to 1 μg/ml. From our findings we concluded that the rate of isolation of MRSA among all the strains of S. aureus isolated from clinical samples was very high. However, none of the MRSA strains were found to be vancomycin intermediate-sensitive or vancomycin-resistant.

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Minimum inhibitory concentration of vancomycin to methicillin resistant Staphylococcus aureus isolated from different clinical samples at a tertiary care hospital in Nepal.

The present study was conducted to evaluate the performance of cefoxitin disc diffusion method and oxacillin broth microdilution method for detection of methicillin resistant S. aureus (MRSA), taking presence of mecA gene as reference. In addition, inducible clindamycin resistance and beta-lactamase production were studied and minimum inhibitory concentration (MIC) of vancomycin for S. aureus isolates was determined. A total of 711 nonrepeated pus/wound swab samples from different anatomic locations were included in the study. The Staphylococcus aureus was identified on the basis of colony morphology, Gram’s stain, and biochemical tests. A total of 110 (15.47%) S. aureus isolates were recovered, of which 39 (35.50%) isolates were identified as MRSA by cefoxitin disc diffusion method. By oxacillin broth microdilution method, 31.82% of the Staphylococcus aureus isolates were found to be MRSA. However, mecA gene was present in only 29.1% of the isolates. Further, beta-lactamase production was observed in 71.82% of the isolates, while inducible clindamycin resistance was found in 10% of S. aureus isolates. The MIC value of vancomycin for S. aureus ranged from 0.016 μg/mL to 1 μg/mL. On the basis of the absolute sensitivity (100%), both phenotypic methods could be employed for routine diagnosis of MRSA in clinical microbiology laboratory; however cefoxitin disc diffusion could be preferred over MIC method considering time and labour factor.

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Detection of Methicillin Resistant Staphylococcus aureus and Determination of Minimum Inhibitory Concentration of Vancomycin for Staphylococcus aureus Isolated from Pus/Wound Swab Samples of the Patients Attending a Tertiary Care Hospital in Kathmandu, Nepal

Mobile phones widely used in our day-to-day lives are potential reservoir for a number of bacteria including Staphylococcus aureus. The study was carried out from February to May 2017 with a major objective of screening methicillin resistant S. aureus (MRSA) from mobile phones used by the staffs and students of Birendra Multiple Campus, Bharatpur, Nepal. Out of 212 swabbed samples of mobile phones analysed by standard microbiological technique, 112 (56%) showed the presence of S. aureus. Gentamicin 101 (90.2%) was the most effective antibiotic whereas cefoxitin 42 (37.5%) was the least effective antibiotic. MRSA 30 (26.8%), Vancomycin Intermediate S. aureus (VISA) 58(51.8%) and MDR S. aureus 24 (21.4%) were detected. Significant associations were noted between the rate of occurrence of MRSA and MDR S. aureus with various attributes such as the gender of the user, the way of handling the mobile phones and also with the length of use of mobile phones (P value < 0.01). Our findings indicate the mobile phones can carry potentially threatening species of S. aureus which can cause severe health hazards to humans. Awareness about regular disinfection of mobile phones, hand hygiene, restricting the use of mobile phones in contaminating areas and proper place for storing mobile phones can be suggested.

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Methicillin-Resistant Staphylococcus aureus Associated with Mobile Phones

MRSA is a public health threat and significant cause of health care-associated and community-associated infections. Vancomycin is considered as gold standard in treating life-threatening infections. Recently, reduced vancomycin susceptibility has been reported across the world. However, infection with S. aureus resistant to vancomycin is clinically rare and less relevant in causing infections. The clinical failure of vancomycin therapy is being increasingly reported with vancomycin intermediate S. aureus (VISA) and hetero-resistant vancomycin intermediate S. aureus (hVISA). The therapeutic option in treating hVISA and VISA remains uncertain. Extensive use of vancomycin over a period of time leads to generation of selective pressure and emergence of resistance. In addition, vancomycin has low tissue penetration, slow bactericidal activity and risk of nephrotoxicity. Although, phenotypic feature of VISA and hVISA were well known, their genetic basis remains unknown. VISA and hVISA is generated by the accumulation of mutation leads to thickening of cell wall. Trapping of vancomycin molecule occurs due to the presence of false targets D-ala D-ala residues in the cell wall, before reaching its target site in cytoplasmic membrane. Despite, it is difficult to detect hVISA using standard susceptibility testing methods. Treatment failure is common among patients with high bacterial load infections. Treating of patients with hVISA/ VISA infections is of great challenge for clinicians.

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Challenges in the Laboratory Diagnosis and Clinical Management ofHeteroresistant Vancomycin Staphylococcus aureus (hVISA)

Infections by Methicillin resistant Staphylococcus aureus (MRSA) is an often encountered therapeutic challenge. The problem is accentuated by the emergence of MRSA strains which are resistant to Vancomycin, the recommended agent for the treatment of MRSA infections. We therefore carried out this study to determine the MIC values ofvancomycin for the MRSA isolated from different clinical specimens in Nepal Medical College. MICs were determined by agar dilution method. Out of the 82 MRSA isolates tested, 18 showed MIC of 2 μg/ml and 29 isolates had MIC of 1 μg/ml and 35 isolates had MIC of 0.5 μg/ml. Although none had a MIC in the intermediate or resistant zone, 18 (2.9%) had MIC in the upper limit of the sensitive zone which is a matter of concern and calls for prompt preventive actions.

Reduced susceptibility to vancomycin in methicillin resistant staphylococcus aureus: a time for action.

Infections by Methicillin resistant Staphylococcusaureus (MRSA) is an often encountered therapeutic challenge. The problem is accentuated by the emergence of MRSA strains which are resistant to Vancomycin, the recommended agent for the treatment of MRSA infections. We therefore carried out this study to determine the MIC values of vancomycin for the MRSA isolated from different clinical specimens in Nepal Medical College. MICs were determined by agar dilution method. Out of the 82 MRSA isolates tested, 18 showed MIC of 2μg/ml and 29 isolates had MIC of 1μg/ml and 35 isolates had MIC of 0.5 μg/ml.Although none had a MIC in the intermediate or resistant zone, 18 (2.9%) had MIC in the upper limit of the sensitive zone which is a matter of concern and calls for prompt preventive actions.

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A Gautam

Papers

Reduced susceptibility to vancomycin in methicillin resistant staphylococcus aureus: a time for action.

Reduced susceptibilityto Vancomycin in methicillin resistant Staphylococccusaureus: a time for action