Vancomycin minimum inhibitory concentrations (MICs) for meticillin-resistant Staphylococcus aureus (MRSA) in Hong Kong (original) (raw)
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Journal of Pure and Applied Microbiology, 2019
Staphylococcus aureus (S.aureus) and coagulase negative Staphylococci (CONS) are the commonest pathogens that lead to severe bacterial infections. It is a bacterium with consistent resistance development against commonly used antibiotics, with emergence of Methicillin resistant staphylococcus aureus (MRSA) causing several infections in patients following hospitalization. Glycopeptides like vancomycin is used as primary drug for treating infectious diseases caused by MRSA. Due to indiscriminate use of vancomycin to treat MRSA, several strains with variable susceptibility to the same have emerged. Evaluation of Vancomycin Minimum Inhibitory Concentration (MIC) in the MRSA isolates obtained from clinical samples received in the diagnostic microbiology laboratory. About 120 Staphylococci obtained from different clinical samples in the diagnostic Microbiology laboratory, at tertiary health care center, South India, were included in the study. The isolates were identified and susceptibility to the relevant antibiotics was done by Vitek 2 an automated system. Vancomycin MIC was detected by Vitek 2 and E-test strip technique. Out of 120 Staphylococcal strains, 79(65.8%) S. aureus and 41(34.1%) CONS were isolated. Methicillin resistance was observed in 38 (48.1%) strains of S. aureus. Almost all 38 MRSA isolates were vancomycin sensitive with MIC range of 0.5-2µg/ml. Maximum isolates had MIC of 1 µg/ml i.e. 65.78% and 71% by E-Test and Vitek 2 respectively. The reported increased MIC of Vancomycin, though within the susceptible range, might experience poor clinical outcomes. Emergence and spread of resistance to glycopeptides like vancomycin needs to be kept in check by rapidly detecting the strains for resistance and strictly obeying the infection control practices.
Future Microbiology
Methicillin-resistant Staphylococcus aureus (MRSA) remains an important cause of serious infection, for which vancomycin is often recommended as the first-choice antibiotic treatment. Appropriate vancomycin prescribing requires accurate measurement of minimum inhibitory concentrations (MICs) to avoid treatment failure, and yet determination can be challenging due to methodological difficulties associated with susceptibility testing. An International Working Group of infectious disease specialists and clinical/medical microbiologists reached a consensus that empirical MRSA infection therapies should be chosen regardless of the suspected origin of the infecting strain (e.g., community or hospital) due to the complex intermingling epidemiology of MRSA clones in these settings. Also, if an elevated vancomycin MIC in the susceptible range is obtained in routine testing, an alternative second method should be used for confirmation and to aid antibiotic therapy recommendations. There is no absolutely dependable method for the accurate determination of vancomycin MIC, but broth microdilution appears to be the most reliable.
Journal of Clinical Microbiology, 2004
We attempted to find a relationship between the microbiological properties of bloodstream isolates of methicillin-resistant Staphylococcus aureus (MRSA) and the efficacy of vancomycin in the treatment of bacteremia. Vancomycin susceptibility testing was performed, and bactericidal activity was determined for 30 isolates from 30 different patients with MRSA bacteremia for whom clinical and microbiological outcome data were available. The majority of these patients had been previously enrolled in multicenter prospective studies of MRSA bacteremia refractory to conventional vancomycin therapy. Logistic regression found a statistically significant relationship between treatment success with vancomycin and decreases in both vancomycin MICs (<0.5 g/ml versus 1.0 to 2.0 g/ml; P ؍ 0.02) and degree of killing (reduction in 1og 10 CFU/milliliter) by vancomycin over 72 h of incubation in vitro (P ؍ 0.03). For MRSA isolates with vancomycin MICs < 0.5 g/ml, vancomycin was 55.6% successful in the treatment of bacteremia whereas vancomycin was only 9.5% effective in cases in which vancomycin MICs for MRSA were 1 to 2 g/ml. Patients with MRSA that was more effectively killed at 72 h by vancomycin in vitro had a higher clinical success rate with vancomycin therapy in the treatment of bacteremia (log 10 < 4.71 [n ؍ 9], 0%; log 10 4.71 to 6.26 [n ؍ 13], 23.1%; log 10 > 6.27 [n ؍ 8], 50%). We conclude that a significant risk for vancomycin treatment failure in MRSA bacteremia begins to emerge with increasing vancomycin MICs well within the susceptible range. Elucidating the mechanisms involved in intermediate-level glycopeptide resistance in S. aureus should begin by examining bacteria that begin to show changes in vancomycin susceptibility before the development of obvious resistance. Prognostic information for vancomycin treatment outcome in MRSA bacteremia may also be obtained by testing the in vitro bactericidal potency of vancomycin.
Journal of Health and Allied Sciences NU, 2013
Methicillin Resistant Staphylococcus aureus (MRSA) is not only an important nosocomial pathogen but also an incipient community pathogen in many geographical areas. Recommended therapeutic agent for treatment of MRSA infections are glycopeptides, in particular vancomycin. The distribution of vancomycin Minimum Inhibitory Concentration (MIC) values among MRSA isolates in our hospital is unknown. We conducted this study to Determine the distribution of vancomycin MIC values among MRSA isolates from clinical samples in our hospital. Materials & Methods : Fifty six MRSA isolates were included in the study. These isolates were obtained from different clinical samples received in the department of Microbiology over a period of six months from august 2012 to January 2013. Screening for MRSA was done by disc diffusion method using Cefoxitin disc. Determination of vancomycin MIC of all the isolates was done by macro broth dilution method. Results : All 56 isolates were sensitive to vancomycin. Out of the 56 isolates tested, 25 (44.64%) and 12 (21.4%) had Vancomycin MIC of 1µg/ml and 2 µg/ml respectively. Conclusion : The high vancomycin MIC values observed among our strains are a cause of concern, as this may have an impact on the success of treatment with vancomycin.
Panacea Journal of Medical Sciences
Staphylococcus aureus infections in current times have become challenging to treat because of advent of Methicillin Resistant Staphylococcus aureus (MRSA) strains which are concurrently resistant to a wide panel of drugs and posing a threat to clinicians and microbiologists globally. The optimal drug for treatment of such MRSA infections is vancomycin but strains with augmented Minimum Inhibitory concentration (MIC) for this drug also have surfaced. Objectives: To know the frequency of MRSA isolates in various clinical samples with their antimicrobial sensitivity patterns and to equate agar dilution and E-test methods for MIC determination of vancomycin to MRSA strains. Materials and Methods: A total of 50 non repeat clinical isolates of staphylococcus aureus isolates were collected from various clinical specimens and were tested for methicillin resistance using the cefoxitin disc diffusion test (30µg). All MRSA isolates were tested for specific MIC by agar dilution and E-test methods. Results: 29 (58%) isolates were resistant to cefoxitin (MRSA). 13.8% isolates had MIC of 4µg/ml for vancomycin (VISA) by both agar dilution and E-test methods. However by agar dilution method 25 (86.2%) isolates exhibited vancomycin MIC of ≤ 2 µg/ml and by E-test 68.9% of the isolates showed MIC ≤ 2 µg/ml. Conclusion: Multidrug resistant MRSA strains are on the rise and alternate drug of choice for these infections; vancomycin also is showing increased MIC so prudent use of this drug is advocated. E-test can detect MRSA strains with intermediate MIC values useful for detection of MIC creep so that vancomycin can be used rationally.
Indian Journal of Medical Microbiology, 2010
Sr. No. Title Page No. 1. Abbreviations vii-viii 2. Distribution list (Controlled copies) ix 3. Amendment sheet x 4. Chapter 1: General guidelines 1-13 5. Chapter 2: Specimen collection, transport & processing Blood CSF Body fluids Ocular specimens Respiratory specimens Pus Urine Fecal specimen Tissue 15-47 6. Chapter 3: Identification of isolates Enterobacteriaceae Salmonella Stenotrophomonas maltophilia, Burkholderia cepacia complex Pseudomonas Acinetobacter Staphylococci Enterococci Fecal isolates Streptococcus sp (beta and alpha hemolytic) Streptococcus pneumoniae 49-77 7. Chapter 4: Antimicrobial Susceptibility Testing Definitions Disc diffusion testing ATCC control strains Preparing antibiotic discs in-house Minimum Inhibitory Concentration (MIC) testing Zone diameters and MIC breakpoints 79-103 8. Chapter 5: Special Tests (Phenotypic) Carba-NP test (For Enterobacteriaceae and Pseudomonas spp.) Modified carbapenem inactivation method (mCIM and eCIM); (For Enterobacteriaceae and Pseudomonas spp.) D-test for inducible clindamycin resistance Vancomycin screen agar for S. aureus and Enterococcus spp. MIC for vancomycin by broth micro dilution method Detection of heteroresistant vancomycin intermediate Staphylococcus aureus (hVISA) population analysis profile/area under curve (PAP/AUC) analysis Combination antimicrobial testing to evaluate the best combination of drugs for MRSA Detection of over-expression of efflux pumps MIC 105-113 9. Chapter 6: Quality control (QC) Reference strains for QC Storing and testing QC strains Frequency of testing Quality control of media