Investigation and control of Vancomycin-resistant Staphylococcus aureus (VRSA): 2015 update (original) (raw)
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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.
Vancomycin‐ResistantStaphylococcus aureusin the Absence of Vancomycin Exposure
Clinical Infectious Diseases, 2004
We report findings from our investigation of the world's second clinical isolate of vancomycin-resistant Staphylococcus aureus (VRSA). An elderly man was hospitalized with an infected chronic heel ulcer and osteomyelitis. Before hospital admission, he received multiple courses of antibiotic therapy but, notably, no vancomycin. Numerous cultures of ulcer specimens (performed on an outpatient basis) grew methicillinresistant, vancomycin-susceptible S. aureus and vancomycin-resistant Enterococcus species. At admission, an additional culture of a specimen from the heel ulcer grew S. aureus that was identified as VRSA (minimal inhibitory concentration for vancomycin [by broth-microdilution], 32 mg/mL). Further evaluation confirmed the presence of the vanA gene mediating vancomycin resistance. To assess VRSA transmission, we performed a carriage study of 283 identified contacts and an environmental survey of the patient's home; no VRSA isolates were recovered. This case illustrates that recent exposure by patients to vancomycin is not necessary for development of vanA-containing VRSA. For clinical and public health reasons, it is essential that microbiology laboratories adequately test for vancomycin-resistance in S. aureus. Staphylococcus aureus is one of the most common causes of serious infection in community and hospital settings [1, 2]. Methicillin-resistant S. aureus (MRSA) is now endemic in health care facilities, with rates of 150% in some health care settings [3]. Also, recent reports describe MRSA carriage in persons in the community who do not have health care-associated risks [4]. The increased incidence of MRSA has led to more frequent use of vancomycin, the drug commonly relied on for treating MRSA infections.
Journal of Clinical Microbiology, 2011
Due to the rise in methicillin-resistant Staphylococcus aureus (MRSA) infections and widespread use of vancomycin, MRSA isolates with reduced susceptibility to vancomycin are emerging (i.e., MIC creep). However, the prevalence of heterogeneous vancomycin-intermediate S. aureus (hVISA) is unknown due to the difficulty in detecting this phenotype. Recently, Etest glycopeptide resistance detection (GRD) strips have been developed to detect hVISA. This study assessed vancomycin susceptibility in MRSA isolates and determined the prevalence of hVISA by Etest GRD and population analysis profile-area under the curve ratio (PAP-AUC). The genetic backgrounds of 167 MRSA isolates collected from 2000 to 2008 were identified by pulsed-field gel electrophoresis. Vancomycin MICs were determined using Etest and two broth microdilution assays, MicroScan and Sensititre. Etest GRD was performed on all isolates, and those exhibiting a hVISA phenotype were further tested by PAP-AUC. The vancomycin MIC modes remained consistent at 1 g/ml, as assessed by Sensititre and MicroScan. Etest reported a significant increase (mode MIC ؍ 1.5 g/ml) in the MIC between 2000 and 2008 (P < 0.01); however, this increase did not reflect a >2-fold change. In addition, the slight MIC increase did not increase linearly from 2000 to 2008, suggesting biological fluctuation, and is inconsistent with the concept of MIC creep. Etest GRD identified six hVISA isolates, two of which were confirmed to be hVISA by PAP-AUC. In conclusion, reduced vancomycin susceptibility was not detected in our hospital over a 9-year period using three different MIC methodologies, and the hVISA incidence was 1.2%, as determined by Etest GRD and PAP-AUC.
Journal of Nepal Medical Association, 2014
Introduction: Methicillin resistant Staphylococcus aureus (MRSA), majorly associated with nosocomial and community infections worldwide, are emerging as resistant strains to many antibiotics narrowing down the efficacy of antimicrobial therapy. In order to investigate the changing resistant pattern of MRSA to empirical drugs, the study was carried out at KIST Medical College and Hospital, Nepal. It also aims to determine the minimum inhibitory concentration of vancomycin among MRSA. Methods: Altogether 3500 clinical samples including 1303 blood, 1489 urine and 708 body fluids were collected and processed. Isolated S. aureus were further screened for methicillin resistance by Kirby-Bauer disk diffusion technique using cefoxitin (30μg) disk. All MRSA were subjected to in vitro determination of MIC of vancomycin by agar dilution method as recommended by CLSI guidelines. Results: Total 287 S. aureus were isolated from the different clinical samples. Altogether 248 (86.41%) were found to...
The Egyptian Journal of Medical Microbiology, 2023
Background: Methicillin-resistant Staphylococcus aureus (MRSA) is a significant pathogen, responsible for infections acquired in both nosocomial and community settings. The first line of defense against life-threatening MRSA infections is vancomycin. The development of vancomycin resistance and a possible failure of MRSA treatment is associated with elevated vancomycin MICs. Objectives: The aim of the study was to detect the antibiotic sensitivity pattern of methicillin-resistant S. aureus and the prevalence of vancomycin resistance among these isolates. Methodology: Fifty-one MRSA isolates were studied. Identification and antimicrobial susceptibility profiles of MRSA isolates were determined by Vitek 2. Results: Community-acquired MRSA (CA-MRSA) strains were isolated from abscesses in soft tissues and skin (76%), while Hospital-acquired MRSA (HA-MRSA) strains were isolated mainly from pus obtained from surgical site infections and diabetic foot (57.7%), We detected 4 VISA/VRSA isolates out of 51 MRSA strains with a prevalence rate of 7.8%. Generally, CA-MRSA isolates were more susceptible to antibiotics than HA-MRSA isolates, except for ciprofloxacin. Conclusion: The study revealed the emergence of VISA/VRSA strains in isolated MRSA that were equally distributed between non-hospitalized and hospitalized patients being more common in young patients suffering from soft tissue and skin infections. All VRSA/VISA isolates were susceptible to tigecycline and linezolid.
2018
DOI: 10.21276/sjpm.2018.3.10.16 Abstract: Staphylococcus aureus is one of the most common causes of Blood Stream infections (BSI), skin and wound infections, osteomyelitis, endocarditis, and nosocomial infections, especially pneumonia, surgical site infections (SSI), and continue to be a major cause of community-acquired infections. Methicillin Resistant Staphylococcus aureus (MRSA) is an important cause of community and hospital acquired infections. MRSA are mainly nosocomial and are increasingly reported from many countries worldwide. The purpose of present study was to determine the sensitivity of S. aureus isolated from infected patients to methicillin and to evaluate the possible presence of VRSA in our tertiary care hospital. Staphylococci were isolated and identified by standard microbiological procedures. Methicillin resistance was detected by using cefoxitin (30 μgm) by disc diffusion method. MRSA strains detected were then subjected to vancomycin agar screen test and E tes...
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.
Detection of Methicillin Resistant Staphylococcus Aureus with Reduced Susceptibility to Vancomycin
The Egyptian Journal of Hospital Medicine, 2018
Background: As there is no molecular-based assays available for the detection of hVISA and VISA. However, increasing amounts of data support a number of methods for the screening and confirmation of heterogeneous vancomycin intermediate S. aureus (hVISA) and vancomycin intermediate S. aureus (VISA) infection. The vancomycin MIC result alone is unable to accurately distinguish hVISA from VSSA isolates, and the use of MIC testing alone will fail to detect hVISA strains that are relatively common among isolates of Staphylococcus aureus (S. aureus) with broth MICs of 2 g per ml. Objective: The aim of the present work was to detect the efficacy of phenotypic and automated methods for detection of MRSA with reduced susceptibility to vancomycin. It aimed also, to determine the best MIC concentration in vancomycin screening agar for detection of VISA among MRSA isolates. Methods: One hundred MRSA isolates were obtained from 100 patients from different departments of Ain Shams University Hospitals during the period from October 2015 to the end of April 2016. They were isolated from different clinical specimens; sputum, wound swabs, blood, pus, urine, and body fluid that were referred to central microbiology laboratory for routine culture and sensitivity. Detection of S. aureus with reduced susceptibility to vancomycin was done by vancomycin screening agar with different concentrations 2,4,6 ug/ml with and without casein, MIC broth microdilution method for vancomycin according to CLSI 2015, and Vitek 2 automated system for determination of vancomycin MIC. Results: Out of 100 MRSA isolates, vancomycin screening agar 2ug/ml with casein showed highest detection rate for VISA isolates (48 %) among other screening agars. Vancomycin screening agar 6 ug/ml without casein gave the lowest detection rate (29%). So, adding casein to vancomycin screening agar did not increase detection of VISA in any of vancomycin screening agar except for that with 2ug/ml vancomycin. Vancomycin screening agar 2ug/ml with casein gave the best sensitivity among all vancomycin screening agar tested. VITEK 2 system failed to detect any isolates with reduced susceptibility to vancomycin. They were sensitive to linezolid (100%) followed by tigecyclin (99%) then Quinupristin-dalfopristin (91%). However, most of the isolates were resistant to tetracycline (85%) followed by gentamicin (80%) then ciprofloxacin (63%). Conclusion: BHI agar with 2ug/ml vancomycin and 16 g/l casein is a reliable, easy to perform, and inexpensive method to screen large number of S. aureus isolates for detection of reduced susceptibility to vancomycin on a daily basis. Applying quadruplicate technique in vancomycin screening agar may increase the yield for detection of VISA isolates. Although vancomycin screening agar 6 ug/ml is recommended by CLSI as a screening method for detection of VISA, yet it did not perform well and underestimated VISA isolates. VITEK 2 system is not an appropriate method for detection of S. aureus with reduced susceptibility to vancomycin (VISA). MRSA isolates with reduced susceptibility to vancomycin can be treated effectively with Linezolid.
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
IP Innovative Publication Pvt. Ltd., 2018
Introduction: Staphylococcus is a major pathogen of community and hospital acquired infections. Vancomycin is used in MRSA caused infections. Emergence of VISA and VRSA has been of great concern in clinical aspects. Materials and Methods: All clinical samples were processed in the laboratory according to standard procedure. Inoculated plates were incubated at 37? C for 24-48 hours. Only S. aureus isolates were included in the present study. Antibiotic susceptibility testing was done by Kirby-Bauer disc diffusion method using a panel of drugs. Cefoxitin disc was used to identify methicillin resistance. The MIC of vancomycin for MRSA isolates was carried out by Agar dilution method and E-test according to standard methods. Heteroresistance to vancomycin was detected by using BHI screen agar. Results: 190 S. aureus were isolated from various clinical samples. Most of the isolates were resistant to amoxyclav (96.2%) followed by ciprofloxacin (84.2%), erythromycin (33.2%), Clindamycin (31.2%), Cotrimoxazole (14.6%), Teicoplanin (4.2%), Mupirocin (2.1%) and none of the isolates were resistant to linezolid. Out of 190 S. aureus isolates, 97 (51.1%) were identified as MRSA. None of the isolates were resistant to vancomycin by agar dilution method and E-test method. Four out of 97 (4.1%) MRSA isolates showed intermediate susceptibility to vancomycin. Among the isolates with MIC of 2µg/ml, 5 (19.2%) showed heteroresistance to vancomycin by BHI screen agar method. Conclusion: Rapid identification of patients harboring VRSA, VISA or hVISA and adherence to infection control protocols are very important in controlling the dissemination of these pathogens. Keywords: MRSA, VISA, VRSA, Heterointermediate resistant Staphylococcus aureus (hVISA), Agar dilution method, E-test.