Staphylococcus Aureus Resistant to vancomycin–United States, 2002

Staphylococcus aureus is a cause of hospital- and community-acquired infections. In 1996, the first clinical isolate of S. aureus with reduced susceptibility to vancomycin was reported from Japan. The vancomycin minimum inhibitory concentration (MIC) result reported for this isolate was in the intermediate range (vancomycin MIC=8 microg/mL) using interpretive criteria defined by the National Committee for Clinical Laboratory Standards. As of June 2002, eight patients with clinical infections caused by vancomycin-intermediate S. aureus (VISA) have been confirmed in the United States. This report describes the first documented case of infection caused by vancomycin-resistant S. aureus (VRSA) (vancomycin MIC > or = 32 microg/mL) in a patient in the United States. The emergence of VRSA underscores the need for programs to prevent the spread of antimicrobial-resistant microorganisms and control the use of antimicrobial drugs in health-care settings. [1]

Vancomycin-Resistant Enterococcal Infections

This article has no abstract; the first 100 words appear below.Enterococci are best known as antibiotic-resistant opportunistic pathogens that are commonly recovered from patients who have received multiple courses of antibiotics and have been hospitalized for prolonged periods.16 These organisms were well established as a cause of endocarditis and urinary tract infections by the early 1900s,3 and members of the species Enterococcus faecalis were known to be a common cause of nosocomial infections by the early 1980s.3,79 The emergence of enterococci with resistance to vancomycin, seen predominantly in the species E. faecium, has been followed by an increase in the frequency with which this species is recovered. [2]

The emergence of vancomycin‐intermediate and vancomycin‐resistant Staphylococcus aureus

Methicillin‐resistant Staphylococcus aureus (MRSA) is well‐recognised as a major cause of infection in the healthcare setting but, even more worryingly, is now emerging in the community. The glycopeptides—notably vancomycin—have traditionally been the mainstay of treatment of MRSA but overuse has led to the emergence of vancomycin‐intermediate and vancomycin‐resistant MRSA (VISA and VRSA, respectively). Although the mechanisms underlying vancomycin resistance are not yet fully understood, changes to the bacterial cell wall—the site of action of the glycopeptides—are believed to be key. Recent evidence also supports the transfer of genetic material among bacteria as contributing to the development of VRSA. Based on the cases identified to date, risk factors for the development of VRSA may include older age, compromised blood flow to the lower limbs, and the presence of chronic ulcers. The true extent of the problem, however, remains to be determined—it is likely that many cases of VISA and VRSA infection go undetected because of suboptimal screening programmes and possible limitations of automated and non‐automated detection methods. Effective screening directed at those patients considered to be most at risk should therefore be a priority. Not surprisingly, the spread of MRSA from the hospital to the community setting, coupled with the emergence of VISA and VRSA, has become a major cause of concern among clinicians and microbiologists. The treatment options available for these infections are now severely compromised and thus new classes of antimicrobial agents effective against MRSA, VISA and VRSA are urgently required. [3]

Determination of Vancomycin and Methicillin Resistance in Clinical Isolates of Staphylococcus aureus in Iranian Hospitals

Aims: The aim of this study was to determine the prevalence of methicillin resistant S. aureus (MRSA), vancomycin resistant or vancomycin intermediate resistant S. aurues (aureus) (VRSA/VISA) among clinical isolates.

Study Design: S.aureus isolates used in this study were randomly collected from in-patient and outpatient of several hospitals of 7 cities in Iran (Tehran, Shiraz, Zahedan, Tabriz, Sannandaj, Sari, and Ahvaz) during 2006-2008.

Methodology: Antibiotic susceptibility of 250 strains of Staphylococcus aureus isolated from Iranian hospitals were determined by disk diffusion method. Minimum inhibitory concentration (MICs) were determined for oxacillin and vancomycin by E-test. PCRs were used by specific primers (PCR used specific primers) for detection of mecA, vanA, vanB genes.

Results: The percentage of resistance by disk diffusion method was as below: methicillin 46%, vancomycin 0%, penicillin 86%, erythromycin 42%, ciprofloxacin 29%, gentamicin 39% and clindamycin 33%. E-test MIC method showed that 43% isolates were resistant to methicillin and 4% isolates were VISA (≤ 8µg/ml). The prevalence of resistance genes in the clinical isolates were: mecA 44%, vanA 0%, vanB 0%.

Conclusion: This study revealed that clinical isolates have rather high resistance to methicillin, erythromycin, gentamicin, penicillin and clindamycin We did not observe resistance to vancomycin. In order to avoid a possible outbreak involving VISA), vancomycin should be used carefully as a drug for treatment of S. aureus infections. [4]

Vancomycin Resistant Enterococci Infections in Trinidad and Tobago

Aims: To document Vancomycin Resistant Enterococci (VRE) infections prevalence, risk factors, antimicrobial susceptibility patterns and evaluation of chromogenic plates in identifying VRE isolates in Trinidad and Tobago.

Study Design: This was a cross sectional prospective observational and descriptive study.

Place and Duration of Study: Study was carried out in all major regional hospitals in Trinidad & Tobago over a four year period, 2009 to 2013.

Methodology: All cases of Enterococcus infections from major hospitals in the country were reviewed. Standardized questionnaire was used to analyze epidemiological and clinical data of VRE infected patients. Enterococcal speciation, minimum inhibitory concentrations (MIC) were evaluated using Microscan Walk Away 96SI (Siemens, USA). Isolates were further identified using 6.5% NaCl and pyrrolidonyl arylamidase activity according to CLSI guidelines. Brain Heart Infusion agar, Bile esculin azide agar containing 6 mg/L of vancomycin and chromogenic agar plates – Chromagar VRE and chrom ID VRE were used to screen and confirm VRE isolates [5]

Reference

[1] Centers for Disease Control and Prevention (CDC, 2002. Staphylococcus aureus resistant to vancomycin–United States, 2002. MMWR. Morbidity and mortality weekly report, 51(26), p.565.

[2] Murray, B.E., 2000. Vancomycin-resistant enterococcal infections. New England Journal of Medicine, 342(10), pp.710-721.

[3] Appelbaum, P.C., 2006. The emergence of vancomycin‐intermediate and vancomycin‐resistant Staphylococcus aureus. Clinical Microbiology and Infection, 12, pp.16-23.

[4] Farhadian, A., Nejad, Q., peerayeh, S., Rahbar, M. and Vaziri, F. (2014) “Determination of Vancomycin and Methicillin Resistance in Clinical Isolates of Staphylococcus aureus in Iranian Hospitals”, Microbiology Research Journal International, 4(4), pp. 454-461. doi: 10.9734/BMRJ/2014/4836.

[5] Kissoon, S., Akpaka, P. and Swanston, W. (2015) “Vancomycin Resistant Enterococci Infections in Trinidad and Tobago”, Microbiology Research Journal International, 9(3), pp. 1-8. doi: 10.9734/BMRJ/2015/18531.

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