American Journal of Epidemiology and Infectious Disease
ISSN (Print): 2333-116X ISSN (Online): 2333-1275 Website: Editor-in-chief: Apply for this position
Open Access
Journal Browser
American Journal of Epidemiology and Infectious Disease. 2013, 1(4), 59-62
DOI: 10.12691/ajeid-1-4-6
Open AccessArticle

Increased Vancomycin Minimum Inhibitory Concentrations of Methicillin-Resistant Staphylococcus aureus Nosocomial Isolates in Southwestern Saudi Arabia

Ahmed Morad Asaad1, and Mohamed Ansar Qureshi1

1Department of Microbiology, College of Medicine, Najran University, Najran, Saudi Arabia

Pub. Date: December 06, 2013

Cite this paper:
Ahmed Morad Asaad and Mohamed Ansar Qureshi. Increased Vancomycin Minimum Inhibitory Concentrations of Methicillin-Resistant Staphylococcus aureus Nosocomial Isolates in Southwestern Saudi Arabia. American Journal of Epidemiology and Infectious Disease. 2013; 1(4):59-62. doi: 10.12691/ajeid-1-4-6


This study aimed to determine the distribution of vancomycin (VAN) MIC values and antimicrobial resistance patterns of MRSA nosocomial isolates from a Saudi tertiary care hospital and evaluate the presenting clinical and demographic features of different infections caused by these isolates. A total of 104 non-duplicating MRSA nosocomial strains were isolated. VAN MICs were determined by standard Etest and the Etest macromethod (MET). Among all isolates, 7.7% had a MIC = 2 µg/ml, 70.2% had a MIC = 1 µg/ml and 22.1% had a MIC = 0.5 µg/ml. No heterogeneous VAN-intermediate S. aureus (hVISA) were detected. Patients infected with high VAN MRSA nosocomial isolates were of significantly older age (p = 0.035), presented more often with bacteraemia (p = < 0.0001) and had longer hospital stays (p = < 0.0001). The presence of high VAN MICs of some MRSA isolates in our hospital is worrying and a cause for concern due to the possibility of the potential failure of treatment of these isolates. Moreover, accurate MIC testing using MET simultaneously or as a supplement to automated systems (i.e. Vitek) is important.

MRSA vancomycin MIC Etest macromethod nosocomial

Creative CommonsThis work is licensed under a Creative Commons Attribution 4.0 International License. To view a copy of this license, visit


[1]  Velazquez-Meza ME, Hernandez-Salgado M, Contreras-Cordero JF, et al. Surveillance of methicillin-resistant Staphylococcus aureus causing nosocomial infections in five medical centers. Arch Med Res, 2013. http: // / 10.1016/ j.arcmed. 2013.09.001.
[2]  Rosenthal VD, Bijie H, Maki DG, et al. International Nosocomial Infection Control Consortium (INICC) report, data summary of 36 countries, for 2004-2009. Am. J. Infect. Control, 2012; 40: 396-407.
[3]  David MZ and Daum RS. Community-associated methicillin-Resistant Staphylococcus aureus: Epidemiology and clinical consequences of an emerging epidemic. Clin. Microbiol. Rev., 2010; 23: 616-687.
[4]  Lodise TP, Graves J, Evans A, et al. Relationship between vancomycin MIC and failure among patients with methicillin-resistant Staphylococcus aureus bacteremia treated with vancomycin. Antimicrob. Agents Chemother., 2008; 52: 3315-3320.
[5]  van Hal SJ, Lodise TP, and Paterson DL. The clinical significance of vancomycin minimum inhibitory concentration in Staphylococcus aureus infections: a systematic review and meta-analysis. Clin. Infect. Dis., 2012; 54: 755-771.
[6]  Pitz AM, Yu F, Hermsen ED, et al. Vancomycin susceptibility trends and prevalence of heterogeneous vancomycin-intermediate staphylococcus aureus in clinical methicillin-resistant S. aureus isolates. J. Clin. Microbiol., 2011; 49: 269-274.
[7]  Fowler VG, Boucher HW, Corey GR, et al. Daptomycin versus standard therapy for bacteremia and endocarditis caused by Staphylococcus aureus. N. Engl. J. Med., 2006; 355: 653-665.
[8]  Rybak MJ, Leonard SN, Rossi KL, et al. Characterization of vancomycin-heteroresistant Staphylococcus aureus from the metropolitan area of Detroit, Michigan, over a 22-year period (1986 to 2007). J. Clin. Microbiol., 2008; 46: 2950-2954.
[9]  Soriano A, Marco F, Martinez JA. et al. Influence of vancomycin minimum inhibitory concentration on the treatment of methicillin resistant Staphylococcus aureus bacteremia. Clin. Infect. Dis., 2008; 46:193-200.
[10]  Clinical and Laboratory Standards Institute. Performance standards for antimicrobial susceptibility testing. In: CLSI approved standard M100-S16. CLSI, Wayne, PA, 2006.
[11]  Kehrmann J, Kaase M, Szabados F, et al. Vancomycin MIC creep in MRSA blood culture isolates from Germany: a regional problem? Eur. J. Clin. Microbiol. Infect. Dis., 2011; 30:677-683.
[12]  Deresinski S. Methicillin-resistant staphylococcus aureus and vancomycin: Minimum inhibitory concentration matters. Clin. Infect. Dis., 2012; 54: 772-774.
[13]  Tenover FC and Moellering RC. The rationale for revising the Clinical and Laboratory Standards Institute vancomycin minimal inhibitory concentration interpretive criteria for Staphylococcus aureus. Clin. Infect. Dis., 2007; 44: 1208-1215.
[14]  Wang J, Wang J, Sheng W, et al. Nosocomial methicillin-resistant Staphylococcus aureus (MRSA) bacteremia in Taiwan: Mortality analyses and the impact of vancomycin, MIC = 2 mg/L, by the broth microdilution method. BMC Infect. Dis., 2010; 10:159-165.
[15]  Musta AC, Riederer K, Shemes S, et al. Vancomycin MIC plus Heteroresistance and Outcome of Methicillin-Resistant Staphylococcus aureus Bacteremia: Trends over 11 Years. J. Clin. Microbiol., 2009; 47: 1640-1644.
[16]  Van Hal SJ, Wehrhahn MC, Barbagiannakos T, et al. Performance of various testing methodologies for detection of heteroresistant vancomycin-intermediate Staphylococcus aureus in bloodstream Isolates. J. Clin. Microbiol., 2011; 49: 1489-1494.
[17]  Baddour MM, Abuelkheir MM, Amal J et al. Trends in antibiotic susceptibility patterns and epidemiology of MRSA isolates from several hospitals in Riyadh, Saudi Arabia. Ann Clin. Microbiol Antimicrob., 2006; 5: 30-40.
[18]  Al-Obeid S, Haddad Q, Cherkaoui A, et al. First detection of an invasive Staphylococcus aureus strain (D958) with reduced susceptibility to glycopeptides in Saudi Arabia. J. Clin. Microbiol., 2010; 48: 2199-2204.
[19]  Horan TC, Andrus M and Dudeck MA. CDC/NHSN surveillance definition of health care-associated infection and criteria for specific types of infections in the acute care setting. Am. J. Infect. Control, 2008; 36, 309-332.
[20]  Clinical and Laboratory Standards Institute. Performance Standards for Antimicrobial Susceptibility Testing: Twenty-second Informational Supplement. M100-S22. CLSI, Wayne, PA, 2012.
[21]  Bignardi GE, Woodford N, Chapman A, et al. Detection of the mec-A gene and phenotypic detection of resistance in Staphylococcus aureus isolates with borderline or low-level methicillin resistance. J. Antimicrob. Chemother., 1996; 37:53-63.
[22]  Wootton M, MacGowan AP, Walsh TR, et al. A multicenter study evaluating the current strategies for isolating Staphylococcus aureus strains with reduced susceptibility to glycopeptides. J. Clin. Microbiol., 2007; 45: 329-332.
[23]  Han JH, Mascitti KB, Edelstein PH, et al. Effect of reduced vancomycin susceptibility on clinical and economic outcomes in Staphylococcus aureus bacteremia. J. Antimicrob. Agents Chemother., 2012; 56: 5164-5170.
[24]  Song J, Hiramatsu K, Suh JY, et al. Emergence in Asian countries of Staphylococcus aureus with reduced susceptibility to vancomycin. J. Clin. Microbiol., 2004; 48: 4926-4928.
[25]  Maor Y, Hagin M, Belausov N, et al. Clinical features of heteroresistant vancomycin-intermediate Staphylococcus aureus bacteremia versus those of methicillin-resistant S. aureus bacteremia. J. Infect. Dis., 2009; 199: 619-624.
[26]  Maor Y, Rahav G, Belausov et al. Prevalence and characteristics of heteroresistant vancomycin-intermediate Staphylococcus aureus bacteremia in a tertiary care center. J. Clin. Microbiol., 2007; 45:1511-1514.
[27]  Lodise TP, Miller CD, Graves J, et al. Predictors of high vancomycin MIC values among patients with methicillin-resistant Staphylococcus aureus bacteraemia. J. Antimicrob. Chemother., 2008; 62: 1138-1141.
[28]  Kao T, Wang J, Weng C, et al. In vitro activity of linezolid, tigecycline, and daptomycin on methicillin-resistant Staphylococcus aureus blood isolates from adult patients, 2006-2008: Stratified analysis by vancomycin MIC. J. Microbiol. Immunol. Infect., 2011; 44: 346-351.
[29]  Picazo JJ, Betriu C, Rodriguez-Avial I, et al. Comparative activities of daptomycin and several agents against staphylococcal blood isolates. Glycopeptide tolerance. Diagn. Microbiol Infect. Dis., 2011; 70: 373-379.
[30]  Rybak MJ, Lomaestro BM, Rotschafer JC, et al. Vancomycin therapeutic guidelines: a summary of consensus recommendations from the Infectious diseases Society of America, the American Society of health system Pharmacists, and the Society of Infectious diseases Pharmacists. Clin. Infect. Dis., 2009; 49: 325-327.
[31]  Hidayat LK, Hsu DI, Quist R, et al. High-dose vancomycin therapy for methicillin-resistant Staphylococcus aureus infections: efficacy and toxicity. Arch. Intern. Med., 2006; 166: 2138-2144.
[32]  Liu C, Bayer A, Cosgrove SE, et al. Clinical practice guidelines by the Infectious Diseases Society of America for the treatment of methicillin-resistant Staphylococcus aureus infections in adults and children. Clin. Infect. Dis., 2011; 52: e18-55.