Skip to main content Accessibility help

A Comparison of Clinical Virulence of Nosocomially Acquired Methicillin-Resistant and Methicillin-Sensitiye Staphylococcus aureus Infections in a University Hospital

  • Ronald C. Hershow (a1) (a2), Walid F. Khayr (a1) and Nina L. Smith (a1)



To compare the clinical virulence of nosocomially acquired methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive S aureus (MSSA) infections in 1989.


A retrospective comparison of host factors, in-hospital exposures, sites of infections, and outcomes of patients with nosocomial MRSA and MSSA infections.


University of Illinois Hospital, Chicago, Illinois.


Forty-four adult patients with nosocomial S aureus infections.


The 22 MRSA-infected and 22 MSSA-infected persons were similar regarding mean age, gender, underlying diseases, and exposure to surgery. Before developing infection, MRSA-infected persons were more likely to have received antibiotics (73% compared with 27%, odds ratio = 7.1, 95% confidence interval [CI95] = 2.0-25.8 p = .003) and to have stayed in the hospital >2 weeks (64% compared with 18%, odds ratio = 7.9, CI95 = 2.0-31.6, p = .002). Bacteremia was the most common presentation in the MRSA and MSSA groups (55% and 59%, respectively). Infectious complications and death were infrequent in both groups.


MRSA and MSSA strains infect patients with similar demographic features and underlying diseases, but MRSA infections are significantly more common among patients with previous antibiotic therapy and a prolonged preinfection hospital stay. Clinical presentations and outcomes did not differ significantly between the 2 groups. Thus, similar to studies in the early 1980s, our findings do not suggest greater intrinsic virulence of MRSA.


Corresponding author

University of Illinois at Chicago, School of Public Health, 2121 W. Taylor St., Chicago, IL 60612


Hide All
1.Haley, RW, Hightower, AW, Khabbaz, RF, et al. The emergence of methicillin-resistant Staphylococcus aureus infections in United States hospitals. Ann Intern Med. 1982;97:297308.
2.Peacock, JE Jr., Moorman, DR, Wenzel, RP, Mandell, DR. Methicillin-resistant Staphylococcus aureus: microbiologic characteristics, antimicrobial susceptibilities, and assessment of virulence of an epidemic strain. J Infect Dis. 1981;144:575582.
3.Vaudaux, P, Waldvogel, FA. Methicillin-resistant strains of Staphylococcus aureus: relation between exoression of resistance and phagocytosis by polymorphonuclear leukocytes. J Infect Dis. 1982;97:309317.
4.Coleman, DC, Cafferkey, M, Keane, CT, et al. Mechanisms of pathogenicity of multi-resistant Staphylococcus aureus. J Hosp Infect. 1986;7(suppl A):2935.
5.French, GL, Cheng, AFB, Ling, JML, Mo, P, Donnan, S. Hong Kong strains of methicillin-resistant and methicillin-sensitive Staphylococcus aureus have similar virulence. J Hosp Infect. 1990;15:117125.
6.Ward, TT, Krause, LK. Adherence of methicillin-susceptible versus methicillin-resistant Staphylococcus aureus to epithelial cells In: Program and Abstracts of the 31st Interscience Conference on Antimicrobial Agents and Chemotherapy. Chicago, Ill: American Society for Microbiology; 1991:163.
7.Jordens, JZ, Duckworth, GJ, Williams, RJ. Production of ‘virulence factors’ by ‘epidemic’ methicillin-resistant Staphylococcus aureus in-vitro. J Med Microbiol. 1989;30:245252.
8.Duckworth, GJ, Jordens, JZ. Adherence and survival properties of an epidemic methicillin-resistant strain of Staphylococcus aureus compared with those of methicillin-sensitive strains. J Med Microbiol. 1990;32:195200.
9.Peacock, JE Jr., Marsik, FJ, Wenzel, RP. Methicillin-resistant Staphylococcus aureus: introduction and spread within a hospital. Ann Intern Med. 1980;93:526532.
10.Crossley, K, Loesch, D, Landesman, B, Mead, K, Chern, M, Strate, R. An outbreak of infections caused by strains of Staphylococcus aureus resistant to methicillin and aminoglycosides, I: clinical studies. J Infect Dis. 1979;139:273279.
11.Boyce, JM, Landry, M, Deetz, TR, DuPont, HL. Epidemiologic studies of an outbreak of nosocomial methicillin-resistant Staphylococcus aureus infections. Infect Control. 1981;2:110116.
12.Sorrell, TC, Packham, DR, Shanker, S, Foldes, M, Munro, R. Vancomycin therapy for methicillin-resistant Staphylococcus aureus. Ann Intern Med. 1982;97:344350.
13.Grieble, HG, Krause, SL, Pappas, SA, Dicostanzo, MB. The prevalence of high-level methicillin resistance in multiply resis tant hospital staphylococci. Medicine. 1981;60:6269.
14.Law, MR, Gill, ON. Hospital-acquired infection with methicillin-resistant and methicillin-sensitive staphylococci. Epidemiol Infect. 1988;101:623629.
15.McManus, AT, Mason, AD, McManus, WE, Pruitt, BA. What's in a name? Is methicillin-resistant Staphylococcus aureus just another S aureus when treated with vancomycin? Arch Surg. 1989;124:14561459.
16.Lewis, E, Saravolatz, LD. Comparison of methicillin-resistant and methicillin-sensitive Staphylococcus aureus bacteremia. Am J Infect Control. 1985;13:109114.
17.Muder, RR, Brennen, C, Wagener, MM, et al. Methicillin-resistant staphylococcal colonization and infection in a long-term care facility. Ann Intern Med. 1991;114:107112.
18.Gamer, JS, Jarvis, WR, Emori, TG, Horan, TC, Hughes, JM. CDC definitions for nosocomial infections, 1988. Am J Infect Control. 1988;16:128140.
19.National Committee for Clinical Laboratory Standards. Performance Standards for Antimicrobial Disc Susceptibility lists. 4th ed. M2-A4. Villanova, Pa: National Committee-for Clinical Laboratory Standards; 1990.
20.Schlesselman, JJ. Case-Control Studies. Design, Conduct, Analysis. New York, NY: Oxford University Press; 1982.
21.Brumtitt, W, Hamilton-Miller, J. Methicillin-resistant Staphylococcus aureus. N Engl /Med. 1989;320:11881196.
22.Raviglione, MC, Boyle, JF, Mariuz, P, Pablos-Mendez, A, Cortes, H, Merlo, A. Ciprofloxacin-resistant methicillin-resistant Staphylococcus aureus in an acute care hospital. Antimicrob Agents Chemother. 1990:34:20502054.
23.Klimek, JJ, Marsik, FJ, Bartlett, RC, Weir, B, Shea, P, Quintiliani, R. Clinical, epidemiologic and bacteriologic observations of an outbreak of methicillin-resistant Staphylococcus aureus at a large community hospital. Am J Med. 1976;61:340345.
24.Saroglou, G, Cromer, M, Bisno, AL. Methicillin-resistant Staphylococcus aureus: interstate spread of nosocomial infections with emergence of gentamicin-methicillin resistant strains. Infect Control. 1980;1:8189.
25.Winn, RE, Ward, TT, Hartstein, Al, et al. Epidemiological, bacteriological and clinical observations on an interhospital outbreak of nafcillin-resistant Staphylococcus aureus. In: Nelson, JD, Grassi, D, eds. Current Chemotherapy and Infectious Disease. Vol 2. Washington, DC: American Society for Microbiology; 1980:10961097.

A Comparison of Clinical Virulence of Nosocomially Acquired Methicillin-Resistant and Methicillin-Sensitiye Staphylococcus aureus Infections in a University Hospital

  • Ronald C. Hershow (a1) (a2), Walid F. Khayr (a1) and Nina L. Smith (a1)


Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed