Antimicrobial Resistance in the US


The emergence and dissemination of antimicrobial-resistant microorganisms in the health care setting represent a complex and enormous challenge to patient-care providers, hospital and public health administrators. Resistance has occurred to both long-established and recently introduced antimicrobials. It has been estimated that at least 70% of healthcare-associated infections identified in hospitals are caused by bacteria that are resistant to at least one drug traditionally used for treatment. An increasing proportion of these infections is resistant to multiple drugs. Less information is available to estimate the prevalence of antimicrobial resistance in non-hospital settings, but most data suggest that resistance is emerging in all health care venues. 1

Over the past decade, we have seen a remarkable increase in resistance among important community- and hospital-acquired pathogens, such as penicillin-resistant Streptococcus pneumoniae (PRSP), vancomycin-resistant enterococci (VRE), and methicillin-resistant Staphylococcus aureus (MRSA). 2,3 Since the first US report in 1997 of S. aureus with intermediate or decreased susceptibility to vancomycin (VISA), the emergence of fully vancomycin-resistant S. aureus (VRSA) has been anticipated. 4 In July 2002, the first documented case of infection caused by VRSA was reported in the US. 5

Penicillin-resistant Streptococcus pneumoniae

Streptococcus pneumoniae is a leading cause of bacteremia, pneumonia, meningitis, and otitis media. Until 1987, it was considered uniformly susceptible to penicillin. Since then, there has been increased identification of penicillin-nonsusceptible S. pneumoniae in the US. 6,7 Data from the CDC Active Bacterial Core Surveillance (ABCS) System (1995-1997) showed that, by 1997, one in four S. pneumoniae isolates demonstrated some degree of resistance to penicillin; one in seven isolates had high-level resistance. 8 In a study that included clinical isolates of S. pneumoniae obtained from 34 US medical centers from November 1997 to April 1998, the overall rate of penicillin resistance was 29.5%, with 12.1% fully resistant. 9

Vancomycin-resistant Enterococci

Enterococci are responsible for approximately 10% of hospital-acquired infections in the US. 1 According to data obtained by the National Nosocomial Infections Surveillance (NNIS) System from January-December 1999, nearly 25% of enterococci associated with nosocomial infections in intensive-care unit (ICU) patients were VRE. This represents an increase of 40% compared with resistance rates obtained from 1994-1998. 10 The rapid increase in VRE infections presents important clinical and public health issues: (1) the lack of available antimicrobial therapy because most VRE are also resistant to drugs previously used to treat such infections; and (2) the possibility that the vancomycin resistance genes in VRE can be transferred to other Gram-positive microorganisms, such as Staphylococcus aureus. 11

Methicillin-resistant Staphylococcus aureus

Staphylococcus aureus, considered to be more virulent than the enterococci, is one of the most common causes of both community- and hospital-acquired infections. 2 Over the past decade, infections caused by S. aureus resistant to methicillin and other beta-lactams (MRSA) have markedly increased. NNIS data obtained from January-December 1999 showed that 53.5% of S. aureus associated with nosocomial infections in ICU patients were MRSA, which represents an increase of 40% from 1994-1998. 10

Vancomycin-resistant Staphylococcus aureus

Vancomycin has been used to treat MRSA. In 1997, S. aureus with decreased susceptibility to vancomycin (VISA) was reported for the first time in the US. Since this first US report of VISA, the emergence of fully vancomycin-resistant S. aureus (VRSA) has been anticipated. 4 The Centers for Disease Control and Prevention (CDC), in collaboration with state health departments, initiated programs to promote the detection and control of VISA. In July 2002, the first documented case of infection caused by VRSA was reported in a patient in the US. 5The emergence of VRSA demonstrates the urgent need to implement preventive programs to address the problem of antimicrobial resistance in all health care settings.

Public Health Dispatch

Vancomycin-resistant Staphylococcus aureus - Pennsylvania, 2002. MMWR October 2002; 51 (40): 902.

Staphylococcus aureus Resistant to Vancomycin - US, 2002. MMWR July 2002; 51 (26): 565-567.

Action Plan to Combat Antimicrobial Resistance

Surveillance is among the four focus areas included in the Public Health Action Plan to Combat Antimicrobial Resistance. The action plan was developed by an interagency Task Force that was created in 1999. The Task Force is co-chaired by CDC, the Food and Drug Administration, and the National Institutes of Health, and also includes the Agency for Healthcare Research and Quality, the Health Care Financing Administration, the Health Resources and Services Administration, the Department of Agriculture, the Department of Defense, the Department of Veterans Affairs, and the Environmental Protection Agency.
CDC: Public health action plan to combat antimicrobial resistance


  1. Preventing antimicrobial-resistant healthcare infections: Beyond 2000. Clinical Updates in Infectious Diseases August 2000; 5 (2): 1-3.
  2. Jarvis W. Preventing the emergence of multidrug-resistant microorganisms through antimicrobial use controls: the complexity of the problem. Infection Control and Hospital Epidemiology August 1996; 17 (8): 490-495.
  3. Hooton TM, Levy SB. Antimicrobial resistance: A plan of action for community practice. American Family Physician March 2001; 63 (6): 1087-1096.
  4. Staphylococcus aureus with reduced susceptibility to vancomycin - United States, 1997. MMWR August 1997; 46 (33): 756-766.
  5. Staphylococcus aureus resistant to vancomycin - United States, 2002. MMWR July 2002; 51 (26) 565-567.
  6. Surveillance for penicillin-nonsusceptible Streptococcus pneumoniae - New York City, 1995. MMWR April 1997; 46 (14): 297-299.
  7. Breiman RF, Butler JC, Tenover FC, Elliot JA, Facklam RR. Emergence of drug-resistant pneumococcal infections in the United States. JAMA 1994; 271: 1831-5.
  8. Preventing emerging infectious diseases. A strategy for the 21 st century. MMWR September 1998; 47 (RR-15).
  9. Doern G, Brueggemann A, Huynh H, Wingert E, and Rhomberg P. Synopsis: Antimicrobial resistance with Streptococcus pneumoniae in the United States, 1997-98. Emerging Infectious Diseases November-December 1999; 5 (6): 757-765.
  10. National Nosocomial Infections Surveillance (NNIS) Semiannual Report. Centers for Disease Control and Prevention, December 2000.
  11. Recommendations for preventing the spread of vancomycin resistance: Recommendations of the Hospital Infection Control Practices Advisory Committee (HICPAC). MMWR September 1995; 44 (RR-12).


Antimicrobial Resistance Surveillance

Communicable Disease

Public Health