US Centers for Disease Control
Update: Staphylococcus aureus with reduced susceptibility to
vancomycin -- United States, 1997
Morb Mort Weekly Rep
(Sep) 46:No.35 1997
Reproduced from MMWR:
Update: Staphylococcus aureus with Reduced Susceptibility to
Vancomycin -- United States, 1997
Staphylococcus aureus is one of the most common causes of both
hospital- and community-acquired infection worldwide. Since the
emergence of methicillin-resistant S. aureus (MRSA) in the 1980s in
the United States, vancomycin has been the antimicrobial agent of
choice for serious MRSA infections. S. aureus with reduced
susceptibility to vancomycin (minimum inhibitory concentration
[MIC]=8 u/mL) was first reported to have caused infection in a
patient in Japan in May 1996 (1). In August 1997, the first S.
aureus isolate intermediately resistant to vancomycin (VISA; MIC=8
u/mL) in the United States was reported in Michigan (2). This
report updates the ongoing investigation in Michigan and describes
preliminary findings of the ongoing investigation of a second case
of VISA infection in a patient in New Jersey.
In July 1997, VISA-associated peritonitis was
diagnosed in a Michigan resident who was being treated with
long-term ambulatory peritoneal dialysis (2). During January-June,
the patient had been treated with multiple courses of both
intraperitoneal and intravenous vancomycin for repeated episodes of
vancomycin-susceptible, MRSA-associated peritonitis. Although
intermediately resistant to vancomycin, the VISA isolate was
susceptible to chloramphenicol, rifampin,
trimethoprim-sulfamethoxazole, and tetracycline. The patient
continues to receive antimicrobial therapy at home. As a part of
the investigation, cultures were obtained from the hands and nares
of the index patient's household contacts, hospital roommates, and
health-care providers. Although S. aureus was isolated from 13
(25.4%) of 51 hand cultures and eight (15.6%) of 51 nares cultures,
none of these cultures were positive for VISA.
In August 1997, a VISA-associated bloodstream
infection was diagnosed in a New Jersey resident with long-term
MRSA colonization and repeated MRSA infections since February. The
patient was not receiving chronic dialysis. In addition, since
February, the patient has had vancomycin-resistant enterococcal
(VRE) colonization. During March-August, the patient had been
treated with multiple courses of vancomycin for repeated MRSA
bloodstream infections. In August, a blood culture from the patient
grew an MRSA strain with intermediate resistance to vancomycin
(MIC=8 u/mL); all previous MRSA strains had been vancomycin
susceptible. This VISA isolate was sent to CDC, where the
intermediate resistance was confirmed; the isolate was susceptible
to gentamicin, trimethoprim-sulfamethoxazole, tetracycline, and
imipenem. The patient continues to receive antimicrobial therapy at
Reported by: R Martin, DrPH, KR Wilcox, MD, State Epidemiologist,
Michigan Dept of Community Health. C Campbell, DVM, H Ellis, MD,
State Epidemiologist, New Jersey Dept of Health and Senior Svcs.
Div of Applied Public Health Training (proposed), Epidemiology
Program Office; Hospital Infections Program, National Center for
Infectious Diseases, CDC.
Since the 1980s (when MRSA emerged in the United
States), vancomycin has been the last uniformly effective
antimicrobial available for treatming serious S. aureus infections.
The findings in this report document two VISA infections in the
United States within a 1-month period. Widespread use of
antimicrobials, such as vancomycin, is a major contributing factor
for the emergence of VRE and other vancomycin-resistant organisms.
In the first case in the United States (case 1), spread of VISA to
other patients and health-care workers probably was prevented by
prompt identification of the isolate and its susceptibility
pattern, isolation of the patient while hospitalized, and
implementation of recommended infection-control practices (3). In
both Michigan and New Jersey, VISA was detected by using a 24-hour
MIC dilutional method that had not changed over the period during
which these patients had repeated S. aureus infections. The
detection of a second U.S. strain of VISA with a different
antimicrobial susceptibility pattern from those isolated previously
suggests that these strains are developing de novo secondary to
vancomycin exposure. Further studies are under way to determine
VISA genotypes and to identify the mechanism(s) of resistance.
The emergence of VISA in the United States suggests that S.
aureus strains with full resistance to vancomycin may eventually
emerge. These episodes emphasize the need to enhance laboratory
capacity at the hospital and state levels to recognize these
strains, the importance of prudent use of antimicrobials, and the
requirement for full implementation of recommended
infection-control measures to prevent transmission of these
strains. To prevent spread of these organisms within and between
facilities, health-care providers and facilities are advised to 1)
use a quantitative method (broth dilution, agar dilution, or agar
gradient diffusion) to identify these strains; 2) ensure
appropriate use of vancomycin, including the review of antibiograms
for alternative antibiotics (4); 3) educate health-care personnel
about the epidemiologic implications of emergence of such strains
and the appropriate infection-control precautions necessary to
prevent their spread; 4) strictly adhere to and monitor compliance
with contact-isolation precautions and other recommended
infection-control practices; and 5) conduct surveillance to monitor
for the emergence of resistant strains. Detailed recommendations to
prevent, detect, and control S. aureus with reduced susceptibility
to vancomycin have been published (3).
The isolation of S. aureus with confirmed or "presumptive"
reduced vancomycin susceptibility should be reported immediately
through state and local health departments to CDC's Investigation
and Prevention Branch, Hospital Infections Program, National Center
for Infectious Diseases, Mailstop E-69, 1600 Clifton Road, N.E.,
Atlanta, GA 30333; telephone (404) 639-6413. Physicians treating
patients with infections caused by staphylococci with reduced
susceptibility to vancomycin can obtain information about
investigational drug therapies from the Food and Drug
Administration's Division of Anti-Infective Drug Products, Center
for Drug Evaluation and Research, telephone (301) 827-2120.
1. CDC. Reduced susceptibility of Staphylococcus aureus to
vancomycin--Japan, 1996. MMWR 1997;46:624-4.
2. CDC. Staphylococcus aureus with reduced susceptibility to
vancomycin--United States, 1997. MMWR 1997;46:765-6.
3. CDC. Interim guideline for prevention and control of
staphylococcal infection associated with reduced susceptibility to
vancomycin. MMWR 1997;46:626-8,635-6.
4. CDC. Recommendations for preventing the spread of vancomycin
resistance: recommendations of the Hospital Infection Control
Practices Advisory Committee (HICPAC). MMWR 1995 (no. RR-12).
Erratum: Vol. 46, No. 35
In the article, Staphylococcus aureus with Reduced
Susceptibility to Vancomycin--United States, 1997," an error
appears in the second sentence of the second paragraph. The
sentence should read, "During January-June 1997, the patient had
been treated ..."