Determinants of Vancomycin Resistance and Death in Enterococcal Bacteremia

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The summary below is from the full report titled "Determinants of Vancomycin Resistance and Mortality Rates in Enterococcal Bacteremia. A Prospective Multicenter Study." It is in the 2 October 2001 issue of Annals of Internal Medicine (volume 135, pages 484-492). The authors are EN Vergis, MK Hayden, JW Chow, DR Snydman, MJ Zervos, PK Linden, MM Wagener, B Schmitt, and RR Muder.

What is the problem and what is known about it so far?

Enterococci (a bacteria) ordinarily live in the colon, but under certain circumstances they can spread to the bloodstream (enterococcal bacteremia) and cause potentially fatal infections. While most enterococci can be treated with many different antibiotics, about 20% of the enterococci found in patients in intensive care units are highly resistant to antibiotics.

Why did the researchers do this particular study?

The researchers wanted to determine the clinical situations associated with the presence of resistant enterococci, the effect of antibiotic resistance on survival, and the effect of appropriate antibiotic therapy on survival.

Who was studied?

391 patients with enterococcal bacteremia who were hospitalized at five institutions between February 1995 and March 1997. An additional 9 patients were added later.

How was the study done?

Blood samples were drawn, and if enterococci were found, the bacteria were tested for susceptibility or resistance to various antibiotics (vancomycin, aminoglycosides, ampicillin, and quinupristin–dalfopristin). The patients' hospital charts were reviewed to evaluate the significance of length of hospitalization before enterococcal bacteremia, underlying disease before infection, measurement of severity of illness at onset of infection (Acute Physiology and Chronic Health Evaluation [APACHE] II score), antibiotic treatment before the infection started, previous treatment with cortisone-type medication (or other medications that interfere with immunity to infection), surgical procedures in the 2 weeks before infection, and antibiotic therapy during the 6 weeks after onset of infection.

What did the researchers find?

Two main types of enterococci were found: Enterococcus faecalis (8% resistant to vancomycin, 37% resistant to gentamicin, 3% resistant to ampicillin, almost completely resistant to quinupristin–dalfopristin and E. faecium [80% resistant to vancomycin, 87% resistant to ampicillin, 60% resistant to gentamicin, 22% resistant to quinupristin–dalfopristin]. Patients with vancomycin-resistant bacteria were more likely than those without resistant bacteria to have underlying illnesses, a higher APACHE II score, a recent surgical procedure, longer hospitalization, treatment with drugs that interfere with immunity to infection, and antibiotic treatment within 14 days before enterococcal bacteremia. Nineteen percent of the patients died within 14 days. Factors associated with death included vancomycin-resistant enterococci, severity of illness (indicated by APACHE II score), and cancer of the blood. Patients who received appropriate antibiotic therapy for enterococcal bacteremia within 48 hours of recognition of infection were much less likely to die of the infection than those who did not receive appropriate therapy.

What were the limitations of the study?

Specific antibiotic treatment programs were not tested to evaluate their effectiveness in decreasing the death rate.

What are the implications of the study?

Vancomycin resistance seems to be an independent predictor of death in patients with enterococcal bacteremia. Timely administration of appropriate antibiotics decreases the death rate.