Antibiotic Stewardship: Resistance and Strategies at the Vancouver Hospital

The discovery of antimicrobial compounds and their development over the past 50 years has been perhaps the greatest medical advance of all time and has influenced the health of communities worldwide. During the 1970s and 1980s, pharmaceutical companies produced many new compounds with specific advantages. For example, cefoxitin, a ‘second-generation’ cephalosporin with activity against anaerobic organisms, and ‘third-generation’ cephalosporins with expanded activity against resistant Gram-negative bacilli, including Pseudomonas aeruginosa, were developed. Accompanying the advances in antimicrobial development were advances in prosthetics, and new, inert plastics that facilitated development of artificial joints and longer-dwelling intravenous lines. Prophylactic antibiotics could then be used to prevent potential infections from complicated surgical procedures. Although the use of antimicrobials has had many advantages in modern medicine, the steady increase in antimicrobial resistance worldwide is now recognized as a major disadvantage. During earlier use of antibiotics, bacterial resistance was viewed in the context of hospital-acquired infection, principally occurring as a result of Gram-negative rod infections. The resistance patterns were often hospitaland even unitspecific, and could be eliminated with appropriate infectioncontrol measures when reservoirs were eliminated. In a cross Canada surveillance study of susceptibilities in Gramnegative rods, Bryce et al (1) documented resistance rates in 20 Canadian intensive care units (ICUs). Compared with resistance rates found in a similar hospital-wide study over the same time period from 20 Canadian hospitals (2), Bryce et al (1) found that resistance rates were higher in ICUs. For example, resistance rates were 27%, 20% and 22% for imipenem, ceftazidime and ciprofloxacin respectively, compared with 23%, 12%, and 5% in the hospital-wide study. Higher rates of resistance may be associated with ICU patients because they have a higher level of acute illness and a larger number of complicated problems. In general, these severely ill patients have taken up more hospital beds in the 1990s than they did 20 years ago. In the 1990s it has become apparent that the greatest enemy among resistant bacteria is not Gram-negative rods but rather Gram-positive cocci, including the following: methicillinresistant Staphylococcus aureus, which comprise 2.3% of all hospital S aureus isolates (3); and high level penicillin-resistant Streptococcus pneumoniae, which comprises as many as 7.1% of clinical isolates in Saskatchewan and 4.4% in a 1996 crossCanada survey (4). Although vancomycin-resistant enterococci (VRE) have appeared in outbreaks in several large Ontario hospitals (5), further outbreaks have been curtailed by intensive screening of patients admitted with a history of exposure to medical facilities in the United States where VRE prevalence is high. Vancomycin-intermediate S aureus, with minimal inhibitory concentrations of 8 mg/L (6), have been reported, and the threat of fully vancomycin-resistant S aureus lies ahead. How have antibiotic-resistant bacterial outbreaks developed, and what can physicians, the major antibiotic prescribers, do to prevent outbreaks? The answer to the first question is indiscriminate overuse of antibiotics, and the answer to the second question is antibiotic stewardship that adopts responsible, discerning practices in prescribing antibiotics and in preventing of bacterial infections.