Therapy for pneumococcal infection at the millennium: doubts and certainties.
Rapidly burgeoning worldwide multiple drug-resistant pneumococcal serotypes pose an urgent demand for new management approaches. Perhaps modern intensive care methods may have alternatives to offer. Indeed, standard assessments such as the admission APACHE II score may overestimate individual risk of death in severe CAP, and mortality can be reduced. However, among those at highest risk for mortality in the early phase of invasive disease, the conclusions reached 2-3 decades ago, that it is questionable whether a more effective drug than penicillin can be developed, and that a reduction in the number of deaths consequent to this infection can be accomplished only by widespread immunoprophylactic measures, remain inescapable. Clearly, as discussed elsewhere in this supplement, the continuing validity of these 20-year-old conclusions and the global prevalence of DRSP demand the development and marketing of new conjugate vaccines, although more widespread use of the existing 23-valent polysaccharide vaccine among high-risk populations is essential in the interim. With respect to resistance selection pressures, antibiotic prescription control may provide the answer. However, patient expectations of antibiotic therapy for trivial respiratory infection is high and, in the United Kingdom, 75% of previously healthy adults will receive it; those who do not will usually consult another physician in an effort to secure such therapy. Thus, without the intervention of government or managed care organizations, self-regulation in prescribing is unlikely. The evidence for beta-lactam treatment failure in meningitis has led to alternative approaches, with vancomycin as the primary agent. Penicillins may remain effective for otitis media, but oral cephalosporins are suspect. Data on pediatric pneumococcal pneumonia continue to suggest use of beta-lactams, at least for disease caused by strains with intermediate penicillin sensitivity. Pallares et al concluded that penicillins and cephalosporins remain the drugs of choice for severe pneumococcal pneumonia in adults. Others who share this conclusion often cite that study as evidence. However, in the case of penicillins, the mortality rate was 6% higher in a subgroup selected for monomicrobial infection and reduced risk factors for mortality when penicillin-resistant infection was present, and the overall mortality was 14% higher with penicillin-resistant strains (taking into account "all comers"). Those who depend on the findings of evidence-based medicine may accept the premise that penicillins and cephalosporins remain the drugs of choice, and agree with Goldstein and Garau that it would indeed be a mistake to adopt alternative therapies. Others may consider the deaths of 6 of 100 patients who were not in the highest-risk group too high a price to pay for statistical significance and may be skeptical of the continued use of beta-lactam therapy on higher-risk patients. In addition, the persistent selection pressure applied by continued use of beta-lactams offers a powerful population-based argument for alternatives. As DRSP continues to spread and resistant strains with penicillin MIC >2 mg/L become more prevalent, new agents such as the azabicyclo-methoxyquinolone, moxifloxacin, and perhaps grepafloxacin, but not the more toxic sparfloxacin and trovafloxacin, will undoubtedly flourish as treatments for CAP. By that time, the results of clinical studies on ketolides and oxazolidinones could offer further choices.
Ball
P
P
School of Biomedical Sciences, University of St. Andrews, Fife, Scotland, United Kingdom.
D000328:Adult; D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D002648:Child; D004352:Drug Resistance, Microbial; D024841:Fluoroquinolones; D006801:Humans; D007769:Lactams; D011008:Pneumococcal Infections / Q000188:drug therapy*; D013296:Streptococcus pneumoniae / Q000187:drug effects*
D000900:Anti-Bacterial Agents; D024841:Fluoroquinolones; D007769:Lactams