Streptococcus pneumoniae in community-acquired pneumonia -: How important is drug resistance?

Because the serum and pulmonary levels achieved with penicillin or related drugs are several times higher than the MICs of the strains, most pneumonias caused by S. pneumoniae currently defined as not susceptible to penicillin should respond well to treatment with a beta-lactam antibiotic using optimal dosing. All studies currently available comparing mortality between patients with pneumonia caused by nonsusceptible and susceptible pneumococci agree that resistance of up to MIC 2 mg/L is not independently associated with an increased mortality. Most, but not all, studies also could not prove an effect of microbial resistance on morbidity. Treatment failures, however, may occur at higher levels of resistance and, therefore, a change in the definition of susceptibility categories toward higher cut-offs for S. pneumoniae seems to be reasonable.