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 pneumonia s caused by S. pneumoniae currently defined as not susceptible to penicilli n should respond well to treatment with a beta-lactam antibiotic using opti mal dosing. All studies currently available comparing mortality between pat ients with pneumonia caused by nonsusceptible and susceptible pneumococci a gree that resistance of up to MIC 2 mg/L is not independently associated wi th 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. pneum oniae seems to be reasonable.