Pneumococci may cause many clinical syndromes depending on the site of infection (e.g. otitis media, pneumonia, bacteremia, or meningitis). For the purposes of national surveillance, "invasive" pneumococcal disease refers only to bacteremia and/or meningitis. Although S. pneumoniae infections involving other normally sterile sites such as joint, pleural, or peritoneal fluid are sometimes considered invasive, these infections are not intended for inclusion under this surveillance system.
A clinically compatible case caused by laboratory-confirmed culture of S. pneumoniae identified as "non-susceptible" (i.e., an oxacillin zone size of less than 20mm) when oxacillin screening is the only method of antimicrobial susceptibility testing performed
A clinically compatible case caused by laboratory-confirmed S. pneumoniae identified as "non-susceptible" according to MIC interpretive breakpoints as outlined in NCCLS guidelines for susceptibility testing to any antimicrobial agent currently approved for use in treating pneumococcal infection*
NCCLS recommends that all invasive S. pneumoniae isolates that are found to be "possibly resistant" to beta-lactams (i.e., an oxacillin zone size of less than 20mm) by oxacillin screening should undergo further susceptibility testing using a quantitative MIC method acceptable for penicillin, extended spectrum cephalosporins, and other drugs as clinically indicated. * Minimum Inhibitory Concentration (MIC) Interpretive Standard (µg/ml) for S. pneumoniae; NCCLS Guidelines 1994.