Clinical DescriptionPneumococci 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.
Laboratory Criteria For Diagnosis
- Isolation of S. pneumoniae from blood or cerebrospinal fluid
- Intermediate and high level resistance (defined by National Committee for Clinical Laboratory Standards [NCCLS] approved methods and interpretive minimum inhibitory concentration [MIC] breakpoints) of the S. pneumoniae isolate to at least one antimicrobial agent currently approved for use in treating pneumococcal infection*
ProbableA 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
ConfirmedA 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.
1. National Committee for Clinical Laboratory Standards (NCCLS). Performance standards for antimicrobial susceptibility testing. Villanova, PA: National Committee for Clinical Laboratory Standards, 1994;14(16); NCCLS document M100-S5.
2. CDC. Defining the public health impact of drug-resistant Streptococcus pneumoniae: Report of a working group. MMWR 1996;45(No. RR-1).