Surveillance for Penicillin-Nonsusceptible Streptococcus pneumoniae -- New York City, 1995

Streptococcus pneumoniae has become a leading cause of bacteremia, pneumonia, meningitis, and otitis media in the United States. Persons at increased risk include young children, immunocompromised persons, and the elderly (1). Until 1987, S. pneumoniae was uniformly susceptible to penicillin; since then, in the United States, there has been increased identification of penicillin-nonsusceptible S. pneumoniae (PNSP) (defined as minimum inhibitory concentration {MIC} to penicillin greater than or equal to 0.1 ug/mL), especially penicillin-resistant S. pneumoniae (PRSP) (defined as MIC to penicillin greater than or equal to 2.0 ug/mL). In addition, PNSP is becoming less susceptible to other antimicrobial drugs, including tetracycline, erythromycin, extended-spectrum cephalosporins, and chloramphenicol; some are susceptible only to vancomycin (2). Because of the emergence of PNSP, in December 1994, the New York City Department of Health (NYCDOH) amended the New York City health code to require reporting of PNSP to monitor the local prevalence of resistance to penicillin. This report summarizes surveillance findings from NYCDOH's data for 1995, which indicate that the highest case rates were among children aged less than 4 years and that, among adults aged 20-44 years with PNSP infections, 71.4% also were infected with human immunodeficiency virus (HIV).

The surveillance case definition for PNSP included S. pneumoniae isolated from any anatomical site with a MIC to penicillin greater than or equal to 0.1 ug/mL confirmed by an approved National Committee for Clinical Laboratory Standards (NCCLS) methodology (3). All reports of PNSP were evaluated by telephone consultation with the reporting laboratory to determine the anatomical site, the oxacillin disk diffusion test result, the MIC-testing methodology, and the quantitative MIC. Confirmed cases with isolates from normally sterile sites were investigated by medical record reviews to determine the clinical presentation, underlying medical conditions (including HIV-infection status), and hospitalization and antibiotic use within the preceding 6 months.

In 1995, a total of 282 PNSP cases were reported to NYCDOH by hospital and commercial laboratories (rate: 3.9 cases per 100,000 population). Among 281 infected persons for whom sex was known, 176 (62.6%) were male (5.1 per 100,000), and 105 (37.4%) were female (2.7 per 100,000). Age was available for 266 (94.3%) persons; the median age was 39.6 years (range: 1 week-98 years). Age-group-specific rates were highest for children aged less than 1 year (30.3 per 100,000) and aged 1-4 years (7.5 per 100,000).

Of the 282 persons with PNSP, 130 (46.1%) had invasive illness with PNSP isolates from normally sterile sites. Chart reviews for 125 of the 130 patients indicated that the sites of infection were blood (99 {79.2%}), tracheal aspirate (16 {12.8%}), cerebrospinal fluid (10 {8.0%}), middle ear aspirate (one {0.8%}), and other sites (five {4.0%}); chart information was incomplete or unavailable for five patients. Six persons had invasive isolates confirmed from more than one site. Charts were not reviewed for the 149 (52.8%) patients with isolates from normally nonsterile sites and for three (1.1%) patients with isolates from unknown sites.

Of the 125 invasive cases reviewed, eight (6.4%) were fatal. During the 6 months preceding illness onset, 43 (34.4%) patients with invasive disease had been hospitalized, and 54 (43.2%) had received antibiotic therapy.

Of the 125 patients with invasive illness whose charts were reviewed, 52 (41.6%) were HIV-seropositive or had acquired immunodeficiency syndrome (AIDS). Other underlying medical conditions included pulmonary disease (36 {28.8%}), cardiovascular disease (23 {18.4%}), cancer (13 {10.4%}), diabetes (10 {8.0%}), renal disease (nine {7.2%}), liver disease (five {4.0%}), and splenectomy (two {1.6%}); more than one underlying illness was present in 60 (48.0%) patients. Of the 27 children aged less than 5 years, 14 (51.9%) had an underlying illness (e.g., HIV/AIDS or pulmonary disease), 10 (37.0%) had been hospitalized recently, and 15 (55.6%) had used antibiotics during the previous 6 months. Of the 51 invasive cases in persons with HIV/AIDS with known age, 30 (71.4%) were among 42 persons aged 20-44 years compared with seven (21.2%) of 33 cases among persons aged less than 20 years and 14 (28.6%) of 49 cases among persons aged greater than 44 years; age was unknown for one person.

Of the 52 patients with HIV/AIDS, 31 (59.6%) had been treated with antibiotics within the previous 6 months compared with 23 (31.5%) of the 73 patients without HIV/AIDS (p less than 0.01). Of the 31 patients with HIV/AIDS who received antibiotics within the previous 6 months, 22 (71.0%) had received trimethoprim-sulfamethoxazole as prophylaxis for Pneumocystis carinii pneumonia.

Quantitative MIC data were available for 123 isolates; 60 (48.8%) were PRSP. Among the 73 patients without HIV/AIDS, 26 (35.6%) had infections with PRSP compared with 34 (68.0%) of 50 patients with HIV/AIDS (p less than 0.01).

Reported by: A Labowitz, A Young, R Heffernan, MPH, S Cato, M Layton, MD, B Mojica, MD, New York City Dept of Health. Childhood and Respiratory Diseases Br, Div of Bacterial and Mycotic Diseases, National Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: The findings in this report indicate that, in New York in 1995, PNSP infections were most common among children aged less than 4 years. This is consistent with results from community-based studies of penicillin-susceptible pneumococcal bacteremia, which documented that rates of pneumococcal disease were higher among younger children than among older children and adults (4). In addition, the findings indicate that physicians caring for persons with HIV/AIDS should be aware of the potential for antibiotic resistance when treating presumptive pneumococcal infections.

Surveillance limited to antibiotic-resistant infections is difficult to interpret because information on nonsusceptible isolates does not provide data about the proportion of all isolates in the community that are antibiotic resistant. To address this need, during 1993-1995 the NYCDOH conducted annual surveys of microbiology laboratories to determine the total number of S. pneumoniae isolates identified and the number identified as nonsusceptible by NCCLS-approved methodologies. The proportion of PNSP isolates increased from 7.2% of all isolates tested in 1993 to 15.0% in 1995 (NYCDOH, unpublished data, 1996). To improve the ability to track antibiotic resistance, in 1996 NYCDOH changed its method for collecting surveillance data on PNSP by requesting hospital laboratories report monthly on the total number of invasive S. pneumoniae isolates identified and the number with confirmed resistance, allowing timely collection, analysis, and dissemination of surveillance data to the medical community.

The NYCDOH has provided laboratory directors, hospital infection-control departments, and clinicians with regular updates about PNSP in New York City at medical rounds in hospitals throughout the city. Other efforts have included publishing data in local medical society newsletters and bulletins to alert clinicians to the increasing proportion of PNSP isolates in New York City and to caution against over-prescribing antibiotics.

CDC has recommended that clinicians base their decisions about empiric antibiotic therapy for presumptive pneumococcal infections on local prevalence data (5). Unlike methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus, which initially emerged as nosocomial infections, PNSP infections are primarily community-acquired (6). Therefore, to understand the impact of this disease in the community, population-based surveillance data need to be collected at the local and state levels. In addition, these data should be sent to CDC for aggregation at the national level to assist in monitoring the scope and magnitude of PNSP.

References

1. Plouffe JF, Breiman RF, Facklam RR. Bacteremia with Streptococcus pneumoniae: implications for therapy and prevention. JAMA 1996;275:194-8.

2. Breiman RF, Butler JC, Tenover FC, Elliott JA, Facklam RR. Emergence of drug-resistant pneumococcal infections in the United States. JAMA 1994;271:1831-5.

3. National Committee for Clinical Laboratory Standards. Performance standards for antimicrobial susceptibility testing; sixth informational supplement. Wayne, Pennsylvania: National Committee for Clinical Laboratory Standards, 1995; NCCLS document no. M100-S6. (Vol 15, no. 14).

4. Klein JO. The epidemiology of pneumococcal disease in infants and children. Rev Infect Dis 1981;3:246-53.

5. CDC. Defining the public health impact of drug-resistant Streptococcus pneumoniae: report of a working group. MMWR 1996;45(no. RR-1).

6. Gaynes R. Surveillance of antibiotic resistance: learning to live with bias {Editorial}. Infect Control Hosp Epidemiol 1995;16:623-6.

   
   

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