Katherine A. Deaver

The Prevalence of Drug-Resistant Streptococcus pneumoniae In Atlanta

BACKGROUND Streptococcus pneumoniae is a major cause of illness, and the emergence of drug-resistant strains threatens to complicate the management of pneumococcal infections. We conducted a laboratory-based surveillance for drug-resistant S. pneumoniae among patients with invasive pneumococcal infections in Atlanta. METHODS From January through October 1994, pneumococcal isolates from 431 patients with invasive disease in metropolitan Atlanta were serotyped and tested to determine their susceptibility to various antimicrobial agents. Susceptibility to the antimicrobial agents was defined according to guidelines established by the National Committee for Clinical Laboratory Standards. RESULTS The annual incidence of invasive pneumococcal infection was 30 cases per 100,000 population. Isolates from 25 percent of the patients were resistant to penicillin (7 percent were highly resistant), and isolates from 26 percent were resistant to trimethoprim-sulfamethoxazole (7 percent highly resistant). Fifteen percent of the isolates were resistant to erythromycin, 9 percent to cefotaxime (4 percent were highly resistant), and 25 percent to multiple drugs. Drug-resistant pneumococci were found in both children and adults. Children under six years of age were more likely than older children and adults to have isolates resistant to multiple drugs or cefotaxime. Whites were more likely than blacks to have invasive pneumococcal infections caused by drug-resistant organisms. Among white children younger than six years, 41 percent of the S. pneumoniae isolates were resistant to penicillin. CONCLUSIONS Drug-resistant strains of S. pneumoniae are common among both children and adults in Atlanta. Although blacks had a higher incidence of invasive pneumococcal infections than whites, whites were more likely to be infected with a drug-resistant isolate. Control of drug-resistant pneumococci will require more judicious use of antimicrobial agents and wider use of the pneumococcal polysaccharide vaccine.

Carriage of Haemophilus influenzae type b in children after widespread vaccination with conjugate Haemophilus influenzae type b vaccines.

Rates of invasive Haemophilus influenzae type b (Hib) disease in children decreased very rapidly after licensure of Hib conjugate vaccines. A role for a vaccine-related reduction in nasopharyngeal carriage of Hib has been suggested. We studied oropharyngeal carriage of Hib and vaccination rates in a population of 2− to 5-year-old children in metropolitan Atlanta. Among 584 children 75% were vaccinated with an Hib conjugate vaccine, 17% had not been vaccinated and 8% had no vaccination records available. Forty-one percent of the children were colonized with H. influenzae. One child was colonized with Hib. Hib carriage (0.17%; upper 95% confidence interval boundary, 0.97%) was substantially lower than the estimates of Hib carriage from prior studies of children who had not received Hib conjugate vaccines. Our data are consistent with a decline in Hib carriage induced by widespread use of conjugate Hib vaccines, which may have contributed to the decline of Hib disease in United States children.

Reduction in the incidence of human listeriosis in the United States. Effectiveness of prevention efforts? The Listeriosis Study Group

BACKGROUND Food-borne transmission is now recognized as a major cause of human listeriosis. OBJECTIVE To assess the impact of prevention efforts, listeriosis rates before interventions were initiated in 1989 were compared with more recent rates (1990 through 1993). DESIGN From 1989 through 1993, multistate, laboratory-based active surveillance was conducted to identify all cases in which Listeria monocytogenes was isolated from cultures or ordinarily sterile sites in an aggregate population of more than 19 million. SETTING All laboratories serving acute care hospitals in up to nine surveillance areas in the United States. INTERVENTIONS In 1989, a well-publicized case report of listeriosis linked to processed poultry led US regulatory agencies to enforce aggressive food monitoring policies and prompted industry to invest in cleanup efforts. In May 1992, consumer guidelines for listeriosis prevention were disseminated. OUTCOME MEASURES Cases of perinatal and nonperinatal listeriosis. RESULTS The rate of listeriosis decreased in all surveillance areas. Projection of these rates to the US population suggests an estimated 1965 cases and 481 deaths occurred in 1989 compared with an estimated 1092 cases and 248 deaths in 1993, a 44% and 48% reduction in illness and death, respectively. Among adults 50 years of age and older, rates declined from 16.2 per 1 million in 1989 to 10.2 per 1 million in 1993 (P = .02). Perinatal disease decreased from 17.4 cases per 100,000 births in 1989 to 8.6 cases per 100,000 births in 1993 (P = .003). Three serotypes (1/2a, 1/2b, and 4b) of L monocytogenes accounted for more than 96% of cases during each year of the study (1989 through 1993). CONCLUSIONS The incidence of listeriosis in study areas was substantially lower in 1993 than in 1989. The temporal association of this reduction with industry, regulatory, and educational efforts suggests these measures were effective.

Comparison of three selective enrichment methods for the isolation of Listeria monocytogenes from naturally contaminated foods

Three selective enrichment procedures-the U.S. Food and Drug Administration (FDA) method, the U.S. Department of Agriculture (USDA) method, and the Netherlands Government Food Inspection Service (NGFIS) method-were compared for isolating Listeria monocytogenes from contaminated foods. The foods were obtained from the refrigerators of patients with culture-proven listeriosis who were identified through multistate active surveillance in a U.S. population of 19 million. The study was designed to identify foods that may be important in transmission of L. monocytogenes in sporadic cases of human listeriosis. Of 899 foods analyzed by all three methods, 121 were positive for L. monocytogenes by at least one method. The three enrichment methods detected L. monocytogenes in 65% (FDA), 74% (USDA), and 74% (NGFIS) of the foods shown to contain L. monocytogenes . The differences among the three methods were not statistically significant. However, the recovery of L. monocytogenes by a combination of any two methods (USDA-FDA 88%, USDA-NGFIS 91%, FDA-NGFIS 87%) was significantly better than that by one method alone (p < 0.02). The differences among the combinations of methods were not statistically significant. These results suggest that at least two enrichment methods must be used in combination to recover L. monocytogenes from contaminated foods with a success rate near 90%. Correlations were observed between negative results and low (<0.3 CFU/g) level of L. monocytogenes contamination for the USDA (p << 0.001) and NGFIS (p << 0.001) methods. A similar but somewhat weaker association was observed for the FDA method (p < 0.06).

Role of Foods in Sporadic Listeriosis. I. Case-Control Study of Dietary Risk Factors

OBJECTIVE To identify dietary risk factors for sporadic listeriosis. DESIGN Case-control study with blinded telephone interviews. SETTING Multistate population of 18 million persons, November 1988 through December 1990. PARTICIPANTS One hundred sixty-five patients with culture-confirmed listeriosis and 376 control subjects matched for age, health care provider, and immunosuppressive condition. RESULTS The annual incidence of invasive listeriosis was 7.4 cases per million population; 23% of the infections were fatal. Cases were more likely than matched controls to have eaten soft cheeses (odds ratio [OR], 2.6; 95% confidence interval [CI], 1.4 to 4.8; P = .002) or food purchased from store delicatessen counters (OR, 1.6; 95% CI, 1.0 to 2.5; P = .04); 32% of sporadic disease could be attributed to eating these foods. Sixty-nine percent of cases in men and nonpregnant women occurred in cancer patients, persons with the acquired immunodeficiency syndrome, organ transplant recipients, or those receiving corticosteroid therapy. Among these immunosuppressed patients, eating undercooked chicken also increased the risk of listeriosis (OR, 3.3; 95% CI, 1.2 to 9.2; P = .02). CONCLUSIONS Foodborne transmission may account for a substantial portion of sporadic listeriosis. Prevention efforts should include dietary counseling of high-risk patients and continued monitoring of food production.