Group B streptococcal disease in newborns: a global perspective on prevention

Group B Streptococcus (GBS) is an important cause of neonatal sepsis in many areas. Although incidence data are available for a minority of countries, the magnitude of illness due to this bacterium appears to vary substantially. Disease may vary due to the prevalence of asymptomatic GBS colonization, the virulence of circulating strains, the frequency of predisposing conditions such as low birth weight, or differences in obstetric practices. Approaches to prevention of neonatal GBS disease include administering antibiotics to high risk mothers intrapartum, use of intrapartum vaginal disinfectants, development of GBS vaccines, and nonspecific approaches. Determinants of prevention policies in a given area depend on the incidence of disease, the structure of health care delivery, cost-effectiveness, and cultural attitudes. Much GBS disease among newborns is now preventable, yet data on incidence are needed to guide selection of appropriate approaches to disease prevention.

Comparison of ribotyping and multilocus enzyme electrophoresis for subtyping of Listeria monocytogenes isolates

Ribotyping was compared with multilocus enzyme electrophoresis (MEE) for subtyping 305 Listeria monocytogenes isolates from clinical and nonclinical sources. For ribotyping, EcoRI-restricted genomic DNA fragments of L. monocytogenes strains were separated by agarose gel electrophoresis, and Southern blots were probed with a cloned Escherichia coli rrnB operon (plasmid pKK3535) labeled with digoxigenin. The L. monocytogenes isolates were divided into 28 distinct ribotypes, while MEE analysis divided the same isolates into 78 electrophoretic types (ETs). On the basis of their ribotype profiles, the strains were divided into two subgroups. The ribotype alpha (RT alpha) subgroup contained serotypes 1/2a, 1/2c, and 3a, and the ribotype beta (RT beta) subgroup contained serotypes 1/2b, 3b, 4b, and 4ab. This division is in complete agreement with MEE analysis, which divides the species into two subgroups (ET groups A and B), with the same serotype distribution in each subgroup. Overall, MEE was more discriminating than ribotyping. However, in several instances ribotyping discriminated between isolates within the same ET. Ribotyping was more discriminating for serotypes 1/2a, 1/2c, and 3a (Simpson's Index for Diversity [DI] = 0.81) than for serotypes 1/2b and 4b (DI = 0.76). A substantial proportion (69%) of serotype 1/2b and 4b strains clustered in five ETs and five ribotypes. These data suggest that ribotyping and MEE do not provide adequate discrimination between strains of serotypes 1/2b and 4b. Methods such as pulsed-field gel electrophoresis and random amplified polymorphic DNA analysis should be explored for further discrimination of strains of these serotypes.

Multistate case-control study of maternal risk factors for neonatal group B streptococcal disease. The Active Surveillance Study Group

Risk factors for early onset disease (EOD) caused by Group B streptococci (GBS) that are the foundation of prevention guidelines were identified in studies conducted in a few hospital centers. We investigated cases of EOD identified through laboratory-based active surveillance during 1991 and 1992 in a multistate population of 17 million. Ninety-nine cases were compared with 253 controls matched for hospital, date of birth and birth weight. Prematurity (< 37 weeks of gestation) was present in 28% of cases; 53% of case mothers had rupture of membranes > 12 hours; and 48% reported intrapartum fever. The incidence of EOD in each surveillance area was higher among blacks. By multivariate analysis, case mothers were more likely than controls to have rupture of membranes before labor onset (adjusted odds ratio 8.7, P < 0.001), intrapartum fever (adjusted odds ratio 11.9, P < 0.001), and history of urinary infection during pregnancy (adjusted odds ratio 4.3, P < 0.05). Young maternal age was also associated with risk of disease. Three-fourths of case mothers had intrapartum fever, < 37 weeks of gestation and/or prolonged rupture of membranes, indicators previously used to select high risk women for intrapartum chemoprophylaxis. Our findings extend data from single hospitals and suggest prenatal screening and selective intrapartum chemoprophylaxis of high-risk mothers could potentially prevent the majority of EOD in the United States.

Comparison of prevention strategies for neonatal group B streptococcal infection. A population-based economic analysis

BACKGROUND

Intrapartum antibiotics can prevent early-onset neonatal group B streptococcal (GBS) disease but have not been widely used. Obstacles include difficulty in implementing screening for GBS colonization and uncertainty about cost-effectiveness. The GBS vaccines for disease prevention are now being developed.

METHODS

We developed a decision analysis model and used standard cost-effectiveness and cost-benefit analysis methods. We compared the outcomes and costs of the recent practice of no intervention with those expected for three prevention strategies: (1) intrapartum antibiotics administered to colonized women with labor complications, (2) an alternative strategy that does not require screening but uses epidemiologic criteria and labor complications to target intrapartum antibiotics, and (3) maternal vaccination. We used data from multistate population-based surveillance to estimate the potential impact of each strategy on disease and costs in the United States.

RESULTS

Intrapartum antibiotic prophylaxis of high-risk women identified by screening could prevent approximately 3300 cases (47% of neonatal disease) annually in the United States and could save approximately $16 million in direct medical costs. Chemoprophylaxis of high-risk women identified using epidemiologic criteria could potentially be equally effective (3200 cases prevented) and would avoid the logistical difficulties of screening; the net savings would be approximately $66 million. Vaccinating 80% of pregnant women with a vaccine that prevents 80% of cases among infants born at or after 34 weeks of gestation would prevent approximately 4100 neonatal cases annually with a net savings of $131 million.

CONCLUSIONS

Universal prenatal screening for GBS and chemoprophylaxis of colonized women with labor complications is likely to be cost-beneficial in the United States. Development of alternative strategies should be further explored for populations in which GBS screening is impractical. Continued development of a GBS vaccine is an important public health priority.

Increased risk of meningitis and bacteremia due to Listeria monocytogenes in patients with human immunodeficiency virus infection

The incidence, demographics, and clinical outcome of infections due to Listeria monocytogenes in individuals infected with the human immunodeficiency virus (HIV) were evaluated by prospective population-based surveillance. During a 2-year study period, 37 cases of invasive listeriosis occurred in metropolitan Atlanta (annual incidence, 0.8 case per 100,000 population). Seven of these cases occurred in known HIV-infected individuals (19% of all cases); five had an AIDS-defining illness, and the other two had CD4 lymphocyte cell counts of < 200/microL. The estimated incidence of listeriosis among HIV-infected patients in metropolitan Atlanta was 52 cases per 100,000 patients per year, and among patients with AIDS it was 115 cases per 100,000 patients per year, rates 65-145 times higher than those among the general population. HIV-associated cases occurred in adults who were 29-62 years of age and in postnatal infants who were 2 and 6 months of age. Mortality among the HIV-infected group was 29%. L. monocytogenes serotypes 1/2a, 1/2b, and 4b were isolated from the HIV-infected patients. L. monocytogenes is an important opportunistic pathogen in HIV-infected patients.

Outbreak of early onset group B streptococcal sepsis

During January and August, 1990, 23 cases of early onset Group B Streptococcus (GBS) disease occurred in a Kansas City, MO, hospital with an attack rate of 14/1000 live births, compared with an annual rate of 1.2 cases/1000 live births for 1988 through 1989. Case infants were compared with controls matched by birth weight, race, maternal age and day of delivery and to a second group of infants of mothers colonized with GBS to identify risk factors and consider intervention strategies during the outbreak. The presence of multiple serotypes among the invasive strains suggested that the outbreak was not caused by a common source. Case mothers were more likely than control mothers to have chorioamnionitis, intrapartum fever or rupture of membranes > 12 hours, and premature case infants were more likely to have a history of rupture of membranes before onset of labor. Multiparous mothers of case infants were more likely to have a history of spontaneous abortion (odds ratio, 6.7; 95% confidence interval, 1.0 to 45.9). No single factor could explain the increase in GBS disease. If intrapartum antibiotic prophylaxis had been used for selected GBS carriers based on presence of either rupture of membranes > 12 hours, intrapartum maternal fever or preterm labor, 7.4% of all deliveries would have received antibiotics and 73% of cases could potentially have been prevented. We conclude that identification of colonized mothers with perinatal risk factors and use of intrapartum antibiotics could be expected to prevent substantial disease during an outbreak of early onset GBS disease.

A population-based assessment of invasive disease due to group B Streptococcus in nonpregnant adults

BACKGROUND

Group B streptococci (Streptococcus agalactiae) are a major cause of meningitis and septicemia in neonates and pregnant women, but the importance of group B streptococcal disease in nonpregnant adults has not been clearly defined.

METHODS

We conducted a prospective surveillance of the pathogens responsible for meningitis for a period of 24 months in 35 hospitals and a referral laboratory in metropolitan Atlanta. We reviewed the clinical and laboratory records of all the nonpregnant adults identified as having invasive group B streptococcal disease during this period.

RESULTS

During 1989 and 1990 there were 424 patients with invasive group B streptococcal disease (annual incidence, 9.2 cases per 100,000 population). Of these patients, 46 percent were 1 month of age or younger, 6 percent were older than 1 month but younger than 18 years of age, and 48 percent were 18 or older. Men and nonpregnant women accounted for 68 percent (n = 140) of all cases among adults (annual incidence, 4.4 per 100,000). Clinical and laboratory records were available for 137. In the nonpregnant adult patients (age, 18 to 99 years), the most common clinical diagnoses were skin, soft-tissue, or bone infection (in 36 percent); bacteremia with no identified source (30 percent); urosepsis (14 percent); pneumonia (9 percent); and peritonitis (7 percent). Risk factors included older age (> or = 60 years), the presence of diabetes mellitus, the presence of malignant neoplasms, and infection with the human immunodeficiency virus. The mortality rate in nonpregnant adults was 21 percent, accounting for 67 percent of all deaths related to group B streptococcal infection during the surveillance period.

CONCLUSIONS

Invasive group B streptococcal infection is a major problem not only in pregnant women and neonates but also in nonpregnant adults, especially those who are elderly and those who have chronic diseases.

Group B streptococcal disease in the United States, 1990: report from a multistate active surveillance system

Group B streptococcal (GBS) disease is the most common cause of neonatal sepsis and meningitis in the United States. It is also an important cause of morbidity among pregnant women and adults with underlying medical conditions. Because most states have not designated GBS disease as a reportable condition, previous estimates of the incidence of GBS disease were based on studies from single hospitals or small geographic areas. This report summarizes the results of population-based active surveillance for invasive GBS disease in counties within four states that had an aggregate population of 10.1 million persons in 1990. A case of GBS disease was defined as isolation of group B streptococcus from a normally sterile anatomic site in a resident of one of the surveillance areas. Age- and race-adjusted projections to the U.S. population suggest that > 15,000 cases and > 1,300 deaths due to GBS disease occur each year. The projected age- and race-adjusted national incidence is 1.8/1,000 live births for neonatal GBS disease and 4.0/100,000 population per year for adult GBS disease. Intrapartum chemoprophylaxis for pregnant women at risk for delivering infants with GBS disease is the most effective strategy available for prevention of neonatal disease. Development of effective GBS vaccines may prevent GBS disease in both infants and adults. Ongoing surveillance for GBS disease is important for targeting preventive measures and determining their effectiveness.

A multistate outbreak of sporotrichosis associated with sphagnum moss

In the spring of 1988, the largest documented US outbreak of cutaneous sporotrichosis to date occurred, with 84 cases among persons from 15 states who were exposed to Wisconsin-grown sphagnum moss used in packing evergreen tree seedlings. In New York State, 13 cases occurred among 109 forestry workers. All 13 cases occurred among 76 workers who had handled evergreen seedlings and moss (attack rate = 17%). For those exposed to evergreens and moss, the risk of infection increased as worktime exposure to moss increased (attack rates: less than 10 hours, 8%; 10-19 hours, 12%; greater than 19 hours, 33%). While environmental samples of moss from the Wisconsin supplier were negative, Sporothrix schenckii was cultured from multiple samples of the sphagnum moss obtained from one of six Pennsylvania tree nurseries, representing the nursery that was identified as the source for 79 (94%) of the moss-associated cases. Differences in tree-handling procedures at this nursery--including the use of 1- to 3-year-old moss to pack seedlings, use of a pond water source to wet the moss, use of an organic polymer gel on the seedling root system, and underground storage and longer storage of moss-packed seedlings before shipping--suggested possible explanations for the association. Efforts to prevent sporotrichosis among persons handling evergreen seedlings should include the use of alternate types of packing material (e.g., cedar wood chips or shredded paper) and protective clothing such as gloves and long-sleeved shirts.

Role of foods in sporadic listeriosis. I. Case-control study of dietary risk factors. The Listeria Study Group

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.

Role of foods in sporadic listeriosis. II. Microbiologic and epidemiologic investigation. The Listeria Study Group

OBJECTIVE

To evaluate the role of foods in sporadic listeriosis.

DESIGN

Microbiologic survey of foods collected from refrigerators of patients with listeriosis identified through active laboratory-based surveillance. Patient and food Listeria monocytogenes isolates were subtyped to identify foods contaminated with the same strain of L monocytogenes that caused illness in the patient; samples of these foods were obtained from the retail source.

SETTING

Multistate population-based study conducted between 1988 and 1990.

RESULTS

Listeria monocytogenes grew from at least one food specimen in the refrigerators of 79 (64%) of 123 listeriosis patients; 11% of more than 2000 food specimens collected in the study contained L monocytogenes. Twenty-six (33%) of 79 refrigerators with foods that grew L monocytogenes contained at least one food isolate of the same strain as that in the corresponding patient, a frequency much higher than would be expected by chance (P less than .001). Multivariate analysis showed that of the food specimens that grew L monocytogenes, foods that were ready-to-eat, foods that grew L monocytogenes by a direct-plating method (a measure of the level of contamination), and foods that contained serotype 4b isolates were independently associated with an increased likelihood of containing the patient-matching strain.

CONCLUSION

We identified specific food and L monocytogenes isolate characteristics--ready-to-eat foods, foods containing higher concentrations of L monocytogenes, and foods containing serotype 4b--which were associated with disease-causing strains. These results can provide guidance to industry and regulatory agencies in developing strategies to prevent listeriosis.

Invasive group B streptococcal disease in adults. A population-based study in metropolitan Atlanta

OBJECTIVE

To define the incidence and clinical spectrum of group B streptococcus infection in adults. To characterize groups at increased risk for infection.

DESIGN

Retrospective population-based surveillance of group B streptococcus infections occurring in adults. Patients were identified by review of microbiology records at all surveillance area hospital laboratories. Demographic and clinical data were abstracted from patient medical records.

SETTING

Metropolitan Atlanta, Ga, 1982 through 1983.

PATIENTS

We identified 70 adult patients with invasive group B streptococcus infections; 14 infections occurred in pregnant women and 56 in nonpregnant adults.

RESULTS

The annual incidence of group B streptococcus infection in men and nonpregnant women was 2.4 cases per 100,000 population. Incidence increased with age and was higher in blacks than in whites. The case-fatality rate was 32%. Group B streptococcus was most often isolated from blood (71%) and soft tissue (16%). Common clinical presentations included skin and soft-tissue infection (36%), bacteremia without focus (34%), pneumonia (11%), arthritis (9%), and endocarditis (9%). Compared with the general population's risk of infection, the risk of infection in persons with diabetes mellitus was increased 10.5-fold (95% confidence interval [CI], 7.8 to 14.4); in persons with cancer, it was increased 16.4-fold (95% CI, 11.5 to 23.3).

CONCLUSIONS

Group B streptococcus infections cause serious disease in adults as well as in neonates, providing an additional rationale for vaccine development. Determining the incidence of adult disease and groups at greatest risk will help in focusing prevention efforts.

Comparison of cold enrichment and U.S. Department of Agriculture methods for isolating Listeria monocytogenes from naturally contaminated foods. The Listeria Study Group

We compared the cold enrichment (CE) and U.S. Department of Agriculture (USDA) methods for isolating Listeria monocytogenes by examining 402 food samples. The food samples were collected from refrigerators of listeriosis patients as part of a multistate active surveillance project to determine the role of foods in sporadic listeriosis in the United States. L. monocytogenes was isolated from 51 food samples (13%). The USDA method was significantly better (P less than 0.001) than the CE method. The isolation efficiencies of the USDA and CE methods were 96 and 59%, respectively. Quantitation of L. monocytogenes in the food samples revealed that many food samples containing less than 0.3 CFU/g were negative as determined by the CE method but positive as determined by the USDA method.

Use of surveillance for invasive pneumococcal disease to estimate the size of the immunosuppressed HIV-infected population

We used population-based surveillance in New Jersey in 1986 to quantify the risk of invasive pneumococcal disease in persons with the acquired immunodeficiency syndrome (AIDS) and in those who went on to develop AIDS. Using pneumococcal surveillance, we also devised a method to estimate the size of the immunosuppressed population infected with the human immunodeficiency virus (HIV), the so-called pre-AIDS population. From rates of pneumococcal disease that occurred in areas with a low incidence of AIDS, we calculated the number of patients expected to contract pneumococcal disease in areas with a high incidence of AIDS. There were 59 more cases of pneumococcal disease observed than expected; 14 of these patients had AIDS by the time of pneumococcal infection. We attributed the remaining 45 cases to the increased risk of pneumococcal infection in pre-AIDS. The pre-AIDS pneumococcal cases and the attack rate of pneumococcal disease in pre-AIDS were used to estimate the size of the 1986 pre-AIDS New Jersey population as 8823 pre-AIDS cases (95% confidence interval, 7377 to 10,714) or 0.37% of the adult New Jersey population. Surveillance for marker diseases may provide a simple, independent method of estimating the pre-AIDS population.

Epidemiology of human listeriosis

During the 1980s, investigation of several large epidemics of listeriosis confirmed that transmission of L. monocytogenes in food causes human disease. Progress in laboratory detection and subtyping of the organism has enhanced our ability to compare human and environmental isolates of L. monocytogenes. Transmission by foodborne organisms is now recognized as causing both epidemic and sporadic listeriosis. Continued study of dietary risk factors associated with listeriosis is needed in order to develop dietary recommendations for the expanding population at increased risk of disease. Current research application of new molecular methods to the study of L. monocytogenes may improve the ability to diagnose pregnancy-associated disease and permit the rapid detection and control of L. monocytogenes in the food supply.

Outbreak of neonatal listeriosis associated with mineral oil

In June, 1989, an outbreak of nosocomial listeriosis occurred in Costa Rica. Listeria monocytogenes was isolated from 9 ill infants 4 to 8 days old who were born after the delivery of an infant with early onset listeriosis. One nosocomial infection was fatal, 2 required mechanical ventilation and 1 resulted in hemiparesis. A higher proportion of cases than other infants born during the outbreak were delivered by cesarean section (55% vs. 24%, P = 0.04). Compared with the mothers of 36 random controls, case mothers were more often primiparous (odds ratio, 6.2, P = 0.03) or received general anesthesia before delivery (odds ratio, 4.4, P = 0.09). All infants were bathed with mineral oil from a multidose container. Culture of the oil by cold enrichment grew L. monocytogenes 4b with the same electrophoretic enzyme type as the outbreak strain. We hypothesize that aspiration of contaminated oil may have resulted in systemic listeriosis. General anesthesia may have increased the risk of aspiration. Lung tissue from the infant who died showed lipid-laden macrophages consistent with oil aspiration and had evidence of L. monocytogenes DNA detected by polymerase chain reaction. This is the first nosocomial outbreak of listeriosis in which a common source suggested epidemiologically was microbiologically confirmed. The high attack rate (greater than 200 times the United States rate of perinatal listeriosis) emphasizes the susceptibility of healthy neonates to L. monocytogenes. The results of our study led to the discontinuation of the use of mineral oil for bathing neonates in Costa Rica.

Toxic shock syndrome and tampons

There has been a substantial reduction in the incidence of toxic shock syndrome in the 10 years since the association between tampons and toxic shock syndrome was first recognized. The decreased incidence is real, and not the result of decreased reporting to the passive surveillance system. The decreased incidence of menstrual toxic shock syndrome can primarily be explained by changes in the absorbency and composition of tampons available to the consumer. The reduction in the occurrence of menstrual toxic shock syndrome can be attributed to the withdrawal of Rely brand, which consisted of a unique composition, and subsequently to the lowering of absorbency of all brands of tampons. The conclusions of the early studies of toxic shock syndrome pointed the way to prompt public health interventions and resulted in the prevention of substantial morbidity.

Population-based risk factors for neonatal group B streptococcal disease: results of a cohort study in metropolitan Atlanta

To determine risk factors for neonatal group B streptococcal (GBS) disease, a cohort study was conducted in Atlanta of infants with invasive GBS disease during 1982 and 1983. Laboratory review detected 71 infants with early-onset disease (1.09 cases/1000 live births) and 37 infants with late-onset disease (0.57 cases/1000 live births). Compared with the 64,858 births in Atlanta in the same period, infants with early-onset GBS disease were more often black, less than 2500 g, and born to teenage mothers. A history of miscarriage increased a woman's risk of delivering an infant with early-onset disease. Black infants had 35 times the risk of late-onset disease that nonblack infants had. Thirty percent of early-onset disease and 92% of late-onset disease could be attributed to black race, independent of other risk factors. Most case-mothers (96%) received prenatal care, suggesting that prevention strategies such as prenatal screening or maternal immunization could reach nearly all the population at risk.