Search

Background: We conducted a retrospective case-control study to evaluate effectiveness of pneumococcal vaccine against invasive disease among adults with human immunodeficiency virus (HIV) infection in San Francisco, Calif, and Atlanta, Ga., Methods: Case patients were 18- to 55-year-old subjects with HIV infection who were admitted to selected hospitals in Atlanta or San Francisco from February 1992 to April 1995 from whom Streptococcus pneumoniae was isolated from a normally sterile site. Controls were HIV-infected patients of similar age matched to cases by hospital of admission and CD4 lymphocyte count (<0.20, 0.20-0.499, >/=0.50 x 10(9)/L [<200, 200-499, >/=500 cells/mm(3)]) or clinical stage of acquired immunodeficiency syndrome. Case and control subjects were restricted to persons known to have HIV infection before hospital admission. Analysis used matched univariate and conditional logistic regression., Results: One hundred seventy-six case patients and 327 controls were enrolled. By univariate analysis, persons with pneumococcal disease were more likely to be black, be current smokers, and have close contact with children. Adjusted for these factors and CD4 cell count, pneumococcal vaccine effectiveness was 49% (95% confidence interval [CI], 12%-70%). Adjusting for all variables and key interaction terms, vaccine effectiveness among whites was 76% (95% CI, 35%-91%), whereas effectiveness among blacks was 24% (95% CI, -50% to 61%). Among controls, vaccination was significantly less common among blacks (29% vs 45%; P<.005)., Conclusions: Pneumococcal vaccine demonstrated protection against invasive pneumococcal infections among white but not black HIV-infected adults. Failure to demonstrate effectiveness among blacks may be due to limited power because of low use of the vaccine in this population, immunization at more advanced stages of immunosuppression, or unmeasured factors. These data support current recommendations for use of pneumococcal vaccine in HIV-infected persons and highlight a clear need for strategies to improve vaccine-induced protection.

Background: Approximately half of otherwise healthy adults with invasive pneumococcal disease are cigarette smokers. We conducted a population-based case-control study to assess the importance of cigarette smoking and other factors as risk factors for pneumococcal infections., Methods: We identified immunocompetent patients who were 18 to 64 years old and who had invasive pneumococcal disease (as defined by the isolation of Streptococcus pneumoniae from a normally sterile site) by active surveillance of laboratories in metropolitan Atlanta, Baltimore, and Toronto. Telephone interviews were conducted with 228 patients and 301 control subjects who were reached by random-digit dialing., Results: Fifty-eight percent of the patients and 24 percent of the control subjects were current smokers. Invasive pneumococcal disease was associated with cigarette smoking (odds ratio, 4.1; 95 percent confidence interval, 2.4 to 7.3) and with passive smoking among nonsmokers (odds ratio, 2.5; 95 percent confidence interval, 1.2 to 5.1) after adjustment by logistic-regression analysis for age, study site, and independent risk factors such as male sex, black race, chronic illness, low level of education, and living with young children who were in day care. There were dose-response relations for the current number of cigarettes smoked per day, pack-years of smoking, and time since quitting. The adjusted population attributable risk was 51 percent for cigarette smoking, 17 percent for passive smoking, and 14 percent for chronic illness., Conclusions: Cigarette smoking is the strongest independent risk factor for invasive pneumococcal disease among immunocompetent, nonelderly adults. Because of the high prevalence of smoking and the large population attributable risk, programs to reduce both smoking and exposure to environmental tobacco smoke have the potential to reduce the incidence of pneumococcal disease.

Haemophilus influenzae haemagglutinating pili are surface appendages that promote attachment to host cells and facilitate respiratory tract colonization, an essential step in the pathogenesis of disease. In contrast to other well-characterized forms of pili, H. influenzae haemagglutinating pili are two-stranded helical structures. Nevertheless, haemagglutinating pili are assembled by a pathway that involves a periplasmic chaperone and an outer membrane usher, analogous to the prototype pathway involved in the biogenesis of Escherichia coli P pili. In this study, we performed site-directed mutagenesis of the H. influenzae HifB chaperone and HifA major pilus subunit at positions homologous to sites important for chaperone-subunit interactions and subunit oligomerization in P pili. Mutations at putative subunit binding pocket residues in HifB or at the penultimate tyrosine in HifA abolished formation of HifB-HifA periplasmic complexes, whereas mutations at the -14 glycine in HifA had no effect on HifB-HifA interactions but abrogated HifA oligomerization. To define further the constraints of the interaction between HifA and HifB, we examined the interchangeability of pilus gene cluster components from H. influenzae type b strain Eagan (hifA-hifEEag) and the related H. influenzae biogroup aegyptius strain F3031 (hifA-hifEF3031). Functional pili were assembled both with HifAEag and the strain F3031 gene cluster and with HifAF3031 and the strain Eagan gene cluster, underscoring the flexibility of the H. influenzae chaperone/usher pathway in incorporating HifA subunits with significant sequence diversity. To gain additional insight into the interactive surfaces of HifA and HifB, we aligned HifA sequences from 20 different strains and then modelled the HifA structure based on the recently crystallized PapD-PapK complex. Analysis of the resulting structure revealed high levels of sequence conservation in regions predicted to interact with HifB, and maximal sequence diversity in regions potentially exposed on the surface of assembled pili. These results suggest broad applicability of structure-function relationships identified in studies of P pili, including the concepts of donor strand complementation and donor strand exchange. In addition, they provide insight into the structure of HifA and suggest a basis for antigenic variation in H. influenzae haemagglutinating pili.

The impact of penicillin susceptibility on medical outcomes for adult patients with bacteremic pneumococcal pneumonia was evaluated in a retrospective cohort study conducted during population-based surveillance for invasive pneumococcal disease in the greater Atlanta region during 1994. Of the 192 study patients, 44 (23%) were infected with pneumococcal strains that demonstrated some degree of penicillin nonsusceptibility. Compared with patients infected with penicillin-susceptible pneumococcal strains, patients whose isolates were nonsusceptible had a significantly greater risk of in-hospital death due to pneumonia (relative risk [RR], 2.1; 95% confidence interval [CI], 1-4.3) and suppurative complications of infection (RR, 4.5; 95% CI, 1-19.3), although only risk of suppurative complications remained statistically significant after adjustment for baseline differences in severity of illness. Among adults with bacteremic pneumococcal pneumonia, infection with penicillin-nonsusceptible pneumococci is associated with an increased risk of adverse outcome.

Limited data are available on clinical outcomes of meningitis due to cefotaxime-nonsusceptible Streptococcus pneumoniae. We analyzed data from 109 cases of pneumococcal meningitis in Atlanta, Baltimore, and San Antonio, which were identified through population-based active surveillance from November 1994 to April 1996. Pneumococcal isolates from 9% of the cases were resistant to cefotaxime, and isolates from 11% had intermediate susceptibility. Children were more likely to have cephalosporin-nonsusceptible pneumococcal meningitis, but mortality was significantly higher among adults aged 18-64 years. Vancomycin was given upon admission to 29% of patients, and within 48 h of admission to 52%. Nonsusceptibility to cefotaxime was not associated with the following outcomes: increased mortality, prolonged length of hospital or intensive care unit (ICU) stay, requirement of intubation or oxygen, ICU care, discharge to another medical or long-term-care facility, or neurological deficit. Empirical use of vancomycin, current prevalence of drug-resistant S. pneumoniae, and degree of nonsusceptibility to cefotaxime may have influenced these findings.

Active, population-based surveillance for invasive group A streptococcal (GAS) disease was conducted in laboratories in metropolitan Atlanta from 1 January 1994 through 30 June 1995. Clinical and laboratory records were reviewed and isolates characterized. One hundred and eighty-three cases of invasive GAS disease were identified (annual incidence, 5.2 cases/100,000). The incidence was highest among blacks (9.7/100,000 per year; relative risk (RR), 1.92; confidence interval (CI), 1.69-2.19; P < .0001) and the elderly, particularly nursing home residents (RR, 13.66; CI, 7.07-26.40; P < .0001). The mean age of patients was 41.3 years (range, 0-95 years). Skin and soft-tissue infections were most common. Mortality was 14.4%; risk of death was significantly higher for patients with streptococcal toxic shock syndrome (STSS) (RR, 9.73; CI, 3.34-29; P = .0008) and individuals infected with M-type 1 (RR, 7.40; CI, 1.5-16; P = .0084). Fourteen percent of invasive GAS infections were STSS and 3% were necrotizing fasciitis. Invasive GAS disease was associated with varicella infection in children (RR, 12.19; CI, 5.58-26.62; P < .0001). M (or emm) types included M1 (16%), M12 (12%), and M3 (11%). Continued study of GAS disease is essential to further define risk factors and risk of secondary cases and to develop effective prevention strategies.

Brazilian purpuric fever (BPF)-associated Haemophilus influenzae biogroup aegyptius strain F3031 contains two identical copies of a five gene cluster (hifA to hifE) encoding pili similar to well-characterized Hif fimbriae of H. influenzae type b. HifE, the putative pilus tip adhesin of F3031, shares only 40% amino acid sequence similarity with the same molecule from type b strains, whereas the other four proteins have 75 to 95% identity. To determine whether pilus cluster duplication and the hifE(F3031) allele were special features of BPF-associated bacteria, we analyzed a collection of H. influenzae strains by PCR with hifA- and hifE-specific oligonucleotides, by Southern hybridization with a hifC gene probe, and by nucleotide sequencing. The presence of two pilus clusters was limited to some H. influenzae biogroup aegyptius strains. The hifE(F3031) allele was limited to H. influenzae biogroup aegyptius. Two strains contained one copy of hifE(F3031) and one copy of a variant hifE allele. We determined the nucleotide sequences of four hifE genes from H. influenzae biogroup aegyptius and H. influenzae capsule serotypes a and c. The predicted proteins produced by these genes demonstrated only 35 to 70% identity to the three published HifE proteins from nontypeable H. influenzae, serotype b, and BPF strains. The C-terminal third of the molecules implicated in chaperone binding was the most highly conserved region. Three conserved domains in the otherwise highly variable N-terminal putative receptor-binding region of HifE were similar to conserved portions in the N terminus of Neisseria pilus adhesin PilC. We concluded that two pilus clusters and hifE(F3031) were not specific for BPF-causing H. influenzae, and we also identified portions of HifE possibly involved in binding mammalian cell receptors.

Predictions that infectious diseases would be eliminated as a major threat to human health have been shattered by emerging and reemerging infections, among them acquired immunodeficiency syndrome (AIDS), hemorrhagic fevers, marked increases in infections caused by antimicrobial-resistant bacteria, and the resurgence of tuberculosis and malaria. Understanding the dynamics of emerging and reemerging infections is critical to efforts to reduce the morbidity and mortality of such infections, to establish policy related to preparedness for infectious threats, and for decisions on where to use limited resources in the fight against infections. In order to offer a multidisciplinary perspective, 23 infectious disease specialists, epidemiologists, geneticists, microbiologists, and population biologists participated in an open forum at Emory University on emerging and reemerging infectious diseases. As summarized below, the group addressed questions about the definition, the identification, the factors responsible for, and multidisciplinary approaches to emerging and reemerging infections.

Brazilian purpuric fever (BPF) is a recently described pediatric septicemia caused by a strain of Haemophilus influenzae biogroup aegyptius. The pilus specified by this bacterium may be important in BPF pathogenesis, enhancing attachment to host tissue. Here, we report the cloning of two haf (for H. influenzae biogroup aegyptius fimbriae) gene clusters from a cosmid library of strain F3031. We sequenced a 6.8-kb segment of the haf1 cluster and identified five genes (hafA to hafE). The predicted protein products, HafA to HafD, are 72, 95, 98, and 90% similar, respectively, to HifA to HifD of the closely related H. influenzae type b pilus. Strikingly, the putative pilus adhesion, HifE, shares only 44% identity with HafE, suggesting that the proteins may differ in receptor specificity. Insertion of a mini-gammadelta transposon in the hafE gene eliminated hemadsorption. The nucleotide sequences of the haf1 and haf2 clusters are more than 99% identical. Using the recently published sequence of the H. influenzae Rd genome, we determined that the haf1 complex lies at a unique position in the chromosome between the pmbA gene and a hypothetical open reading frame, HI1153. The location of the haf2 cluster, inserted between the purE and pepN genes, is analogous to the hif genes on H. influenzae type b. BPF fimbrial phase switching appears to involve slip-strand mispairing of repeated dinucleotides in the pilus promoter. The BPF-associated H. influenzae biogroup aegyptius pilus system generally resembles other H. influenzae, but the possession of a second fimbrial gene cluster, which appears to have arisen by a recent duplication event, and the novel sequence of the HafE adhesin may be significant in the unusual pathogenesis of BPF.

With the decline in the rate of infections caused by Haemophilus influenzae serotype b, H. influenzae serotype f (Hif) is becoming a relatively important cause of invasive disease due to H. influenzae. We identified 91 cases of invasive Hif infections in a multistate area over a 6-year period. The incidence of invasive Hif disease was 0.5 case per 1,000,000 population in 1989 and 1.9 cases per 1,000,000 population in 1994. The proportion of all invasive H. influenzae disease caused by Hif rose from 1% in 1989 to 17% in 1994. Seventy-two percent of cases occurred in adults, and 26% of cases occurred in children younger than 5 years of age. Respiratory tract infections accounted for 82% of adult cases, and most adults had significant underlying diseases. In children, pneumonia and meningitis each accounted for 40% of cases, respectively. Overall mortality was 30% among adults, and 21% among children. Molecular typing demonstrated limited overall diversity in Hif isolates. Continued surveillance is warranted to evaluate the trend toward the increasing incidence of Hif disease that was noted in this study.

Objective: To define the incidence, demographics, clinical features, and risk factors for sporadic meningococcal disease in adults (> or = 18 years) residing in metropolitan Atlanta., Design: Prospective, population-based surveillance, with retrospective review of clinical and laboratory records., Setting: Eight-county metropolitan Atlanta area., Patients: All adult patients in whom Neisseria meningitidis was isolated from normally sterile sites (blood, cerebrospinal fluid) during the period 1 December 1988 to 30 November 1993., Measurements: Incidence, relative risk, clinical and laboratory parameters, and serogroup of meningococcal isolates., Results: For the 5-year period, 44 (33%) of 132 cases of meningococcal disease in Atlanta occurred in adults (annual incidence, 0.50/100,000 adults per year). Twenty-three (52%) of the 44 adults presented without rash or meningitis, the two most obvious signs of meningococcal disease. Pneumonia, sinusitis, or purulent tracheobronchitis, but without rash, were the likely sources of meningococcal bacteremia in 15 (34%) of the 44 adults. Twelve of the 15 patients with meningococcal respiratory infection were older than 50 years of age or were immunocompromised (or both), and three fourths of the 15 patients had disease caused by serogroups B, Y, and W-135. Overall, two thirds of adults older than 24 years of age with meningococcal disease had one or more immunocompromising conditions (for example, low complement 50 level [CH50], corticosteroid use, congestive heart failure, multiple myeloma, human immunodeficiency virus infection). Meningococcemia or meningococcal meningitis, often caused by serogroup C, were the presentations in 14 of 15 adults 18 to 24 years old; only 2 had an identified underlying condition., Conclusions: In this 5-year population-based study, one third of all cases of sporadic meningococcal disease occurred in adults. Over half of the adults presented without rash or meningitis. Pneumonia, sinusitis, and tracheobronchitis are important sources of bacteremic meningococcal disease, especially in immunocompromised patients and elderly persons.

Objective: To determine risk factors for community-acquired and nosocomial group B streptococcal disease in adults., Design: Case-control study., Setting: 3 metropolitan areas in the United States with an aggregate population of 6.6 million persons., Patients: 219 nonpregnant adults with invasive group B streptococcal infection identified by a population-based surveillance in 1991 and 1992 and 645 hospital-matched controls., Results: The following conditions were associated with a significantly increased risk for community-acquired group B streptococcal infection after controlling for age in multivariate analysis: cirrhosis (odds ratio, 9.7 [95% CI, 3.5 to 26.9]; P < 0.001), diabetes (odds ratio, 3.0 [CI, 1.9 to 4.7]; P < 0.001), stroke (odds ratio, 3.5 [CI, 1.9 to 6.4]; P < 0.001), breast cancer (odds ratio, 4.0 [CI, 1.6 to 9.8]; P = 0.002), decubitus ulcer (odd ratio, 4.0 [CI, 1.6 to 9.8]; P = 0.002), and neurogenic bladder (odds ratio, 4.6 [CI, 1.4 to 15.1]; P = 0.01). Sixty-three percent of community case-patients had at least one of these conditions. Nosocomial infection (48 cases [22%]) was independently associated with the placement of a central venous line (odds ratio, 30.9 [CI, 5.2 to 184.1]; P < 0.001), diabetes, congestive heart failure, and seizure disorder., Conclusions: Several chronic conditions were independently associated with group B streptococcal disease, and most case-patients had at least one of these conditions. If group B streptococcal vaccines being developed for prevention of neonatal disease are protective in adults, a vaccination strategy targeting those at highest risk has the potential to substantially reduce the burden of invasive group B streptococcal infection in adults.

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.

Group B streptococcal infection has recently been recognised as an important and apparently increasingly common cause of invasive disease in nonpregnant adults. The annual incidence of invasive disease has been estimated at 4.4 per 100,000 nonpregnant adults and is highest among adults over 60 years of age. The most common clinical diagnoses include skin and soft-tissue infections, bacteraemia with no identified source, osteomyelitis, urosepsis and pneumonia. Other important but less common infections include peritonitis, infectious arthritis, meningitis and endocarditis. The majority of adults with group B streptococcal infections have underlying diseases including diabetes mellitus, malignant neoplasms and liver disease. Nosocomial infection and polymicrobial bacteraemia occur in a significant proportion of patients with invasive group B streptococcal disease. Mortality from invasive disease is particularly high in the elderly. For treatment of serious group B streptococcal infections, high doses of benzylpenicillin (penicillin G) are recommended because of the somewhat higher minimal inhibitory concentrations. In addition to parenteral antibiotic therapy surgical management may be required for successful treatment, particularly in the case of soft-tissue or bone infection. Invasive group B streptococcal infection is a major problem in elderly adults and those with chronic diseases, and efforts should be made to identify and treat such infections early. Future approaches may include vaccine prevention of serious group B streptococcal infection in adults at highest risk.

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.

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.

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.

We have cloned and sequenced the Brazilian purpuric fever (BPF)-associated Haemophilus influenzae biogroup aegyptius (Hae) pilin gene. The sequence contained a 648-bp open reading frame encoding a mature pilin protein of 191 amino acids with a calculated mass of 20.5 kDa. There was 82% homology between the open reading frames of the BPF strain F3031 and H. influenzae type b (Hib) (strain M43) pilin genes and 71% homology at the amino acid level between the mature pilin proteins. However, areas of diversity were noted throughout the gene. A 17-bp probe corresponding to an area of diversity in the N-terminal region of the BPF-associated gene hybridized with other BPF strains but not with non-BPF Hae or Hib. In summary, the pilin protein of BPF-associated Hae is highly homologous to Hib pilin yet remains structurally distinct.

Objective: To define the incidence of and possible risk factors for invasive Haemophilus influenzae disease in adults., Design: Prospective, population-based surveillance of hospital and referral bacteriology laboratories., Setting: Metropolitan Atlanta, Georgia community., Patients: All patients with H. influenzae isolated from normally sterile sites (blood, cerebrospinal fluid, joint, pleura) from 1 December 1988 through 31 May 1990., Measurements: Isolates of H. influenzae were analyzed for serotype and biotype status, outer membrane proteins, lipooligosaccharide phenotypes, ribotyping patterns and beta-lactamase production., Results: A total of 194 cases of invasive H. influenzae occurred (annual incidence of 5.6 cases/100,000 population), of which 47 (24%) were in adults 18 years old or older (annual incidence 1.7 cases/100,000 adults). Adults with invasive H. influenzae ranged from 18 to 96 years; 79% were women. Bacteremic pneumonia accounted for 70% of the adult cases. Other sources for invasive H. influenzae in adults were obstetric infections, epiglottitis, and tracheobronchitis; one patient had meningitis. Underlying conditions were noted in 92% of the patients. Chronic lung disease was the most common risk factor, but pregnancy (annual incidence, 4.9/100,000 pregnant women), HIV infection (annual incidence, 41/100,000 known HIV-infected adults), and malignancy were also important. Overall mortality was 28% in adults, and over half of pregnancy-related infections resulted in fetal death. Fifty percent of the 40 isolates available for testing were serotype b; 47.5%, nontypable; and 2.5%, serotype f. Sixteen of the 45 isolates (36%) were ampicillin-resistant. Based on biotypes, outer membrane protein profiles, lipooligosaccharide phenotypes, and ribotyping patterns, the type b isolates showed less heterogeneity than the nontypable isolates but were distinguishable from one another., Conclusions: Adult cases currently represent one quarter of all cases of invasive H. influenzae disease. Half of the reported adult cases were caused by type b H. influenzae, and the rate of ampicillin resistance in H. influenzae isolates from adults was higher than previously reported. Haemophilus influenzae is an important cause of bacteremia in compromised adults.

The human nasopharynx is the natural habitat and reservoir for Neisseria meningitidis and Haemophilus influenzae type b (Hib). Meningococcal and Hib pathogenesis was studied in human nasopharyngeal tissue in organ culture. Inocula of greater than or equal to 10(6) meningococci or cfu of Hib were required for consistent production of infection in these cultures. By 24 hours meningococci and Hib grew to 10(8)-10(10) cfu/mL in culture supernatants, while 10(4)-10(7) cfu per organ culture were tissue associated. These studies further indicated that nasopharyngeal mucus contains components that specifically bind Hib; that both meningococci and Hib cause cytotoxicity, resulting in breakdown of tight junctions of epithelial cells, sloughing of ciliated cells, and ciliostasis; that pili are the most important components mediating initial attachment of meningococci to non-ciliated epithelial cells of the human nasopharynx; that Hib expresses both pilus and nonpilus adhesions that facilitate attachment to nonciliated cells; and that meningococci and Hib both invade the epithelial surface to reach the submucosa but do so by different routes. Meningococci and Hib have evolved successful, although divergent, mechanisms by which to infect the human nasopharynx.

The role of pili of Haemophilus influenzae type b (Hib) in binding to human erythrocytes and in colonization and invasion of human nasopharyngeal (NP) organ cultures has been evaluated. Hib strains 1009 and 1007, NP and cerebrospinal fluid isolates from the same child with Hib meningitis, were studied. Strain 1009 was piliated (P+), produced pilin of approximately 24 kDa, and was hemadsorption-positive (HA+); strain 1007 was nonpiliated (P-), did not produce pilin, and was hemadsorption-negative (HA-). The rate of transition from one hemadsorption phenotype to the other in broth cultures and NP organ culture supernatants was 3 x 10(-4) per bacterium per generation for HA+ to HA- and 7 x 10(-4) per bacterium per generation for HA- to HA+. Growth in human NP organ culture supernatants of the P+HA+ strain was greater than that of the P-HA- strain at 6 and 12 h after infection. No difference was noted when the strains were grown in nutrient broth. Strain 1009 (P+HA+) attached in large clusters to cellular debris and nonciliated cells, a phenomenon never noted with strain 1007 (P-HA-). NP organ cultures infected with strain 1007 showed greater mucosal invasion than those infected with the 1009 strain. While P+HA+ and P-HA- Hib both attached to NP mucosa, P+HA+ strains may have a selective advantage in mucosal colonization but P-HA- strains may be more invasive.

We evaluated mucosal attachment, colonization, and invasion by Haemophilus influenzae in an experimental model of human nasopharyngeal tissue in organ culture. Nonpiliated, encapsulated, and nonencapsulated, IgA1 protease-deficient mutants of H. influenzae were compared with their isogenic IgA1 protease-producing parents. Damage to peripheral ciliary activity was first noted 6 hr after infection and was associated with sloughing of ciliated cells to which H. influenzae were not attached. Infection of organ cultures with each strain resulted in similar degrees and rates of ciliary damage. H. influenzae attached selectively to nonciliated epithelial cells or was associated with surface mucus. Later, disruption of epithelial tight junctions was observed, and clusters of H. influenzae were found between epithelial cells. Organisms were also seen within phagocytic vacuoles of mononuclear cells located above and below the basement membrane. In summary, encapsulated and nonencapsulated H. influenzae damaged the ciliary function of human nasopharyngeal organ cultures, attached to the mucosal surface, and invaded the epithelium. H. influenzae IgA1 protease, however, was not essential for the pathogenic steps observed in this human nasopharyngeal organ culture model.

We used an in vitro model of human nasopharyngeal tissue in organ culture to evaluate the effects of Neisseria meningitidis on human cilia and ciliary function. Encapsulated, viable meningococci damaged ciliated epithelium of nasopharyngeal organ cultures, whereas Neisseria subflava, a commensal species, did not. Meningococcus-induced ciliary damage was due to loss of ciliated cells to which meningococci were not attached. Damage was seen with piliated and nonpiliated meningococci and did not appear to require the presence of other specific meningococcal surface proteins. Meningococcal viability was a requirement for both ciliary damage and interactions of meningococci with microvilli of nonciliated epithelial cells. That is, filter-sterilized supernatants from meningococcus-infected organ cultures, heat-killed meningococci at high inoculum, and purified meningococcal or gonococcal lipopolysaccharide at concentrations of 100 micrograms/ml did not damage ciliary activity of nasopharyngeal organ cultures. In contrast, meningococcal lipopolysaccharide at 10 micrograms/ml markedly damaged ciliary activity of human fallopian tube organ cultures, suggesting a selective toxicity of lipopolysaccharide for specific human ciliated cells. Damage to nasopharyngeal ciliated epithelium by N. meningitidis may be an important first step in meningococcal colonization of the human nasopharynx, but meningococcal lipopolysaccharide does not appear to be directly responsible for this toxicity.

Bactericidal activity and binding of a 57,000-dalton cationic antimicrobial neutrophil granule protein (CAP57) are determined by the presence on bacteria of O-antigen polysaccharide chains and the availability of negatively charged groups in the lipid A region, the inner core region, or both regions of lipopolysaccharide. Polymyxin B (PMB)-resistant mutants with well-defined alterations in lipid A structure and charge (pmrA) are also more resistant to CAP57. We used biologically active radioiodinated CAP57 to study the characteristics and kinetics of binding to a sensitive Rb lipopolysaccharide chemotype, Salmonella typhimurium SH9178, and the relatively resistant pmrA mutant strain SH7426. Binding occurred rapidly and was specific and saturable. Because CAP57 appears to be bound in a manner similar to that of PMB, competition binding studies were performed. Excess PMB did compete with CAP57 for binding to SH9178. Nonapeptide, a polycationic derivative of PMB that has lost its hydrophobic portions, demonstrated a marked decrease in ability to compete for binding with CAP57 compared with PMB. This demonstrated the importance of hydrophobic binding in the interaction of CAP57 with the microbial surface. Thus, we have shown that binding of CAP57 to SH9178 is specific, saturable, and similar to binding of PMB. Both hydrophobic and ionic properties of CAP57 appear to be necessary for binding.

A 57,000-dalton protein (CAP57) purified from human polymorphonuclear leukocytes has antimicrobial activity against a number of gram-negative bacteria. We developed a procedure using solid-phase Iodo-gen to radiolabel CAP57 without destroying its antibacterial activity. Iodinated and native CAP57 were electrophoretically identical. Autoradiographs of sodium dodecyl sulfate-polyacrylamide gels revealed greater than 95% of the 125I in a single heavy band in the 57,000-molecular-weight region. The quantity of [125I]CAP57 bound to bacterial test strains was directly proportional to the sensitivity to CAP57.