Progress toward the global control of Neisseria meningitidis: 21st century vaccines, current guidelines, and challenges for future vaccine development.

The control of meningitis, meningococcemia and other infections caused by Neisseria meningitidis is a significant global health challenge. Substantial progress has occurred in the last twenty years in meningococcal vaccine development and global implementation. Meningococcal protein-polysaccharide conjugate vaccines to serogroups A, C, W, and Y (modeled after the Haemophilus influenzae b conjugate vaccines) provide better duration of protection and immunologic memory, and overcome weak immune responses in infants and young children and hypo-responsive to repeated vaccine doses seen with polysaccharide vaccines. ACWY conjugate vaccines also interfere with transmission and reduce nasopharyngeal colonization, thus resulting in significant herd protection. Advances in serogroup B vaccine development have also occurred using conserved outer membrane proteins with or without OMV as vaccine targets. Challenges for meningococcal vaccine research remain including developing combination vaccines containing ACYW(X) and B, determining the ideal booster schedules for the conjugate and MenB vaccines, and addressing issues of waning effectiveness.

Environmental survival of Neisseria meningitidis.

Neisseria meningitidis is transmitted through the inhalation of large human respiratory droplets, but the risk from contaminated environmental surfaces is controversial. Compared to Streptococcus pneumoniae and Acinetobacter baumanni, meningococcal viability after desiccation on plastic, glass or metal surfaces decreased rapidly, but viable meningococci were present for up to 72 h. Encapsulation did not provide an advantage for meningococcal environmental survival on environmental surfaces.

Prevention of cryptococcosis in HIV-infected patients with limited access to highly active antiretroviral therapy: evidence for primary azole prophylaxis.

Despite advances in the treatment of HIV disease, the incidence and mortality of invasive cryptococcal disease remain significant. A matched, case-control study was performed to examine the impact of highly active antiretroviral therapy (HAART) and azole use on the incidence of invasive cryptococcal disease in HIV-infected patients. The study was performed at a metropolitan hospital with a large indigent population and an incidence of seven cases of cryptococcal disease per 1000 persons with AIDS. Bivariate analysis, matched on CD4 count, revealed that both HAART use [odds ratio (OR) 0.43; 95% confidence interval (CI) 0.23-0.99] and azole use (OR 0.14; 95% CI 0.06-0.34) had a protective effect. Conditional logistic regression stratified on CD4 lymphocyte count revealed a protective role for azole use (OR 0.15; 95% CI 0.06-0.40) but not for HAART use (OR 0.47; 95% CI 0.18-1.26). Of note, the prevalence of HAART use was low in both cases and controls, with only 12% of cases and 23% of controls on HAART. The results of this study support previous evidence that azole use prevents invasive cryptococcal disease. Although current guidelines for the prophylaxis of opportunistic infections do not suggest routine prophylaxis for cryptococcal infection, this issue should be reconsidered, especially in populations that have a low prevalence of HAART use.

Bioterrorism-related inhalational anthrax: the first 10 cases reported in the United States.

From October 4 to November 2, 2001, the first 10 confirmed cases of inhalational anthrax caused by intentional release of Bacillus anthracis were identified in the United States. Epidemiologic investigation indicated that the outbreak, in the District of Columbia, Florida, New Jersey, and New York, resulted from intentional delivery of B. anthracis spores through mailed letters or packages. We describe the clinical presentation and course of these cases of bioterrorism-related inhalational anthrax. The median age of patients was 56 years (range 43 to 73 years), 70% were male, and except for one, all were known or believed to have processed, handled, or received letters containing B. anthracis spores. The median incubation period from the time of exposure to onset of symptoms, when known (n=6), was 4 days (range 4 to 6 days). Symptoms at initial presentation included fever or chills (n=10), sweats (n=7), fatigue or malaise (n=10), minimal or nonproductive cough (n=9), dyspnea (n=8), and nausea or vomiting (n=9). The median white blood cell count was 9.8 X 10(3)/mm(3) (range 7.5 to 13.3), often with increased neutrophils and band forms. Nine patients had elevated serum transaminase levels, and six were hypoxic. All 10 patients had abnormal chest X-rays; abnormalities included infiltrates (n=7), pleural effusion (n=8), and mediastinal widening (seven patients). Computed tomography of the chest was performed on eight patients, and mediastinal lymphadenopathy was present in seven. With multidrug antibiotic regimens and supportive care, survival of patients (60%) was markedly higher (<15%) than previously reported.

Macrolide resistance among invasive Streptococcus pneumoniae isolates.

CONTEXT: Macrolide antibiotics, including erythromycin, clarithromycin, and azithromycin, are the mainstays of empirical pneumonia therapy. Macrolide resistance among Streptococcus pneumoniae, the most common cause of community-acquired pneumonia, is increasing in the United States. Whether resistance is a significant problem or whether macrolides remain useful for treatment of most resistant strains is unknown. OBJECTIVE: To examine the epidemiology of macrolide-resistant pneumococci in the United States. DESIGN AND SETTING: Analysis of 15 481 invasive isolates from 1995 to 1999 collected by the Centers for Disease Control and Prevention's Active Bacterial Core surveillance system in 8 states. MAIN OUTCOME MEASURES: Trends in macrolide use (1993-1999) and resistance and factors associated with resistance, including examination of 2 subtypes, the M phenotype, associated with moderate minimum inhibitory concentrations (MICs), and the MLS(B) phenotype, associated with high MICs and clindamycin resistance. RESULTS: From 1993 to 1999, macrolide use increased 13%; macrolide use increased 320% among children younger than 5 years. Macrolide resistance increased from 10.6% in 1995 to 20.4% in 1999. M phenotype isolates increased from 7.4% to 16.5% (P<.001), while the proportion with the MLS(B) phenotype was stable (3%-4%). The median erythromycin MIC (MIC(50)) of M phenotype isolates increased from 4 microg/mL to 8 microg/mL. In 1999, M phenotype strains were more often from children than persons 5 years or older (25.2% vs 12.6%; P<.001) and from whites than blacks (19.3% vs 11.2%; P<.001). CONCLUSIONS: In the setting of increasing macrolide use, pneumococcal resistance has become common. Most resistant strains have MICs in the range in which treatment failures have been reported. Further study and surveillance are critical to understanding the clinical implications of our findings.

The structure of the lipooligosaccharide (LOS) from the alpha-1,2-N-acetyl glucosamine transferase (rfaK(NMB)) mutant strain CMK1 of Neisseria meningitidis: implications for LOS inner core assembly and LOS-based vaccines.

The inner core structures of the lipooligosaccharides (LOS) of Neisseria meningitidis are potential vaccine candidates because both bactericidal and opsonic antibodies can be generated against these epitopes. In an effort to better understand LOS biosynthesis and the potential immunogenicity of the LOS inner core, we have determined the LOS structure from a meningococcal rfaK mutant CMK1. The rfaK gene encodes the transferase that adds an alpha-N-acetylglucosaminosyl residue to O-2 of the inner core heptose (Hep) II of the LOS. The LOS oligosaccharide from this mutant was previously shown to contain only Hep, 3-deoxy-D-manno-2-octulosonic acid (Kdo), and multiple phosphoethanolamine (PEA) substituents (Kahler et al., 1996a, J. Bacteriol., 178, 1265-1273). The complete structure of the oligosaccharide (OS) component of the LOS from mutant CMK1 was determined using glycosyl composition and linkage analyses, and 1H, 13C, and 31P nuclear magnetic resonance spectroscopy. The CMK1 OS structure contains a PEA group at O-3 of Hep II in place of the usual glucosyl residue found at this position in the completed L2 LOS glycoform from the parent NMB strain. The PEA group at O-6 of Hep II, however, is present in both the CMK1 mutant LOS and parental NMB L2 LOS structures. The structure of the OS from CMK1 suggests that PEA substituents are transferred to both the O-3 and O-6 positions of Hep II prior to: (1) the incorporation of the alpha-GlcNAc on Hep II; (2) the synthesis of the alpha-chain on Hep I; and (3) the substitution of the glycosyl residue at the O-3 Hep II, which distinguishes L2 and L3 immunotypes. The LOS structure of the CMK1 mutant makes it a candidate immunogen that could generate broadly cross-reactive inner-core LOS antibodies.

Structure and dissemination of a chromosomal insertion element encoding macrolide efflux in Streptococcus pneumoniae.

Macrolide resistance associated with macrolide efflux (mef) has rapidly increased in Streptococcus pneumoniae. We defined the genetic structure and dissemination of a novel mefE-containing chromosomal insertion element. The mefE gene was found on the 5' end of a 5.5- or 5.4-kb insertion designated as the macrolide efflux genetic assembly (mega), which is found in > or =4 distinct sites of the pneumococcal genome. The element was transformable and conferred macrolide resistance to susceptible S. pneumoniae. The first 2 open-reading frames (ORFs) of the element formed an operon composed of mefE and a predicted adenosine triphosphate-binding cassette homologous to msrA. Convergent to this efflux operon were 3 ORFs with homology to stress response genes of Tn5252. Mega was related to the recently described mefA-containing element Tn1207.1 but lacked the genes necessary for transposition and had unique termini and insertion sites. In metropolitan Atlanta, macrolide resistance due to mega rapidly increased in S. pneumoniae by clonal expansion and horizontally by transformation.

Polymorphisms in pilin glycosylation Locus of Neisseria meningitidis expressing class II pili.

We have located a locus, pgl, in Neisseria meningitidis strain NMB required for the glycosylation of class II pili. Between five and eight open reading frames (ORFs) (pglF, pglB, pglC, pglB2, orf2, orf3, orf8, and avtA) were present in the pgl clusters of different meningococcal isolates. The Class I pilus-expressing strains Neisseria gonorrhoeae MS11 and N. meningitidis MC58 each contain a pgl cluster in which orf2 and orf3 have been deleted. Strain NMB and other meningococcal isolates which express class II type IV pili contained pgl clusters in which pglB had been replaced by pglB2 and an additional novel ORF, orf8, had been inserted between pglB2 and pglC. Insertional inactivation of the eight ORFs of the pgl cluster of strain NMB showed that pglF, pglB2, pglC, and pglD, but not orf2, orf3, orf8, and avtA, were necessary for pilin glycosylation. Pilin glycosylation was not essential for resistance to normal human serum, as pglF and pglD mutants retained wild-type levels of serum resistance. Although pglB2 and pglC mutants were significantly sensitive to normal human serum under the experimental conditions used, subsequent examination of the encapsulation phenotypes revealed that pglB2 and pglC mutants expressed almost 50% less capsule than wild-type NMB. A mutation in orf3, which did not affect pilin glycosylation, also resulted in a 10% reduction in capsule expression and a moderately serum sensitive phenotype. On the basis of these results we suggest that pilin glycosylation may proceed via a lipid-linked oligosaccharide intermediate and that blockages in this pathway may interfere with capsular transport or assembly.

Transcriptional regulation of divergent capsule biosynthesis and transport operon promoters in serogroup B Neisseria meningitidis.

The clinically important serogroups B, C, Y, and W-135 of Neisseria meningitidis produce sialic acid capsules that are critical in pathogenesis. In each of these serogroups, the capsule transport (ctrABCD) and capsule biosynthesis (synABCD) operons are divergently transcribed from putative promoters located in a 134-bp intergenic region (J. S. Swartley, J. H. Ahn, L. J. Liu, C. M. Kahler, and D. S. Stephens, J. Bacteriol. 178:4052-4059, 1996). In this study we further assessed the role of the intergenic sequence in the transcriptional regulation of the sialic acid capsules of N. meningitidis. Insertional mutagenesis or deletions of the 134-bp sequence in the serogroup B meningococcal strain NMB resulted in a marked reduction or elimination of ctrABCD and synABCD transcription, with a concomitant loss of encapsulation. Chromosomal transcriptional lacZ-ermC reporter fusions of syn and ctr promoters were constructed through allelic exchange. Using these constructs, both operons were found to be constitutively transcribed in meningococci, the biosynthesis operon about fourfold higher than the transport operon. Both promoters showed increased activity during stationary-phase growth. In addition to the promoters, a 70-bp 5' untranslated region (UTR) upstream of synA was found to have a direct repeat and an inverted repeat that overlapped three putative integration host factor binding sites. Mutation of this 70-bp UTR and of the direct repeat upregulated both syn and ctr transcription. Regulation through the synA UTR was absent in a K1 Escherichia coli strain that produces identical capsular polysaccharide, implicating species-specific regulation. Meningococcal sialic acid capsule expression is initiated by divergent promoters in a 134-bp intergenic region, is repressed at the transcriptional level by the 5' UTR of synA, is increased during stationary-phase growth, and shows species-specific regulation. Transcriptional regulation is another important control point for sialic capsule expression in N. meningitidis.

exl, an exchangeable genetic island in Neisseria meningitidis.

The genetic structure and evolution of a novel exchangeable meningococcal genomic island was defined for the important human pathogen Neisseria meningitidis. In 125 meningococcal strains tested, one of three unrelated nucleotide sequences, designated exl (exchangeable locus), was found between a gene required for heme utilization, hemO, and col, encoding a putative Escherichia coli collagenase homologue. The 5' boundary of each exl cassette was the stop codon of hemO, whereas the 3' boundary was delineated by a 33-bp repeat containing neisserial uptake sequences located downstream of col. One of the three alternative exl cassettes contained the meningococcal hemoglobin receptor gene, hmbR (exl3). In other meningococcal strains, hmbR was absent from the genome and was replaced by either a nucleotide sequence containing a novel open reading frame, exl2, or a cassette containing exl3. The proteins encoded by exl2 and exl3 had no significant amino acid homology to HmbR but contained six motifs that are also present in the lipoprotein components of the lactoferrin (LbpB), transferrin (TbpB), and hemoglobin-haptoglobin (HpuA) uptake systems. To determine the evolutionary relationships among meningococci carrying hmbR, exl2, or exl3, isolates representing 92 electrophoretic types were examined. hmbR was found throughout the population structure of N. meningitidis (genetic distance, >0.425), whereas exl2 and exl3 were found in clonal groups at genetic distances of <0.2. The commensal neisserial species were identified as reservoirs for all of the exl cassettes found in meningococci. The structure of these cassettes and their correlation with clonal groups emphasize the extensive gene pool and frequent horizontal DNA transfer events that contribute to the evolution and virulence of N. meningitidis.

The emergence of Streptococcus pneumoniae resistant to macrolide antimicrobial agents: a 6-year population-based assessment.

From 1994 through 1999, the available isolates (4148 isolates) from active population-based surveillance of invasive pneumococcal disease in metropolitan Atlanta were serotyped and were tested for antimicrobial susceptibility. Macrolide-resistant isolates were studied for the presence of ermAM (a ribosomal methylase gene), mefE (a macrolide efflux gene), and tetM (the class M tetracycline resistance gene). Macrolide resistance increased from 16% of all invasive isolates in 1994 to 32% in 1999. Of the macrolide-resistant pneumococcal isolates studied, 99% contained genomic copies of mefE or ermAM. Isolates with ermAM were mainly serotypes 6B, 23F, 14, or 19F and contained tetM; mefE-associated isolates were predominantly serotypes 14, 6A, or 19F, and most did not contain tetM. The frequency of the ermAM-mediated phenotype in invasive Streptococcus pneumoniae remained stable over the 6-year surveillance. However, the mefE-mediated phenotype increased from 9% in 1994 to 26% of all isolates in 1999 and was noted in new serotypes. By 1999, 93% of the mefE-containing strains had minimum inhibitory concentrations >/=8 microgram/mL. Dissemination of the mefE determinant accounted for the rapid increase in the rate of macrolide resistance in our S. pneumoniae population.

Evaluation of effectiveness of the 23-valent pneumococcal capsular polysaccharide vaccine for HIV-infected patients.

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.

Epidemiology and pathogenesis of Neisseria meningitidis.

Neisseria meningitidis, an exclusive pathogen of humans, remains the leading worldwide cause of meningitis and fatal sepsis, usually in otherwise healthy individuals. In recent years, significant advances have improved our understanding of the epidemiology and genetic basis of meningococcal disease and led to progress in the development of the next generation of meningococcal vaccines. This review summarizes current knowledge of the human susceptibility to and the epidemiology and molecular pathogenesis of meningococcal disease.

The changing epidemiology of meningococcal disease in the United States, 1992-1996.

New meningococcal vaccines are undergoing clinical trials, and changes in the epidemiologic features of meningococcal disease will affect their use. Active laboratory-based, population-based US surveillance for meningococcal disease during 1992-1996 was used to project that 2400 cases of meningococcal disease occurred annually. Incidence was highest in infants; however, 32% of cases occurred in persons >/=30 years of age. Serogroup C caused 35% of cases; serogroup B, 32%; and serogroup Y, 26%. Increasing age (relative risk [RR], 1.01 per year), having an isolate obtained from blood (RR, 4.5), and serogroup C (RR, 1.6) were associated with increased case fatality. Among serogroup B isolates, the most commonly expressed serosubtype was P1.15; 68% of isolates expressed 1 of the 6 most common serosubtypes. Compared with cases occurring in previous years, recent cases are more likely to be caused by serogroup Y and to occur among older age groups. Ongoing surveillance is necessary to determine the stability of serogroup and serosubtype distribution.

The epidemiology of candidemia in two United States cities: results of a population-based active surveillance.

We conducted prospective, active population-based surveillance for candidemia (defined as any Candida species isolated from blood) in Atlanta and San Francisco (total population, 5.34 million) during 1992-1993. The average annual incidence of candidemia at both sites was 8 per 100,000 population. The highest incidence (75 per 100,000) occurred among infants

Neisseria meningitidis serogroup B outer membrane vesicle vaccine in adults with occupational risk for meningococcal disease.

Vaccination provides a safe and effective means of reducing the risk of laboratory-acquired infection due to some Neisseria meningitidis serogroups. However, there is currently no serogroup B meningococcal vaccine licensed for use in the US. We used an investigational N. meningitidis serogroup B outer membrane vesicle (B:15:P1.7,16) vaccine produced by the National Institute of Public Health (NIPH) in Norway to immunize 20 researchers with occupational risk for disease. Three doses of vaccine were administered via intramuscular injection at 8-week intervals. The vaccine produced moderate or severe pain with 19 (33%) of the 58 doses administered. Reactions were similar following first, second and third doses. The number and severity of reactions peaked at 24 h postvaccination and then gradually waned. Of 16 vaccinees with results available from all blood draws, 12 (75%) showed a fourfold or greater rise in serum bactericidal activity (SBA) against the vaccine type-strain following two doses of vaccine, and 15 (94%) responded after three doses. Geometric mean titers increased by more than sixfold following two doses of vaccine when compared with prevaccination levels, and by more than 11-fold following a third dose. There was no significant difference between SBA measured using the vaccinee's own complement versus a donor complement source. The NIPH vaccine elicited an excellent bactericidal response against the vaccine type-strain in researchers with an occupational risk for disease. It may be useful for other laboratory personnel who routinely work with meningococcal strains containing similar outer membrane antigens. These findings reconfirm that the NIPH vaccine is immunogenic in adults and support the validity of using properly screened human donor complement in serum bactericidal assays against serogroup B meningococci.