The descriptive epidemiology of pneumococcal meningitis in New York City

Nitric oxide synthase 2A (NOS2A) polymorphisms are not associated with invasive pneumococcal disease

Background

Streptococcus pneumoniae (pneumococcus) is responsible for over one million deaths per year, with young children, the elderly and immunocompromised individuals being most at risk. Approximately half of East African children have been reported to be asymptomatic carriers of pneumococcus with invasive infection occurring after the disruption of the respiratory membrane which is believed to be caused by the host immune response. Racial incidence of invasive pneumococcal disease (IPD) is higher in certain populations even after adjusting for environmental factors suggesting a genetic component to disease susceptibility. The nitric oxide synthase 2A (NOS2A) gene is responsible for the production of nitric oxide under pathological conditions including host defence against bacterial infection. Nitric oxide is a modulator of apoptotic and inflammatory cascades and endothelial permeability. We hypothesised that genetic variants within this gene may predispose to disease risk and survival.

Methods

A cohort of 299 children with IPD (221 meningitis, 41 pneumonia and 37 with bacteraemia) and 931 age matched controls from Malawi were used in this study. We investigated nine haplotype tagging single nucleotide polymorphisms within the NOS2A gene and compared the presence or absence of the minor alleles in cases and controls and survivors and non-survivors within the cases.

Results

We observed no significant associations between cases and controls or with survival in either all IPD cases or in the separate analysis of meningitis cases. A near significant association was obtained for the comparison of rs8078340 in cases and controls (p-value, 0.078). However, results were unadjusted for multiple testing.

Conclusion

Our results suggest that polymorphic variation within the NOS2A gene does not influence invasive pneumococcal disease susceptibility or survival.

Incidence of Invasive Pneumococcal Disease among Individuals with Sickle Cell Disease before and after the Introduction of the Pneumococcal Conjugate Vaccine

BACKGROUND

We sought to determine the incidence of invasive pneumococcal disease (IPD) among individuals with sickle cell disease (SCD) before and after the introduction of the pneumococcal conjugate vaccine (PCV).

METHODS

Individuals with SCD who were enrolled in Tennessee Medicaid from January 1995 through December 2004 were identified using SCD-specific International Classification of Diseases, Ninth Revision, Clinical Modification codes. Population-based surveillance data were used to identify individuals with IPD and were linked to patients with SCD in the Tennessee Medicaid database to determine incidence rates of IPD. Clinical data were collected on all subjects with IPD, and antibiotic susceptibility testing and serotyping were performed on all available pneumococcal isolates.

RESULTS

We identified 2026 individuals with SCD, who constituted 13,687 person-years of follow-up. During the study period, 37 individuals with SCD developed IPD, and 21 of these patients were aged <5 years. In a comparison of the pre-PCV period (1995-1999) with the post-PCV period (2001-2004), the rate of IPD decreased by 90.8% in children aged <2 years (from 3630 to 335 cases per 100,000 person-years; P<.001) and by 93.4% in children aged <5 years (from 2044 to 134 cases per 100,000 person-years; P<.001). Rates of IPD for patients with SCD who were aged >or=5 years decreased from 161 cases per 100,000 person-years during the pre-PCV period to 99 cases per 100,000 person-years during the post-PCV period (P=.36).

CONCLUSION

The rate of IPD among children with SCD who are aged <5 years has decreased markedly since the introduction of routine administration of PCV to young children.

Prospects for pneumococcal vaccination in African children

Streptococcus pneumoniae (pneumococcus) remains a major cause of morbidity and mortality in both developed and undeveloped countries. Accurate disease burden estimates for developing countries and Africa in particular, where diagnostic facilities are less adequate and a disease surveillance system virtually non-existent, is difficult. However, from conservative estimates, the pneumococcus is probably responsible for at least 1 million of the 4 million deaths that occur from acute lower respiratory infections in children aged less than 5 years. The global burden of disease has been accentuated by the rising menace of multi-drug resistant strains, which defy geographic and racial borders. Thus, now more than ever before, there is an urgent need to identify and implement preventive measures to avert this problem. The currently licensed pneumococcal polysaccharide vaccine, comprises 23 capsular polysaccharides of the pneumococcus, many of which are poorly immunogenic in the very vulnerable age group of under-fives. A possible solution to the problem of poor immunogenicity is to use a protein/polysaccharide conjugate vaccine similar to that recently introduced successfully for Haemophilus influenzae type b (Hib) and using this approach, several workers have reported promising results from safety and immunogenicity studies. However, unlike Hib, the development of conjugate vaccine against pneumococcal disease is complicated by the existence of more serotypes than can be feasibly incorporated in a single conjugate vaccine formulation. Whilst this challenge has been taken on by some vaccine manufacturers, novel approaches such as the identification or construction of protective protein antigen, common to all clinically important strains are being explored. Novel application of the pneumococcal polysaccharide vaccines in pregnancy for protection of disease in early infancy is an approach that has not been evaluated. For maximum impact, the ultimate vaccine formulation should be affordable and available to resource poor countries where the burden of disease is highest. Establishing disease surveillance systems in such countries now will greatly facilitate the introduction of the vaccines.

The epidemiology of pneumococcal infection in children in the developing world

Pneumonia causes about three million deaths a year in young children, nearly all of which are in developing countries. Streptococcus pneumoniae (the pneumococcus) is the most important bacterial cause of pneumonia in young children and so is likely to be responsible for a high proportion of these deaths. The pneumococcus is also responsible for a substantial proportion of the 100,000-500,000 deaths that occur from meningitis in children each year. The incidence of invasive pneumococcal disease in children in the developing world is several times higher than in industrialized countries. This discrepancy may, in part, be due to socio-economic differences but genetic factors may also play a role. Children with sickle cell disease have a substantially increased risk of invasive pneumococcal infection and a search is being made for other possible genetic risk factors. Infection with human immunodeficiency virus (HIV) also predisposes to invasive pneumococcal disease and so the incidence of this disease in young children is expected to rise as increasing numbers of African and Asian children are born with a perinatally acquired HIV infection. Until recently, pneumococcal infections could be treated effectively with penicillin, a cheap and safe antibiotic. However, pneumococci that are resistant to penicillin are becoming prevalent in many countries, necessitating a change to more costly antibiotics which may be beyond the reach of the health services of poor, developing countries. The spread of antibiotic resistance has provided an added stimulus to the development of vaccines that might be able to prevent pneumococcal disease in infants. Recently developed polysaccharide-protein conjugate vaccines show promise and are now undergoing field trials. How deployment of these vaccines will influence the balance between invasive pneumococcal infections and asymptomatic nasopharyngeal carriage of pneumococci is uncertain.

Surgical intervention and heparin-anticoagulation improve prognosis of rhinogenic/otogenic and posttraumatic meningitis

It is still controversial, whether early surgical removal of infectious material and heparin-anticoagulation to reduce vascular complications will improve outcome in acute meningitis. In the present pilot-study 40 patients with acute or delayed post-traumatic or oto-/rhinogenic purulent bacterial meningitis were analysed for neurological outcome by using the Glasgow outcome score (GOS) and the Tuthill functional score; patients were treated either by early surgical revision of the septic focus (Group 1, within 6 days, n = 15), late surgery (Group 2, later than 6 days, n = 19), or no surgery at all (Group 3, n = 6). All patients, independent of surgical approach, received therapeutic heparin-anticoagulation. Patient groups were otherwise comparable for antibiotic treatment, osmotherapy, microbiology, CSF-findings, CT-scans and prognostic factors. Outcome according to GOS was superior in Group 1 compared with Groups 2/3 (non-significant). Although there was no significant difference on admission in the Tuthill functional score, Group 1 achieved a superior final outcome of 96 points compared with Groups 2 and 3, who gained 72 points (p < 0.01). In addition, Group 1 patients had significantly less intracranial complications (8/15 patients versus 21/25 patients in Groups 2/3, p < 0.01) and were dependent upon respirator treatment for fewer days (10.2 days) than Groups 2/3 (12.5 days, non-significant). In 31 patients CSF-leakage was identified: among these, 17 patients had CSF-leakage, which had not been anticipated by clinical/neuroradiological examinations and revealed only by surgery. The overall mortality in this study population was very low (2.5%), therefore, therapeutic heparin seems to represent an additional favorable treatment measure.(ABSTRACT TRUNCATED AT 250 WORDS)

Pneumococcal bacteraemia during a recent decade

We retrospectively reviewed 159 episodes of bacteraemic pneumococcal infection in 157 adult patients at the Helsinki University Central Hospital during two periods between 1976 and 1979 and 1986 and 1989. We looked especially at changes in underlying diseases and prognostic factors. The overall case fatality rate was 21% and there was a small diminishing trend in that rate from 28% (16/58) in the late 1970s to 17% (17/101) in the late 1980s. The patients who died in the late 1980s were younger than those who died in the earlier period. The most common underlying factors were alcohol abuse, cardiovascular diseases and chronic obstructive pulmonary diseases. Old age was neither a predisposing factor nor did it predict the outcome. No significant changes in underlying diseases or prognostic factors were noted during the two periods studied except a small decrease in connective tissue diseases as underlying conditions. The factors related to increased fatality included hepatic cirrhosis, a combination of pneumonia and meningitis, complications such as shock, respiratory insufficiency, central nervous system disorders and circulatory acidosis, and laboratory findings such as thrombocytopenia, absence of leucocytosis and increased amounts of serum creatinine, aspartate aminotransferase and alanine aminotransferase on admission to the hospital. Previous splenectomy and malignant diseases were not associated with higher mortality. The thrombocytopenia at the time of positive blood culture and the circulatory acidosis as a complication seemed to be independently the most useful predictive factors for a fatal outcome using multivariate logistical regression analysis after adjustment to classic risk factors.

Clinical evaluation of pneumococcal meningitis in adults over a twelve-year period

A retrospective study was performed to review the clinical features and outcome of 39 episodes of pneumococcal meningitis in 36 adult patients over a 12-year period. Overall mortality was 33.3%. Only a few of the deaths were directly related to the central nervous system disease and most of them were due to cardiorespiratory failure. Univariate analysis showed that death was more likely to occur in patients with advanced age, an absence of neck stiffness, a high pulse rate, an associated pneumonia, internal complications, or a long duration of the disease (greater than 7 days) before treatment was started. Patients who died had a higher erythrocyte sedimentation rate and serum bilirubin level and a lower serum sodium level than those who survived. Discriminant analysis showed the development of internal complications to be the strongest predictive factor of a poor outcome of illness. Two other important predictors of a poor outcome were the absence of neck stiffness and associated pneumonia. The history of a skull fracture or head surgery was significantly correlated with a better than average prognosis. The incidence of sequelae in survivors at the time of discharge amounted to 72%. None of the clinical features were significantly correlated with the development of sequelae, except a higher cerebrospinal fluid protein content.

Infections in sickle cell disease

Bacterial infections are considered a major cause of morbidity and mortality in patients, particularly children, with sickle cell disease. Infections including pneumonia, meningitis, osteomyelitis, pyelonephritis and general sepsis are more prevalent in patients with these genetic abnormalities than in normal individuals. Generally, infections are more prevalent in children than in older patients. The most common cause of severe infections in hemoglobinopathies include Diplococcus, Staphylococcus, Pneumococcus, Salmonella and Streptococcus. Several investigations have been conducted to determine the possible defects in the host defense mechanisms. Functional asplenia, defects in alternate pathway and in opsonic activity and phagocytosis of Streptococci, Staphylococci and Salmonella in sickle cell anemia patients are considered important factors predisposing these patients to bacteremia. On the other hand, a beneficial association has been demonstrated between the sickle cell gene and malaria. The hemoglobin S (Hb S) provides a natural resistance against the malarial parasite resulting in an improvement in fitness and survival over the normal (Hb AA) individuals. This communication reviews infections in sickle cell disease with a comparison of results in various populations.