Michele A Monteil

The pneumococcal problem.

Summary points Mortality from bacteraemic pneumonia has remained unchanged at 25% over the last 40 years Globally, Streptococcus pneumoniae causes over 1 million deaths in children under the age of 5 years Antibiotic resistant strains of S pneumoniae are increasing world wide. In Spain over 50% of isolates are resistant to one or more antibiotics Patients at increased risk of severe pneumococcal infection should be:

A glycoprotein pneumococcal conjugate vaccine primes for antibody responses to a pneumococcal polysaccharide vaccine in Gambian children.

BACKGROUND Streptococcus pneumoniae is a major cause of acute respiratory infections and acute bacterial meningitis in children. Pneumococcal polysaccharide vaccines are poorly immunogenic in this highly vulnerable group, but protein polysaccharide conjugate vaccines are likely to be more effective. OBJECTIVES To determine whether immunization of infants with a pneumococcal conjugate vaccine induces immunologic memory. METHODS Eighty-four Gambian children, who had been vaccinated previously with two or three doses of a pentavalent pneumococcal conjugate vaccine (CRM197) or with a Haemophilus influenzae type b (Hib) conjugate vaccine were immunized when approximately 2 years old with a 23-valent pneumococcal polysaccharide vaccine, and a blood sample was obtained 10 days later. Pneumococcal antibody titers in prevaccination and postvaccination sera were measured by enzyme-linked immunosorbent assay and by an opsonophagocytic assay. RESULTS On revaccination with a pneumococcal polysaccharide vaccine, children who had previously received pneumococcal conjugate vaccine had higher antibody concentrations to each of the five polysaccharide components of the conjugate vaccine than did control children. For type 6B polysaccharide, which is poorly immunogenic in young children, postvaccination antibody concentrations were 0.37, 27.6 and 50.9 microg/ml in children who had received no previous pneumococcal immunization or two or three doses of conjugate vaccine, respectively. Type 14 antibodies produced after revaccination were of high avidity and had opsonic activity. CONCLUSION Vaccination of young infants with two or three doses of a pneumococcal conjugate vaccine primes the immune system to respond strongly and rapidly on subsequent exposure to pneumococcal polysaccharide.

Climatic variables are associated with seasonal acute asthma admissions to accident and emergency room facilities in Trinidad, West Indies

Objectives To determine if there is seasonal variation in acute asthmatic visits to accident and emergency (A&E) facilities in Trinidad and to identify the climatic variables associated with such visits.

Prevalence and antimicrobial susceptibility pattern of methicillin resistant Staphylococcus aureus isolates from Trinidad & Tobago

BackgroundMethicillin-resistant Staphylococcus aureus (MRSA) has become increasingly prevalent worldwide since it was first reported in a British hospital. The prevalence however, varies markedly in hospitals in the same country, and from one country to another. We therefore sought to document comprehensively the prevalence and antimicrobial susceptibility pattern of MRSA isolates in Trinidad and Tobago.MethodsAll Staphylococcus aureus isolates encountered in routine clinical specimens received at major hospitals in the country between 2000 and 2001 were identified morphologically and biochemically by standard laboratory procedures including latex agglutination test (Staphaurex Plus; Murex Diagnostics Ltd; Dartford, England); tube coagulase test with rabbit plasma (Becton, Dickinson & Co; Sparks, MD, USA), and DNase test using DNase agar (Oxoid Ltd; Basingstoke, Hampshire, England). MRSA screening was performed using Mueller-Hinton agar containing 6 μg oxacillin and 4% NaCl, latex agglutination test (Denka Seiken Co. Ltd, Tokyo, Japan) and E-test system (AB Biodisk, Solna, Sweden). Susceptibility to antimicrobial agents was determined by the modified Kirby Bauer disc diffusion method while methicillin MICs were determined with E-test system.ResultsOf 1,912 S. aureus isolates received, 12.8% were methicillin (oxacillin) resistant. Majority of the isolates were recovered from wound swabs (86.9%) and the least in urine (0.4%) specimens. Highest number of isolates was encountered in the surgical (62.3%) and the least from obstetrics and gynaecology (1.6%) facilities respectively. Large proportions of methicillin sensitive isolates are >85% sensitive to commonly used and available antimicrobials in the country. All MRSA isolates were resistant to ceftriaxone, erythromycin, gentamicin and penicillin but were 100% sensitive to vancomycin, rifampin and chloramphenicol.ConclusionThere is a progressive increase in MRSA prevalence in the country but the present rate is still low in comparison to values in some other countries. Vancomycin is still the drug of choice for treating multidrug resistant MRSA infections. Further use of molecular studies to monitor the epidemiology of MRSA in these hospitals in the country is highly recommended too.

Descriptive Epidemiology of Asthma in Trinidad, West Indies

This cross-sectional study documents the demographic features of asthmatics seeking acute asthma care at four institutions on the island of Trinidad from January 1 to December 31, 1997. More than 15,000 (15,035) different patients made 27,353 visits during the study period. Pediatric and adolescent male patients outnumbered females, but this was reversed in patients aged 20-69 years. Frequency of visits per patient ranged from 1 to 242. Significant variation in monthly admissions was observed; admission rates were highest in the last quarter of the year but were lowest in July and August. The overall crude prevalence rate was estimated at 1.71 per 100 (range 1.16-2.34).

Specific IgG subclass antibody levels and phagocytosis of serotype 14 pneumococcus following immunization.

Complement and specific antibody directed against capsular polysaccharide are necessary for efficient phagocytosis of pneumococci. In normal adults, specific antibody to pneumococci is predominantly of the IgG2 subclass. However, the role of IgG2 in bacterial clearance is debatable. We therefore decided to investigate the relationship between specific IgG subclass antibody levels and phagocytosis of serotype 14 pneumococcus, before and after immunization with a pneumococcal capsular polysaccharide vaccine. Specific IgG subclass antibody was measured by an ELISA technique and the effect of serum on phagocytosis of radiolabelled pneumococci by normal polymorphs was determined. We found that in the presence of complement, phagocytosis correlated significantly with both specific IgGl and IgG2 antibody titres(r= 0.547, P= 0.002 and r= 0.464. P= 0.009, respectively). However, in decomplemented sera, the correlation with IgGl antibody was lost, whereas that with IgG2 antibody was strengthened (r= 0.641. P= < 0.001). The possibility that IgG2 binds to receptors on polymorphs should be considered.

Comparison of prevalence and severity of asthma among adolescents in the Caribbean islands of Trinidad and Tobago: results of a nationwide cross-sectional survey

BackgroundAsthma is a growing problem in the Caribbean but the prevalence in most islands is unknown and possible inter-island variation in prevalence has not been determined. A nationwide cross-sectional survey was conducted to compare the prevalence of asthma symptoms among high school students in the two islands of the Republic of Trinidad and Tobago.MethodsQuestionnaire and video instruments based on those developed by the International Study of Asthma & Allergy in Childhood (ISAAC) were used to assess asthma prevalence among 6394 children (age range, 11–19 years; mean age, 14.08 yrs) in the second and third years of 35 randomly selected high schools in Trinidad and Tobago. This cross sectional survey was conducted between September and December 2002.ResultsA total of 4988 questionnaires were available for analysis (3519 in Trinidad and 1469 in Tobago). Among respondents from the two islands, there were no significant differences in the prevalence of ever wheezing (24.1% and 24.3% for Trinidad and Tobago, respectively, RR 0.99, 95% CI, 0.90–1.08); wheezing in the previous 12 months (13.1% & 13.4%, RR 0.98, 95% CI 0.84–1.15); a previous or current diagnosis of asthma (12.8% & 13.5%, RR 0.95, 95% CI 0.82–1.12) and night cough in the past 12 months (35.4% & 38.3%, RR0.93, 95% CI 0.86–1.00). However, symptoms of severe asthma were significantly more common among students from Tobago and included having had more than one acute attack in the past year (13.4% & 15.8%, RR 0.85, 95% CI 0.73–1.00, p = 0.0004), night waking as a result of wheeze (7.4% & 10.9%, RR 0.68, 95% CI 0.56–0.83, p < 0.0001) and speech limitation in the past year (5.2% & 8.7%, RR 0.59, 95% CI 0.47–0.74, p < 0.001) Exercise-associated wheezing was also more frequent among Tobagonian adolescents (17.5% & 20.2%, RR 0.87, 95% CI 0.76 – 0.98, p = 0.04).ConclusionSelf-reported wheeze is common among adolescents in Trinidad and Tobago. Variation in symptoms was found between the two territories; high school students from Tobago, the less industrialized of the two islands, reported more symptoms of severe asthma and exercise-induced wheeze. Difference in the ethnic composition rather than socio-economic factors may be contributing to the observed differences in symptom prevalence.

Human papillomavirus genotypes and their prevalence in a cohort of women in Trinidad

OBJECTIVE Human papillomavirus (HPV) genotypes and their relative prevalences were determined in a cohort of 310 sexually active women in Trinidad, West Indies. METHODS Cervical samples were collected with Ayres spatulas and endocervical brushes. Samples were used for the conventional Papanicolaou test and for determining HPV genotypes by amplification of a section of the viral L1 gene, followed by DNA sequencing and probe hybridization. RESULTS HPV infections were identified in 126 of 310 (40.6%) women. Of them, 83 (65.8%) were infected with high-risk HPV, 16 (12.7%) with low-risk HPV, and 27 (21.4%) with HPV types of unknown risk. HPV 52 (12.7%) was the most frequently occurring high-risk type, followed by HPV 66 (10.3%), HPV 16 (9.5%), and HPV 18 (8.6%). High-risk types HPV 16 and HPV 66 were each found in 3 (20.0%) and HPV 18 was found in 1 (6.6%) of the 15 women with abnormal cytology. CONCLUSIONS Cervical HPV prevalence and heterogeneity of HPV genotypes are high in this Trinidad cohort. The relative importance of HPV genotypes in the development of cervical lesions needs further investigation in Trinidad in order to better understand the epidemiology of HPV infections as well as to determine the role of HPV testing in the screening, prevention, and control of cervical cancer. This pilot study provided important information on the prevalence of HPV genotypes, which will be used in future nationwide studies.

Defective antibody-mediated opsonisation of S. pneumoniae in high risk patients detected by flow cytometry

Invasive pneumococcal infection continues to be a significant cause of morbidity and mortality especially in patients with antibody deficiencies and disorders affecting the reticulo-endothelial system. Current recommendations for prophylaxis in these patients include immunization with 23-valent pneumococcal polysaccharide capsular vaccines. Post-immunization responses are commonly assessed by measuring serum antibody levels. However, there is no defined protective antibody range and this approach fails to determine the functional capacity of the antibodies. A simple, reproducible flow cytometric method of assessing the antibody-mediated opsonic activity against S. pneumoniae is described. This assay detected defective opsonic function in post-immunized at-risk patients who developed invasive pneumococcal infection.

Medical Geology in Mexico, Central America and the Caribbean

An overview of the occurrence, concentrations, and possible sources of toxic elements released by geogenic processes that may threat the health of millions of people of Mexico, Central America, and the Caribbean is presented. The geology and tectonic characteristics of Mexico and Central America constitute an appropriate environment for the presence of arsenic and fluoride in groundwater of many zones of the area. Health problems linked with As-tainted water consumption have been documented in Mexico and Nicaragua where epidemiological and toxicological studies have been developed. Fluorosis has been recognized mainly in the central and northern part of Mexico and also in Antigua, Puerto Rico, and Trinidad. Specific health effects resulting from exposure to natural dust transported from Africa have been identified in the Caribbean. Radon exposure may also affect the population living in volcanic and active tectonic environments. However, this problem has only been studied by some researchers, mainly in Mexico and Nicaragua. Collaboration among research groups and authorities has been scarce. The review presented here, although not exhaustive, shows the urgency for increasing that collaboration specially to identify polluted areas, sources, and health effects, of the routine collection and analysis of arsenic and fluoride in all potable water sources of the area, and of developing short-term measures to decrease their concentrations to safe levels.