Showing papers by "Martin Antonio published in 2008"

Progression to Active Tuberculosis, but Not Transmission, Varies by Mycobacterium tuberculosis Lineage in The Gambia

Abstract: Considerable variability exists in the outcome of M. tuberculosis infection. We hypothesized that M. africanum was less likely than M. tuberculosis to transmit and progress to tuberculosis disease. In a cohort study of tuberculosis patients and their household contacts in the Gambia, we categorized 1,808 HIV negative tuberculosis contacts according to exposure to M. tuberculosis or to M. africanum. A positive skin test indicated transmission and development of tuberculosis during 2 years of follow-up indicated progression to disease. Transmission was similar, but progression to disease was significantly lower in contacts exposed to M. africanum than to M. tuberculosis (1.0% vs 2.9%; Hazard Ratio (HR) 3.1, 95% CI 1.1–8.7). Within M. tuberculosis sensu stricto, contacts exposed to a Beijing family strain were most likely to progress to disease (5.6%; HR 6.7 (2.0–22) relative to M. africanum). M. africanum and M. tuberculosis transmit equally well to household contacts, but contacts exposed to M. africanum are less likely to progress to tuberculosis disease than those exposed to M. tuberculosis. The variable rate of progression by lineage suggests that TB variability matters in clinical settings and should be taken into account in studies evaluating tuberculosis vaccines and treatment regimens for latent tuberculosis infection.

Seasonality and outbreak of a predominant Streptococcus pneumoniae serotype 1 clone from The Gambia: expansion of ST217 hypervirulent clonal complex in West Africa.

Abstract: Streptococcus pneumoniae serotype 1 causes > 20% of invasive disease, among all age groups combined, in The Gambia. In contrast, it is rarely detected in carriage studies. This study compares the molecular epidemiology of S. pneumoniae serotype 1 causing invasive disease in The Gambia between 1996 and 2005 to those carried in the nasopharynx between 2004 and 2006. A total of 127 invasive and 36 nasopharyngeal carriage serotype 1 isolates were recovered from individuals of all age groups and were analyzed by serotyping, antibiotic susceptibility testing and MLST. MLST analysis revealed 23 different sequence types (STs), 18 of which were novel. The most prevalent clone among the 163 isolates was ST618 (70.5%), followed by ST3575 (7.4%), ST2084 (2.5%) and ST612 (2.5%). A single ST (ST618), previously shown to belong to the ST217 hypervirulent clonal complex, was frequent among carriage (61.1%) and invasive (72.7%) serotype 1 isolates. ST618 causing both paediatric and adult disease peaked annually in the hot dry season and caused outbreak in 1997 and 2002. For over a decade, isolates of ST618 have been the dominant lineage among serotype 1 carriage and disease isolates circulating in the Gambia. This lineage shows similar epidemiological features to those of the meningococcus in the African meningitis belt being able to cause outbreaks of disease

Molecular epidemiology of pneumococci obtained from Gambian children aged 2–29 months with invasive pneumococcal disease during a trial of a 9-valent pneumococcal conjugate vaccine

Abstract: Background The study describes the molecular epidemiology of Streptococcus pneumoniae causing invasive disease in Gambian children

Comparative evaluation of BACTEC MGIT 960 with BACTEC 9000 MB and LJ for isolation of mycobacteria in The Gambia

Abstract: Background: The BACTEC MGIT 960 was evaluated and compared with BACTEC 9000 MB and Lowenstein-Jensen medium for recovery rate of mycobacteria, time to detection, and contamination rate. Methodology: 147 sputum samples obtained from patients with suspicion of tuberculosis were processed and inoculated into BACTEC MGIT 960, BACTEC 9000 MB and Lowenstein-Jensen medium using standardized procedures. Results: BACTEC MGIT 960 detected 57.1%; BACTEC 9000 MB detected 57.8%; and LJ medium detected 43.5% specimens with Mycobacterium tuberculosis complex (MTBC). BACTEC MGIT 960 had the shortest mean number of days (10.3) to detection, followed by BACTEC 9000 MB (13.2) and LJ medium (26.1). Sign rank test showed all three methods had significant difference in days to detection (each P<0.0001). About 39% of detection by BACTEC MGIT 960 took place within the first week, compared to 27.0% and 0.0% by BACTEC 9000 MB and LJ medium respectively. The best yield was obtained with BACTEC 9000 MB, but when compared with the BACTEC MGIT 960, it was not statistically significant. Performances were the same when the combination of a liquid plus a LJ medium were measured (P=0.05). Contamination rates were significantly higher in BACTEC MGIT 960 (12%) than in BACTEC 9000 MB (7%) (P=0.041) and LJ (4%) medium (P=0.022). BACTEC 9000 MB and LJ medium have lower contamination rates (P=0.607). Conclusions: BACTEC MGIT 960 had a shorter time to detection of MTBC than BACTEC 9000 MB and L J medium. Despite a higher contamination rate, its performance did not appear to be inferior.

A novel Campylobacter jejuni sequence type from a culture-negative patient in the Gambia.

Abstract: The introduction of molecular diagnostic methods is crucial for improved understanding of the aetiology and epidemiology of bacterial infections in communities in resource poor settings. A blood sample from a 7 month old patient diagnosed with malaria in 2001 in a Gambian outpatient clinic was reported as culture negative after it was subjected to traditional bacterial culture protocols. We re-addressed the analysis of the blood sample from this case more recently (after 6.5 years in archival storage) in pilot work establishing 16S rRNA PCR in our molecular laboratory. Initial 16S rRNA PCR results confirmed the presence of bacterial DNA in the sample. 16S rRNA sequence analysis identified the organism as Campylobacter spp. In light of the molecular evidence we successfully grew the organism using appropriate culture conditions and subsequently biochemically confirmed that the isolate was Campylobacter jejuni. PCR and DNA sequencing of a set of seven C. jejuni housekeeping genes and in silico Multilocus Sequence Typing (MLST) analysis revealed that the isolate exhibits a novel sequence type (ST) of C. jejuni (ST 2928) and belongs to ST-443 clonal complex. This study demonstrates the potential for molecular tools to enhance the diagnosis of bacterial infections, which remain a major killer globally, not least in children in the developing world. Improvements in diagnostics are needed, and will be important not only for sick individuals but also for populations, where better measures of disease burden will contribute significantly to the improvement of public health policy.