Dynamics of nasopharyngeal bacterial colonisation in HIV-exposed young infants in Tanzania.

OBJECTIVES: To estimate the prevalence of nasopharyngeal bacterial colonisation (NPBC) patterns in young Tanzanian HIV-exposed infants and to analyse the influence of maternal NPBC and of the infant's HIV status on the NPBC pattern. METHODS: Longitudinal cohort study of neonates born to HIV-infected mothers visiting Kilimanjaro Christian Medical Centre, Tanzania, between 2005 and 2009. Demographic and clinical data and nasopharyngeal bacterial cultures were obtained at the age of 6 weeks, 3 and 6 months, and at one time point, a paired mother-infant nasopharyngeal swab was taken. RESULTS: Four hundred and twenty-two swabs were taken from 338 eligible infants. At 6 weeks of age, colonisation rates were 66% for Staphylococcus aureus, 56% for Streptococcus pneumoniae, 50% for Moraxella catarrhalis and 14% for Haemophilus influenzae. Colonisation with S. aureus diminished over time and was more common in HIV-infected infants. S. pneumoniae and H. influenzae colonisation rose over time and was more prevalent in HIV-uninfected children. Co-colonisation of S. pneumoniae with H. influenzae or M. catarrhalis was mostly noticed in HIV-infected infants. S. pneumoniae and M.catarrhalis colonisation of the mother was a risk factor for colonisation in HIV-uninfected infants, while maternal S. aureus colonisation was a risk factor for colonisation in HIV-infected infants. Among the 104 S. pneumoniae isolates, 19F was most prevalent, and 57 (55%) displayed capsular serotypes represented in the 13-valent pneumococcal conjugate vaccine. CONCLUSIONS: NPBC was common in Tanzanian HIV-exposed infants. The significant prevalence of pneumococcal vaccine serotypes colonising this paediatric population justifies the use of the 13-valent pneumococcal vaccine to reduce the burden of pneumococcal invasive disease.

CD36 c.1264 T>G null mutation impairs acquisition of IgG antibodies to Plasmodium falciparum MSP119 antigen and is associated with higher malaria incidences in Tanzanian children.

Polymorphisms in genes that encode crucial signalling molecules have been proposed as factors that influence susceptibility to, and outcome of malaria. We studied the role of a mutation, c.1264 T>G, that causes CD36 deficiency on IgG responses to MSP-119 antigen and malaria incidence. Children were genotyped for the c.1264 T>G mutation at the beginning of the study using PCR-RFLP. IgG levels [optical density (OD) readings] and per cent seropositivity to MSP-119 were determined at baseline by ELISA. Children were followed for 12 months for acquisition of anti-MSP-119 IgG antibody and malaria incidence. We observed a significant increase in the production of anti-MSP-119 IgG antibody in normal and heterozygous children during the 12 months of follow-up, but not in homozygous mutants. Normal children had a significantly lower malaria incidence rate compared to other genotypes (χ² = 115.59; P < 0.01). We conclude that the presence of the c.1264 T>G mutation that leads to CD36 deficiency is closely associated with reduced IgG production and higher malaria incidence. It is most likely that deficiency of CD36 which is known to modulate dendritic cell function suppresses the production of protective IgG antibodies directed to Plasmodium falciparum MSP-119 antigen, which predisposes to the acquisition of clinical malaria in children.

Light-emitting diode with various sputum smear preparation techniques to diagnose tuberculosis.

SETTING: Mawenzi Regional Hospital, northern Tanzania. OBJECTIVE: To determine the value of light-emitting diode (LED) microscopy in diagnosing tuberculosis (TB) on bleach-treated and direct sputum smears. DESIGN: Sputum samples were collected from patients suspected of pulmonary TB who presented consecutively at the laboratory for smear evaluation between December 2009 and February 2010. Four smears were prepared from each specimen: conventional Ziehl-Neelsen (ZN), direct auramine, bleach centrifugation and bleach short sedimentation auramine smears. A light microscope was used to examine ZN smears and an LED fluorescent microscope to examine auramine-stained smears. RESULTS: Of the 267 sputum samples examined, respectively 78 (29%), 62 (23%), 74 (28%) and 48 (18%) were acid-fast bacilli (AFB) positive by the bleach centrifugation, bleach short sedimentation, direct auramine and ZN methods. Bleach centrifugation identified 30 (11%) more positives than ZN microscopy (P < 0.001), but was not superior to the direct auramine method (P = 0.46), which yielded 26 (10%) more positives than ZN microscopy (P < 0.001). Fluorescent LED required a shorter smear reading time (1.5 min on average), while the light microscope took 4 min (P < 0.001). CONCLUSION: Fluorescent LED microscopy with direct smear preparation is rapid and effective. Further studies are needed to ascertain its performance under routine conditions.