No abstract

The re-emerging importance of type 2 diabetes mellitus (DM) to tuberculosis (TB) control is of growing concern, but the basis for this relationship is poorly understood. Given the importance of mononuclear phagocytes for TB control and the reported alterations in monocytes of DM patients, we evaluated whether the initial interaction between both was affected in diabetics. M. tuberculosis-naïve individuals with and without DM were group matched by age and gender and the efficiency of M. tuberculosis association (attachment and ingestion) with their monocytes was assessed in the presence of autologous serum. The association of M. tuberculosis with monocytes was significantly lower in diabetics (19.2±6.1) than non-diabetics (27.5±7.9; p=0.02). Multivariate analysis controlling for host sociodemographics, DM characteristics and serum lipids indicated that male gender (p=0.04) and poorly-controlled DM (high HbA1c and hyperglycemia; p=0.01) were significantly associated with the lower interaction of M. tuberculosis with monocytes. Serum heat-inactivation reduced the association of M. tuberculosis to similar levels in both study groups (p=0.69) suggesting alterations in the complement pathway of DM patients. These findings suggest an altered route of entry of the pathogen in DM patients that may influence the downstream activation of signaling pathways in the monocyte and the survival of mycobacteria.

No abstract

Colombian field isolates of Plasmodium falciparum were analyzed for genetic diversity. Fifty-three samples were collected as thick smears from patients living in Panguí, an isolated area with low migration. While the samples were being collected, Panguí was experiencing an epidemic outbreak of malaria. The samples were typified using nested polymerase chain reaction (PCR) amplification of block 2 of the merozoite surface protein 1 (MSP1) gene and nested PCR with mutation-specific primers for position 108 of the dihydrofolate reductase enzyme gene. The results for the circulating population of parasites in Panguí show low diversity-four allelic forms-using MSP1 as a marker, a fact that contrasts with data reported for certain Asian and African zones. A high percentage of mixed infections was observed, as was high complexity of the infection. No differential distributions were found for any allelic type.

A major challenge for tuberculosis control is mycobacterial detection in paucibacillary disease, particularly in pediatric, extrapulmonary and smear-negative pulmonary infections. We developed a simple and efficient DNA extraction and real-time quantitative PCR (qPCR) protocol for mycobacterial detection and quantification in paucibacillary specimens. The method was refined using an in vitro model mimicking blood specimens which are characterized by the presence of numerous qPCR inhibitors. Mycobacterial DNA detection in blood is of interest given the high sensitivity we previously reported using conventional PCR in blood of patients with tuberculosis lymphadenitis. Mechanical lysis of mycobacteria in the presence of an organic solvent provided the highest sensitivity. Mycobacterial DNA amplification was compromised when the human:bacterial genome ratio was at least 190:1. Separation of the specimen into bacterial-and host-rich fractions prior to DNA extraction improved mycobacterial DNA detection by 30%. Preliminary testing of our protocol in smear-negative, culture-positive specimens (gastric and lymph node aspirates, pleural and cerebrospinal fluid, blood) confirmed the applicability of our technique to a range of paucibacillary specimens for the detection, quantification and speciation (M. tuberculosis versus M. avium) of mycobacteria, several weeks before culture results were available. Our protocol provides a novel efficient and simple strategy to improve the performance of qPCR in paucibacillary specimens, including those with excess human DNA background. This tool is useful to study the pathophysiology of early pulmonary or occult tuberculosis, and for more rapid and accurate diagnosis in difficult to diagnose infections.