Quantiferon-Tb gold and tuberculin skin test for the diagnosis of latent tuberculosis infection in children

Background: Appropriate diagnosis and treatment of latent tuberculosis infection [LTBI] play the most important role in the control of tuberculosis. This study aimed to determine the prevalence of LTBI among healthy tuberculosis unexposed children vaccinated with BCG using the tuberculin skin test [TST] and QuantiFERON TB Gold In-Tube [QFT-GIT] and comparing the agreement between the two tests

Methods: Across-sectional study was carried out between October 2009 and March 2010 in 24 schools and 11 daycare centers. A total of 967 children were divided into 15 age groups, with a minimum of 64 children per group

Results: The prevalence rates of LTBI with TST were 3.8%, and 2.2% with QFT-GIT. One case was positive in TST and QFT-GIT, 20 cases were QFT-GIT positive, but TST negative and 36 cases were TST positive, but QFT-GIT negative, and finally, 910 cases were negative in both. There was poor agreement between TST and QFT-GIT [1.8%, 95%, CI: 0%-5.3%, k-0.007]. The specificity of QFT-GIT in the BCG vaccinated, children aged 1-15 years old, was 97.8% [97.8%, 95% CI: 96.8%-98.8%]. After three months, 2/17[11.8%] of those initially QFT-GIT negative converted, and 10/15 [66%] of those initially QFT-GIT positive reverted

Conclusion: It seems that TST and QFT-GIT are not appropriate tests for the diagnosis of LTBI among healthy tuberculosis unexposed BCG vaccinated children. There was a low reproducibility rate of QFT-GIT. The cause of the the poor agreement requires further studies

Relationship between O serotype and virulent genes in Escherichia coli causing urinary tract infections

Escherichia coli are the most frequent pathogens in acute urinary infections. They are classified based on various types of O antigen. Escherichia coli strains that cause urinary tract infections possess several genes encoding urovirulent factors. To assay the relation of virulent factors of E coli in acute urinary infections, the serotypes and virulence factor genotypes were determined. We studied 96 E coli isolates from children with acute urinary infections. Four urovirulence determinants were analyzed by DNA colony hybridization, including the genes for type 1 fimbriae [pil], P fimbriae [pap], S fimbriae [sfa], hemolysin [hly], and cytotoxic necrotizing factor 1 [cnfl]. O serotypes were also determined. The most frequently found virulence factor-encoding gene in the E coli strains studied was the gene for type 1 fimbriae [27.4%]. The prevalence of pap, sfa, hly, and cnf1 were higher in serotypes causing pyelonephritis than cystitis. The most common type of O antigen was O1 [12.2%]. There was a significant correlation between serotype and genotype in uropathogenic E coli. The high prevalence of O6 serotypes in children urinary tract infections and the high percentage of virulent genes in serotype O6 suggested a close relation between serotype and genotypes of uropathogen E coli

Comparison of arbitrarily primed-polymerase chain reaction and plasmid profiles typing of Pseudomonas aeruginosa strains from burn patients and hospital environment

To identify the strengths and weakness of arbitrary primed-polymerase chain reaction [AP-PCR] and plasmid profiles for typing of Pseudomonas aeruginosa [P. aeruginosa] and tracking of source of infections. Seventy-four strains of P. aeruginosa were isolated from burn patients and hospital environment between January to April 2003 in Ghotbadden Burn Hospital, Shiraz, Iran. The strains were classified by photo Capt Mw program, similarity and clustering of strains were assessed using NTSYS-PC version 2.02K software. Based on 50% and 64.7% and 67.5% similarity on the plotted dendrogram, 38 plasmid profiles were classified into: 2, 3 and 5 clusters, respectively. Photo Capt Mw program categorized AP-PCR products to 47 different types of 6 to 12 bands between 0.376 to 3.7 kb. Based on dendrogram pattern 3 levels [62%, 81% and 84.6%] of similarity were selected. Using these criteria 2, 5and 11 clusters were obtained, respectively. As compared with plasmid profiles, AP-PCR analysis protocol is rapid, reproducible and differentiated the isolates with higher discrimination power. These results suggest that during admission of patients in burn center a limited number of common strains cross-contaminate burn victims. However, transmissions of infection from hospital environment to patients also occur in the minority of the victims. To control cross-contamination of the patient wounds with antibiotics resistant isolates, strong disinfection of patients' bathroom after scrubbing of each patient wounds is mandatory