Detection of virulence-associated genes in pathogenic and commensal avian Escherichia coli isolates.

Poultry colibacillosis due to Avian Pathogenic Escherichia coli (APEC) is responsible for several extra-intestinal pathological conditions, leading to serious economic damage in poultry production. The most commonly associated pathologies are airsacculitis, colisepticemia, and cellulitis in broiler chickens, and salpingitis and peritonitis in broiler breeders. In this work a total of 66 strains isolated from dead broiler breeders affected with colibacillosis and 61 strains from healthy broilers were studied. Strains from broiler breeders were typified with serogroups O2, O18, and O78, which are mainly associated with disease. The serogroup O78 was the most prevalent (58%). All the strains were checked for the presence of 11 virulence genes: 1) arginine succinyltransferase A (astA); ii) E.coli hemeutilization protein A (chuA); iii) colicin V A/B (cvaA/B); iv) fimbriae mannose-binding type 1 (fimC); v) ferric yersiniabactin uptake A (fyuA); vi) iron-repressible high-molecular-weight proteins 2 (irp2); vii) increased serum survival (iss); viii) iron-uptake systems of E.coli D (iucD); ix) pielonefritis associated to pili C (papC); x) temperature sensitive haemaglutinin (tsh), and xi) vacuolating autotransporter toxin (vat), by Multiplex-PCR. The results showed that all genes are present in both commensal and pathogenic E. coli strains. The iron uptake-related genes and the serum survival gene were more prevalent among APEC. The adhesin genes, except tsh, and the toxin genes, except astA, were also more prevalent among APEC isolates. Except for astA and tsh, APEC strains harbored the majority of the virulence-associated genes studied and fimC was the most prevalent gene, detected in 96.97 and 88.52% of APEC and AFEC strains, respectively. Possession of more than one iron transport system seems to play an important role on APEC survival.

Effect of zinc on the tuberculin response of children exposed to adults with smear-positive tuberculosis.

The tuberculin test (PPD) is used frequently in the diagnosis of tuberculosis. PPD, however, relies on an intact cell-mediated immunity and infected children often have false negative results. This study assessed whether a single oral zinc supplement modifies the PPD induration size and its association with nutritional status in Brazilian children. Ninety-eight children below 15 years of age who had been exposed to adults with smear-positive pulmonary TB in 1998 were tested by PPD in 1998 and 2000. Children were randomised in 2000 to receive a single oral dose of zinc sulphate or a placebo at the time of administering the PPD. Forty-three (44%) children were PPD-positive in 1998 and 54 (55%) in 2000. A higher proportion of children were classified as PPD-positive in 2000 in the zinc-supplemented group (57.1%) than in the placebo group (53.1%). PPD indurations were larger in children receiving zinc (mean 18.5 and 15.5 mm in the zinc and placebo groups, respectively) (p < 0.03). Mean induration sizes in 2000 were larger in zinc-supplemented children, regardless of their nutritional status. Our study demonstrates that zinc increases the PPD induration size in children irrespective of nutritional state. Zinc supplementation could work by correcting asymptomatic or marginal zinc deficiencies or as a non-specific booster of immunological mechanisms (whether or not there is a deficiency).

Use of purified protein derivative to assess the risk of infection in children in close contact with adults with tuberculosis in a population with high Calmette-Guérin bacillus coverage.

SETTING: Household contacts <15 years of age of adults with tuberculosis (TB) attending a reference center in Aracaju, Sergipe, Northeast Brazil. OBJECTIVE: To assess the use of purified protein derivative (PPD) and frequency of infection in children with high Calmette-Guérin bacillus (BCG) coverage who were recently exposed to TB. DESIGN: Cross-sectional study of 141 exposed household contacts <15 years of age and 506 nonexposed neighborhood controls. Children were examined and assessed for degree of exposure to index cases, BCG vaccination and scar and were tested with PPD. RESULTS: Exposed children were younger and less up to date in their vaccination schedule than controls (P < 0.05). BCG had been given to 95.6% of exposed children and 97.4% of controls, but only 80.9% of exposed vs. 88.5% of controls had a scar (P < 0.05). Scar sizes of exposed children were smaller (medians, 4.5 and 7 mm, respectively; P < 0.05). Children had lower weight for age z scores and height than the National Center for Health Statistics standards. Exposed children had lower weight for age z scores than controls (P < 0.05). Sixty-seven (47.5%) exposed children and 18 (3.6%) controls had PPD readings of >10 mm. Positivity and induration sizes increased with age, although this was significant only in the controls. The presence of a BCG scar was not associated with having a positive PPD. The degree of exposure was an important factor for PPD positivity; 66 (60.6%) of the 109 children with close exposure were positive compared with 1 (3.1%) of 32 with less intimate exposure. PPD indurations among close contacts were also larger than those with restricted exposure and controls (16.3, 11 and 9.4 mm, respectively; P < 0.05). PPD positivity was associated with the quantification of acid-fast bacilli in the adult; 38.5% of contacts with adults with sputum with (+) were positive, compared with 42.3% of those with (++) and 58.4% with (+++) (P < 0.05). CONCLUSION: PPD is a useful test to identify children infected with TB independently of whether they had received BCG or not. Children exposed to adults with TB are at high risk of infection. The risk of infection is associated with the intimacy of contact and the number of bacilli expectorated in sputum.