Reply to “Tuberculosis in infants less than 3 months of age from Risaralda, Colombia”

Dear Editor,

We appreciate Zapata-Martín A.’s letter on tuberculosis in infants under 3 months of age in the department of Risaralda (Colombia). This letter brings to light the difficulties involved in clinical and microbiological diagnosis in these patients. In the case series, 2 infants had a diagnostic delay of more than 3 weeks, and only 3 of the 7 infants under 3 months of age in whom tubercular disease was suspected underwent gastric juice culture.

BCG vaccination, which is performed at birth in Colombia, invalidates the interpretation of the tuberculin test. The new immunological diagnostic tests (IGRAs) are not available in many laboratories and have low sensitivity in small infants. Gastric aspirate culture requires collecting several samples and has low sensitivity compared to sputum culture in adults. However, the diagnostic yield of bacilloscopy and gastric juice culture in infants under 3 months of age exceeds that in older children.¹ In addition, microbiological confirmation is considered the gold standard for diagnosing the disease and allows an antibiogram to detect resistant strains to be performed.² Colombia has a very high rate of resistance to anti-tuberculosis drugs in children under 15 years of age (21% in 2009), with rates of resistance to isoniazid exceeding 12% and rates of multi-drug resistant strains of 6.5%.³ Therefore, we believe that every effort should be made to collect microbiological samples in all patients, especially those with no isolation in the index case.

In 3 of the infants studied, the index case was unknown. Our series also found 3 patients with an unknown index case, but with a strong suspicion of maternal genital tuberculosis, as the mothers had a positive tuberculin test, a normal chest X-ray and no identified contact with bacilliferous tuberculosis. Tuberculosis in an infant under 3 months of age involves congenital infection or postnatal transmission from a bacilliferous adult. Therefore, it is essential to conduct a full contact study to prevent the transmission of the disease and the appearance of new cases of tuberculosis.⁴

Finally, we would like to make a consideration with respect to treatment. All infants were treated according to the regimen recommended in Colombia for children under 15 years of age. This regimen consists of administering 3 drugs (isoniazid, rifampicin and pyrazinamide) for 8 weeks followed by bitherapy with isoniazid and rifampicin 2 times per week until 6 months have elapsed.⁵ We believe that, given the high rate of resistance, it would be important to start treatment with 4 drugs if the sensitivity of the strain from the child or from the index case is unknown. In addition, we recommend continuing treatment for at least 9 months in infants under 3 months of age with tuberculosis, and extending it up to 12 months in those with meningeal involvement.⁶

Funding

No funding was received to complete this study.

Conflicts of interest

The authors declare that they have no conflicts of interest.