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Drug-resistant TB passed through families
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Drug-resistant tuberculosis can and most likely is “transmitted and amplified within families,” according to study findings published online.
James A. Seddon MBBS, MA, a pediatrician from the London School of Hygiene and Tropical Medicine, and colleagues are part of an investigative team researching the treatment of drug-resistant and extensively drug-resistant TB among children in a suburban community of Cape Town, South Africa. The team reported on transmission sequences among two families after a child in each family contracted this form of the illness.
The first family included in the research was identified because a 19-month-old female member of the family received a diagnosis of TB after a 6-month prophylactic course of isoniazid. The child’s family consisted of 18 people, and the investigators reported that the infection likely began with a drug-resistant TB infection of the mother of one of the child’s uncles who “probably transmitted it to her son,” who in turn transmitted it to his niece, whom he cared for daily.
The investigators reported for the second family, whose index case was a 13-year-old female, that the oldest brother may have had drug-resistant TB before his sister having pre-XDR TB. The disease was then transmitted to the child’s mother, brother and sister, which the researchers noted the “potential for resistance to be transmitted and amplified within families.”
Seddon and colleagues said their study highlights the importance of carrying out household contact tracing in all newly diagnosed drug resistant TB patients to identify contacts “who may have subclinical disease that could be treated at an early stage.”
“It is important to always consider drug resistance in children presenting with TB, especially if there are any family members with drug-resistant TB,” added Seddon.
In terms of treating drug-resistant TB, Seddon said the options available for children are limited. To treat drug-resistant TB, a child is often hospitalized, administered multiple drugs, including some that are given by injection. The researchers urged for new drug options to treat TB in this population because often these medications are older with potentially severe adverse events.
Disclosure: Dr. Seddon reports no relevant financial disclosures.
Perspective
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Andrea T. Cruz, MD, MPH
The interesting article by Seddon and colleagues in South Africa describes escalating levels of drug resistance within families, as illustrated by the “TB pedigrees” of two children.
This paper demonstrates several important points about childhood TB. First, there is difficulty identifying a child’s source case in areas where TB is hyper-prevalent. As well-tolerated oral treatment regimens may be expensive and difficult to design, children often receive isoniazid prophylaxis unless a specific source case with drug resistance is identified. Second, TB is the ultimate family disease; children tend to get infected by their caregivers, perpetuating the cycle within the home. Third, TB in a child is reflective of almost “real-time” epidemiology in the community, given the short incubation period of TB in many children. Thus, the drug susceptibility patterns identified may more closely approximate circulating strains than reactivation disease in adults. Fourth, it illustrates that many children have primary drug resistance (the M. tuberculosis isolate they acquire has already developed resistance), whereas non-adherent adults may be more likely to have developed via secondary drug resistance, whereby an isolate initially may be susceptible, and resistance is selected out through inappropriate use of medications. Finally, this study illustrates the importance of epidemiology in treating children with TB. Many children with TB will have negative cultures, and identifying the source case in conjunction with public health authorities is imperative to optimize the child’s care.
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