Burden of drug-resistant pulmonary tuberculosis in Pakistani children: A cross-sectional study

Introduction

Globally, there are approximately 67 million children suffering from Mycobacterium tuberculosis (MTB) infection. It is estimated that 5 million children are infected with Isoniazid (INH) mono-resistant MTB strains and 2 million with multidrug-resistant (MDR) strains. In 2014 alone, an estimated 850,000 children developed pulmonary tuberculosis with 25,000 multidrug-resistant cases¹. The statistics surged drastically, and in 2017 1 million new cases of paediatric TB were reported². Adding to the current poor trajectory there have also been reports of extensive drug resistance (XDR) in paediatric pulmonary tuberculosis, with almost 100,000 children found infected with XDR strains¹.

In TB patients, drug resistance results from spontaneous genetic mutations in the MTB genome. The risk of genetic mutation increases with increasing bacterial load, explaining why resistance is more commonly seen in adult cavitary TB, which has large bacilli load. In children the more common reasons of drug resistance are transmission of a resistant bacillus and previous treatment with anti-tuberculous therapy (ATT). Other factors that predispose to drug-resistant TB include inappropriate drug regimens, monotherapy, and drug non-adherence³.

Pakistan is among the top 20 TB-endemic countries, which share 84% of global TB burden and 87% of multidrug-resistant tuberculosis (MDR-TB) burden, according to the World Health Organization (WHO)². Though, there have been various studies highlighting the incidence of MDR-TB in Pakistani adults⁴, and some studies also included children; we couldn’t find any study from Pakistan that discussed the incidence of paediatric MDR-TB in particular. The aim of this study is to assess the pattern of sensitivity to 1^st line and 2^nd line ATT among Pakistani children (≤18 years).

Methods

A prospective, cross-sectional study was conducted from 1^st July 2018 to 31^st Dec 2018 in the Department of Paediatrics, Civil Hospital, Jamshoro. Known cases of pulmonary tuberculosis being followed up at the outpatient TB clinic were recruited. The inclusion criteria included children <18 years with a working diagnosis of pulmonary TB who had been taking 1^st line ATT for two months but still had sputum smears (or sputum culture) positive for MTB. For children less than five years old, informed consent was taken from their parents/guardians. For children of age five years or above, informed consent from the parents/guardians and assent from the children was taken. Children who had become negative for MTB on sputum smear or culture with 1^st line ATT, indicating response to these drugs, were not included. Children who were sputum positive but also non-compliant to their medications (those not taking/not given their medications regularly as assessed from their TB dosage card) were also excluded. Follow up patients in the TB clinic whose parents/guardians did not consent or children older than 5 who did not assent to participate were also excluded.

For culture and sensitivity, either sputum sample was utilized or bronchoalveolar lavage specimen (in cases of no sputum production). The samples were not specifically taken for this research, but were a part of their standard management, hence, no additional burden was placed on the participants of the study. Mycobacterium was isolated from the specimens by using Lowenstein-Jensen medium and Mycobacterium Growth Indicator Tube (MGIT) medium (Becton Dickinson, Franklin Lakes, NJ, USA). BACTEC NAP test (Becton Dickinson) was then performed on the isolated mycobacterium to differentiate MTB from other mycobacteria. Drug sensitivity testing was then done using an agar proportion method on enriched Middle brook 7H10 medium (BBL Microbiology Systems, Cockeysville, MD, USA) following the standard laboratory protocols of the Civil Hospital, Jamshoro. Concentrations used for every drug was: isoniazid (INH) 0.2μg/ml, rifampicin (RIF) 1μg/ml, ethambutol (EMB) 5μg/ml, and streptomycin (SM) 2μg/ml and 10μg/ml. For pyrazinamide (PZA) sensitivity, BACTEC 7H12 medium was used with pH 6.0, at 100μg/ml (BACTEC PZA test medium, Becton Dickinson). Strains which were resistant to INH and RIF were termed as MDR strains. MDR-TB strains were then tested for sensitivity to 2^nd anti-tuberculosis agents: capreomycin 10μg/ml, ofloxacin 2μg/ml, ethionamide 5μg/ml, and kanamycin 6 μg/ml.

A brief questionnaire (See Extended data⁵) was generated which included patient demographics such as age, gender, history of TB contact, and duration of treatment. Data was entered and analyzed using SPSS Version 22.0. Armonk, NY: IBM Corp. Mean ± standard deviation (SD) was calculated for continuous variables such as age and duration of treatment. Frequency and percentages were calculated for all other variables including drug sensitivity.

Results

The study was completed by 50 children. There were 32 male (64%) and 18 female (36%) children in the study. Their mean age was 12.84 ± 2.54 years with the youngest child being 7 and the oldest 18. The demographic profile of these patients is shown in Table 1 (data at patient level is available as Underlying data⁵).

The sensitivity pattern of 1^st line ATT is shown in Table 2. There were 32 (64%) children with combined sensitivity to INH and RIF and 18 (36%) children were multidrug-resistant i.e., combined resistance to INH and RIF. Other than MDR cases, and among the first line drugs used alone, RIF showed the highest isolated resistance (n=33; 66%), while two of those MDR cases were also resistant to Ofloxacin (PreXDR-TB).

Of the 18 MDR cases, 10 (55.6%) were boys and 8 (44.4%) were girls. Their mean age was 14.01 ± 1.50 years with the youngest of aged 12 and oldest aged 15.

The sensitivity pattern of second-line line ATT is shown in Table 3.

A positive history of household TB contact (either resistant or non-resistant) was seen to have a statistically significant impact on incidence of MDR-TB as seen in Table 4.

Discussion

The incidence of drug-resistant TB among children is a global health concern. Public health specialists must pay keen attention to this issue in order to prevent unnecessary mortalities. Pakistan is already a high TB burden country. Poor detection, diagnosis, and management of TB, along with child household contacts of MDR-TB cases not being screened and managed appropriately, has markedly contributed to the rising incidence of MDR-TB among both adults and children in Pakistan⁶. This study reported 66% of children to be resistant to RIF, 36% to be MDR, and although no case of extensive drug resistance was seen, 24% of children tested positive for fluoroquinolone resistance. It can be extracted from the provided data that out of the total 33 cases of rifampin resistant strains, 15 were mono-resistant to rifampin. Including Pakistan, in other countries the incidence of rifampin resistance is rising and our results are parallel^7–9.

Comparatively, in a Pakistani study conducted in 2010–14, of all the MDR-TB cases in the study, only 1.6% were aged 0–14⁴. In another survey from 2013–14, household contacts of 209 diagnosed cases of MDR-TB were screened. It was seen that 378 of 1463 contacts (26%) were children aged 0–15. Of these, 11 children were symptomatic for TB, were tested, and 4 cases of TB were diagnosed from these children, all of which were MDR¹⁰. This study highly reinforces the impact of household TB contact on the development of MDR-TB in children, which has also been highlighted in our study. In another study, with 62% individuals resistant to all first-line agents, ofloxacin resistance was among 52.7%; which is relatively low in the current study (24%)¹¹.

This study highlights the prevailing situation of anti-tuberculosis resistance in Pakistani children and their predisposing factors. It emphasizes the need to protect the children from TB infected persons. This study has its limitations too. It was based in one institute only which is in the rural part of Pakistan. The actual aim of this study was to identify drug resistance to ATT in children of all ages, however, most study participants are adolescents. Hence, this study doesn't represent all TB population and the data cannot be compared to data of more general drug resistance surveys. Multi-center studies all across Pakistan must be conducted to completely understand the current status of anti-tuberculosis drugs resistance in Pakistan among both children as well as adults. Studies should also be conducted to evaluate disease outcome in these patients.

Conclusion

Drug-resistant TB, especially in the pediatric population, is a public health concern. Awareness programs on national and international levels are needed to educate the masses regarding importance of preventing TB household contact especially among the children. With the selected method used to identify mainly older children with drug resistance, the yield for drug-resistant TB was found to be high. Long term studies should be conducted to study the prognosis of children with MDR-TB and deduce strategies to prevent drug resistance.

Ethical approval and consent to participate

The study was assessed and approved by the Institutional Review Board of Civil Hospital, Jamshoro (IERB: 18-679) with informed consent taken from all participants.

Data availability