Subodh Katiyar, MD, Shivesh Prakash, MBBS, (Email: [email protected]) and Shailesh Bihari, MD, (Email: [email protected]) are from the Deptt. Of Tuberculosis and Respiratory Diseases, GSVM Medical College, Kanpur
Corresponding Author: Dr Shivesh Prakash, Dr. ML Chest Hospital, GSVM Medical College, Kanpur-208002. [Phone 09335603232; E-mail: [email protected]]
In a resource poor country like India, it is essential to carefully prioritize tools of diagnosis and treatment based on intricate balance of cost and yield. Culture and susceptibility of mycobacterium tuberculosis has been regarded as the backbone of management of MDR Tuberculosis. However, it can be very misguiding especially due to high dependency on quality control at each step which can be lacking. Alternative cheap options for management of MDR tuberculosis like ‘drug history-based regimen modification’ have been shown to yield similar or even better outcomes. The case presented is that of suspected, relatively rare primary drug resistance which deteriorated clinically, bacteriologically and radiologically in spite of 5 years of ‘culture and susceptibility guided anti-tubercular therapy’. This highlighs the un-reliability of culture and sensitivity testing in India, along with two crucial issues fueling the fire of drug resistance in the country: from the doctor’s side – mismanagement, improper regimen and insufficient dosage and on the patient’s front – Poor compliance and defaults, especially in the pediatric age group.
Key words: Pulmonary tuberculosis, drug resistance, susceptibility testing, drug history based regimen
The incidence of multidrug resistant (MDR) tuberculosis is increasing in spite of constant efforts on the part of health organizations to curb it.1 The milieu is particularly worrying in resource poor developing countries. The index of MDR risk in India is 16.3%.2 It is at this front where the war against tuberculosis needs to be fought with better resource management and carefully prioritized tools of diagnosis and treatment based on intricate balance of cost and yield. Culture and sensitivity test, though costly, is regarded as an essential tool in the management of resistant tuberculosis. However its use in resource-poor developing countries can be less rewarding given the issues like cost, need for strict quality control, and inter-lab variability.
The case presented is that of suspected, relatively rare primary drug resistance highlighting the un-reliability of culture and sensitivity testing in India, which along with other two vital issues, continue to fuel the fire of drug resistance in the country, ie
A 16 year old male student was admitted on 16/9/05 with history of cough with expectoration of yellowish, non-foul smelling sputum for the past 5 years, breathlessness on exertion for 1 year which had increased during the last 1 month, and bilateral chest pain (dull, poorly localized), moderate-to-high grade continuous fever, not associated with chills or rigors, for the past 15 days. On admission, the patient was found to be sputum-smear positive for AFB and had a culture done 4 months back which grew M. tuberculosis.
The past history was significant in terms of the long history of anti-tubercular treatment that the patient had been taking for 5 years.
The patient had first been diagnosed as a case of pulmonary tuberculosis based upon sputum smear examination in 2000 when he was put on daily regimen containing rifampicin, isoniazid, pyrazinamide, and ethambutol on 4/4/2000 which he took regularly for 16 months during which he improved and was found to be sputum-smear negative at the end of 16 months. Sputum status during treatment was not monitored. After stopping treatment, however, the patient experienced recurrence of symptoms and, on 10.8.01, after a gap of about 2.5 months the patient was once again found to be sputum smear positive for AFB and was started again on same regimen by the same physician which the patient took regularly for 7 months during which he improved and became asymptomatic and defaulted. Two months after stopping treatment the patient deteriorated. This time he consulted another physician and was again found to be sputum smear positive for AFB. Once again, he was started on the same daily regimen containing rifampicin, isoniazid, pyrazinamide, and ethambutol on 3/5/02 which he took for 4 months and defaulted as there was no relief.
After 3 months of no treatment, the patient consulted another physician who, on 1/12/02, found him to be sputum smear positive and started rifampicin, isoniazid, levofloxacin, paraamino salicyclic acid, and ethionamide. The sputum culture and sensitivity after 5 months of initiating treatment grew Myco tuberculosis [BBL MGIT mycobacterial growth indicator tube culture, flurometric method was used for detection of mycobacteria]. The results are shown in table 1.
Based upon culture sensitivity results
the patient was put on streptomycin, isoniazid,
pyrazinamide, ethionamide, PAS and ofloxacin
which continued for about 6 months when on
23/11/2003 the patient was again found to be
+++ for AFB. (Table 2). A 2nd sputum
culture and sensitivity was got done again from
one of the best labs in the country which used
radiometric culture and sensitivity. Growth was
detected and recorded by BACTEC 460 TB
instrument. The culture grew mycobacterium
tuberculosis. The sensitivity data is shown in
table 2. The patient was initiated on
streptomycin (250 I/M injections), ethionamide,
cycloserine, PAS, isoniazid, and ofloxacin, which
he has been taking for the last 2 years. In these 2
years, based on several consultations, the patient took ethambutol and azithromycin also off and
on. About 16 months after starting the above
treatment he was found to be sputum
AFB in two consecutive sputum samples. On
strong suspicion of multi-drug resistant tubercle
bacilli a 3rd culture and sensitivity of sputum
was done once again on 23/12/2004. This was
from the same lab as the previous one. The
culture was positive at the end of the 2nd week.
The report is shown in table 3.
Sputum culture and sensitivity was repeated again on 18/2/2005 from a different laboratory, again, with very high quality standards. Radiometric method was used to detect the mycobacterium tuberculosis growth. Culture was found positive after 6 weeks; M. tuberculosis was differentiated by NAP test. The susceptibility report is shown in table 4.
The sputum culture for fungus was negative. HIV Elisa test was also negative. As seen below throughout the period of 5 years there has been slow but progressive radiological deterioration.(figure 1 to 4).
Important causes of increased incidence of MDR TB:
The case depicts a mix of all the above causes. In spite of many efforts by the health organizations the incidence of multi drug resistant tuberculosis is increasing1. An important cause is mismanagement in terms of improper regimen and dosage selection. Private practioners and quacks which are so very prevalent in the society provide significant portion of health care2. The practice of these care givers are often not under surveillance and supposedly are the point where mismanagement is done and ultimately leading to emergence of drug resistance. In this case firstly sputum examination was not done during the treatment obscuring the early diagnosis of treatment failure. Secondly when after regular treatment with conventional regimen for the given duration the patient was found to be sputum smear positive, a diagnosis of resistant tuberculosis should have been considered. A culture and sensitivity though was warranted but even drug history based change in regimen alone would have been beneficial and would have stopped the progress of the destructive disease3.
This problem of mismanagement could be tackled by administering tuberculosis treatment strictly by qualified authorized health care providers who are under active surveillance. ATT availability should also be restricted to authorized centers which provide drugs on production of cards and maintain records.
Patient had no previous history of ATT. Case appears to be that of primary drug resistance. The first culture showed resistance to second line drugs which patient never took, while first line drugs where sensitive except ethambutol. Primary resistance to second line drugs is very rare. Primary drug resistance to first line drugs is likely as patient was found to be sputum positive inspite of prolonged treatment with first line drugs. However there is a possibility of inadequate dosing as the dose details are not available. One of the objectives of TBTC 26 4 study is validation of accuracy of weight-based dosing in children.
If the bacilli were sensitive to first line drugs then what could be the cause of persistent treatment failure? Besides poorly designed drug regimens, other reasons for treatment failure could be (1) poor patient compliance with therapy especially with pediatric population as in this case, (2) mediocre drug quality, and/or (3) inadequate supervision of the patient by health authorities, (4) bio-availability and achievement of critical concentration at the site of infection, (5) interaction with other drugs (6) problems related to intestinal mobility or hepatic metabolism. TB therapy will be successful if (1) the critical proportion of organisms and the critical concentration of drugs are strictly adhered to, and (2) the strain is fully susceptible to front-line drugs in vitro. Resistance of M tuberculosis to anti-TB drugs is the result of a spontaneous genetic event and, worse, “a manmade amplification of the natural phenomenon”5. To facilitate rapid therapeutic decisions for patients harboring MDR TB organisms, critical concentrations have been established for second-line drugs as well as for newer drugs such as capreomycin, ethionamide, amikacin, kanamycin, clofazimine, ofloxacin, and rifabutin6. An important strategy to detect drug resistance involves determining minimal inhibitory concentrations (MICs) of drugs. Well known as labor intensive, this procedure has been considerably facilitated by the E-test.7 Large array of techniques has become available to detect mutations in genes associated with resistance mechanisms in mycobacteria. Among them are, in particular, DNA sequencing (mostly 16S rDNA), but also other techniques such as gel electrophoresis (single-stranded conformation polymorphism [SSCP]-PCR, dideoxy fingerprinting) and hybridization on solid phase (line probe assay, DNA chip technology) or on liquid phase (heteroduplex analysis, mismatch cleaving assay, molecular beacon)8.
There is also inter-lab variation in results. The intrinsic accuracy of susceptibility testing results (performed under the best circumstances) varies with the drug tested: it is most accurate for rifampicin and isoniazid and less for streptomycin and ethambutol.2 Bacilli where found to be resistant against ethambutol, ethionamide, cycloserine, thiacetazone in the first test however in the second test bacilli where found to be sensitive against these and other drugs inspite of three years of persistent failure of anti-tubercular treatment. Test repeated after a gap of 1year 5 months showed resistance against rifampicin. Again the test was repeated 2 months later and this time bacilli where found to be resistant against streptomycin and intermediate sensitivity against ethionamide. The variability of results raises question on reliability of this costly investigation. Both quality control (i.e., inside the laboratory) and proficiency testing (external evaluation) are essential to improve quality assurance. Biological safety cabinets built to internationally recognised standards (class I or II) are an absolute requirement whenever work is done with pure cultures, and particularly with aqueous suspensions. Any minor error at any level could render this test highly unreliable. In a review of 14 studies that included sputum cultures of more than 100 patients, false positive cultures were identified in 13 (93%) of them which may occur because of contamination of clinical devices, clerical errors, and laboratory cross contamination.9 overall it is difficult to perform susceptibility testing accurately even when skilled personnel are available and laboratory facilities are of a high standard. in countries were skilled manpower and adequate facilites for such tests are scarce, accuracy is even more difficult to achieve.10 Due to inaccurate drug susceptibility testing resistant strains may be classified as susceptible and vice versa. If susceptible strains are reported as resistant, regimens may be changed unnecessarily and reserve drugs may be introduced which are more toxic, less effective and more costly than drugs used for primary treatment.9,11.
Quality control is a very important under-estimated under looked issue in this investigation. Given the inter-lab variability of this costly investigation especially in resource poor heavy tuberculosis burden countries, Poor reliability warrants cautious interpretation. Drug history based regimen modifications as an option is worth considering. Similar outcomes in drug history based and sensitivity based regimen modifications have been concluded by studies3. If done, MIC values should be provided. Assuring tuberculosis management by qualified hands could help in curbing development of drug resistance.
Fig. 1. Chest x-ray done after 2 years,
7 months of first treatment (RHZE)
on 4/4/2000. By this time the patient
had taken RHZE for a total duration of 27 months.
Fig 3. X-ray chest after 2 yrs
on second line drugs
Fig. 2. Chest x-ray of the patient after
4 years of starting treatment and
1 year 4 months on second line drugs
- rifampicin, isoniazid, levofloxacin, para-amino
salicyclic acid, ethionamide.
Fig. 4: Chest x ray after 2 ½ years
on second line drugs