Observations on categorisation of new TB cases: implications for controlling drug resistance.

In the context of rising rates of drug-resistant tuberculosis (TB) in India, this communication presents some field observations during screening of new cases registered with the Revised National Tuberculosis Control Programme (RNTCP) in urban and rural areas of Maharashtra, India. It appears that erroneous categorisation and treatment that contributes to multiple drug resistance results from a lack of patient screening for previous treatment, ambiguity in categorisation and reluctance to disclose a history of anti-tuberculosis treatment. Suggested measures include detailed screening of new cases, computerisation of patient records and an empathetic dialogue between patient and health care provider.

Rhodococcus and Mycobacterium Tuberculosis: masquerade or mixed infection.

Rhodocci have a morphology similar to that of Mycobacterium tuberculosis (TB), and are indistinguishable from normal diphtheroid flora. Symptoms include fever, productive/non-productive cough and pleuritic chest pain. Rhodococcal infections, being resistant to routine anti-tuberculosis medications, may be misdiagnosed as drug-resistant TB, thus prompting treatment for TB with rifampicin-containing regimens that promote the emergence of resistance. We present here a sputum smear AFB-positive case who, although clinically cured, remains unresolved despite a series of technological investigations as to the cause of infection being purely rhodococci or mixed infection with M. tuberculosis.

Longitudinal trends in serum levels of mycobacterial secretory (30 kD) and cytoplasmic (65 kD) antigens during chemotherapy of pulmonary tuberculosis patients.

Antigen 85 (mol. wt 30,000) (30 kD), secreted by actively growing mycobacteria under axenic conditions, and mol. wt 65,000 (65 kD), a cytoplasmic antigen released during mycobacterial lysis, were used to monitor the efficacy of chemotherapy in previously untreated pulmonary tuberculosis (UPTB) patients using enzyme-linked immunosorbent assay. Sera from 125 UPTB patients were examined for each of the 2 antigens individually and for the ratio of secretory (30 kD) to cytoplasmic (65 kD) antigen (SCR), before commencement of treatment, after intensive phase (IP), completion of optimum period of treatment (COPT) and 6 months post-COPT. 116 controls (normals and contacts) were also checked for these antigens. The detection of 30 kD and 65 kD antigens in UPTB patients had a sensitivity ranging from 50-57% (mean 30 kD value: 0.64 +/- 1.24 ngs/ml) to 20-22% (mean 65 kD value: 0.51 +/- 1.87 ngs/ml), respectively, whereas in controls it ranged from 2-8% (0.05 +/- 0.28 ngs/ml) to 14-47% (0.09 +/- 0.22 ngs/ml), respectively. Although the decline in 30 kD positivity was more evident at COPT, computation of the SCR denoted efficacy of chemotherapy more readily at IP. Similarly, SCR resolved the ambiguity between individual antigen levels and the clinical status of a patient. Since significant numbers of patients demonstrated 30 kD at IP it may be computed that the lifespan of circulating 30 kD in serum could be at least 2 months after the start of treatment, declining gradually thereafter. Although seromonitoring for secretory antigen generally reflects the efficacy of chemotherapy, the interpretation of findings clearly requires further elucidation.

Views on the sustenance of resistant Mycobacterium tuberculosis in the environment.

Microbial resistance to conventional as well as newly introduced drugs is a hallmark feature of several infectious diseases, notably tuberculosis. It is hypothesized that the greater the selective pressure exerted by increasingly potent drugs, the more rapidly is an organism able to adapt to a drug-containing environment. The roles of drug-containing environments, and the immunological status of the host and bacterial molecular mechanisms of development of drug resistance to Mycobacterium tuberculosis have been examined and examples cited for implementation of modified drug regimens in tuberculosis-control programmes. The views expressed, albeit restricted to Mycobacterium tuberculosis, encourage consideration of drug regimens on a disease evolution basis as well as understanding of the natural rules that govern development and sustenance of drug resistance in the microbial world.

Effect of T-cell depletion on bacterial multiplication and pattern of nerve damage in M. leprae-infected mice.

Various mechanisms for nerve damage in tuberculoid leprosy have been proposed. A common feature amongst them is the crucial role played by T-cells. Therefore, the present study was designed to determine the role of T-cells in the induction of nerve damage in leprosy using two different protocols for obtaining graded levels of T-cell depletion: (i) Cyclosporine A, for depletion of T-helper cells and (ii) Anti Thy 1.2, for total depletion of T-cells. The findings indicate that the early changes seen in the unmyelinated fibres may not involve T-cells. However, the later stages of nerve damage associated with demyelination are dependent on T-cell responses.

Blocking of Mycobacterium leprae adherence to dissociated Schwann cells by anti-mycobacterial antibodies.

The association of Mycobacterium leprae with Schwann cells may represent an early crucial step in M. leprae pathogenesis. Using a dissociated Schwann-cell system and anti-mycobacterial monoclonal and polyclonal antibodies directed against surface and cytoplasmic components, we investigated the nature of M. leprae epitopes that mediate cytadhesion. Antibodies to polysaccharide and lipid components of M. leprae cell wall inhibited cytadhesion, whereas those directed against both surface and cytoplasmic protein epitopes did not show any such effect. No synergistic or antagonistic activity in inhibiting cytadhesion was observed when antibodies were used in combination. Thus, the association of M. leprae with Schwann cells may be mediated collectively by more than one of its lipid/polysaccharide epitopes. Also, a role for humoral immunity in intervention in the initial steps of M. leprae pathogenesis needs to be considered.

Effects of a derivative of serotonin (deoxyfructoserotonin) and other antileprosy drugs on attachment and uptake of Mycobacterium leprae by Schwann cells in vitro.

The association (attachment and/or uptake) of Mycobacterium leprae with cultured Schwann cells was studied at 8 and 72 h in the presence of a new antileprosy compound, deoxyfructoserotonin (DFS), as well as conventional antileprosy drugs such as rifampin (RFP) and 4,4'-diaminodiphenyl sulfone (DDS). DFS significantly inhibited bacterial association with Schwann cells at 8 h. RFP also affected the association of M. leprae but not to the same extent as DFS. A similar inhibition at 8 h was noted when M. leprae but not Schwann cells were pretreated with DFS or RFP for 5 days before infection of cultures, implying that modulation was achieved through some form of drug action on bacteria. DDS had no effect on M. leprae association; however, the combination of DFS and DDS was neither antagonistic nor additive. At 72 h postinfection, when attached but noninternalized bacteria were removed with trypsin-EDTA from Schwann cell cultures containing DFS or RFP, a 50% reduction in the number of bacteria in the drug-treated group was obtained as compared with the numbers in drug-free cultures. This indicated a slow entry of M. leprae into Schwann cells in the presence of these drugs. Collectively, these observations point to differing requirements for late and early association of M. leprae with Schwann cells, besides suggesting a role for DFS and RFP in the prevention and minimization of M. leprae-induced nerve damage in vivo.