Use of vancomycin in the culture of Mycobacterium tuberculosis from gastric lavage

Background & objectives: Earlier studies from the Tuberculosis Research Centre, Chennai, on culture of Mymbocterium (tuberculosis from gastric lavage (GL) specimens in selective Kirchner's medium (SK) resulted in a loss of 60 per cent culture results due to contamination with aerobic spore bearers (ASB). Addition of vancomycin to SK (SKV) effectively reduced the contamination rate to 20 per cent. The objective of the present study was to further reduce the contamination by collecting the specimens in bottles containing vancomycin, thus providing continuous exposure of the sample to the drug, which is bactericidal to ASB. Methods: One thousand GL specimens coIIected from children in vancomycin containing bottles were decontaminated and cultured in SK medium, with and without vancomycin, subcultured on Lowenstein Jensen (W) medium and the culture results compared. Results: The contamination of cultures in SK and SKV was 15 and 4 per cent respectively when the specimens were collected in bottles containing vancomycin compared to 60 and 20 per cent contamination reported in the earlier studies. interpretation & conclusion: The reduced contamination in SK and SKV is most likely due to the collection of sample in vancomycin containing bottles. Although a concurrent comparison of samples processed in vancomycin free conditions would have been ideal, it could not be done due to practical difficulties. The study thus confirms the value of vancomycin as a major deterrent for contamination due to aerobic spores and better results can be obtained if vancomycin is used in sample collection bottles, transport media and liquid culture media used in mycobacteriology laboratories particularly in humid and tropical environment

Evaluation of various methods of susceptibility to ofloxacin in strains of Mycobacterium tuberculosis

A comparison of three methods of susceptibility testing was undertaken on 30 susceptible and 25 resistant strains of Mycobacterium tuberculosis to determine an acceptable in vitro definition of resistance of ofloxacin. The strains were tested by the proportion method on Lowenstein Jensen (L-J) and 7H11 media and also by the BACTEC radiometric method. Using a criterion of 1 per cent or more growth at a concentration of 2 mg/1, there was a 100 per cent agreement with the conventional MIC method by the proportion tests on L-J as well as on 7H11 media. The BACTEC radiometric method, at the same concentration, yielded 98 per cent agreement. Thus, any of these methods could be used depending upon the infrastructure available

The Anomalous Diamagnetism of Graphite

It describes the Anomalous Diamagnetism of Graphite@IAC

Nocardia bacteraemia in an HIV-positive patient - a case report

Nocardiosis has been recognized in recent times as an unusual opportunistic infection associated with HIV. Bacteraemia due to this pathogen is even rarer and only few cases have been reported in the literature. We report here a case of pulmonary nocardiosis with bactcracmia, which was initially diagnosed as pulmonary tuberculosis. A high index of suspicion is required to diagnose this infection as the clinical presentation and radiographic features mimic pulmonary tuberculosis

Investigations on ancient Indian metallurgy. I. A pre-historic bronze bowl

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Vancomycin for controlling contamination of selective Kirchner’s liquid medium in the culture of gastric lavage for tubercle bacilli

Gastric lavage (GL) was collected for culture of tubercle bacilli from children too young to expectorate sputum. The selective Kirchner’s liquid medium (SKLM), routinely used as one of the media for culture of all extrapulmonary specimens, was found to often get contaminated when cultured with GL. We have shown that vancomycin at a concentration of 10 mg/l successfully reduced the contamination from about 60 to 20 per cent, and enhanced the Isolation rate of tubercle bacilli from 3 to 6 per cent. Decontamination of the liquid culture before subculture on solid medium also helped to reduce the contamination rate. Vancomycin was found to be an effective selective drug for use In the Kirchner’s liquid medium for culture of tubercle bacilli

Early results from indirect drug susceptibility test for tubercle bacilli

The indirect susceptibility test results on L-J medium for tubercle bacilli against streptomycin, isoniazid and rifampicin were read at the end of 2 wk and compared with the results at 4 wk. It was found that drug resistance could be correctly predicted in over 70 per cent of cultures including multi-drug resistant tuberculosis (MDR TB) strains at the end of 2 wk. The susceptibility to para-nitrobenzoic acid (PNB) read at 2 wk was able to distinguish non-tuberculous mycobacteria from Mycobacterium tuberculosis cultures. The early detection of resistance by this procedure requires only minimum inputs, and can benefit the majority of patients harbouring drug resistant tubercle bacilli

Secondary bacterial flora in patients with pulmonary tuberculosis - a preliminary report

Sputum samples from 100 smear positive or skiagram positive pulmonary tuberculosis patients were cultured for superinfecting or co-injecting bacteria. These patients were equally divided into five groups. This included Croup-I who are not treated; Group-II who are treated up to three months; Group-III who are treated for more than three but less than six months; Group-IV treated more than six months and lastly Group-V who have completed the prescribed treatment schedule of varying durations. Neisseria catarrhalis and Strep. viridans predominated in all patients irrespective of group, other organisms isolated, were Micrococci, E.Coli, Serratia, Proteus and Pseudomonas. There was no significant difference in the pattern of organisms isolated from different group of patients. The antibiogram showed the usual susceptibility pattern

Comparison of different methods of assessing in vitro resistance of Mycobacterium tuberculosis to rifampicin

Background & objectives: Definitions of in vitro resistance to rifampicin in. strains of Mycobacterium tuberculosis by different methods have not been consistent, leading to variations in the interpretation and validity of results. This study compared three methods of defining in vitro resistance to rifampicin. Methods: (i) A total of 598 clinical isolates of M. tuberculosis were concurrently compared by the minimal inhibitory concentration (MIC) and the proportion method on Lowenstein-Jensen medium; (ii) 54 strains tested by the MIC method were retested by the proportion method and the BACTEC radiometric method; and (iii) 72 strains which yielded an MIC of 64 mg/l by the MIC method were retested by the same method. Results: Out of 598 cultures tested by the MIC and the proportion methods, identical classification as susceptible or resistant was observed in 99.7 per cent. A 100 per cent agreement was observed when 54 strains were tested by the MIC, proportion and BACTEC radiometric methods. When 72 strains with an MIC of 64 mg/l were retested by the same method, 61 (85%) yielded a lower MIC, 9 (12%) gave the same MIC while 2 (3%) yielded a higher MIC of 128 mg/l, reflecting perhaps the inherent limitations of the variations in the inoculum size. Interpretation & conclusion: All 3 definitions of resistance, viz., an MIC of 128 mg/l, a proportion of I per cent or more on 40 mg/l by the proportion method, both on L-J medium and a growth of 1 per cent or more on 2 mg/l by the radiometric method were found to be equally satisfactory

Transportation of lymph node biopsy specimens in selective Kirchner’s liquid medium for culture of tubercle bacilli

Lymph node biopsy specimens, obtained from 297 paediatric and adult patients with tuberculous lymphadenitis at Madurai, were transported in selective Kirchner’s liquid medium (KL-T) to the Tuberculosis Research Centre, Madras and processed for culture. Mycobucterium tuberculosis was isolated from 201 (68%) specimens. Of the 192 specimens received within 4 days of resection, 134 (69.8%) yielded M. tuberculosis on culture and of the 105 specimens received after 5 days, 67 (63.8%) were culture positive; the difference was not statistically significant. By incubating KL-T alone further, after removing the gland for processing, it was found that mere contact with the excised node during transportation was enough to retrieve 77 (38.3%) of the total of 201 positive isolates obtained, the delay did not affect the culture positivity rate. Thus, lymph node specimens for culture of tubercle bacilli can be stored in the refrigerator for up to 15 days and transported in KL-T at ambient temperature for 18-20 h without any loss in culture positivity