Tubercle, Lond., (1964), 45, 239

N I A C I N P R O D U C T I O N A N D V I R U L E N C E IN T H E G U I N E A - P I G O F I N D I A N

T U B E R C L E B A C I L L I

By BALBIR S1NGH* and M. D. SHARMA

from the Department of Microbiology, Maulana Azad Medical College, New Delhi

SUMMARY

No association was found between the niacin production and the virulence in the guinea- pig of 32 strains of tubercle bacilli obtained from Indian patients.

Tubercle bacilli from Indian patients, unlike those from European patients, have been shown to have wide variation in their virulence in the guinea-pig (Mitchison and others, 1960; Singh, 1964). The niacin production of strains obtained from Indian patients was investigated to determine whether it was related to the degree of virulence.

Methods Strains o f Tubercle Bacilli

Thirty-two strains, freshly isolated from Indian patients, were used. These strains were sensitive to PAS, streptomycin and isoniazid and had had their virulence in the guinea-pig determined previously by one of the authors (B.S.).

Niacin Production The strains were grown in Sauton medium, and filtrates were obtained as described by Konno ,

Kurzmann & Bird (1957). The content of nicotinic acid (niacin) in the filtrates was determined by the method of Swaminatllan (t942). Two ml. of 40 70 NaOH was added to the 10 nal. filtrate and the volume made up to 50 mls. by the addition of distilled water. Coenzyme nicotinamide and nicotinic acid precursor were hydro]ysed by heating in a water bath at 100 ~ C. for 1 hour. To 1.0 ml. of the hydrolysed culture filtrate, in a colorimeter cuvette, was added 1.0 nal. of 4 70 aniline, in 96 % ethanol and 1 ml. of 10 70 cyanogen bromide. The optical density was read at 440 m.u. and compared with a control containing 1 ml. each of filtrate, aniline solution and distilled water. The concentration of nicotinic acid was read from a standard curve constructed from readings on Sauton medium con- taining 1,2, 3, 4, 5, 6, 7, 8 and 9 ~g. nicotinic acid per 10 nal. medium.

Results

All of the 32 strains produced niacin, the highest concentration in the filtrate being 32 Ezg./ml., and the lowest concentration, 4 ~tg./ml. Niacin production is related to the virulence of the strains in Table I. A concentration of 20-32 ~tg./ml. niacin was found in 4 of 16 strains of high virulence, in 5 of 8 strains with moderate virulence and in 5 of 8 strains of low virulence. No association is evident.

* Present address: Willingdon Hospital, New Delhi.

240 TUBERCLE

TABLE I.--NIACIN PRODUCTION AND VIRULENCE IN THE GUINEA-PIG OF 32 INDIAN STRAINS OF TUBERCLE BACILLI

Niacin concentration ill

filtrate ~g./ml.)

20-.-32 10---19 4---9

Virulence in the guinea-pig*

High Moderate Low (80-100) (50-79) (10-49)

4 5 5 9 2 2 3 ! 1

* Range of Feldman indices for gross lesions.

Commen t

T h e absence of an as soc ia t ion be tween niac in p r o d u c t i o n a n d v i ru lence conf i rms the s imi la r conc lus ion o f K o n n o , K u r z m a n n & Bird (1957).

The authors are grateful to Indian Council for Medical Research who financed this enquiry.

REFERENCES KONNO, K., KURZMANN, R., & BIRD, K. T. (1957). Amer. Rev. Tuberc., 75, 529. MITCHISON, D. A., WALLACE, J. G., BHATIA, A. L., SELKON, J. B., SUBBAIAH, T. V., & LANCASTER, M. C. (1960).

Tubercle, Lond., 41, 1. SINGH, B. (1964). Amer. Rev. resp. Dis., 89, 1. SWAMINATHAN, M. (1942). Indian J. reed. Res., 30, 537.