Differential Identification of Mycobacterium kansasii and Mycobacterium marinum

This report deals with the differential diagnosis between Mycobacterium marinum and M. kansasii. We found that the two species could be differentiated by using six main tests, namely, the nitrate reduction test, the arylsulfatase test, the ability to grow in the presence of 10.0 mug of amithiazone per ml, the ability to grow in the presence of 5.0 mug of kanamycin per ml, the temperature-ratio test, and the rate of growth on solid medium. In contrast to M. kansasii, considerable variation was observed among strains of M. marinum. However, the evidence obtained was not considered sufficient to justify the conclusion that more than one species was represented among the strains identified as M. marinum.     

Biogenesis of β-Carotene in Mycobacterium kansasii

The biogenesis of beta-carotene in the photochromogen Mycobacterium kansasii consists of two reactions. The first reaction is photochemical, and is dependent on the wavelength of the incident light and on oxygen but is independent of temperature. The second reaction does not require illumination, and is dependent on the temperature and on oxygen. The latter, or dark reaction, requires the synthesis of new protein, and was shown to have the characteristics of an inducible system. Carotenogenesis was stimulated by incident light of wavelengths of 420, 540, and 650 nm. Immediately after illumination there was an increase in the synthesis of ribonucleic acid and beta-carotene accumulation started after a lag of 8 to 10 min. The synthesis of beta-carotene exhibited temperature dependence with an optimum of about 36 C.     

Recombinants between Clock Mutants of CHLAMYDOMONAS REINHARDI

Mutants affecting the period length of the biological clock in Chlamydomonas reinhardi have been isolated and a start has been made on analyzing the genetics of this system. In four mutants, the long period characteristic seems to be controlled by single genes at separate loci. Crosses between single mutants, as well as crosses involving three or four mutant genes, yielded progeny with periods characteristic of the parents as well as recombinant types, including normal period (wild type) and extra-long periods (double, triple and quadruple mutants). It was found that the period lengthening effect is additive; that is, the period of double mutants is lengthened by the sum of the period lengthening of the single mutants.     

In Vitro Effect of Rifampin on Mycobacteria

Rifampin inhibited 20 strains of Mycobacterium tuberculosis in concentrations of 0.005 to 0.02 mug/ml in 7H-9 broth with Tween 80 and killed all or nearly all of the inoculum in four to eight times greater concentrations. In the same medium without Tween 80, as well as on 7H-10 agar, about 16 to 64 times these amounts were required to produce the same effect. Rifampin was also active against M. kansasii and some of the nonchromogenic mycobacteria. The incidence of mycobacterial cells resistant to rifampin within the cultures studied was in the range of one to four per 10(8) to 10(9) colony-forming units with concentrations of 4 to 125 mug of rifampin per ml. Only one of the Battey cultures and that of M. fortuitum yielded cells resistant to rifampin at 125 mug/ml but not at 500 mug/ml. The same strains yielded more than double that number of organisms resistant to streptomycin and up to 100 times more organisms resistant to isoniazid. All three drugs stopped the growth or reduced the mycobacterial population in growing cultures after contact for 24 to 48 hr. Complete inhibition of growth was produced by rifampin at 1.0 mug/ml in an average of 6 days and by streptomycin at 5.0 mug/ml in 3 days. After an average contact of 10.7 days with rifampin, five of seven strains resumed growth and all strains began regrowth after exposure to streptomycin for 9.4 days. The marked susceptibility of M. tuberculosis and of atypical mycobacteria to rifampin in vitro and the relatively low incidence of resistant mutants suggests that this agent may have clinical usefulness in the treatment of tuberculosis and some other mycobacterioses.     

Effect of Diurnal Temperature Cycles on the Production of Aflatoxin

Exposures to short periods of high temperature (40 to 50 C) in each 24-hr diurnal temperature cycle (average temperature ca. 25 C) reduced growth of Aspergillus parasiticus and production and accumulation of the aflatoxins when compared with cultures held continuously at 25 C. In contrast, diurnal cycles with an average temperature of ca. 25 C but with minima as low as 10 C did not appreciably affect either growth or toxin production. The ratio of production of aflatoxin B to aflatoxin G increased as the maximal temperature was raised but remained essentially unchanged with decreasing minimal temperatures.     

Bacterial Metabolism of Mevalonic Acid

Soluble cell-free extracts of actinomycete S4 grown on media containing mevalonate catalyze acetoacetate formation from mevalonate, mevaldate, and β-hydroxy-β-methylglutaryl-coenzyme A (CoA). Conversion of mevalonate to acetoacetate involves formation of free β-hydroxy-β-methylglutaryl-CoA, but not free mevaldate. The reaction favors mevalonate oxidation, and nicotinamide adenine dinucleotide, rather than nicotinamide adenine dinucleotide phosphate, acts as oxidant.     

Cholelithiasis and Cholecystitis in Childhood

Six cases of cholecystitis and cholelithiasis confirmed by x-ray examination and surgical operation were observed in a ten-year period. Due to the wide variability in signs and symptoms in children, cholecystitis and cholelithiasis can be diagnosed only with a high degree of clinical suspicion and roentgenological examination. Gallbladder disease is uncommon in childhood but should be considered in children with vague abdominal pains or bouts of unexplained jaundice. If a normal appendix is found at laparotomy in the “acute abdomen,” the surgeon would be wise to palpate other specific organs within the abdomen, including the liver and gallbladder.The treatment of choice is cholecystectomy. The prognosis for recovery is excellent if there is no complicating systemic disease.