- Volume 24, Issue 3, 1974

One hundred strains of Mycobacterium fortuitum(M. ranae) were characterized. Strains now recognized as belonging to the species M. chelonei were excluded. Seven serotypes of M. fortuitum showed some correlation with cell wall lipids, colony types, temperature tolerance, Bönicke’s biotypes, and other properties. Serotype I was frequently associated with disease, whereas serotype II, although common in the environment, never was. M. fortuitum subsp.fortuitum and M. fortuitum subsp. giae belong to serotypes I and V,respectively; the other serotypes were not considered worthy of special subspecific designation. A list of the constant and variable characteristics of M.fortuitum is given.

The degree of homology between group D (Streptococcus faecalis and S. faecium) and group N(S. lactis)streptococci was assessed by deoxyribonucleic acid (DNA)-DNA hybridization. Interspecific DNA duplexes between S. faecalis and S. faecium exhibited high levels (>75%) of formation at 60 and 70 C, and low levels (<10%) of DNA duplex formation were observed between group D and group N organisms at 60 and 70 C. Thermal stability studies indicated less than 2% unpaired bases in these duplexes. Atypical strains which have characteristics of both group D and group N streptococci were included in an attempt to identify them with established species. The results indicate that DNA-DNA hybridization studies may be useful in placing atypical strains in a particular species if screening of physiologic properties is used to separate these strains into groups resembling S. faecalis, S. faecium and S. lactis. Results obtained with an authentic strain of S. faecium subsp. casseliflavus Mundt and Graham indicate that this organism deserves the subspecific designation.

An acid-fast, slow-growing scotochromogenic mycobacterium was isolated from a medium specific for hydrogen-utilizing chemolithotrophs. The organism grew well in pure culture in simple mineral salts media under an atmosphere of hydrogen, oxygen, and carbon dioxide. No growth occurred in the absence of the gas mixture unless organic substrates were added. Four tested strains of the tap-water scotochromogen, Mycobacterium gordonae, were also able to grow autotrophically, whereas none of eight tested strains of M. scrofulaceum grew using hydrogen. Twenty-one other mycobacterial strains were negative for autotrophic growth; a strain of M. xenopi grew very slowly. The isolated scotochromogen conformed to the properties of M. scrofulaceum except for its ability to grow at 19 C and its autotrophic ability. This organism exhibited two major colony types. During autotrophic cultivation, a flat, rough colony form was dominant; heterotrophic cultivation caused a population shift to a smooth, domed variety. The two colony forms exhibited qualitatively similar biochemical properties, and the unusual rough-to-smooth transition seemed to correlate with the quantitatively enhanced heterotrophic growth capacities of the smooth strain. Rough-to-smooth variation was reversible, and predominantly smooth inocula gave rise to predominantly rough populations under conditions of chemoautotrophy. The ability to grow autotrophically may be a useful characteristic for distinguishing the saprophytic scotochromogens from the more pathogenic strains.

The characterization of several isolates of a new lactic acid bacterium which produces a malty aroma is presented. Strains MX5R, MX5S, 674S, and 628S were asporogenous, catalase-negative, gram-positive, aciduric rods of varying length which did not reduce nitrate. The above strains also formed L(+)-lactic acid, produced 0.3 to 0.4% acidity in sterile milk, and grew at 7, 15, 25, and 32 C but not at 45 C. In addition, all strains produced limited amounts of CO2 from gluconate, did not produce C02 from glucose, required riboflavin and folic acid but not thiamine for growth, and demonstrated fructose-1,6-diphosphate aldolase (EC 4.1.2.13) activity. The guanine plus cytosine contents of deoxyribonucleic acid (DNA) extracted from representative strains MX5R and MX5S were 36.0 and 36.1 mol%, respectively. All isolates produced an extracellular nuclease which hydrolyzed ribonucleic acid as well as DNA. Like Streptococcus lactis subsp. maltigenes, all strains produced 2-methyipropanal, 2-methylpropanol, 3-methylbutanal, and 3-methylbutanol in skim milk and Trypticase soy broth. The characteristic malty aroma is most likely due to the production of the above aldehydes. On the basis of the data presented, the malty strains were placed in a new species, Lactobacillus maltaromicus, in the subgenus Streptobacterium. Strain MX5 (ATCO 27865) was designated the type strain of L. maltaromicus.

During the course of a periodic epidemiological survey for leptospirosis of a herd of bulls at the University of Illinois Agricultural Research Center, Dixon Springs, anew leptospiral strain was isolated from the urine of a clinically healthy Hereford bull, no. 3055. The strain was found to be antigenically unrelated to known pathogenic (Leptospira interrogans) and “saprophytic” (Leptospira bilflexa) serotypes. Phenotypically, it most closely resembled L. biflexa strains; however, in view of the reported distinct genetic characteristics of strain 3055, its species classification is not recommended at this time.

On the basis of long-term experience with the preservation of the pathogenic bacteria of the Czechoslovak National Collection of Type Cultures, it is concluded that the suspending medium is a factor of primary importance in the preservation of these organisms in the freeze-dried state. The primary index of suspending medium effectiveness is the level of protection it affords against the adverse effects of low (subzero) temperatures, dehydration, long-term storage, and rehydration. A number of simple and compound suspending media were studied for their protective effects on cultures from over 50 genera of predominantly pathogenic bacteria. The results indicate that not only each bacterial genus and species but also frequently every strain of a given serological type must be looked upon as a distinct biological entity, the preservation of the viability, activity, and desirable characters of which must be tested in different protective media in preliminary experiments. Heat testing (at 75 to 100 C) of freeze-dried cultures kept under high vacuum is recommended as a good indicator of adequate protection provided by a suspending medium. With the freeze-drying technique used, the best results for the largest number of species were obtained with a mixture of calf serum or defibrinated sheep blood and lactose solution (to a final concentration of 5 to 10%) and Annear’s peptone-containing medium. Individual suspending media were evaluated in relation to individual strains, and recommendations are made as to the preferred medium on the basis of control tests performed at 5-, 10-, and 15-year intervals.

Strains of M. fortuitum, M. abscessus, and M. borstelense showed different polyacrylamide gel electrophoretic patterns of their cell proteins. M. fortuitum strains could easily be distinguished from those of M. abscessus and M. borstelense, and they appear to belong to a single homogeneous group. M. abscessus and M. borstelense gels showed similar patterns, thus tending to confirm recent suggestions that they both belong to one and the same species, the correct name of which is M. chelonei.