Resistance of Small Colony Variants (G-Forms) of a Staphylococcus Towards the Bacteriostatic Activity of Penicillin

Abstract

75gen, glycerol, or 2,3-butylene glycol could be detected, and only traces of acetyl methyl carbinol or diacetyl could be shown. A fair carbon and hydrogen balance5 was obtained for the fermentation of glucose in a medium initially containing 326 mg glucose, 45 mg Difco yeast extract, 3 mg proline, 3 mg phenylalanine, 1.5 mg cystine, 1 mg isoleucine, 1 mg valine, 45 mg NH4C1, 45 mg MgSO4 7 HzO, 2 mg CaC12, and 1 mg FeCI3 per 100 cc of 0.05 M Sorensen phosphate buffer at pH 7.5. During the fermentation the medium was neutralized at intervals with 5 Doudoroff, JI., J . Bird., 1942, 4.4; 461. NaOH, until all of the sugar had disappeared. The results are presented in Table I.Although the carbon recovery appears to be satisfactory, the ratio of two-carbon to onecarbon derivatives (see 5 ) is extraordinarily high for an ordinary fermentation, being approximately 3.2. This might indicate that a portion of the one-carbon derivatives remains unaccounted for (as unidentified products in the medium or in the bacterial) or, perhaps that part of the 2-carbon compounds may arise, not through the splitting of a 3-carbon degradation product of sugar, but by some other method such as the reduction of carbon dioxide.

The Influence of Antibiotics on the Origin of Small Colonies (G Variants), of Micrococcus Pyogenes var. Aureus1

“…The results are shown in Table II. With reversion there was a return which confirms the observations of others (20,38). On the other hand, Hale (21) reported that the G colony was four times more sensitive to penicillin than the parent strain.…”

“…These substances include lithium chloride, barium chloride, 2-methyl-1,4-naphthoquinone, and sterile filtrates of bacterial cultures (9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23). Appearance of G colonies in cultures of filtrates of "transitional" colonies of Salmonella, which appeared on MacConkey agar, has also been reported (24).…”

“…The selection of G colonies with antibiotics in vitro was first described by Schnitzer, Camagni, and Buck (20) when they observed small colonies in areas where growth of staphylococci had been inhibited by a crude extract of Penicillium notatum. These minute colonies reverted to normal colonial forms when cultivated in the absence of the antibiotic.…”

MODE OF ACTION OF STREPTOMYCIN ON TYPE b H. INFLUENZAE

“…According to the latter theory, which is well supported by experimental data from a number of investigators (12)(13)(14)(15)(16)(17) and which conforms also to our own results, the emergence of resistance represents a selective process. The usual in vitro sensitivity tests, involving relatively small numbers of organisms and thus failing at times to include samples of the comparatively rare resistant members of the initial bacterial population, reflect a conventional degree of sensitivity of the strain under investigation to the antibiotic used.…”

Clinical Significance and Pathogenesis of Staphylococcal Small Colony Variants in Persistent Infections

“…During the following decades, reports on SCVs designated them as a specific kind of staphylococcal "dissociants" or as "dwarf" and "G" ("gonidial") colonies (2)(3)(4)(5)(6)(7). An overview of clinical reports on S. aureus SCVs between 1950 and 1980, prior to their definitive association with persistent and relapsing infections, is given by Proctor et al (8).…”