Tellurite and Tetracycixne Resistance in Enterococci

APPLEMAN, M. D. (University of Southern California, Los Angeles), AND I. M. HEINMILLER. Comparison of tellurite resistance and tetracycline resistance among the enterococci. Appl. Microbiol. 9:391-394. 1961.-A correlation was found to exist between tellurite and tetracycline resistance in the enterococci. Fleming (1932) reported that species of bacteria which were susceptible to penicillin were resistant to the action of potassium tellurite and vice versa. Enterococci, common molds, and yeasts were resistant to both agents. Utilizing the observation of Fleming that potassium tellurite had a selective effect on bacteria resistant to penicillin, Bornstein (1940) found that 27 strains of I This investigation was supported in part by a PHS Research Grant E-1994 from the Allergy and Infectious Diseases Division, Public Health Service. 2 The authors wish to express their appreciation to Benj amin Saltzer, who assisted in these experiments under the U.S.C. talented student program. enterococci would grow in the presence of both penicillin and potassium tellurite. The lactic group was inhibited only by the latter agent, whereas the viridans group was completely sensitive to both the antibiotic and the tellurite. Watson (1944) tested the sensitivity of various serological groups of streptococci to penicillin, finding that organisms of group M were the most sensitive, whereas those of group D were the most resistant. Nyman (1949) reported that of 449 strains of fecal streptococci tested, 89% were resistant to 1: 1,700 potassium tellurite. He concluded that high potassium tellurite resistance was characteristic of the fecal streptococci and believed that media containing tellurite were suitable for the isolation of enterococci from urinary tract infections. The enterococci have been divided into two welldefined groups, namely, tellurite-resistant and telluritesensitive strains, by Skadhauge (1950), which meet the major requirements of Sherman and Stark (1931) and Sherman, Mauer, and Stark 1937 for the enterococci, i.e., growth at 10 C and 45 C, tolerance to 1961] 391 on A uust 5, 2017 by gest ht://aem .sm .rg/ D ow nladed fom M. D. APPLEMAN AND I. M. HEINMILLER 6.5 % NTaCl, and to pH 9.6. Three variants of Streptococcus faecalis are differentiated on the basis of their hemolytic and proteolytic power, S. faecalis var. liquefaciens, S. faecalis var. haemolyticus, and S. faecalis var. zymogenes. The tellurite-sensitive strains include Streptococcus faecium and S. faecium var. durans which characteristically do not ferment sorbitol. Sherman et al. (1931, 1937) made no distinction between S. faecalis and S. faecium as they considered them identical. Orla-Jensen, however, who originally described S. faecium (1919), strongly opposed this view stating that differences existed in fermentive activity, temperature range for growth, and salt tolerance. In addition, tellurite sensitivity now appears to be a characteristic of this group. MATERIALS AND METHODS The organisms used in this experiment were 13 cultures of enterococci derived from various sources. This group included S. faecalis ATTC 349,3 ATCC 828,3 and N83,4 S. faecalis var. liquefaciens 14A,5 S. faecalis var. liquefaciens 14B,5 S. faecalis var. zymogenes 15A,5 S. faecalis var. zymogenes 15B,5 S. faecium var. durans 14C1I6 S. faecium var. durans S5,6 S. faecium K6A,6 R55,6 HGH9,4 and P13.4 3 T. A. Nevin, National Institute of Dental Research. 4E. M. Barnes, University of Cambridge. 5 R. A. Greene and M. J. Kaplan, College of Osteopathic Physicians and Surgeons. 6 C. F. Niven, American Meat Institute. The casein hydrolyzate medium was prepared according to the directions of Nevin (personal communication, 1957). For the determination of tellurite sensitivity, chocolate tellurite agar was used. Bacto-tellurite blood solution was added to sterile Bacto-dextrose proteose no. 3 agar in amounts which would give final concentrations of 1:1,500, 1:2,000, and 1:2,500 tellurite. The mixture was heated to 75 to 80 C, cooled to 50 C, and poured into previously sterilized Petri dishes. Each of the 13 strains was spread over the surface of a series of tellurite agar plates which were examined after 20 hr of incubation at 37 C for the presence of jet-black, butyrous colonies. Antibiotic Qensitivity was determined by using a technique modified from that of Lederberg and Lederberg (1952). A 0.1-ml aliquot of a 24-hr broth culture was streaked over the surface of antibiotic-free agar. After 24 hr incubation, each plate was examined and the one developing 30 to 300 well-distributed colonies was selected as the "master" for the replica plating. The concentrations of antibiotic used were 0.07, 0.7, 7.0, 21.0, and 70.0 ppm of tetracycline, chlortetracycline, and oxytetracycline. Control plates of casein hydrolyzate agar were stamped last. RESULTS AND DIscussIoN The spectrum of resistance to tetracycline, chlortetracycline, oxytetracycline, and tellurite is presented in Table 1. These organisms showed marked variation TABLE 1. Antibiotic resistance of parent strains of enterococci as determined by the replica plating technic Tetracycline (ppm) Chlortetracycline (ppm) Oxytetracycline (ppm)