In vitro studies of plasmid-mediated penicillinase from Streptococcus faecalis suggest a staphylococcal origin.
Year: 1986
Type: article
Abstract: described (1).This strain is highly resistant (minimal inhibitory c ncen- tration [MIC]l > 2,000 ug/ml) to gentamicin, is penicillin-r istant A strain of Streptococcus faecalis with plasmid-mediated peni- (PENR) at high inocula, and produces ja-lactamase (BlaB).HH222 ENs cillinase production was studied further.Partially purified pen- is a novobiocin-treated derivative of HH22 which no longer pr uces icillinase from the S. faecalis strain hydrolyzed penicillin, am- penicillinase but is still GMR.Other -.iajor bacterial strains and pi mids picillin, and ureido-penicillins but not penicillinase-resistant used in this study are listed in Table I with their relevant pro flies.semisynthetic penicillins, cephalosporins, or imipenem; hydro- Staphylococcus aureus strain RNl753 containing p1524 was obtmed lysis was inhibited by clavulanic acid.Hydrolysis of a given an- from Richard Novick, The Public Health Research Institute of th City tibiotic correlated with a marked increase in the minimal inhib- of NY (3), and the recombinant plasmid pJMI 3 was a gift fro Jesse itory concentration (MIC) of that drug when a high inoculum C. Rabinowitz (4), University of California, Berkeley, CA.Plasmi from wasused.As with most thegram-negative bacteria which were used in hybridizations iclude was used.Aswlithnmostenterococcithe Incsllo cephalosporins R6K(TEM-1), RP4(TEM-2), R57b(OXA-3), R16(OXA-2) (5 and and penicillinase-resistant semisynthetic penicillins were too high pMG2 1 7(PSE-1) (supplied by G. A. Jacoby [6], Massachusetts G neral for clinical usefulness, although these agents did not show an Hospital, Boston, MA).inoculum effect.Based upon hybridization under stringent con- Susceptibility testing.MICs were determined in brain-heart in sion ditions of plasmid DNA from the S. faecalis strain to cloned broth by tube dilution as previously described (1); a final inocul m of penicillinase genes from Staphylococcus aureus, it appears thatI03 colony forming units (CFU)/ml is referred to as a "low inoc lum" these resistance determinants are highly homologous and sug- and 107 CFU/ml as a "high inoculum."Antibiotics used are shw in gests that this enzyme was introduced into streptococci fromTables II-IV; they and the fl-lactamase inhibitors were obtain from staphylococci, their respective manufacturers or from Sigma Chemical Co., St. ouis, MO.The chromogenic cephalosporin nitrocefin was a gift from axo Laboratories, Middlesex, England.a wavelength that corresponded to the peak absorbance for each com- Bacterial strains.S. faecalis strain HH22 was isolated from a urine spec- pound (8, 9).These peaks were determined before the addition ofenzyme; imen at Hermann Hospital, Houston, TX in 1981 and has been previously all were in the 250-300 nm range.The effects ofsulbactam and clavulanic acid were studied in two ways.In order to determine the effect on the This work was presented in part at the 24th Interscience Conference on MIC of penicillin, I07 CFU/ml of HH22 were preincubated for 30 min Antimicrobiol Agents and Chemotherapy, Washington, DC, October with varying dilutions of the fl-lactamase inhibitors before the addition 1984. of penicillin.The effect of inhibitors on the hydrolysis of nitrocefin was Address correspondence to Dr. Murray, Program in Infectious Dis- determined by preincubating 106 CFU of HH22 with various concen- eases and Clinical Microbiology, University of Texas Medical School trations of inhibitor, then adding nitrocefin (250 gg/ml) in a final volume Houston, TX 77030.of 200 td, and incubating at 250C (8-10).
DOI: 10.1172/jci112289
Authors: B E Murray, B Mederski-Samoraj, S K Foster, J L Brunton, P Harford
Language: English
Subfield: Molecular Medicine
Domain: Life Sciences
Open Access status: bronze
Award: G2361022006
OpenAlex ID: W2034360859