Minocycline Resistance in Staphylococcus aureus: Effect on Phage Susceptibility

Abstract

Tetracycline-resistant strains ofStaphylococcus aureus are minocycline sensitive, with the exception of strains susceptible to phages ofthe 83A/84/85 complex and some methicillin-resistant strains of other phage types. Strains of the 83A/ 84/85 complex yield mutants with increased mimocycline resistance. Transduction of minocycline resistance into the susceptible strain RN 450 was obtained with donor strains possessing either markers for both extrachromosomal tetracycline resistance (tet) and chromosomal tetracycline + minocycline resistance (tmn R), or only for chromosomal tmn R resistance. The chromosomal marker was differentiated from the extrachromosomal marker by the lack of detectable extrachromosomal deoxyribonucleic acid after transfer into strain RN 450, transfer into a rec+ strain, lack of transfer into rec-acceptor strain, and cotransduction with chromosomal determinants for guanine biosynthesis. Both chromosomal and extrachromosomal tetracycline resistance can be induced by tetracycline. Induction by tetracycline of chromosomal tetracycline resistance resulted in simultaneous induction of minocycline resistance. The mutation toward increased minocycline resistance (tmn -) tmn R) is a regulatory mutation toward constitutivity or semiconstitutivity. Constitutive resistance is dominant in tmn R/tet diploids. Transfer of the tet marker does not affect the phage susceptibility of the acceptor strain. The tmn R marker, originating from donor strains of the 83A/84/85 complex, renders strain RN 450 resistant to several typing phages, with the exception ofphages ofthe 83A/84/85 complex. This could possibly account for the phage typing patterns ofminocycline-resistant staphylococci.In most instances tetracycline resistance in Staphylococcus aureus and gram-negative bacteria is extrachromosomal (21, 25). Chromosomal resistance has been reported for a methicillin-resistant strain of S. aureus (15) and Escherichia coli (8). The mechanism oftetracycline resistance in S. aureus and E. coli is still not fully understood. A decrease in the accumulation of tetracycline by resistant cells appears to be an important element in the mechanism of resistance (11,12,30), but the role of other factors, such as the appearance ofa new protein in resistant cells, has still to be elucidated (2,5,20). Minocycline (7-dimethylamino-6-deoxy-6-demethyltetracycline) is a semisynthetic derivative of tetracycline to which most tetracyclineresistant strains of S. aureus are susceptible (10, 16). Experiments of Kuck and Forbes (17) with E. coli and Sompolinsky and Krausz (33) with S. aureus indicate that tetracycline-resistant cells which retain their susceptibility to minocycline show a decreased accumulation of tetracycline but retain the ability to accumulate minocycline. Resistance to both tetracycline and minocycline determined by some R factors (29, 31) is accompanied by a decrease in the accumulation of both tetracycline and minocycline (17).Phair and Carleton (27) found that S. aureus strains of phage group m, although susceptible ...

Methicillin-Resistant Strains of Staphylococcus aureus Phage Type 92

“…The the three Mecr donor strains indicated that the presence of minocycline resistance is indicative transductants lost their susceptibility to interof the chromosomal location of the tetracycline national typing phages 6, 42E, 53, 54, 75, 83A, resistance marker (22). Genetic transfer was at-and 85, but retained susceptibility to experimentempted with phages induced in Mecr strains tal phages 89 and 92 and, to a lesser degree, to and phage preparations obtained by propagation phages 88 and 90.…”

“…tion of chromosomal tetracycline resistance is The Mecr transductants retained the phage susaccompanied by loss of susceptibility to several ceptibility of the acceptor strain 8825 P524. The typing phages such as 6, 47, or 75 and retention transduction experiments were repeated by usof susceptibility to phages 83A and especially 85 ing tetracycline-resistant transductants from (21,22 In contrast to the majority of Mecr Staphylococcus strains described in the literature (1, 24), with the exception of strain VIII, all Mecr strains tested possess homogeneous methicillin resistance, resulting in similar zone sizes at 30 and 37°C. Strain VIII was also the only strain found to be lipase negative.…”

“…Lysogenic phages harbored by Mecr strains isolated at different hospitals were induced with mytomycin C (22). All phage preparations were tested with strain RN 450, which does not harbor detectable lysogenic phages, thus eliminating potential interference with the phages introduced from Mecr strains.…”

Bacteriophage-mediated acquisition of antibiotic resistance by Staphylococcus aureus type 88

“…For transfer on solid medium, 0.1 ml of the control cultures and 0.1 ml of an equal mixture of the two strains were plated on LB agar. After overnight incubation, suspensions of approximately 5 x 108 cells in LB broth were plated on LB medium with 3 ,ug of novobiocin and 2 jig of rifampin per ml (NR media) and the following concentrations of antibiotics: tetracycline, 2.5 ,ug/ml; erythromycin, 20 ,ug/ml; clindamycin, 5 ,ug/ml; methicillin, 10 ,ug/ml; penicillin, 10 ,ug/ml; gentamicin, 10 ,ug/ml; streptomycin, 50 ±g/ml; kanamycin, 25 ,ug/ml; chloramphenicol, 30 p.g/ml; and Cd(NO3)2, 2 x 10-5 M. In some instances, antibiotic media with novobiocin but without rifampin were used.…”

“…After reisolation, nonlysogenic colonies were tested for sensitivity to phage 188 and for lack of phage production after induction with mitomycin C. Transduction procedures. Transduction procedures were performed as described previously (10). The transducing phage was added at a multiplicity of 0.1 to 0.2 PFU per colony-forming unit (CFU).…”