Elimination of extrachromosomal streptomycin resistance in staphylococci by experimental variations in geomagnetic field intensity

The article comprises the data on the elimination of streptomycin resistance in Staphylococcus aureus after its passage for a long time in a low permanent magenetic field (PMF) with H = 0.5 oe and in a space screened from the geomagnetic field in a permaloy chamber (H = 10(-2). Under these conditions the eliminating effect of the geomagnetic field intensity on the streptomycin resistance of Staphylococci became perceptible after 5--10 their passage under unusual conditions. At the next stages of investigation the eliminating effect of low PMF and of screening was enhanced. At the end of the experiment after 25--40 passages of Staphylococcus aureus throung MF of different intensity the elimination of streptomycin resistance was recorded in all the 11 cultures studied. The quantity of eliminates in populations of experimental substrains of Staphylococcus increased by 1.5--10 and more times as compared to the control.     

Transduction transmission of the extrachromosomal markers of antibiotic resistance in staphylococcal populations]

Transduction of extrachromosomal markers of resistance to penicillin and erythromycin in staphylococcal strains isolated from patients was studied. Two transduction methods were compared, i. e. transduction with a phage filtrate of the donor culture resistant to erythromycin and transduction on mixed cultivation of the donor and recipient. A higher transduction rate was observed with the latter method. Mixed cultivation of the donor cultures resistant to penicillin or erythromycin and the recipient strains of the wild type sensitive to these antibiotic resulted in transduction of the respective markers. Transductants which acquired prophage 6 simultaneously with marker Egg became donors of erythromycin resistance.     

Induction of penicillinase by staphylococci in vitro and in vivo

Eyckmans, Luc (Cornell University Medical College, New York, N.Y.), and Edward W. Hook. Induction of penicillinase by staphylococci in vitro and in vivo. J. Bacteriol. 91:997-1003. 1966.-Staphylococci in mice with peritoneal infection showed no significant increase in penicillinase activity 6 hr after administration of penicillin G. In contrast, induction of penicillinase was readily demonstrated in leukopenic animals under similar conditions. Induction of penicillinase by staphylococci in vitro was inhibited by including leukocytes and immune serum in the mixtures. The role of leukocytes in inhibiting induction of penicillinase by staphylococci in response to penicillin was investigated.     

Mupirocin resistance in staphylococci: development and transfer of isoleucyl-tRNA synthetase-mediated resistance in vitro

Mupirocin resistance could be transferred from highly resistant clinical isolates of Staphylococcus aureus to highly sensitive recipients of Staph. aureus, Staph. epidermidis and Staph. haemolyticus. Transconjugants of the latter two organisms could transfer this resistance into mupirocin-sensitive Staph. aureus. Moderately resistant strains did not transfer this resistance to sensitive recipients, nor did strains with high-level mupirocin resistance developed by serial transfer or habituation. The inhibitory effects of mupirocin on crude isoleucyl-tRNA synthetases (IRS) isolated from mupirocin-sensitive and -resistant strains of Staph. aureus have been determined. Drug concentrations needed to produce 50% inhibition, I50 values, were very low against IRS from a highly sensitive strain, somewhat higher against IRS from moderately resistant strains, much higher against enzyme from strains trained in vitro to high-level resistance, and considerably higher still against IRS extracted from clinical isolates possessing high-level mupirocin resistance and from the transconjugates of such strains resulting from crosses with mupirocin-sensitive strains. It is concluded that high-level resistance in clinical isolates is plasmid-mediated involving a second, mupirocin-resistant IRS whereas in moderately resistant strains, and in strains trained in vitro to high-level resistance, chromosomal mutations are likely to be responsible for decreasing IRS sensitivity.     

Influence in vitro of panthenol on the resistance of staphylococci to antibiotics and sulfonamides

Summary The action in vitro of the panthenol on the resistance of the staphylococci to the antibiotics and sulfonamides has been studied. We have been able to etablish that the panthenol has a “stimulating” effect on the action of the antibiotics and the sulfonamides. This effect was however insufficient to render a resistant strain sensitive.     

Ultrastructure,in vitro and in vivo,of staphylococci exposed to antibiotics

The ultrastructure of staphylococci from the peritoneal fluid of mice treated with oxacillin and from sputum of a patient treated with ampicillin was comparable to the structure of staphylococci grown on filter membranes exposed to oxacillin, but was different from the same organisms grown in broth with oxacillin. The selection of a solid phase support growth medium, such as a filter membrane for in vitro studies of drug induced morphology, appears necessary if such studies are to reflect bacterial ultrastructure in vivo.     

The transmission ratio distortion of the th2-haplotype in vivo and in vitro

The th2-haplotype is transmitted at low frequencies (less than 0.30) by +/th2 males in normal matings. In the studies described here, the transmission frequency of the th2-haplotype from Rb7/th2 males was determined for normal and delayed matings and in vitro inseminations. The data show the transmission frequency from the two in vivo inseminations to be less than 0.30 and to be statistically equivalent. However, the in vitro transmission frequency (0.80) is significantly greater than either of the in vivo frequencies. The results show that the environment in which fertilization occurs affects the transmission frequency of this specific t-haplotype significantly.     

The in vivo and in vitro transmission frequencies of the tw5-haplotype in mice

The recessive tw5-haplotype, a complete haplotype, is transmitted by heterozygous male mice at very high frequencies (greater than 0.90) in normal matings. The present studies were undertaken to determine the effects of delayed matings and in vitro fertilizations on this phenotypic expression. Males carrying the tw5-haplotype (+/tw5) were first tested for their frequencies of transmission of the mutant 17th chromosome in both normal and delayed matings. Spermatozoa obtained from these same males were then used to fertilize eggs in vitro. The in vivo and in vitro transmission frequencies were found to be statistically equivalent in all types of inseminations. An in vitro fertilization time course study showed that the same percentages of eggs are fertilized by tw5-bearing spermatozoa when the gametes are coincubated for either 2 or 6 h. The data lead to the conclusion that the transmission frequency of the tw5-haplotype is not affected either by the length of time elapsing between insemination and fertilization or by the environment in which fertilization occurs.     

Factors influencing methicillin resistance in staphylococci

Methicillin resistance in staphylococci is due to an acquired penicillin-binding protein, PBP2' (PBP2a). This additional PBP, encoded by mecA, confers an intrinsic resistance to all beta-lactams and their derivatives. Resistance levels in methicillin-resistant Staphylococcus aureus (MRSA) depend on efficient PBP2' production and are modulated by chromosomal factors. Depending on the genetic background of the strain that acquired mecA, resistance levels range from phenotypically susceptible to highly resistant. Characteristic for most MRSA is the heterogeneous expression of resistance, which is due to the segregation of a more highly resistant subpopulation upon challenge with methicillin. Maximal expression of resistance by PBP2' requires the efficient and correct synthesis of the peptidoglycan precursor. Genes involved in cell-wall precursor formation and turnover, regulation, transport, and signal transduction may determine the level of resistance that is expressed. At this stage, however, there is no information available on the functionality or efficacy of such factors in clinical isolates in relation to methicillin resistance levels.