Effect of the anthracycline group antibiotics, mitomycin C and bruneomycin, on the transduction of drug resistance in staphylococci]

The effect of various concentrations of antitumor antibiotics, such as carminomycin, rubomycin, adriamycin, mitomycin C and bruneomycin on transduction of erythromycin resistance from the donor strain 8325 P II/de of Staph, aureus to the recipient strain 8325-I in different transduction systems was studied. It was shown that the above antibiotics inhibited the transduction in the systems with constant presence of the drugs. Preliminary treatment of the recipient cells with the drugs in the subbacteriostatic doses did not decrease the transfer frequency. The preliminary treatment of the donor cells resulted in an increase in the phase titer and the transfer frequency in the "preliminary-treated donor + recipient" system.     

Transduction of plasmid antibiotic resistance determinants with pseudo-T-even bacteriophages

Transduction of antibiotic resistance determinants of the plasmid pBR322 with pseudoT-even bacteriophages RB42, RB43, and RB49 was studied. It is established that antibiotic resistance determinants of plasmid pBR322 from Escherichia coli recA(+)- and recA(-)-donor strains do not differ significantly in respect to the efficiency of transduction. Amber mutants RB43-21, RB43-33, and a double amber mutant RB43am21am33 were obtained. These mutants facilitated transduction experiments in some cases. Transduction of antibiotic resistance markers of the vector plasmid pBR325 and recombinant plasmid pVT123, containing a DNA fragment with hoc segE uvsW genes of phage T4, was studied. The frequency of appearance of transductants resistant to pseudoT-even bacteriophages used in transduction was determined, and the sensitivity of resistant transductants to 32 RB bacteriophages and also to phages lambda, T2, T4, T5, T6, T7, and BF23 was estimated. The efficiency of plating pseudoT-even bacteriophages RB42 and RB43 on strain E. coli 802 himA hip carrying mutations in genes that encode subunits of the Integration Host Factor (IHF) was shown to be higher than on isogenic strain E. coli 802. The growth of pseudoT-even bacteriophages limited in vivo by modification-restriction systems of chromosomal (EcoKI, EcoBI), phage (EcoP1I), and plasmid (EcoRI, EcoR124I, and EcoR124II) localization was analyzed. It was shown that these phages were only slightly restricted by the type I modification-restriction systems EcoBI, EcoR124I, and EcoR124II. Phage RB42 was restricted by systems EcoKI, EcoP1I, and EcoRI; phage RB43, by systems EcoKI and EcoRI; and phage RB49, by the EcoRI modification-restriction system.     

凝固酶阴性葡萄球菌临床耐药性的连续性研究

目的了解凝固酶阴性葡萄球菌的耐药性情况。方法分析2008年至2010年沈阳军区总医院临床分离的484株凝固酶阴性葡萄球菌的药敏结果。结果 2008年至2010年凝固酶阴性葡萄球菌的分离率分别为4.7%、3.6%和3.1%。耐甲氧西林凝固酶阴性葡萄球菌（MRSCN）分别为76.6%、78.5%和79.9%。青霉素G、红霉素和苯唑西林的耐药率较高,平均分别为91.2%、87.5%和82.6%。万古霉素、替考拉宁和利奈唑胺的耐药率均为0。结论 2008年至2010年凝固酶阴性葡萄球菌检出率相对稳定,对常用抗菌药物的耐药率相对稳定,这为临床用药选择及加强感染控制提供了有力指导。     

Donor activity of methicillin resistant staphylococci in transduction experiments]

Antibiotic resistance gene transmission from methicillin resistant strains of Staphylococcus aureus (MRSA), isolated in a burn care unit, was studied in transduction experiments with type phages 29, 52, 52A and in experiments with prophage induction. The results of the experiments demonstrated high donor activity of MRSA. Recombinants with different antibiotic resistance phenotypes were revealed, but there were no methicillin resistant staphylococci among them. Stability of cloramphenicol resistance gene transmission in the experiments on specific transduction with the prophage induction could be indicative of the prophage localization near the chloramphenicol resistance genes. Variety of the antibiotic resistance combinations in the transductants from the clinical strains of MRSA could prove heterogeneity of the strains even under conditions of one hospital.     

Characterization of the drug resistance plasmid NTP16

A functional and physical analysis of the multicopy plasmid NTP16 is presented. The plasmid-encoded drug resistance determinants are located, as are regions encoding the origin of replication, incompatibility functions, copy number determinants, and mobility functions. It is demonstrated that NTP16 probably arose from the closely related plasmid NTP1 by the acquisition of a novel kanamycin resistance transposon, Tn4352, followed by deletion of some NTP1 sequences. The incompatibility behavior of NTP16 derivatives indicates a system of control rather more complex than that which operates in ColE1. In addition to the RNA I/primer RNA system, the production of a further trans-acting product is demonstrated and its site of action located. A series of derivative plasmids have been created which may prove useful as vectors for genetic engineering.     

Sensitivity of the Burkholderia cepacia complex and Pseudomonas aeruginosa to transducing bacteriophages

Burkholderia cepacia is now recognised as a life-threatening pathogen among several groups of immunocompromised patients. In this context, the proposed large-scale use of these bacteria in agriculture has increased the need for a better understanding of the genetics of the species forming the B. cepacia complex. Until now, little information has been available on the bacteriophages of the B. cepacia complex. Transducing phages, named NS1 and NS2, were derived from the lysogenic B. cepacia strains ATCC 29424 and ATCC 17616. The frequency of transduction per phage particle ranged from 1.0x10(-8) to 7.0x10(-6) depending on the phage and recipient strain used. The host range of NS1 and NS2 differed but in each case included environmental and clinical isolates, and strains belonging to several species and genomovars of the B. cepacia complex. The host range of both phages also included Pseudomonas aeruginosa. Some B. cepacia complex isolates were sensitive to the well-characterised P. aeruginosa transducing phages, B3, F116L and G101. The lytic activity of NS1 and NS2 was inhibited by B. cepacia lipopolysaccharide suggesting that this moiety is a binding site for both phages. The molecular size of the NS1 and NS2 genomes was approximately 48 kb.     

Isolation and characterization of plaque-forming lambdadnaZ+ transducing bacteriophages.

The Escherichia coli dnaZ gene, a deoxyribonucleic acid (DNA) polymerization gene, is located 1.2 min counterclockwise from purE, at approximately min 10.5 on the E. coli map. From a lysogen with lamdacI857 integrated at a secondary attachment site near purE, transducing phages (lambdadnaS+) that transduced a dnaZts (lambda+) recipient to temperature insensitivity (TS+) were discovered. Three different plaque-forming transducing phages were isolated from seven primary heterogenotes. Genetic tests and heteroduplex mapping were used to determine the length and position of E. coli DNA within the lambda DNA. Complementation tests demonstrated that the deletions in all three strains removed both att P and the int gene, i,e., DNA from both prophage ends. Heteroduplex mapping confirmed this result by demonstrating that all three strains had deletions of lambda DNA that covered the b2 to red region, thereby removing both prophage ends. Specifically, the deletions removed lambda DNA between the points 39.3 to 66.5% of lambda length (measured in percent length from the left and of lambda phage DNA) in all three strains. The three strains are distinct, however, because they had differing lengths of host DNA insertions. These phages must have been formed by an anomalous procedure, because standard lambda transducing phages are deleted for one prophage end only. In lambdagal and lambdabio strains, the deletions of lambda DNA begin at the union of prophage ends (i.e., position 57.3% of lambda length) and extend leftward or rightward, respectively (Davidson and Szybalski, in A, D. Hershey [ed.], The Bacteriophage Lambda, p. 45-82, 1971). Models for formation of the lambdadnaZ+ phages are discussed.     

Effect of 1,3,5-triazines on various bacteriophages and their hosts]

In the agar diffusion test 24 triazines were investigated with regard to their action on the mulplication of DNA phages (lambda and LPP-1) and RNA phages (M12 and Qbeta). In several cases the amount of plaques was diminished or increased depending on the kind of triazine and virus. The investigations demonstrate the triazines to be able to interfere with the formation of plaques by virulent and temperate viruses of procaryotes.