Isolation and characterization of a kanamycin resistance plasmid from Staphylococcus aureus

Impact of plasmids and genetic change on the numerical classification of staphylococci

Newly isolated bacterial strains often contain extrachromosomal DNA as plasmid DNA. These accessory components of the DNA gene pool confer additional phenotypic properties on their host but, despite this, little attention has been paid to the impact of plasmid-mediated characters on bacterial classification. In the present study, the effect of antibiotic resistance plasmids on the classification of representative staphylococci was determined using numerical phenetic techniques. Over sixty percent of the eighty-one test strains contained one or more plasmids which varied in molecular weight from 1.4 to 36 Mdal. Antibiotic resistance phenotypes were eliminated from strains of S. aureus, S. chromogenes, S. cohnii, S. hyicus and S. xylosus, and from a laboratory isolate, to give sixteen derivative strains. Fourteen had lost one or more plasmids and two had deleted plasmids. In addition three further derivative strains were isolated which showed no plasmid loss but exhibited gross phenotypic changes. The test and derivative strains were the subject of numerical phenetic analyses based on seventy-eight unit characters. Data were examined using the simple matching, Jaccard and pattern coefficients and clustering achieved using the unweighted pair group method with arithmetic averages algorithm. Cluster composition was not markedly affected by the statistics used or by test error, estimated at 1.02%. Numerically circumscribed clusters and subclusters were equated with the established species S. aureus, S. chromogenes, S. cohnii, S. hyicus, S. lentus, S. intermedius, S. sciuri and S. xylosus. The sixteen derivative strains with either lost or delected plasmids were recovered in the same cluster or subcluster as their corresponding parent indicating that the removal of plasmid-expressed characters had little effect on the structure of the numerical classification. In contrast, two of the three strains of S. xylosus with genomically-derived phenotypic variation formed a cluster that separated from their parent strain at the 70% similarity level in the SSM, UPGMA analysis.

Antimicrobial resistance of Staphylococcus aureus: genetic basis

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Molecular cloning and analysis of Staphylococcus aureus chromosomal aminoglycoside resistance genes

Most of the aminoglycoside resistant Staphylococcus aureus strains isolated in France are resistant to all the antibiotics belonging to this family. Two aminoglycoside-modifying enzymes were detected in the wild-type strains studied: an APH3'III and an AAC6'-APH2". These strains also carry two types of streptomycin resistance: high-level resistance due to chromosomal mutation(s) affecting ribosome affinity and low-level resistance, the mechanism of which was not characterized. All the aminoglycoside resistance genes were located on the chromosome. DNA fragments of 1.5 and 1.95 kb carrying the aphA and aacA genes, respectively, were isolated, by cloning, from the cellular DNA of a clinical isolate. When these genes were introduced into Escherichia coli and Bacillus subtilis strains, the enzymes synthesized were indistinguishable from those produced by the S. aureus strains. When the cellular DNAs of wild-type and resistant strains were hybridized with the cloned fragments, sequences homologous to the fragment carrying the aphA gene were found to be located at the same chromosomal site, while those hybridizing with the fragment carrying the aacA gene were at different chromosomal sites.

The chromosomal 3',5"-aminoglycoside phosphotransferase in Streptococcus pneumoniae is closely related to its plasmid-coded homologs in Streptococcus faecalis and Staphylococcus aureus

The apparently chromosomally encoded 3',5"-aminoglycoside phosphotransferase (type III), from the high-level aminoglycoside-resistant Streptococcus pneumoniae BM4200, was compared with homologous enzymes coded for by the plasmids pJH1 and pSH2, originally isolated from Streptococcus faecalis and Staphylococcus aureus, respectively, and also found in a wild strain of S. aureus, BM4600. The enzymes appeared to be indistinguishable, and we conclude that the gene encoding 3',5"-aminoglycoside phosphotransferase (type III) can cross generic barriers within gram-positive cocci.

Kinetic studies of aminoglycoside acetyltransferase and phosphotransferase from Staphylococcus aureus RPAL. Relationship between the two activities

In the Staphylococcus aureus strain harbouring the plasmid RPAL, the resistance to aminoglycoside antibiotics results from two inactivating reactions catalyzed by a 6'-N-aminoglycoside acetyltransferase and a 2"-O-amino-glycoside phosphotransferase. These enzymes are copurified with a constant ratio between the two activities, the purification process consisting in affinity chromatography, native electrophoresis and gel exclusion chromatography. The kinetic mechanisms of each activity have been determined from studies of initial velocities, as well as product and dead-end inhibitions. Both activities follow a random rapid equilibrium mechanism. The substrates and cofactors of one reaction have been tested as effectors of the other reaction. No interaction between the two activities has been observed. However, the GTP cofactor of phosphotransferase protects, at weak concentrations, the acetyltransferase against thermal inactivation, which suggests that the two activities may be associated.

Aminoglycoside-modifying enzymes of Staphylococcus aureus; expression in Escherichia coli

Staphylococcus aureus plasmids PSH2, RN1956 and pWA1 code for an aminoglycoside phosphotransferase; plasmid pWA1 also encodes an aminoglycoside-aminocyclitol adenylyltransferase. S. aureus plasmid pWA2 confers resistance to erythromycin and sulfonamide. Using plasmid ColE1-ApR (RSF2124) as a vehicle, we have transferred the genes determining aminoglycoside phosphotransferase and aminoglycoside-aminocyclitol adenylyltransferase activities from S. aureus to Escherichia coli. The new plasmids obtained confer aminoglycoside-aminocyclitol resistant phenotypes to E. coli, similar to, and by the same mechanisms as "naturally" occurring plasmids. By contrast, the results obtained after cloning of plasmid pWA2 indicate that certain S. aureus antibiotic resistance determinants (e.g. for erythromycin (Em) and sulfonamide (Su) cannot be phenotypically expressed in E. coli. The DNA of the constructed hybrid plasmids has been analysed by agarose gel electrophoresis following digestion with restriction endonucleases, by ultracentrifugation in cesium chloride, by hybridization, and by electron microscopy. Each hybrid is a cointegrate replicon, composed of an entire S. aureus plasmid covalently joined to ColE1-ApR.

New plasmid (pTU512), mediating resistance to penicillin, erythromycin, and kanamycin, from clinical isolates of Staphylococcus aureus

Multiply drug-resistant strains of Staphylococcus aureus were isolated from pediatric patients with severe staphylococcal infections in 1974 through 1976. Resistance to benzylpenicillin, erythromycin, and kanamycin was jointly eliminated without exception from these multiply drug-resistant strains by treatment with ethidium bromide. It was also found that the triple drug resistance in a representative strain, TK512-200, was always transduced to a susceptible strain simultaneously. Moreover, a single class of plasmid deoxyribonucleic acid was isolated from a transductant and found to be 14.4 +/- 0.6 mum in length, with a molecular weight corresponding to 29.8 x 10(6). From these results, it is concluded that the plasmid (pTU512) is a new one, mediating resistance to penicillin, erythromycin, and kanamycin.

Characterization of Staphylococcus aureus plasmids introduced by transformation into Bacillus subtilis

Covalently closed circular DNA from five Staphylococcus aureus plasmids has been introduced into Bacillus subtilis. Four of these plasmids (pUB110, pCM194, pSA2100, and pSA0501) have been selected for further study. These plasmids replicate as multicopy autonomous replicons in both Rec+ and Rec- B. subtilis strains. They may be transduced between B. subtilis strains or transformed at a frequency of 10(4) to 10(5) transformants per microgram of DNA. The molecular weights of these plasmids were estimated, and restriction endonuclease cleavage site maps are presented. Evidence is given that pSA2100, an in vivo recombinant of pSA0501 and pCM194 (S. Iordănescu, J. Bacteriol. 124:597-601, 1975), arose by a fusion of the latter plasmids, possibly by insertion of one element into another as a translocatable element. Genetic information from three other S. aureus plasmids (pK545, pSH2, and pUB101) has also been introduced into B. subtilis, although no covalently closed circular plasmid DNA was recovered.

Infections due to gentamicin-resistant Staphylococcus aureus strain in a nursery for neonatal infants

An apparently homogeneous strain of Staphylococcus aureus resistant to gentamicin (Gmr), kanamycin, tobramycin, and sisomicin, but susceptible to amikacin and netilmicin, caused multiple infections in neonatal infants in a special care nursery. Nasal cultures revealed a high rate of carriage of the Gmr staphylococcus in infants without clinical infection. Segregating patients according to a modified cohort system and use of careful aseptic techniques led to apparent elimination of the Gmr strain. The resistance to aminoglycosides in this strain was mediated by an aminoglycoside 6'-N-acetyltransferase and a gentamicin phosphotransferase. Genetic determinants for these enzymes were borne on a circular covalently closed plasmid of approximately 11 megadaltons. These resistance determinants closely resemble those found in isolates of S. aureus that have caused nosocomial infections in patients in Europe.

Plasmid-medicated aminoglycoside phosphotransferase of broad substrate range that phosphorylates amikacin

A plasmid-mediated aminoglycoside phosphotransferase that phosphorylates amikacin has been detected in clinical isolates of Staphylococcus aureus. This enzyme does not confer detectable amikacin resistance to the strains.

New plasmid-mediated nucleotidylation of aminoglycoside antibiotics in Staphlococcus aureus

A wild-type strain of Staphylococcus aureus, which inactivates a wide variety of aminoglycosides (except the gentamicin components), has been found to harbor a plasmid (RAp01) that mediates the biosynthesis of a nucleotidyltransferase. This enzyme modifies the 4'-hydroxy function of these antibiotics. The plasmid has been studied, the enzyme responsible for this resistance pattern has been isolated by affinity chromatography, and its kinetics and physicochemistry have been characterized. The target of this enzyme has also been located by demonstrating the structure of one inactivated compound, 4'-(O)-adenylyltobramycin.

Plasmid deoxyribonucleic acid in clinical isolates of Neisseria gonorrhoeae

Two different sizes of circular covalently closed deoxyribonucleic acid plasmids have been identified in four independent clinical isolates of Neisseria gonorrhoeae. All four strains contained a small plasmid with a molecular weight of 2.8 X 10-6 and two of the four stains also contained a large plasmid with a molecular weight of 24.5 X 10-6. The avirulent derivative of each of these four strains had the same plasmid complement as its virulent parent. There was no correlation between the presence of these plasmids and antibiotic resistance, piliation, and colony type associated with virulence, or ability to grow without seven specific amino acid supplements.