Resistance to gentamicin, tobramycin and amikacin among clinical isolates of bacteria

Two blood culture isolates of Acinetobacter calcoaceticus subsp. anitratus (Herellea vaginicola) were recently observed to be unusually resistant to aminoglycosides. Each strain was found to contain aminoglycoside-modifying enzymes which have not been described previously in this species, including 2"-adenylyltransferase, 3"-adenylyltransferase, 3'-phosphotransferase-III, and 3-acetyltransferase. Treatment of one strain (H-S) with novobiocin led to a loss of resistance to multiple antimicrobial agents and a loss of two aminoglycoside-modifying enzymes; agarose gel electrophoresis of lysates of this strain revealed that the loss of resistance markers was associated with the loss of a large-molecular-weight plasmid. Treatment of the second strain (H-D) with novobiocin produced derivative strains with three different resistance patterns. Agarose gel electrophoresis of deoxyribonucleic acid from crude lysates and from cesium chloride-ethidium bromide gradients of this strain showed only a small plasmid (molecular weight, 5 X 10(6)) common to all variants and failed to explain the loss of resistance markers.

mentioning

confidence: 55%

Evidence of plasmid-mediated production of aminoglycoside-modifying enzymes not previously described in Acinetobacter

Murray¹,

Moellering²

1980

“…Furthermore, in our hospital, A. calcoaceticus subsp. anitratus is the most frequently isolated gram-negative organism resistant to one or more aminoglycosides (24).…”

mentioning

confidence: 99%

“…Alternatively, 0.5 ml of the donor culture was mixed with 4.5 ml of the recipient culture, and 3 ml of this mixture was then filtered. Duplicate filters were incubated on brain heart infusion plates for 24 Transformation. The procedure used for transformation experiments was that of Lederberg and Cohen (19), with deoxyribonucleic acid (DNA) purified from cesium chloride density gradient centrifugation (8).…”

mentioning

confidence: 99%

Aminoglycoside-Modifying Enzymes Among Clinical Isolates of Acinetobacter calcoaceticus subsp. anitratus ( Herellea vaginicola ): Explanation for High-Level Aminoglycoside Resistance

Murray

Moellering

1979

Self Cite

Acinetobacter calcoaceticus subsp. anitratus (Herellea vaginicola) is an important cause of nosocomial infection in our hospital where A. calcoaceticus subsp. anitratus is the most frequently isolated gram-negative species resistant to one or more of the aminoglycoside antibiotics. Of 167 strains tested for susceptibility to aminoglycosides, only 6 strains were found that were resistant to 2128 ,ug of kanamycin per ml; all others were susceptible to c32 ,ug/ml. Five of these six strains were found to produce aminoglycoside-modifying enzymes. Two strains produced a phosphotransferase which mediates resistance to kanamycin and neomycin; three strains produced an acetyltransferase which mediates resistance to kanamycin, tobramycin, and amikacin (minimal inhibitory concentration -128 pug/ml for each drug). No strain with lower level resistance to kanamycin, tobramycin, or amikacin had enzyme activity. Fourteen strains resistant to gentamicin failed to show significant enzymatic modification of that antibiotic.though agarose gel electrophoresis of deoxyribonucleic acid preparations from he enzyme-producing strains showed plasmid bands in all, no transfer of ami«oglycoside resistance could be achieved, nor was it cured by exposure to novobiocin, ethidium bromide, acridine orange, heat, or prolonged storage. Resistance to mercuric chloride, present in 2 of 60 strains, was lost by 1 strain after exposure to novobiocin, and the loss of resistance was associated with an apparent deletion of plasmid deoxyribonucleic acid.

“…Particularly problematic pathogens have been Klebsiella and Providencia spp., Pseudomonas aeruginosa, and Serratia marcescens. Many isolates have become resistant not only to gentamicin but also to the new aminoglycosides, such as tobramycin and amikacin (15,17). This increase in resistance poses serious therapeutic problems for clinicians.…”

mentioning

confidence: 99%

Resistance of gram-negative bacilli as related to hospital use of antimicrobial agents

Y.¹,

Goldstein²,

Friedman³

et al. 1983

The development of resistance of gram-negative bacilli, which are common nosocomial pathogens, is an increasing problem. It is generally accepted that this resistance may directly reflect the frequency of use of various antimicrobial agents. Because our institution experienced in 1976 a dramatic change in the pattern of antimicrobial use, primarily a marked decrease in prescribing cephalosporins, we attempted to evaluate retrospectively the effects of this change upon the resistance of gram-negative bacilli that are common nosocomial pathogens. Susceptibilities of Klebsiella and Providencia spp., Pseudomonas aeruginosa, and Serratia marcescens were determined for the years 1975 to 1979. Not unexpectedly, we observed a substantial decrease in cephalosporin resistance. An unexpected finding was a decrease in aminoglycoside resistance, despite increased use of these agents. The possibility that decreased cephalosporin use may lead to decreased aminoglycoside resistance is an intriguing and provocative thesis which can only be speculative at this time but which would seem worthy of additional formal investigation.