Barbara E. Murray

Cardiac risk factors and complications in non-cardiac surgery.

In an attempt to assess cardiac risk in non-cardiac surgery, 1001 patients over 40 years of age who underwent major operative procedures were examined preoperatively, observed through surgery, studied with at least one postoperative electrocardiogram, and followed until hospital discharge or death. Documented postoperative myocardial infarction occurred in only 18 patients; though most of these patients had some pre-existing heart disease, there were few preoperative factors which were statistically correlated with postoperative infarction. Postoperative pulmonary edema was strongly correlated with preoperative heart failure, but 21 of the 36 patients who developed pulmonary edema did not have any prior history of heart failure. Nearly all of these 21 patients were elderly, had abnormal preoperative electrocardiograms, and had intraabdominal or intrathoracic surgery. In the absence of an acute infarction, bifascicular conduction defects, with or without PR interval prolongation, never progressed to complete heart block. Spinal anesthesia protected against postoperative heart failure but not against other cardiac complication. By multivariate regression analysis, postoperative cardiac death was significantly correlated with (a) myocardial infarction in the previous 6 months; (b) third heart sound or jugular venous distention immediately preoperatively; (c) more than five premature ventricular contractions per minute documented at any time preoperatively; (d) rhythm other than sinus, or premature atrial contractions on preoperative electrocardiogram; (e) age over 70 years; (f) significant valvular aortic stenosis; (g) emergency operation; (h) a 33% or greater fall in systolic blood pressure for more than 10 minutes intraoperatively. Notably unimportant factors included smoking, glucose intolerance, hyperlipidemia, hypertension, peripheral atherosclerotic vascular disease, angina, and distant myocardial infarction.

Virulence effect of Enterococcus faecalis protease genes and the quorum-sensing locus fsr in Caenorhabditis elegans and mice

ABSTRACT The expression of two Enterococcus faecalis extracellular virulence-related proteins, gelatinase (GelE) and serine protease (SprE), has been shown to be positively regulated by the fsr quorum-sensing system. We recently developed a novel system for studying E. faecalis pathogenicity that involves killing of the nematode worm Caenorhabditis elegans and showed that an E. faecalis fsrB mutant (strain TX5266) exhibited attenuated killing. We explore here the role of the fsr/gelE-sprE locus in pathogenicity by comparing results obtained in the nematode system with a mouse peritonitis model of E. faecalis infection. Insertion mutants of fsrA (TX5240) and fsrC (TX5242), like fsrB (TX5266), were attenuated in their ability to kill C. elegans. A deletion mutant of gelE (TX5264) and an insertion mutant of sprE (TX5243) were also attenuated in C. elegans killing, although to a lesser extent than the fsr mutants. Complementation of fsrB (TX5266) with a 6-kb fragment containing the entire fsr locus restored virulence in both the nematode and the mouse peritonitis models. The fsr mutants were not impaired in their ability to colonize the nematode intestine. These data show that extracellular proteases and the quorum-sensing fsr system are important for E. faecalis virulence in two highly divergent hosts: nematodes and mice.

The Enterococcus faecalis fsrB gene, a key component of the fsr quorum-sensing system, is associated with virulence in the rabbit endophthalmitis model.

ABSTRACT We used a rabbit endophthalmitis model to explore the role of fsrB, a gene required for the function of the fsr quorum-sensing system of Enterococcus faecalis, in pathogenicity. A nonpolar deletion mutant of fsrB had significantly reduced virulence compared to wild type. Complementation of mutation restored virulence. These data corroborate the role of fsrB in E. faecalis pathogenesis and suggest that the rabbit endophthalmitis model can be used to study the in vivo role of quorum sensing.

Aminoglycoside-modifying enzymes among clinical isolates of Acinetobacter calcoaceticus subsp. anitratus (Herellea vaginicola): explanation for high-level aminoglycoside resistance.

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 ≥128 μg of kanamycin per ml; all others were susceptible to ≤32 μg/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 μg/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. Although agarose gel electrophoresis of deoxyribonucleic acid preparations from the enzyme-producing strains showed plasmid bands in all, no transfer of aminoglycoside 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. Images

In vitro activity of azithromycin against bacterial enteric pathogens.

The in vitro activity of azithromycin against enteric bacterial pathogens was determined by agar dilution. Azithromycin was highly active against Campylobacter spp. (MIC for 90% of strains tested [MIC90] = 0.125 micrograms/ml) and against enterotoxigenic, enterohemorrhagic, enteroinvasive, and enteropathogenic Escherichia coli (MIC90 = 2 micrograms/ml), Shigella spp. (MIC90 = 1 micrograms/ml), and Salmonella spp. (MIC90 = 4 micrograms/ml), including Salmonella typhi (MIC90 = 1 microgram/ml). On the basis of the in vitro activity of the drug against these organisms, clinical studies of azithromycin in enteric diseases should be considered; the high intracellular concentrations achieved by azithromycin may be particularly relevant for organisms like S. typhi, Campylobacter spp., and Shigella spp. which typically invade cells as part of their infectious process.

Ribosomal resistance of clinical enterococcal to streptomycin isolates.

The mechanism of high-level resistance to streptomycin was studied in 12 clinical isolates of Streptococcus faecalis. Six strains produced streptomycin-modifying enzymes. Each of three enzyme-negative strains tested demonstrated ribosomal resistance to streptomycin. Lack of ribosomal susceptibility is a significant cause of high-level streptomycin resistance among clinical enterococcal isolates.

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

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. Images

In-Vivo Acquisition of Two Different Types of Aminoglycoside Resistance by a Single Strain of Klebsiella pneumoniae Causing Severe Infection

Multiple isolates of Klebsiella pneumoniae obtained from a patient were of the same biotype and capsular type and had three common plasmids. Initially, three isolates (from blood) were susceptible to aminoglycosides. Three other isolates, obtained after gentamicin treatment was begun, were susceptible to amikacin but resistant to gentamicin and tobramycin, produced 2-aminoglycoside adenylytransferase, and had acquired an R-factor. A later isolate, obtained after amikacin therapy was begun, was susceptible to gentamicin and tobramycin, resistant to amikacin, was a small-colony variant, produced no aminoglycoside-modifying enzymes, and no longer contained the R-factor. In-vitro protein synthesis by ribosomes from this isolate was inhibited by amikacin whereas uptake of amikacin was markedly less than with previous isolates. Thus, this case illustrates the apparent in-vivo acquisition of plasmid-mediated resistance to gentamicin and tobramycin followed by loss of the plasmid and development of amikacin resistance due to decreased aminoglycoside uptake.

In vitro activity of three tetracycline antibiotics against Acinetobacter calcoaceticus subsp. anitratus.

The in vitro activity of three tetracycline antibiotics against 127 strains of Acinetobacter calcoaceticus (Herella vaginicola) were compared. Almost all strains were susceptible to minocycline and doxycycline, whereas most strains were resistant to tetracycline.