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Biomedical subjects

N J Legakis

Publications and source records attributed to N J Legakis.

142 records · Page 8Linked to original sources
PubMed1976

Cultural factors influencing the utilization or production of acetate by Butyrivibrio fibrisolvens.

Utilization of acetate by four strains of Butyrivibrio fibrisolvens was influenced by the composition of their growth medium. Growth-limiting glucose concentrations, low availability of CO2 and the presence of sodium lactate all stimulated acetate uptake by three strains. The type strain, D1, utilized acetate if the concentration of acetate added to the medium was at least 15 mumol ml-1. In batch culture, all strains produced acetate before entering a phase of acetate uptake. Continuous-culture studies with one strain showed that acetate uptake was dependent upon growth rate. The amount of n-butyrate produced in batch or continuous culture was closely linked to the amount of acetate taken up.

Acetates↗
PubMed1976

Inositol as a selective substrate for the growth of Klebsiellae and Serratiae.

A synthetic basal salts medium containing inositol as the sole source for carbon and energy and bromothymol blue as pH indicator, selectively supports the growth of Klebsiella pneumoniae and Serratia spp. On this medium incubated at 37 degrees C for 24 hr, all cultures of Kl. pneumoniae, Serratia liquefaciens and S. marcescens form yellow colonies. The medium may be used selectively for the primary isolation of the aforementioned bacteria from faeces and as a differential medium for their isolation from saliva and urine.

Culture Media↗
PubMed1975

Thin-layer chromatographic technique for rapid detection of bacterial phospholipases.

Silica gel thin-layer chromatography was employed to detect lecithinase activity induced from bacterial resting cell preparations induced from bacterial resting cell preparations incubated at 37 C for 4 h in the presence of purified egg yolk lecithin. Bacillus subtilis, Bacillus cereus, Serratia marcescens, and Pseudomonas aeruginosa hydrolyzed lecithin with the formation of free fatty acids as the sole lipid-soluble product. In none of the Escherichia coli and Citrobacter freundii strains tested could lecithinase activity be detected. Four among eight strains of Enterobacter aerogenes and one among 12 strains of Proteus tested produced negligible amounts of free fatty acid.

Bacillus cereus↗
PubMed1975

Selective medium for growth of Proteus.

A medium containing heart infusion agar supplemented with bile salts, lithium chloride, sodium thiosulfate, and sodium citrate was developed for the selective growth of Proteus.

Agar↗
PubMed1975

In vitro activity of ticarcillin, carbenicillin and ampicillin against some gram-negative bacilli.

alpha-Carboxy-3-thienylmethyl penicillin (ticarcillin) is a relatively new semisynthetic penicillin which is more active than carbenillin against Pseudomonas aeruginosa. Among the strains tested, those isolated from the respiratory tract showed an increased susceptibility to carbenicillin and ticarcillin. As with carbenicillin, synergistic activity against P. aeruginosa could be demonstrated with ticarcillin in combination with gentamicin. Like other penicillins, the antibacterial activity was influenced by the inoculum size. The antibacterial activity of ticarcillin showed the compound to be almost equally active with carbenicillin and ampicillin against Escherichia coli and Klebsiella aerogenes, but less active than acrbenicillin and ampicillin against indole-negative Proteus strains. Regarding the indole-positive Proteus species, at relatively low antibiotic concentrations the proportion of strains sensitive to ticarcillin was greater than to carbenicillin or ampicillin whereas at relatively high antibiotic concentrations the converse was the case. It is interesting to note that a high proportion of strains of E. coli and K. aerogenes were resistant to the three penicillins even at a concentration of 200 mug/ml, while 70% of Proteus strains were inhibited by these drugs at the same concentration. Disc susceptibility tests with ticarcillin were carried out according to BAUER-KIRBY method.

Ampicillin↗
PubMedDate not supplied

Bacterioides fragilis: production and sensitivity to bacteriocins.

Bacteriocin production and sensitivity to bacteriocins have been successfully applied as an epidemiological tool in several species of bacteria. However, little work has been carried out on the bacteriocins produced by Bacteroides fragilis, which is the most frequently isolated anaerobe species from clinical specimens. Thirty two clinical isolates of B. fragilis grown anaerobically on a 0.22 microm membrane filter spotted on an agar plate, were tested for bacteriocin production and used in a screen for bacteriocin sensitivity. Sensitivity to at least one bacteriocin was found in 94% of the strains, 62.5% were sensitive to two bacteriocins, whereas 34.4% were sensitive to three or more and finally one strain was found sensitive to 17 bacteriocins. Of the strains studied, 94% inhibited at least one strain, 66% inhibited two strains, and 30% inhibited at least three strains or more. Finally, one strain was extremely active by inhibiting the growth of 17 strains. Bacteriocin types are characterised by geographic variation, and their epidemiological investigation by a simple method could be promoted.

Journal Article↗
PubMedDate not supplied

In vitro activity of cefpirome against selected clinical enterobacterial isolates with beta-lactamase-mediated resistance.

Previous studies have shown that there is a high incidence of resistance to cephalosporins among enterobacteria isolated in Greek hospitals. This resistance is mainly due to either the derepression of chromosomal cephalosporinases or the acquisition of plasmids coding for SHV-5 type beta-lactamase. In the present study the activity of cefpirome against a number of enterobacteria (Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, Enterobacter aerogenes and Serratia marcescens) possessing the mechanisms mentioned above was examined. Cefpirome was found active against all the strains characterized by stable derepression of chromosomal class-C enzymes. The antibiotic was less potent against strains expressing SHV-5 type beta-lactamase due to its hydrolysis by the enzyme. Also cefpirome exhibited good activity against E. aerogenes strains with reduced susceptibility to imipenem. These in vitro data suggest that cefpirome might be useful in treating infections caused by these resistant microorganisms that are frequently encountered in Greek hospitals.

Cephalosporins↗
PubMedDate not supplied

Structural alterations in the envelope of a gentamicin-resistant rough mutant of Pseudomonas aeruginosa.

Comparative studies of a gentamicin-sensitive strain (P28-0) of Pseudomonas aeruginosa and a gentamicin-resistant mutant (P23-800) have been carried out. No aminoglycoside-modifying enzymes were detected in extracts of the mutant. Electron microscopy of thin sections and the loss of O-antigenicity suggested that resistance of the mutant to gentamicin was related to an alteration in the outer membrane. Analysis of the lipopolysaccharide (LPS) components of the cell walls revealed significant differences. The LPS from strain P28-0 was typical of wild-type P. aeruginosa strains of Habs serotype O6, with quinovosamine and aminogalacturonic acid as O-specific aminocomponents. The LPS from the resistant mutant lacked the O-specific polymer, but had a core oligosaccharide similar to that of the parent strain. Both LPS were rich in phosphorus, part of which was present in triphosphate residues. Although the 31P nuclear magnetic resonance spectra of the LPS differed in some respects, these differences did not seem to correlate with the disparity in sensitivity to gentamicin of the two organisms.

Cell Wall↗
PubMedDate not supplied

In vitro activity of loracarbef against TEM extended-spectrum beta-lactamase-producing Escherichia coli strains and its interaction with the enzymes.

The in vitro activity of loracarbef was evaluated against Escherichia coli strains producing TEM extended-spectrum beta-lactamases (ESBLs). The MICs of loracarbef were lower than those of cefaclor and cephalothin. The antibiotic was active (MICs < or = 2 mg/l) against strains producing TEM-6, TEM-8, TEM-10, TEM-16, TEM-26 and TEM-28 beta-lactamases. The MICs for TEM-3-, TEM-5- and TEM-24-producing strains were higher (> or = 16 mg/l). Hydrolysis studies indicated that the latter beta-lactamases inactivated loracarbef more efficiently than the remaining TEM-type ESBLs examined.

Cephalosporins↗
PubMedDate not supplied

In vitro activity of cefetamet against enterobacteria expressing an SHV-5-type beta-lactamase.

The in vitro activity of cefetamet against Escherichia coli, Klebsiella pneumoniae and Serratia marcescens strains expressing an SHV-5-type beta-lactamase was evaluated. Most of the examined strains were susceptible to the antibiotic. Cefetamet was found to be considerably more active than ceftazidime and aztreonam. Its activity was comparable to that of cefotaxime. Cefetamet MIC values were related to the quantity of the enzyme expressed. The SHV-5-type enzyme hydrolysed cefetamet with an efficiency (Vmax/Km) similar to that of ceftazidime.

Ceftizoxime↗
PubMedDate not supplied

Changing patterns of bacterial nosocomial infections: a nine-year study in a general hospital.

Surveillance data on 12,944 bacterial isolates derived from nosocomial infections, reported to the Department of Microbiology and Infectious Diseases of the Hellenic Air Force and VA General Hospital over a 9-year period (1986-1994), were analyzed by the use of a microbial infection control software system. Overall, the isolation rate of Escherichia coli decreased from 25.2% in 1986 to 18.2% in 1994 and Proteus spp. from 5.3 to 2.6%. Remarkably, Pseudomonas spp. increased from 7.2 to 11.3%, Enterobacter spp. from 1.6 to 5.1%, Klebsiella spp. from 5.9 to 7.8% and Enterococcus spp. from 3 to 7.4%. Interestingly, the above phenomenon was paralleled by a significant increase in resistance rate to various antibiotics. Specifically, Staphylococcus aureus and coagulase-negative staphylococci, though they did not display any significant variation in isolation rates, showed an alarming increase in resistance rate to oxacillin, from 11 and 21% in 1986 to 51 and 75% in 1994, respectively. Enterococcus spp. sensitivity to vancomycin remained unlatered at 90%. The above-mentioned serious shift towards more resistant bacteria should be a matter of consideration.

Bacteremia↗
PubMedDate not supplied

Bacterial resistance to ciprofloxacin in Greece: results from the National Electronic Surveillance System. Greek Network for the Surveillance of Antimicrobial Resistance.

According to 1997 susceptibility data from the National Electronic System for the Surveillance of Antimicrobial Resistance, Greece has high rates of ciprofloxacin resistance. For most species, the frequency of ciprofloxacin-resistant isolates (from highest to lowest, by patient setting) was as follows: intensive care unit > surgical > medical > outpatient. Most ciprofloxacin-resistant strains were multidrug resistant.

Anti-Infective Agents↗
PubMedDate not supplied

Molecular typing of multidrug-resistant Salmonella Blockley outbreak isolates from Greece.

During 1998, a marked increase (35 cases) in human gastroenteritis due to Salmonella Blockley, a serotype rarely isolated from humans in the Western Hemisphere, was noted in Greece. The two dominant multidrug-resistance phenotypes (23 of the 29 isolates studied) were associated with two distinct DNA fingerprints, obtained by pulsed-field gel electrophoresis of genomic DNA.

DNA Fingerprinting↗
PubMedDate not supplied

Outer membrane proteins in a carbenicillin-resistant strain of Pseudomonas aeruginosa.

The outer membrane of a clinical isolate of Pseudomonas aeruginosa sensitive to carbenicillin, and its derivative adapted to grow in the presence of carbenicillin were analysed by polyacrylamide gel electrophoresis. The lack of beta-lactamase activity showed that the resistance of the adapted strain was not due to hydrolysis of carbenicillin. The appearance of several outer membrane proteins almost exclusively in the resistant strain supports the view of altered cell envelope properties in this strain.

Bacterial Proteins↗
PubMedDate not supplied

Direct quantitative determination of acidic end products in clinical specimens for presumptive diagnosis of anaerobic infections.

Acidic metabolic products determined directly in clinical specimens of 51 anaerobic and 12 aerobic infections by quantitative gas-liquid chromatography (GLC) were correlated with the bacteriologic findings. The presence of appreciable amounts of succinic acid, more than 1 microM per ml, propionic and isovaleric acid, at concentrations not exceeding 3 microM per ml, was strong evidence for Bacteroides fragilis infections. When isobutyric acid was also detected, a B. melaninogenicus infection could be presumed. However, the presence of other anaerobes or aerobes could not be excluded. The presence of Clostridium spp. could also be presumed by the detection of butyric acid at a concentration greater than 4 microM per ml and of acetic, propionic and isobutyric acid at relatively high concentrations. In specimens from aerobic infections, no other acid except acetic and lactic acid could be detected. Our data also show that quantitative GLC is not valid in Peptococcus and Peptostreptococcus spp. infections except in some cases where Peptococcus alone or together with aerobic organisms are found.

Anaerobiosis↗