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N J Legakis

Publications and source records attributed to N J Legakis.

At least 109 records · Page 6Linked to original sources
PubMed1990

Enhanced in-vitro activity of liposome-trapped penicillin-G against Pseudomonas aeruginosa.

The growth inhibition of four Pseudomonas aeruginosa strains by liposome-trapped penicillin-G was investigated. There were indications of an association of the efficacy of liposomal penicillin-G with the nature of the 0-antigenic polymeric side chain. Namely, P28-800 and PCF-95 strains, characterized by a rough polysaccharide chain, were the most susceptible, whereas strain P28-0, possessing an intact lipopolysaccharide, resisted the activity of the entrapped drug. Among the rough strains, P642, a beta-lactamase producer, was not affected by the encapsulated drug. The composition of liposomes seems to have a significant impact in arresting the growth of the P. aeruginosa strain.

Calcium↗
PubMed1990

Resistance mechanisms of multiresistant serotype 012 Pseudomonas aeruginosa isolated in Europe.

Serotype 012 Pseudomonas aeruginosa resistant to gentamicin (MIC greater than 4 mg/l) and carbenicillin (MIC greater than 128 mg/l) occur widely in Europe and are homogeneous in their phenotypic and genetic properties. It has been suggested that a single multiresistant strain of this serotype has become widespread. This study examined the resistance mechanisms present in multiresistant serotype 012 P. aeruginosa isolates from Austria, Belgium, France, Greece, Italy, Holland, West Germany and the UK. Disseminated isolates produced a PSE-1 type beta-lactamase, correlating with their resistance to the known substrates of this enzyme (carbenicillin, azlocillin and cefsulodin). These isolates also reacted with gene probes for the aminoglycoside modifying enzymes AAC(6')I and ANT(3'). The probe for AAC(6')I is known to cross-react with the gene for AAC(6')II. The fact that the organisms were resistant to netilmicin, gentamicin, sisomicin and tobramycin, but less so to amikacin, suggested that the latter enzyme was produced rather than AAC(6')I. PSE-1 beta-lactamase and the gene for AAC(6')I/AAC(6')II were absent from the International Antigenic Typing Scheme 012 reference strain, which was sensitive to beta-lactams and aminoglycosides, and also from a multiresistant serotype 012 strain isolated at a London burns unit in 1987. These organisms have been shown previously to be distinct from the disseminated multiresistant strain in their phenotypic properties. Two 012 isolates appeared to have additional resistance determinants to amikacin and isepamicin.

Aminoglycosides↗
PubMed1990

Prevalence of a transferable SHV-5 type beta-lactamase in clinical isolates of Klebsiella pneumoniae and Escherichia coli in Greece.

Analysis with a double-disc synergy test (DDST) of clinical isolates of Klebsiella pneumoniae and Escherichia coli during the period October 1988-September 1989 revealed that 24% of the former and 4% of the latter, mainly isolated from urine, possessed an extended-spectrum beta-lactamase. During this period no DDST was positive for isolates of other enterobacterial species. Transfer of ceftazidime resistance was demonstrated from six K. pneumoniae and two E. coli isolates resistant to third generation cephalosporins and aztreonam. Apart from one strain of K. pneumoniae, these strains harboured self-transferable multiresistance plasmids (c. 91 kb) with closely related EcoRI, HindIII, AvaII and PstI restriction patterns. These plasmids encoded an extended-spectrum beta-lactamase that conferred an unusually high level of resistance to ceftazidime and aztreonam (MIC greater than or equal to 64 mg/l). This enzyme had a pI of 8.2 and a substrate profile similar to that of the SHV-5 enzyme isolated initially in Chile, and later in France (CAZ-4). The remaining K. pneumoniae isolate harboured a transmissible multiresistance plasmid (c. 182 kb) that encoded the widely distributed SHV-2 enzyme. The resistance to cefoxitin that was observed in some of these strains was associated with outer membrane protein alterations.

Bacteria↗
PubMed1989

Multiresistant serotype O 12 Pseudomonas aeruginosa: evidence for a common strain in Europe.

A survey was made of serotype association and multiple antibiotic resistance in strains of Pseudomonas aeruginosa in Europe. Of 208 epidemiologically distinct strains from 16 laboratories in 10 countries, 48 were resistant to carbenicillin (MIC greater than 128 micrograms/ml) and gentamicin (MIC greater than 4 micrograms/ml), and 12 of these strains were of serotype O 12. Representative O 12 strains from different countries were compared with two multiresistant O 12 strains isolated 5 years apart, from a British burns unit and the antibiotic sensitive serotype reference strain. All O 12 strains were similar by phage and pyocin typing but lysogenic phage profiles indicated that two strains (the later burns isolate and the serotype strain) were distinct from the others. Electrophoretic characterization of outer membrane proteins, lipopolysaccharides and esterase enzymes corroborated the relationship of the strains and restriction fragment length polymorphism of DNA fragments hybridized with a cDNA probe copy of rRNA from P. aeruginosa provided further proof of their relatedness. We propose that the uniformity of characters of multiresistant O 12 P. aeruginosa in Europe is suggestive of a common origin for the strains.

Anti-Bacterial Agents↗
PubMed1989

Relationship of antibiotic resistance phenotype to the R-pyocin susceptibility pattern in clinical isolates of Pseudomonas aeruginosa.

One hundred sixteen clinical isolates of Pseudomonas aeruginosa were collected from 7 hospitals in Athens. All strains were studied for their susceptibility to cefotaxime, ceftazidime, carbenicillin, aztreonam, imipenem, nalidixic acid, ciprofloxacin, gentamicin, and chloramphenicol. In addition, the R-pyocin susceptibility pattern was determined and the strains were O-serotyped and tested for their agglutination in acriflavine. The isolates included 53 strains resistant to both gentamicin and carbenicillin, 13 to carbenicillin only, 20 to gentamicin only, and 30 sensitive to gentamicin and carbenicillin. The multiresistant isolates displayed relatively higher resistance to all other antibiotics except aztreonam and cefotaxime. Remarkably 30 out of 53 multiresistant isolates reacted with one pyocin only, namely pyocin R2. This R-pyocin response was not encountered in any other strains of the other antibiotic resistance phenotypes. These isolates belonged to the 0-12 serogroup. The 0-12 serogroup was represented only in a minority of strains giving other R-pyocin reactions. It is interesting that strains reacting with pyocin R5 only were mostly susceptible to antibiotics. The results clearly indicate lipopolysaccharide-core mutations in multiresistant clinical isolates of P. aeruginosa. Despite the fact that the R-pyocin resistance pattern can not define the precise possible defect, the multiple and high level resistance associated with R2-pyocin reaction seems to be an interesting trait.

Bacteriocins↗
PubMed1989

Outer membrane alterations in multiresistant mutants of Pseudomonas aeruginosa selected by ciprofloxacin.

Spontaneous mutants of Pseudomonas aeruginosa selected by ciprofloxacin were studied for outer membrane alterations. Acquisition of ciprofloxacin resistance was at least partially related to defects in lipopolysaccharide synthesis. When ciprofloxacin resistance was combined with resistance to beta-lactams and aminoglycosides, several alterations in outer membrane proteins were noted.

Bacterial Outer Membrane Proteins↗
PubMed1987

Importance of carbenicillin and gentamicin cross-resistant serotype 0:12 Pseudomonas aeruginosa in six Athens hospitals.

One hundred and six clinical isolates of Pseudomonas aeruginosa, collected from various hospitals were typed with O-antisera and studied for their susceptibility to antibiotics and phages. Forty-four of 49 multiresistant isolates belonged to the O12 serogroup, a serogroup rarely found among strains of other resistance phenotypes. Eleven of the 45, O12 isolates were resistant to all phages, and 31 were sensitive only to phage 68. The latter pattern was encountered in nine of the 61 strains comprising the other O-serogroups.

Bacteriophage Typing↗
PubMed1986

Anaerobic bacteria in dentoalveolar abscesses.

The present study was initiated to determine the bacteriology of 40 orofacial abscesses of dental origin in patients who had taken antibiotics for several days. Bacteria were isolated from all but 2 specimens. Aerobic or facultative anaerobic bacteria were isolated in 21 cases, obligate anaerobic bacteria in 17 cases, whereas in 11 cases, polymicrobial growth was revealed. The average number of bacterial species was 2.1 per specimen. Gram positive aerobic micro-organisms predominated, namely, Staphylococcus epidermidis followed by Streptococci (group A) and Staphylococcus aureus. Among obligate anaerobes, Gram positive micro-organisms, peptostreptococci and peptococci were more often isolated, in the following decreasing order: Ps. productus, Ps. intermedius, Ps. parvulus, Ps. anaerobius, Pc. constellatus, Pc. prevotii. Gram negative anaerobic rods were detected in a small number of cases, namely B. corrodens, B. fragilis, B. melaninogenicus, B. ochraceus, B. oralis. Quantitative determination did not show any meaningful difference between aerobic and anaerobic isolates. Susceptibility tests against a series of antibiotics showed that ampicillin was the most active in aerobes and cefoxitin in anaerobes.

Adolescent↗
PubMed1986

Survey of aminoglycoside resistance patterns.

We studied the susceptibility of 545 gram-negative clinical isolates to six aminoglycosides: gentamicin, tobramycin, netilmicin, amikacin, 2'-N-ethylnetilmicin, and 6'-N-ethylnetilmicin. The resistant strains (359) have been classified into aminoglycoside resistance (patterns) phenotypes (AGRPs) corresponding to known resistance mechanisms. The results clearly demonstrated that most strains of Proteus spp., Klebsiella spp., Escherichia coli and Pseudomonas aeruginosa appeared to be able to adenylate the 2'-hydroxyl group (ANT(2'')) of aminoglycosides. Of the AGRPs reflecting acetylating activity, the AAC(3)-II and AAC(3)-I predominated. The AGRP AAC(2') was limited mainly to Proteus and Providencia isolates. It is noteworthy that permeability type resistance (PTR) was observed only among P. aeruginosa strains. Statistical evaluation of the results, using a discriminant regression analysis showed that PTR P. aeruginosa strains were isolated less often from urine than from other clinical sources (P less than 0.05). On the contrary the ANT(2'') Proteus strains were more common isolates from urinary infections as compared to those from other sources (P less than 0.05). Other correlations between frequency of AGRPs, bacterial groups, and various clinical sources were not statistically significant. However such differences in the frequency of occurrence of AGRPs among diverse bacterial groups were noted in relation to hospitals.

Amikacin↗
PubMed1985

Pseudomonas aeruginosa: evidence for the involvement of lipopolysaccharide in determining outer membrane permeability to carbenicillin and gentamicin.

The role of lipopolysaccharide (LPS) in determining the permeability of the outer membrane of Pseudomonas aeruginosa to carbenicillin and gentamicin was investigated. The susceptibility of P. aeruginosa isolates to smooth LPS-specific phages and to pyocin R1 gave indirect evidence of an altered LPS structure in strains resistant to carbenicillin, gentamicin, or both. Some secondary mutation, however, also appeared to be required for acquisition of the antibiotic-resistant phenotype. Phage- and pyocin-resistant variants demonstrating both wild-type and mutant responses to the drugs were subsequently isolated. Four-, eight-, and 16-fold increases in resistance to carbenicillin, supersusceptible responses to gentamicin, or both, were associated with a number of the LPS-altered mutants. The results supported the hypothesis that a primary mutation involving LPS, in combination with some undefined secondary mutation, determines the permeability of the outer membrane to carbenicillin and to gentamicin.

Bacteriophages↗
PubMed1985

In-vitro activity of ciprofloxacin against clinical isolates of mycobacteria resistant to antimycobacterial drugs.

The activity of ciprofloxacin against 42 clinical isolates of mycobacteria was studied in vitro by the 1% standard proportion method on Lowenstein-Jensen medium. Ciprofloxacin was found active against all strains of Mycobacterium tuberculosis sensitive to streptomycin, isoniazid, ethambutol and rifampicin. The MIC of ciprofloxacin was 3.2 mg/l. This concentration of ciprofloxacin was sufficient to inhibit almost all strains showing intermediate sensitivity or resistance to one or more of the above agents. The same phenomenon was also observed with the atypical isolates.

Ciprofloxacin↗
PubMed1985

Outer surface changes of Pseudomonas aeruginosa in relation to resistance to gentamicin and carbenicillin.

The outer surface structure of clinical isolates of Pseudomonas aeruginosa resistant to carbenicillin or gentamicin or both was studied by thin-section electronmicroscopy and compared with that of sensitive isolates. The latter had a fairly smooth outer layer. Strains resistant to both antibiotics were characterised by extrusions that appeared to constitute extensions of the outer membrane. The outer membrane appeared wavy with distortion of its tripartite structure. The latter findings were also present in isolates resistant to only one of the two antibiotics. The disorganisation of the outer membrane might contribute to the expression of resistance.

Acetyltransferases↗
PubMed1984

Interaction between Clostridium difficile and polymorphonuclear leucocytes from the elderly and post-operative cancer patients: phagocytosis and bactericidal function.

The ability of polymorphonuclear leucocytes (PMNs) from elderly healthy subjects and post-operative cancer patients to ingest and kill Clostridium difficile was studied. The percentage of phagocytosis in clinically healthy subjects aged 69-82 years ranged from 20.2 +/- 3.2 (mean +/- SD) to 34.1 +/- 4.2, depending on the strain of C. difficile, from 6.7 +/- 2.2 to 11.2 +/- 2.2 in post-operative cancer patients aged 65-69, and from 68.4 +/- 3.1 to 81.1 +/- 6.3 in young healthy control subjects. In both study groups, the defect was in part serum-associated. Although the total number of bacteria killed by the PMNs was reduced in the two study groups, the percentage of ingested bacteria killed by the PMNs was similar to that in the young healthy subjects. These differences were not noted when Escherichia coli and Staphylococcus aureus were used as the test organisms. The defective PMN function against C. difficile in the elderly and post-operative cancer patients described in this study may offer an explanation as to why these individuals are at high risk of developing antibiotic-associated colitis.

Adult↗
PubMed1984

Comparison of in vitro activities of eight new beta-lactam compounds against cephalothin-resistant Enterobacteriaceae from hospital patients.

The in vitro antibacterial activity of eight newer beta-lactam antibiotics (mecillinam, piperacillin, mezlocillin, cefoxitin, cefotaxime, moxalactam, ceftriaxone and ceftazidime) was determined against 87 cephalothin-resistant strains of Enterobacteriaceae isolated during 6 months in a general hospital. Ceftriaxone, cefotaxime, moxalactam and ceftazidime proved to be highly active; only a minority of strains required higher concentrations than 0.125 microgram/ml for inhibition of growth. Cefoxitin, mecillinam, mezlocillin and piperacillin were less active. Mecillinam displayed greater efficacy against Escherichia coli, Klebsiella and Enterobacter spp., while the same was the case for piperacillin against Proteus mirabilis and Serratia marcescens, and for cefoxitin against indole-positive Proteus spp. The production of beta-lactamase was correlated with a reduced activity of mecillinam, mezlocillin and piperacillin but not of cefoxitin or the other beta-lactamase-stable cephalosporins. However, some strains, mainly those of Proteus, Enterobacter and Serratia, though resistant to mecillinam, mezlocillin and piperacillin did not produce beta-lactamases. This observation might indicate that ceftriaxone, moxalactam, cefotaxime and ceftazidime, besides their indifference to beta-lactamases, are characterized also by a high degree of intrinsic activity.

Anti-Bacterial Agents↗