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F H Kayser

Publications and source records attributed to F H Kayser.

At least 19 recordsLinked to original sources
PubMed1992

Correlation between regulation of mecA transcription and expression of methicillin resistance in staphylococci.

Total RNA was used to study the effect of penicillinase plasmid pI524 and of mecR, the regulatory region located on the methicillin resistance determinant (mec), on the expression of mecA, the gene coding for the low-affinity penicillin-binding protein PBP2', in methicillin-resistant staphylococci. In the present report, we show that the regulation of methicillin resistance occurs primarily at the level of mecA transcription and that in the presence of intact plasmid pI524 or mecR, the gene undergoes negative control. The relative amount of mecA mRNA present during exponential growth in uninduced cultures matches the type of mecA regulation and decreases in the following order: constitutive greater than pI524 greater than mecR-dependent mecA expression. Induction of mecA by methicillin is faster in pI524- than in mecR-controlled strains. The overall mRNA half-life is similar for all strains analyzed. Our results indicate that methicillin resistance under mecR control in certain staphylococcal strains could escape detection by the standard disk diffusion test and broth microdilution test because of the very slow derepression of the mecA gene. This finding is of importance for the clinical detection of this type of methicillin resistance.

Methicillin↗
PubMed1992

Survey of the methicillin resistance-associated genes mecA, mecR1-mecI, and femA-femB in clinical isolates of methicillin-resistant Staphylococcus aureus.

The restriction site polymorphism of the chromosomal femAB region and the first appearance of the regulatory element mecR1-mecI associated with the methicillin resistance determinant (mec) were analyzed in 192 initially methicillin resistant (Mcr) Staphylococcus aureus clinical isolates collected between 1965 and 1990 in the Zurich area. Forty-three of the strains lost the resistance spontaneously. All isolates that were still Mcr hybridized with mecA, the gene for the low-affinity penicillin-binding protein PBP 2'. Mcr strains isolated before 1977 lacked sequences that hybridized with mecR1-mecI, a regulatory element controlling the expression of mecA; exceptions to this were one strain isolated in 1966 and one strain isolated in 1972. The size of the EcoRV fragment carrying femA, a chromosomally encoded factor involved in pentaglycine side chain formation of the peptidoglycan and essential for the expression of methicillin resistance, was conserved in all strains but one, which was susceptible to methicillin even though it carried a functional mecA gene. The methicillin susceptibility of this particular strain was presumably due to a spontaneous femA-like mutation. The 192 strains belonged to seven different EcoRV restriction fragment patterns recognizable with a 10.5-kb probe covering the femAB region. Some 93% of the 149 Mcr strains belonged to pattern A, and the remaining Mcr strains shared patterns A' and B. The 42 isolates which spontaneously lost their resistance upon storage and revival represented all seven different patterns. This strong conservation of femA suggests an important role for femA in cell wall metabolism and methicillin resistance.

Genes, Bacterial↗
PubMed1992

Mapping and characterization of multiple chromosomal factors involved in methicillin resistance in Staphylococcus aureus.

Chromosomal factors, termed fem or aux factors, are needed for the expression of methicillin resistance in methicillin-resistant (Mcr) Staphylococcus aureus; also needed is the mec-encoded low-affinity penicillin-binding protein PBP 2'. These factors make up part of the normal set of genes present in susceptible and resistant strains of S. aureus and can be identified by Tn551-mediated insertional inactivation of the methicillin resistance. In this study, we characterized different Tn551 inserts and mapped them into four distinct loci on the SmaI chromosomal map of S. aureus NCTC 8325, thereby identifying two new loci which code for fem factors. The largest fragment, SmaI-A, carries three loci, two coding for both closely linked factors femA and femB and a novel third locus (femC) that is not linked to the other two. An additional, fourth, locus, femD, was identified in fragment SmaI-I. femA and femB inactivation reduced overall methicillin resistance, whereby femB had less of an influence on the resistance level. femC and femD inactivation reduced mainly the basal resistance level in heterogeneously Mcr strains and had less of an impact on the subpopulation with high-level resistance. Inactivation of either of these factors was shown to have no influence on the production of PBP 2', the main factor mediating methicillin resistance. In addition, no changes were observed in the banding patterns of the major autolysins in whole-cell extracts of the fem mutants, suggesting that the reduced cell wall turnover and autolysis observed in some of the insertionally inactivated strains were due to changes either of the substrate or in the autolysin control.

Autolysis↗
PubMed1992

Ribotyping of coagulase-negative staphylococci with special emphasis on intraspecific typing of Staphylococcus epidermidis.

Coagulase-negative staphylococci (CoNS), particularly Staphylococcus epidermidis, are increasingly being recognized as opportunistic pathogens. They are often multiply antibiotic resistant and can cause nosocomial outbreaks. For clinical and epidemiological reasons, accurate species identification and typing are imperative. Ribotyping, i.e., the generation of characteristic fragment patterns by hybridization of restriction endonuclease fragments of total DNA with labeled standard rRNA from Escherichia coli, has been applied to CoNS for species identification by various investigators. The present study, involving 115 randomly collected clinical isolates of CoNS, provides ambiguous evidence with respect to those findings. Eighty six S. epidermidis strains were ribotyped intraspecifically. Eleven different ribotypes were found after digestion with EcoRI, and 10 were found with HindIII. A combination of the two restriction endonucleases resulted in an increase in the discriminatory power (DP) from 14.3 to 31.6%. A combination of ribotyping with biotyping raised the DP to a maximum of 48.6%. The reproducibility of ribotyping was 100% after greater than 400 generations of growth. No correlation between methicillin resistance and certain ribotypes among the S. epidermidis strains was observed. Ribotyping is considered a useful tool for the intraspecific typing of CoNS for epidemiological purposes. The DP can be increased by the use of additional restriction endonucleases.

Bacterial Typing Techniques↗
PubMed1992

Changes in the spectrum of organisms causing respiratory tract infections: a review.

Over the last decade, the spectrum of organisms causing community-acquired acute lower respiratory tract infections has changed. Streptococcus pneumoniae now causes approximately 30% of outpatient acute pneumonia-less than in former decades-whereas Mycoplasma pneumoniae is found in both young and elderly patients. The Enterobacteriaceae and Staphylococcus aureus are now seen more frequently as respiratory tract pathogens in community-acquired pneumonia patients, and they are the major organisms causing pneumonia in residents of homes for the elderly or nursing homes, and in immuno-compromised patients. Agents that were previously considered non-pathogenic for the respiratory tract include serotypes of Haemophilus influenzae other than type b, H. parainfluenzae and Moraxella (Branhamella) catarrhalis; these organisms affect mainly patients with underlying cardiopulmonary disease. Legionella species can cause sporadic as well as epidemic disease of the lower respiratory tract. Chlamydia pneumoniae is a newly recognized pathogen responsible for mild to severe upper and lower respiratory tract infections. In 60-80% of cases, hospital-acquired pneumonias are caused by Gram-negative bacilli and S. aureus. These organisms colonize the mucosal membranes of the upper respiratory tract and penetrate into the lower tract by aspiration or intubation.

Bronchitis↗
PubMed1991

[Bacterial sensitivity to chemotherapeutic agents (Zurich, 1990)].

This paper describes the incidence of susceptibility of gram-negative and positive bacteria towards antibacterial agents. The data are based on all susceptibility tests performed at the Department of medical microbiology of the University of Zurich. The evaluation of the results from 1975 to 1990 shows that susceptibilities against the antimicrobial agents tested have not changed markedly in this period. These tables may be a help for the physician in his decision for a "calculated chemotherapy" of bacterial infections.

Anti-Bacterial Agents↗
PubMed1991

The interaction of macrophages and bacteria: a comparative study of the induction of tumoricidal activity and of reactive nitrogen intermediates.

The abilities of various bacteria to induce in a pure population of bone marrow-derived mononuclear phagocytes (BMM phi) tumoricidal activity and/or the generation of reactive nitrogen intermediates (RNI) were comparatively assessed. Interaction of BMM phi with bacteria led to expression of these functional activities, indicating that the organisms were recognized as foreign. As the majority of bacteria elicited in BMM phi either tumoricidal activity (that is maintained for days) or the production of RNI, measured by the release of nitrite (that is short-lived), it appears that the two functions are under separate control. However, both functions are inhibited or even abrogated by arginase or the L-arginine analogue, NG-monomethyl-L-arginine, suggesting that their expression is dependent on L-arginine.

Animals↗
PubMed1991

Interpretive criteria for disk diffusion susceptibility testing of sparfloxacin.

Sparfloxacin disk susceptibility test criteria for the NCCLS and ICS/DIN methods were determined by testing 400 bacterial wild-type isolates. Disks containing 5 micrograms of the drug could be used satisfactorily in both procedures. The following interpretive zone size breakpoints for the NCCLS and ICS/DIN methods were proposed: less than or equal to 18 and 20 mm respectively for resistance (MIC greater than 1 mg/l), and greater than or equal to 23 and 25 mm respectively for susceptibility (MIC less than or equal to 0.5 mg/l). These criteria were based on preliminary maximum serum concentrations of approximately 1.5 mg/l after a single oral dose of 400 mg of the drug. Regression equations for both methods correlating MICs and zone sizes based on test results for 361 organisms are presented. The equations allow calculation of breakpoints for higher or lower serum peak levels. Sparfloxacin was two to four times more active than ciprofloxacin against gram-positive cocci, and showed equal activity against gram-negative rods. Zone diameter quality control values for Escherichia coli ATCC 25922 were 26-30 mm (NCCLS) and 30-33 mm (ICS/DIN), and for Staphylococcus aureus ATCC 29213 27-28 mm (NCCLS) and 29-31 mm (ICS/DIN).

Anti-Infective Agents↗
PubMed1991

The Staphylococcus aureus mec determinant comprises an unusual cluster of direct repeats and codes for a gene product similar to the Escherichia coli sn-glycerophosphoryl diester phosphodiesterase.

The DNA sequence located between mecA, the gene that codes for penicillin-binding protein PBP2', and insertion sequence-like element IS431mec has been termed hypervariable because of its length polymorphism among different staphylococcal isolates. We sequenced and characterized the hypervariable region of the methicillin resistance determinant (mec) isolated from Staphylococcus aureus BB270. Within the 2,040-bp hypervariable region, we identified an unusual accumulation of long direct repeats. Analysis of the DNA sequence revealed a minimal direct repeat unit (dru) of 40 bp which was repeated 10 times within 500 bp. The dru sequences are responsible for the length polymorphism of mec. Moreover, we identified an open reading frame that codes for 145 amino acids (ORF145), whose deduced amino acid sequence showed 57% amino acid sequence similarity to the N terminus of the glycerophosphoryl diester phosphodiesterase (UgpQ) of Escherichia coli.

Amino Acid Sequence↗
PubMed1990

[In-vitro activity of cefuroxime-axetil against pathogens of bacterial infections of the respiratory tract].

Cefuroxime-Axetil is an ester of cefuroxime, which can be used as an oral antimicrobial agent. The prodrug is hydrolysed by esterases of the gut mucosa, setting free the active cefuroxime. This second generation cephalosporin is well known since more than a decade as a cephalosporin possessing high stability against gram positive and gram negative beta-lactamases. Due to its pharmacokinetic properties and its wide spectrum of activity, cefuroxime-axetil was recommended to be used as an oral agent in bacterial infections of the respiratory tract. This paper describes the in vitro activity of cefuroxime against respiratory tract pathogens and compares it with that of ampicillin and amoxicillin, amoxicillin/clavulanic acid, cefaclor, chloramphenicol, tetracycline, erythromycin and trimethoprim/sulphamethoxazole. Cefuroxime had good activity against beta-lactamase-producing and beta-lactamase-negative H. influenzae and M. catarrhalis. As expected, the aminopenicillins showed reduced activity against beta-lactamase-producing strains of these organisms. Amoxicillin/clavulanic acid and, to a lesser degree, cefaclor also showed good activity against these bacteria. Cefuroxime was highly active against penicillin-susceptible pneumococci, but showed impaired activity against penicillin-resistant strains. Therefore, this drug should not be used in infections caused by penicillin-resistant pneumococci. Resistance to penicillin in pneumococci isolated in Switzerland is not a problem at the present time. For many years, such strains were isolated only sporadically. Cefuroxime showed also a high in vitro activity against streptococci of serogroups A, B, C and G, which are encountered as respiratory tract pathogens. Against beta-lactamase-positive and -negative staphylococci, cefuroxime showed good activity. The drug was inactive, however, against methicillin-resistant strains.

Anti-Bacterial Agents↗
PubMed1990

Use of a ribosomal RNA gene probe for the epidemiological study of methicillin and ciprofloxacin resistant Staphylococcus aureus.

Conventional bacteriophage typing was combined with ribotyping in the analysis of methicillin and ciprofloxacin resistant Staphylococcus aureus strains isolated in increasing frequency since the introduction of the new 4-quinolones as therapeutic agents in the Tel-Aviv Medical Center. Whole-cell DNA was digested with EcoRI and HindIII restriction endonucleases. Agarose gel electrophoresis, Southern blotting, and hybridization by biotinylated probe DNA coding for ribosomal RNA revealed 7 to 14 bands. Analysis of the patterns established a single DNA type in EcoRI as well as in HindIII digests for all strains except one. Control strains from other sources differed in their band patterns. Bacteriophage typing confirmed the results of DNA typing. Thus, the frequent occurrence of staphylococcal isolates resistant to 4-quinolones in the hospital was not due to mutational development of resistance in many strains, but to the spread of a resistant strain.

Anti-Infective Agents↗
PubMed1990

Mechanism of imipenem resistance acquired by three Pseudomonas aeruginosa strains during imipenem therapy.

Imipenem sensitive pretherapy isolates (MICs 1-2 mg/l) and the corresponding resistant posttherapy isolates (MICs 16 mg/l) of Pseudomonas aeruginosa from three patients undergoing imipenem treatment were analyzed to establish the resistance mechanism. The identity of pyocin types, serotypes, DNA restriction endonuclease profiles and plasmid profiles strongly suggested isogenicity of pre- and posttherapy isolates. The imipenem resistant posttherapy isolates showed cross-resistance only to another carbapenem, meropenem. There were neither qualitative nor quantitative differences between pre- and posttherapy isolates in beta-lactamase production. Affinity of the penicillin-binding proteins 1A, 1B, 2, 3, 4,4' and 5 for [14C]imipenem was the same in pre- and posttherapy isolates. One-dimensional and two-dimensional gel electrophoresis of outer membrane protein preparations showed diminished expression of an outer membrane protein of about 46.5 and 47.5 kilodaltons, respectively, in the posttherapy isolates. This protein had an apparent isoelectric point of about pH 5.2 in two-dimensional gel electrophoresis. Growth in proteose peptone no. 2 broth did not reduce expression of this outer membrane protein, which spoke against its identity with the outer membrane protein D1. The permeability of the outer membrane for imipenem was reduced in the posttherapy isolates, since addition of 0.5 or 0.25 of the MIC of the permeabilizing agent ethylene-diaminetetraacetate reduced the MICs of imipenem for all isolates from each patient to the same (susceptible) level. The diminished expression of one of the outer membrane proteins might be the reason for this reduced permeability.

Bacterial Outer Membrane Proteins↗
PubMed1990

The Second European Collaborative Study on the frequency of antimicrobial resistance in Haemophilus influenzae.

In the second European survey of the prevalence of antimicrobial resistance in Haemophilus influenzae, 2529 clinical isolates collected in 1988/89 from 78 laboratories in nine countries (Austria, Belgium, Federal Republic of Germany, France, Italy, The Netherlands, Spain, Switzerland, United Kingdom) were examined. Of these, 23.8% were type b strains. The overall rate of beta-lactamase production was 9.1%, being slightly higher in type b isolates (10.5%) compared to non-type b isolates (8.6%). The MICs of six antimicrobials (ampicillin, cefaclor, chloramphenicol, erythromycin, tetracycline, and cotrimoxazole) were determined by an agar dilution procedure at a single central laboratory. The proportion of isolates resistant to the antimicrobials varied considerably amongst the individual countries. The highest incidence of resistance to all six drugs was observed in strains collected in Spain, whereas resistance was rarely encountered among strains isolated in Austria and the FRG. Resistance to ampicillin (MIC greater than or equal to 4 mg/l) among strains that lacked beta-lactamase activity was uncommon (0.3%). Based on the NCCLS Haemophilus influenzae breakpoints, the rates of susceptibility and resistance to cefaclor, chloramphenicol, tetracycline, and cotrimoxazole were 96.4/1.5, 96.2/2.8, 92.4/4.7, and 87.9/7.3%, respectively. The rate of susceptibility and resistance to erythromycin was 2.3/19.9. Multiple resistance to ampicillin, chloramphenicol, tetracycline, and cotrimoxazole was observed in 15 isolates (0.6%), and resistance to three drugs simultaneously in 72 (1.5%). The incidence of beta-lactamase producing strains was similar to that seen in the first European study performed in 1986 (9.1% vs. 10.9%), and was half that observed in US isolates collected in 1986.(ABSTRACT TRUNCATED AT 250 WORDS)

Ampicillin Resistance↗
PubMed1990

Prevalence of antimicrobial resistance in Haemophilus influenzae in Greece, Israel, Lebanon and Morocco.

Between 40 and 43 Haemophilus influenzae isolates obtained from Greece, Lebanon, Israel and Morocco respectively (a total of 167 strains) were analysed for prevalence of resistance to six different drugs. Of these isolates 12.6% produced beta-lactamase and were resistant to ampicillin. All isolates, except a single strain from Greece, were susceptible to cefaclor. The frequency of resistance to chloramphenicol and tetracycline was below 2%. The frequency of isolates susceptible and resistant to erythromycin and cotrimoxazole varied from country to country.

Ampicillin Resistance↗
PubMed1990

Appearance of amikacin and tobramycin resistance due to 4'-aminoglycoside nucleotidyltransferase [ANT(4')-II] in gram-negative pathogens.

Following the use of amikacin as the principal aminoglycoside at a Denver hospital, amikacin resistance appeared first in Pseudomonas aeruginosa and then in Escherichia coli, Klebsiella pneumoniae, and other enteric organisms from debilitated and compromised patients who had spent time in intensive care units and who had been treated with multiple antibiotics, usually including amikacin. In a P. aeruginosa isolate, resistance to amikacin and tobramycin was transferable by the IncP-2 plasmid pMG77, while in E. coli and K. pneumoniae resistance was carried by the transmissible plasmids pMG220, pMG221, and pMG222 belonging to the IncM group. Isolates and transconjugants produced an enzyme with adenyltransferase activity with substrates having a 4'-hydroxyl group, such as amikacin, kanamycin, neomycin, Sch 21768, isepamicin (Sch 21420), or tobramycin, but not with aminoglycosides lacking this target, such as dibekacin, netilmicin, sisomicin, or gentamicin C components. Genes encoding the 4'-aminoglycoside nucleotidyltransferase [ANT(4')] activity were cloned from pMG77, pMG221, and pMG222. A DNA probe prepared from the ANT(4') found in P. aeruginosa hybridized with the ANT(4') determinant found in E. coli. A probe for the ANT(4') from Staphylococcal spp., which differs in its modification of substrates, like dibekacin, that have a 4"- but not a 4'-hydroxyl group, failed to hybridize with the gram-negative ANT(4') determinant, which consequently has been termed ANT(4')-II.

Amikacin↗
PubMed1990

Evidence of a novel staphylococcal mec-encoded element (mecR) controlling expression of penicillin-binding protein 2'.

A region was identified on the methicillin resistance determinant (mec) isolated from Staphylococcus epidermidis and cloned into Staphylococcus carnosus which was responsible for a novel downregulation of the expression of methicillin resistance. The presence of this region reduced the overall expression of methicillin resistance and the synthesis of the mec-encoded penicillin-binding protein 2' (PBP 2') in S. carnosus. This region was located by Bal31 deletion mutagenesis upstream of the structural gene for PBP 2'. Deletions within this region resulted in higher levels of expression of methicillin resistance and increased levels of PBP 2' synthesis. We tentatively called this region mecR. Analysis of selected Mcr strains of Staphylococcus aureus and S. epidermidis by Southern hybridization suggested that the natural occurrence of two types of mec resistance determinants differ by the presence or absence of mecR-specific sequences.

Bacterial Proteins↗