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Biomedical subjects

J E Mortensen

Publications and source records attributed to J E Mortensen.

At least 37 records · Page 2Linked to original sources
PubMed1994

Ribosomal RNA gene (rrn) organization in enterococci.

A cloned 1.8-kb probe containing the 3' end of 16S ribosomal RNA and the 5' end of 23S ribosomal RNA from Enterococcus hirae was used to analyze various endonuclease digests of enterococci. In the ATCC strains tested we observed a remarkable conservation of the ApaI sites in the rrn operons, and a partial conservation of EcoRI sites. Using a number of other endonuclease digestions with the ApaI rrn probe, we estimate the number of rrn operons in enterococci to be between five and six.

DNA, Bacterial↗
PubMed1994

Quantitative skin cultures at potential catheter sites in neonates.

OBJECTIVE: To identify and quantify the bacterial and fungal flora present at body sites used for vascular catheterization of infants in a neonatal intensive care unit. DESIGN: Quantitative skin cultures were obtained from a group of neonatal patients to determine the bacterial flora found on the skin at four sites. Quantitative cultures of the jugular, subclavian, umbilical, and femoral sites were obtained on 50 infants, ranging in age from 2 days to 3 months old. SETTING: The neonatal intensive care unit of St. Christopher's Hospital for Children, a university-affiliated tertiary care children's hospital. RESULTS: Colony counts ranged from 0 to 10(6) colony-forming units/10 cm2. Types of organisms found were consistent with other published studies and included coagulase-negative staphylococci, Staphylococcus aureus, yeast, aerobic gram-negative rods, Enterococcus species, Corynebacterium species, and alpha-hemolytic streptococci. There was a significantly higher mean colony count at the combined jugular/femoral sites versus the subclavian site (P < 0.01) and umbilical site (P < 0.05). Mean colony counts did not differ significantly between the jugular and femoral site, or between the subclavian and umbilical site. The umbilical site was more likely to be colonized with aerobic gram-negative rods, Enterococcus species, and yeast, while the subclavian had coagulase-negative staphylococci as the predominant organism. The jugular and femoral sites demonstrated a higher colony count of aerobic gram-negative rods, Enterococcus species and yeast than the other sites. If central venous catheters need to be in place for extended periods of time, placement at a site with lower bacterial densities on the skin may help minimize catheter-associated infections. This study supports the subclavian as the preferred site.

Bacteriological Techniques↗
PubMed1993

Comparison of susceptibility test methods to detect penicillin-resistant Streptococcus pneumoniae.

The detection of penicillin-resistant Streptococcus pneumoniae was assessed by six different methods: agar dilution, oxacillin screen by disk diffusion, E-test, and three overnight microdilution test methods that included commercial panels from MicroScan and Micro Media and in-house-made conventional panels using a commercial Haemophilus test medium (HTM) broth. Of the 52 pneumococcal isolates tested, 12 were resistant, 16 were relatively resistant, and 24 were susceptible to penicillin as defined by the reference agar dilution method. The oxacillin screen detected as resistant all 28 resistant and relatively resistant strains. The percentage of penicillin-resistant isolates detected by each minimum inhibitory concentration (MIC) test method was as follows: E-test (100%), Micro Media (75%), MicroScan (0%), and HTM (0%). With the relatively resistant isolates, the detection percentage was as follows: E-test (88%), Micro Media (94%), MicroScan (69%), and HTM (69%). In conclusion, the E-test and Micro Media MIC tests are acceptable confirmatory tests for detecting penicillin resistance among S. pneumoniae isolates.

Culture Media↗
PubMed1993

Source of Pseudomonas cepacia: ribotyping of isolates from patients and from the environment.

Ribotyping, an analysis of bacterial strain identity based on chromosomal restriction fragment length polymorphisms, was performed on 68 isolates of Pseudomonas cepacia recovered from patients receiving care at the two children's hospitals in Philadelphia and from environmental samples. Twenty different ribotypes were identified. Ribotype R3 predominated among isolates from all three sources. These findings are consistent with the acquisition of P. cepacia from the environment or by person-to-person transmission.

Burkholderia cepacia↗
PubMed1993

Identification of clinical yeast isolates by using the Microring YT.

The Microring YT (MYT; Medical Wire & Equipment Co., Victory Gardens, N.J.) is a system for the rapid (24 to 48 h) identification of yeasts. The MYT system was evaluated and compared with the API20C (Analytab Products, Plainview, N.Y.) system for its ability to identify 677 clinical yeast isolates. Only 458 isolates (68%) were correctly identified by the MYT system, and the accuracy of the system varied considerably (0 to 96%), depending on the species. While MYT was less expensive and convenient to use and results were available 24 h sooner, it is inadequate for identification of many commonly isolated yeasts and is not designed for the identification of Cryptococcus species.

Candida↗
PubMed1992

Modification of bactericidal fatty acids by an enzyme of Staphylococcus aureus.

Certain strains of Staphylococcus aureus produce an enzyme capable of inactivating the bactericidal fatty acids produced in staphylococcal abscesses by esterification to various alcohols. The enzyme, called FAME (fatty acid modifying enzyme), has a pH optimum between 5.5 and 6.0 and a temperature optimum of about 40 degrees C. Enzyme activity is not affected by edetic acid or by the presence or absence of sodium and potassium ions. Although FAME can utilise methanol, ethanol, 1-propanol, 2-propanol, 1-butanol or cholesterol as substrates, cholesterol appears to be the preferred substrate. FAME esterifies without being an esterase operating in reverse. Strains capable of producing the enzyme can synthesise it in trypticase soy broth and in a chemically defined medium, but not necessarily in equal amounts. FAME production is correlated with the ability of a strain to grow and survive within the tissues.

Abscess↗
PubMed1992

Effect of capsulation on the resistance of Staphylococcus aureus to the bactericidal lipids produced in abscesses.

Staphylococcus aureus strains differ in their sensitivity to some of the bactericidal lipids produced by the host in staphylococcal abscesses. To evaluate whether the presence of a capsule might account for these differences, capsulate and non-capsulate S. aureus strains were compared for their sensitivity to staphylococcal abscess homogenates and the neutral lipid fraction derived from such material. Although the presence of a capsule appeared to reduce sensitivity, two non-capsulate mutants were only about three-to-four times more sensitive than their capsulate parent strains. Another strain, known for its resistance to these bactericidal lipids, was not capsulate. This suggests that mechanisms other than capsule formation must also determine sensitivity to the lipids.

Abscess↗
PubMed1991

Ribotype stability of serial pulmonary isolates of Pseudomonas cepacia.

Eighty-three isolates of Pseudomonas capacia were recovered from respiratory secretions from 12 chronically colonized cystic fibrosis patients and examined by ribotype analysis. In 9 patients, the ribotype of the cultured P. cepacia remained unchanged throughout the entire period of observation, indicating chronic pulmonary colonization with a single strain. In each of the remaining 3 patients, two genetically distinct strains were detected among serial P. cepacia isolates. No significant change in clinical condition was correlated with the change in identity of the colonizing strain. In control experiments, the stability of strain ribotype was demonstrated among isolated that had been subcultured 100 times in vitro and among isolates recovered from chronically colonized mice. These data demonstrate the utility of ribotype analysis and indicate that most chronically colonized cystic fibrosis patients harbor a single strain of P. cepacia for prolonged periods.

Animals↗
PubMed1990

Pathogenic factors of Pseudomonas cepacia isolates from patients with cystic fibrosis.

One hundred and nineteen isolates of Pseudomonas cepacia, 98 of which were from cystic fibrosis (CF) patients and 21 from environmental and other human sources, were examined for biochemical and exo-enzymatic properties that may contribute to the pathogenicity of this bacterium. The following characteristics were demonstrated significantly more frequently in isolates from CF patients than in control isolates: production of catalase, ornithine decarboxylase, valine aminopeptidase, C14 lipase, alginase and trypsin; reduction of nitrate to nitrite; hydrolysis of urea and xanthine; complete haemolysis on bovine red blood cells; cold-sensitive haemolysis on human red blood cells; greening of horse and rabbit red blood cells. The role of these factors in the pulmonary disease associated with cystic fibrosis is not clear. However, several factors which have been reported previously as being associated with pathogenic processes with other bacteria have now been described in P. cepacia. Additional factors not previously reported as "pathogenicity factors" are also described.

Amino Acids↗
PubMed1990

Comparative in vitro activity of cefixime against Haemophilus influenzae isolates, including ampicillin-resistant, non-beta-lactamase-producing isolates, from pediatric patients.

The in vitro activity of cefixime was comparatively tested against 232 non-type b and 102 type b isolates of Haemophilus influenzae derived from clinical specimens of pediatric patients, including 10 non-type b strains that did not produce beta-lactamase and demonstrated resistance to ampicillin. Cefixime was active against the ampicillin-susceptible and ampicillin-resistant, beta-lactamase-producing isolates; however, its activity against some non-beta-lactamase-producing, ampicillin-resistant isolates appeared to be limited.

Ampicillin Resistance↗
PubMed1987

Susceptibility testing of fastidious organisms in the API microdilution panel.

It has become increasingly important to perform routine susceptibility tests on certain anaerobic bacteria, Haemophilus influenzae and Streptococcus pneumoniae, as a result of the decreasing predictability of their antimicrobial susceptibility patterns. The antimicrobial susceptibilities of 49 anaerobic isolates, 25 H. influenzae isolates, and 25 S. pneumoniae isolates were determined concurrently by API Uniscept MIC trays and a conventional broth microdilution method using Wilkins-Chalgren broth, 5% Fildes in Schaedler broth, or 5% lysed horse blood in Mueller-Hinton broth, respectively. Analysis of 490 anaerobic organism-antibiotic combinations, 144 H. influenzae-antibiotic combinations, and 125 S. pneumoniae-antibiotic combinations showed that 98.9%, 100%, and 99.2%, respectively, of the API results were within +/- 1 log2 dilution of the reference system. The API Uniscept MIC panel would be acceptable for use as a routine susceptibility system for anaerobic organisms in a clinical microbiology laboratory. To eliminate trailing endpoints, however, further studies need to be performed to evaluate additional broth media for the susceptibility testing of H. influenzae and S. pneumoniae in the API panels.

Anti-Bacterial Agents↗
PubMed1987

Protein fingerprinting for the determination of relatedness in Acinetobacter calcoaceticus subspecies anitratus isolated from patients in a surgical intensive care unit.

The use of protein fingerprinting for the establishment of relatedness among isolates of Acinetobacter calcoaceticus subspecies anitratus, isolated from patients in a surgical intensive care unit was examined. Polyacrylamide gel electrophoresis was used to analyze the cellular proteins from whole cell lysates of 14 intensive care unit A calcoaceticus subspecies anitratus isolates and 11 control strains. Antimicrobial susceptibilities and plasmid profiles were also determined for all isolates. All intensive care unit A calcoaceticus subspecies anitratus isolates exhibited identical cellular protein fingerprints, no detectable plasmids, and minimum inhibitory concentrations within +/- 1 log2 dilution of the mode value for each of the antimicrobial agents tested. The other clinical isolates demonstrated a range of antimicrobial susceptibilities, various numbers and sizes of plasmids, and distinctly different protein fingerprints. These data indicate that protein fingerprinting may be useful as an epidemiologic tool in A calcoaceticus subspecies anitratus outbreaks and this method deserves further study.

Acinetobacter↗
PubMed1986

Susceptibility testing of methicillin-resistant Staphylococcus aureus with three commercial microdilution systems.

The antimicrobial susceptibilities of 100 methicillin-resistant Staphylococcus aureus isolates were determined concurrently by API Uniscept KB, Micro-Media, MicroScan, standardized disk diffusion, and reference broth microdilution to evaluate whether these commercial microdilution systems would reliably defect methicillin-resistant S. aureus. The methicillin minimal inhibitory concentration for all isolates was greater than or equal to 16 micrograms/ml as determined by the reference minimal inhibitory concentration panels containing 2% NaCl supplemented Mueller-Hinton broth. Using the breakpoints established by the National Committee for Clinical Laboratory Standards for reporting susceptible and resistant methicillin results, there was 100% agreement between the reference methods and API Uniscept KB at 24 hr. The Micro-Media and MicroScan systems had 47% and 8% very major discrepancies at 24 hr, respectively. At 48 hr, these two systems exhibited 15% and 0% very major discrepancies. Micro-Media and MicroScan were in agreement with the reference microdilution method (+/- 1 log2 dilution) for 62% and 68% of the strains at 24 hr, respectively and 88% and 85% of the isolates at 48 hr, respectively. The results of this study indicate that API Uniscept KB would provide a practical and reliable method for the detection of methicillin-resistant S. aureus.

Anti-Bacterial Agents↗
PubMed1986

Antimicrobial susceptibility of clinical isolates of Brucella.

A number of antimicrobial agents have been used in the treatment of human brucellosis with varying effectiveness. The purpose of this study was to test the in vitro susceptibility of isolates of four Brucella species to a variety of antimicrobial agents, and to study in vitro synergy of combinations of agents. Minimal inhibitory concentrations (MICs) were determined using conventional broth microdilution methods and commercially available systems. Conventional checkerboard synergy microdilutions were prepared for gentamicin or streptomycin plus tetracycline, and rifampicin plus tetracycline. Synergy or antagonism was determined by the fractional inhibitory concentration index. Penicillin G and ampicillin showed in vitro activity against Brucella (MIC90 4 micrograms/ml), whereas the antipseudomonal penicillins were less active (carbenicillin MIC90 12 micrograms/ml, piperacillin MIC90 32 micrograms/ml). Among the third generation cephalosporins tested, cefotaxime (MIC90 2 micrograms/ml) demonstrated greatest activity. As a class, aminoglycosides were equivalent (MIC90 1-4 micrograms/ml). All strains were sensitive to tetracycline (MIC90 0.25 microgram/ml), trimethoprim-sulfamethoxazole (MIC90 1/19 micrograms/ml), and rifampin (MIC90 1 microgram/ml). Erythromycin (MIC90 greater than 8 micrograms/ml) and vancomycin (MIC90 greater than 16 micrograms/ml) demonstrated no activity. In vitro synergy (fractional inhibitory concentration index less than 0.5) was demonstrated with tetracycline plus rafampin in six of eight isolates tested.

Anti-Bacterial Agents↗