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PubMedDate not supplied

Use of thermonuclease testing to identify Staphylococcus aureus by direct examination of blood cultures.

Blood cultures submitted to the Clinical Microbiology Laboratory, Queen Alia Military Hospital, Amman during 1999-2001 were examined to evaluate thermonuclease testing for identifying Staphylococcus aureus in blood culture broths growing gram-positive cocci. Of 170 cultures studied, 129 yielded gram-positive staphylococci and 41 yielded other gram-positive cocci. Toluidine blue-deoxynucleic acid agar plates were used to test for thermonuclease activity. Standard tube coagulase tests were performed on the isolates. Direct detection of thermonuclease activity in 76 blood culture broths containing gram-positive staphylococci showed 100% correlation with subsequent tube coagulase tests. The thermonuclease test provides a fast, specific and reliable confirmation of S. aureus bacteraemia by direct examination of blood culture broths that contain gram-positive cocci. This allows for timely, optimal antibiotic therapy.

Bacteremia↗
PubMed1999

Detection of methicillin-resistant Staphylococcus aureus (MRSA) from growth on mannitol salt oxacillin agar using PCR for nosocomial surveillance.

This study evaluated a polymerase chain reaction (PCR) method for detection of methicillin-resistant Staphylococcus aureus (MRSA) in specimens referred for nosocomial surveillance. PCR was used to detect the mecA and nuc gene targets using yellow growth on mannitol salt agar containing 6 mg/liter oxacillin (MSO-6) as a source of DNA (N = 645). The diagnostic values for PCR compared with culture methods were 97% specificity, 100% sensitivity, 96% positive predictive value, and 100% negative predictive value. Total cost for PCR per test is $3.62 compared to $4.77 for culture. However, the total cost per specimen is significantly lower due to only 20% of all surveillance specimens producing yellow colonies on MSO-6. The average turnaround time for the PCR method is 48 h compared with 82 h for culture. PCR amplification of mecA and nuc genes using yellow colonies on MSO-6 is a simple, fast, accurate and cost-effective method for routine use in clinical laboratories for detecting MRSA in surveillance specimens.

Agar↗
PubMed1986

Formation of a covalent complex between the terminal protein of pneumococcal bacteriophage Cp-1 and 5'-dAMP.

Incubation of extracts of Cp-1-infected Streptococcus pneumoniae with [alpha-32P]dATP produced a labeled treatment with micrococcal nuclease and sensitive to treatment with proteinase K. Incubation of the 32P-labeled protein with 5 M piperidine for 4 h at 50 degrees C released 5'-dAMP, indicating that a covalent complex between the terminal protein and 5'-dAMP was formed in vitro. When the four deoxynucleoside triphosphates were included in the reaction mixture, a labeled complex of slower electrophoretic mobility in sodium dodecyl sulfate-polyacrylamide gels than the terminal protein-dAMP complex was also found, indicating that the Cp-1 terminal protein-dAMP complex can be elongated and, therefore, that it is an initiation complex. Treatment of the 32P-labeled terminal protein-dAMP complex with 5.8 M HCl at 110 degrees C for 2 h yielded phosphothreonine. These results, together with the resistance of the terminal protein-DNA linkage to hydroxylamine, suggest that the Cp-1 terminal protein is covalently linked to the DNA through a phosphoester bond between L-threonine and 5'-dAMP, namely, a O-5'-deoxyadenylyl-L-threonine bond.

Bacteriophages↗
PubMed1997

Metabolic fate of [3H]1-beta-D-arabinofuranosyl-5-[(E)-2-bromovinyl]uracil in herpes simplex virus type 1-infected cells.

The metabolic fate of 1-beta-D-arabinofuranosyl-5-[(E)-2-bromovinyl]uracil (BV-araU) in herpes simplex virus type 1-infected cells was studied using tritium-labeled BV-araU. [3H]BV-araU was selectively taken-up by infected cells. Approximately 10% of the total uptake of [3H]BV-araU was recovered from the acid-insoluble fraction at any time post-infection. Both cellular uptake of [3H]BV-araU and its incorporation into the acid-insoluble fraction increased with increasing incubation time through 8 hr post-infection. Uptake of [3H]BV-araU and its incorporation into the acid-insoluble fraction also increased proportionally to the duration of exposure to [3H]BV-araU. An alkaline sucrose gradient sedimentation analysis revealed that the radioactive DNA obtained from cells pulse-labeled with [3H]BV-araU were small DNA fragments which remained at the top following a chasing period in isotope-free medium, whereas that pulse-labeled with [3H]thymidine was chased to a fraction of high molecular weight DNA. Nuclease P1 digestion reduced 99% of the [3H]BV-araU-labeled DNA extracted from infected cells to a low molecular weight. Following digestion of [3H]BV-araU-labeled DNA with micrococcal nuclease and spleen exonuclease, all of the radioactivity was recovered as [3H]BV-araU 3'-monophosphate. Thus, BV-araU strongly inhibits the elongation of viral DNA strands as demonstrated by the alkaline sucrose gradient sedimentation analysis, whereas at least a portion of the [3H]BV-araU is incorporated inside viral DNA strands in infected cells.

Acyclovir↗
PubMed1976

Antibody response and protective ability of rabbits inoculated with Staphylococcus aureus strain CH-91.

Rabbits were inoculated subcutaneously with the protease-producing strain, CH-91, of Staphylococcus aureus of chicken origin. Dermatolysis was observed at the site of inoculation in them. Then the lesion outwardly healed up 5 to 6 weeks after the inoculation. When these recovered rabbits were reinoculated subcutaneously with the same number of viable cells as used in the first inoculation, none of them were affected with dermatolysis; that is, they had acquired a protective ability against an experimental challenge with viable cells. Antibodies against staphylococcal cells, alpha-hemolysin, and protease were detected in the serum of these rabbits 10 or 20 days after the first inoculation, but antibody against nuclease or beta-hemolysin was not. After the reinoculation, those antibodies showed a remarkable rise in most of the rabbits. These results suggest indirectly that the inoculated cells might have produced sufficient amounts of alpha-hemolysin and protease in the cutaneous tissue of rabbits. When rabbits were immunized with detoxicated culture supernatant of S. aureus strain CH-91, they exhibited antibody responses to alpha-hemolysin and protease mainly. Moreover, they were proved to have acquired a protective ability to an experimental challenge with viable cells when examined for the occurrence of dermatolysis as a marker of infection. On the contrary, when rabbits were immunized with killed cells, they presented a remarkable antibody response to staphylococcal cells. The immunized rabbits, however, acquired no protective ability.

Animals↗
PubMed1980

The structure of herpes simplex virus type 1 DNA as probed by micrococcal nuclease digestion.

Micrococcal nuclease digestion was used to probe the structures in which herpes simplex virus type I (HSV-I) DNA is found during virus replication. Parental DNA, progeny DNA and DNA in nucleocapsids were analysed. Parental DNA was examined after infection of Vero cells with 32P- or 3H-thymidine-labelled HSV-I. Progeny DNA was examined after HSV-I-infected Vero cells were pulse-labelled with 3H-thymidine during HSV-I DNA synthesis. In both cases, nuclei were isolated and digested with micrococcal nuclease. Digestion products were analysed by agarose or polacrylamide gel electrophoresis (PAGE). Most parental DNA remained as intact molecules. However, a small amount was degraded into fragments which were heterogeneous in size or the size of nucleosomal cell DNA. These two classes of fragments were also produced upon digestion of progeny DNA. The heterogeneous fragments and nucleosomal fragments comprised major and minor fractions, respectively, of digested progeny DNA. When digested DNA from HSV-I-infected cells was transferred from composite polyacrylamide-agarose gels to diazobenzyloxymethyl paper, nucleosomal fragments hybridized to 32P-labelled HSV-I DNA as well as to 32P-labelled Vero cell DNA.. Therefore, nucleosomal fragments contained HSV-I DNA sequences. HSV-I DNA in nucleocapsids was analysed by micrococcal nuclease digestion after nucleocapsids were disrupted with PH 9.3 buffer, pyridine, Sarkosyl or NcCl/urea. Only fragments of heterogeneous size were produced. Thus, HSV-I DNA is found predominantly in structures other than nucleosomes during virus replication.

Animals↗