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Donald Morrison

Publications and source records attributed to Donald Morrison.

15 recordsLinked to original sources
PubMed2007

Supplementary biochemical tests useful for the differentiation of oxidase positive staphylococci.

Differentiation of the oxidase positive staphylococci, Staphylococcus sciuri, Staphylococcus lentus, Staphylococcus vitulinus and Staphylococcus fleurettii, based on tributyrin, urease, caseinase, gelatinase and DNase activity is described. These tests may be used for preliminary identification of oxidase positive isolates of staphylococci resulting in more accurate identification of these species.

Animals↗
PubMed2006

Molecular identification and characterization of mannitol-negative methicillin-resistant Staphylococcus aureus.

We report on the isolation, molecular identification, and characterization of 5 mannitol-negative methicillin-resistant Staphylococcus aureus (MRSA) from clinical samples in KwaZulu-Natal (KZN) province, South Africa. Identification based on phenotypic testing and polymerase chain reaction detection of the S. aureus species-specific nuc gene and the coagulase gene indicated that the mannitol-negative isolates were S. aureus. Furthermore, they were mecA positive, and SCCmec typing demonstrated that all the isolates harbored type IV SCCmec. API STAPH (Biomerieux, Marcy-l'Etoile, France) misidentified 2 mannitol-negative MRSA that belonged to the major clone in KZN province, as Staphylococcus lugdunensis. Although the prevalence and mechanism of mannitol-negative MRSA is unknown, laboratories are encouraged to investigate S. aureus with atypical characteristics.

Bacterial Proteins↗
PubMed2006

Identification and molecular characterization of mannitol salt positive, coagulase-negative staphylococci from nasal samples of medical personnel and students.

The identification of mannitol salt positive, coagulase-negative staphylococci (CNS) is often disregarded when Staphylococcus aureus is screened in clinical samples using mannitol salt agar. However, the emergence of CNS as important human pathogens has indicated that reliable methods for the identification of clinically significant CNS are of great importance in understanding the epidemiology of infections caused by them. The identification and molecular characterization of mannitol salt positive CNS from nasal samples of medical personnel and students is reported here. A total of 84 mannitol salt positive staphylococcal isolates were obtained from 240 nasal samples, of which 15 were CNS. The API STAPH system classified the CNS isolates into six species, and one-third of the isolates were identified with confidence levels of <80 %. 16S-23S rRNA intergenic spacer length polymorphism analysis (ITS-PCR) identified only two species (Staphylococcus haemolyticus and Staphylococcus saprophyticus). This identification was confirmed by antibiotyping, species-specific PCR and PFGE. The results from this study indicate that ITS-PCR is a potentially useful and reliable tool, enabling hospital laboratories to obtain rapid, full and accurate identification of CNS at the species level.

Bacterial Typing Techniques↗
PubMed2006

Evaluation of phenotypic and molecular methods for detection of oxacillin resistance in members of the Staphylococcus sciuri group.

In this paper we report on an experimental evaluation of phenotypic and molecular methods as means for the detection of oxacillin resistance in members of the Staphylococcus sciuri group. A total of 109 S. sciuri group member isolates (92 S. sciuri isolates, 9 S. lentus isolates, and 8 S. vitulinus isolates) were tested by the disk diffusion method, the agar dilution method, the oxacillin salt-agar screening method, slide latex agglutination for PBP 2a, and PCR assay for mecA as the reference method. The mecA gene was detected in 29 S. sciuri isolates, and the true-positive and true-negative results of the other tests were defined on the basis of the presence or the absence of the mecA gene. For the different methods evaluated, the sensitivities and specificities were as follows: for the disk diffusion test with a 1-microg oxacillin disk, 100% and 55.9%, respectively; for the disk diffusion test with a 30-mug cefoxitin disk, 93.5% and 100%, respectively; for the agar dilution method, 100% and 50%, respectively; for the oxacillin salt-agar screen test (with 6 microg of oxacillin per ml and 4% NaCl) 100% and 100%, respectively; and for the slide latex agglutination test for PBP 2a, 100% and 100%, respectively. The disk diffusion test with various beta-lactam antibiotics was performed to evaluate their use for the prediction of oxacillin resistance. The results indicate that meropenem, cefazolin, cefamandole, cefuroxime, cefotetan, cefoperazone, cefotaxime, ceftriaxone, moxalactam, cefaclor, and cefprozil may be used as surrogate markers of oxacillin resistance, although further studies of their use for the detection of oxacillin resistance are required.

Animals↗
PubMed2005

Guidelines for the laboratory diagnosis and susceptibility testing of methicillin-resistant Staphylococcus aureus (MRSA).

These evidence-based guidelines have been produced after a literature review of the laboratory diagnosis and susceptibility testing of methicillin-resistant Staphylococcus aureus (MRSA). We have considered the detection of MRSA in screening samples and the detection of reduced susceptibility to glycopeptides in S. aureus. Recommendations are given for the identification of S. aureus and for suitable methods of susceptibility testing and screening for MRSA and for S. aureus with reduced susceptibility to glycopeptides. These guidelines indicate what tests should be used but not when the tests are applicable, as aspects of this are dealt with in guidelines on control of MRSA. There are currently several developments in screening media and molecular methods. It is likely that some of our recommendations will require modification as the new methods become available.

Anti-Bacterial Agents↗
PubMed2005

A real-time PCR assay to detect the Panton Valentine Leukocidin toxin in staphylococci: screening Staphylococcus schleiferi subspecies coagulans strains from companion animals.

Recent reports suggest that methicillin-resistant strains of Staphylococcus schleiferi subspecies coagulans are now commonly isolated from dogs. Given the association of a potentially mobile SCCmec type IV element with lysogenic phage-encoded Panton Valentine Leukocidin (PVL) toxin genes in community-acquired methicillin-resistant Staphylococcus aureus strains we hypothesized that methicillin-resistant S. schleiferi ssp. coagulans strains may also encode PVL toxin genes. Forty S. schleiferi ssp. coagulans strains isolated from companion animals were studied. Susceptibility to oxacillin was determined by broth microdilution and all isolates were screened by PCR for the presence of the mecA gene. SCCmec typing was performed on 14 isolates. A real-time PCR assay was developed for the detection of the PVL genes using a SmartCycler. Pulsed-field gel electrophoresis (PFGE) was performed to determine whether S. schleiferi ssp. coagulans strains were homogeneous. Twenty-eight of the 40 isolates (70%) were resistant to oxacillin and 26/28 possessed the mecA gene by PCR. SCCmec IV was identified in seven strains; the other seven isolates were not typable by this technique. All 40 strains were negative for the PVL toxin gene. PFGE showed a heterogeneous population and 13 different profiles were determined. In conclusion, this study showed that PVL toxin genes were not detected in a heterogeneous population of methicillin-resistant S. schleiferi ssp. coagulans strains isolated from companion animals.

Animals↗
PubMed2005

A comparative evaluation of phenotypic and molecular methods in the identification of members of the Staphylococcus sciuri group.

Members of the Staphylococcus sciuri group (S. sciuri, S. lentus, and S. vitulinus) are coagulase-negative, novobiocin-resistant staphylococci that could be distinguished from other staphylococci on the basis of positive oxidase activity. In the present study, a scheme based on conventional methods and utilization of various carbohydrates was evaluated for the identification of oxidase-positive staphylococci, and validated using two molecular techniques. Of the 173 oxidase-positive staphylococcal tested strains, 161 were identified as S. sciuri, 9 as S. lentus, 2 as S. vitulinus, and one as S. fleurettii by our scheme. The level of agreement with tRNA intergenic length polymorphism analysis (tDNA-PCR) was high (97.5-100% correlation). The accuracy and ease of use of this protocol suggest that it may be useful and valuable in microbiological laboratories for the identification of members of this group.

Bacterial Typing Techniques↗
PubMed2005

Isolation and molecular characterization of Staphylococcus sciuri in the hospital environment.

Staphylococcus sciuri is a principally animal-associated bacterial species, but its clinical relevance for humans is increasing. Our study aimed to provide the first insight into the prevalence of this bacterium in a hospital environment. A 3-month surveillance was conducted in a hospital located in Belgrade, Serbia, and 1,028 samples taken from hands of medical personnel, medical devices, and various hospital surfaces were screened for S. sciuri presence. In total, 108 isolates were obtained, which resulted in a relatively high rate of colonization (10.5%). These isolates, along with 7 S. sciuri strains previously isolated in the same hospital (n = 115), were phenotypically and genotypically characterized. Antimicrobial susceptibility testing revealed that 73% of the strains were resistant to one or more antibiotics, with 4.3% strains displaying multiresistance. Examination of 16S-23S ribosomal DNA intergenic spacer length polymorphism identified the strains at the subspecies level, and 74 (64.3%) strains of S. sciuri subsp. sciuri, 37 (32.2%) strains of S. sciuri subsp. rodentium, and 4 (3.5%) strains of S. sciuri subsp. carnaticus were established. Pulsed-field gel electrophoresis (PFGE) analysis showed 21 distinct pulsotypes, including 17 main types and 4 subtypes. One dominant cluster with 62 strains was found, while 19 (90.5%) of the PFGE types and subtypes identified had 5 or fewer strains. The predominance of small PFGE clusters suggests that the ubiquitous presence of S. sciuri in the outside environment presents the continuous source for colonization of the hospital environment. The presence of one dominant PFGE cluster of strains indicates that some S. sciuri strains may be capable for adaptation to hospital environment conditions and continuous existence in this environment.

Anti-Bacterial Agents↗
PubMed2005

Survey of genes encoding staphylococcal enterotoxins, toxic shock syndrome toxin 1, and exfoliative toxins in members of the Staphylococcus sciuri group.

Genes encoding staphylococcal enterotoxins (sea to see, seg, and seh), toxic shock syndrome toxin 1 (tst), and exfoliative toxins (eta and etb) were not detected in a large panel of 48 Staphylococcus sciuri group isolates tested. This strongly suggests that production of the staphylococcal exotoxins by these bacteria is highly unlikely.

Bacterial Toxins↗
PubMed2005

The discovery of a multi-resistant Staphylococcus haemolyticus clone in the hospital and community environment in south western Nigeria.

Among clinically significant isolates of coagulase negative staphylococci, Staphylococcus haemolyticus is ranked second after Staphylococcus epidermidis. It has been associated with septicemia in newborns and various infections in persons with compromised host defenses and implanted foreign bodies. The existence of a multi-resistant Staphylococcus haemolyticus clone was discovered during a study on patients with skin and soft tissue infections at two local health clinics and in a referral hospital in South Western Nigeria. The clonal nature of these strains was determined by antibiotic susceptibility profile and pulsed field gel electrophoresis. This represents the first report of what appears to be a hospital-acquired and transmitted Staphylococcus haemolyticus clone in South Western Nigeria. Careful infection control measures and strain typing are urgently needed to understand species epidemiology and to limit the spread of multi-resistant strains within and beyond healthcare facilities.

Academic Medical Centers↗
PubMed2004

Isolation and molecular characterization of multiresistant Staphylococcus sciuri and Staphylococcus haemolyticus associated with skin and soft-tissue infections.

The isolation, molecular identification and genotyping of multiresistant Staphylococcus sciuri and Staphylococcus haemolyticus from skin and soft-tissue infections are reported. Accurate and full identification of three coagulase-negative staphylococcal isolates was achieved using PCR, while the API STAPH method failed to identify an isolate of S. haemolyticus fully. The PCR assay, which detects polymorphism in the 16S-23S rRNA spacer region, is shown to be potentially useful for rapid and accurate identification of coagulase-negative staphylococci. Identical PFGE type and antibiotic-resistance profiles of two methicillin-resistant S. haemolyticus isolates in this study suggest the existence of a multiresistant community clone.

Adult↗
PubMed2002

Identification and characterization of teicoplanin-intermediate Staphylococcus aureus blood culture isolates in NE Scotland.

The study objective was to screen both methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive S. aureus (MSSA) isolates from blood cultures for reduced susceptibility to vancomycin and teicoplanin. A total of 72 MRSA and 143 MSSA isolates were screened on brain-heart infusion agar containing either 4 mg/L vancomycin or 8 mg/L teicoplanin, using an inoculum of approximately 10(6) organisms. MICs were determined by Etest, broth microdilution and agar incorporation. Isolates were characterized by PFGE, mecA and nuc PCR, transmission electron microscopy (TEM) and analysis of cell proteins (proteomics). Based on British Society for Antimicrobial Chemotherapy (BSAC) breakpoints, seven MRSAs and seven MSSAs were teicoplanin resistant, with MICs of up to 16 and 24 mg/L respectively, but were vancomycin sensitive. Based on higher NCCLS breakpoints, five MRSAs and six MSSAs were teicoplanin intermediate, vancomycin sensitive. All the MRSAs belonged to the EMRSA-16 clone and subdivided into two groups. The MSSAs belonged to five different clones. TEM showed the resistant variants to have slightly thicker cell walls than sensitive variants. Most notably, the resistant variants possessed characteristic dark, granular material concentrated in the middle of the cells, believed to be chromosome. Proteomics showed the resistant variants to overexpress phosphoglycerate kinase. Both MRSA and MSSA with reduced teicoplanin susceptibility may remain vancomycin sensitive by NCCLS and BSAC criteria and it is important to screen clinical isolates of MRSA and MSSA for reduced susceptibility to both agents.

Blood↗
PubMedDate not supplied

Re-emergence of early pandemic Staphylococcus aureus as a community-acquired meticillin-resistant clone.

During the 1950s, the notorious penicillin-resistant clone of Staphylococcus aureus known as phage type 80/81 emerged and caused serious hospital-acquired and community-acquired infections worldwide. This clone was largely eliminated in the 1960s, concurrent with the widespread use of penicillinase-resistant beta lactams. We investigated whether early 80/81 isolates had the genes for Panton-Valentine leucocidin, a toxin associated with virulence in healthy young people. Multilocus sequence analysis suggested that descendants of 80/81 have acquired meticillin resistance, are re-emerging as a community-acquired meticillin-resistant S aureus (MRSA) clone, and represent a sister lineage to pandemic hospital-acquired MRSA.

Australia↗