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B C Mayall

Publications and source records attributed to B C Mayall.

17 recordsLinked to original sources
PubMed2001

Treatment failure due to methicillin-resistant Staphylococcus aureus (MRSA) with reduced susceptibility to vancomycin.

We report the first instance in Australia of treatment failure due to a strain of methicillin-resistant Staphylococcus aureus (MRSA) with reduced susceptibility to vancomycin--heteroresistant vancomycin-intermediate S. aureus (hVISA). The infection occurred in a 41-year-old man with multiple risk factors. No transmission of the organism to other patients or the environment was detected. This case may herald the beginning of a new phase of staphylococcal resistance in Australia.

Adult↗
PubMed2001

Use of denaturing gradient gel electrophoresis to detect mutation in VS2 of the 16S-23S rDNA spacer amplified from Staphylococcus aureus isolates.

To develop a double gradient denaturing gradient gel electrophoresis (DG-DGGE) based typing method that rapidly and accurately types clinical isolates of Staphylococcus aureus, the VS2 region of the 16S-23S rRNA spacer region (ISR) was chosen because of its potential high variation. The VS2 region was amplified with a 40-mer GC-clamp attached to the 5'-end of the reverse primer. The 145 bp PCR product was then separated by DG-DGGE using denaturant concentrations of 25-40% and polyacrylamide concentrations of 6-12%. Of the five mutations identified in 336 S. aureus isolates, one mutation was found to be highly specific for 161/171 (94%) of methicillin-resistant S. aureus (MRSA) isolates from different geographic locations and isolation times. This same mutation was found in 15/160 (9%) of penicillin- or methicillin-sensitive S. aureus isolates. In some isolates two mutations occured together in the one genome suggesting some S. aureus isolates have two copies of VS2. In these 336 isolates nine genotypes with different combinations of the five mutations were identified. In 18 coagulase-negative staphylococci (CNS), the MRSA-specific mutation was found along with two other mutations in all isolates demonstrating consistent differences in the presence of these mutations between CNS and S. aureus. The marked differences in VS2 sequences found between MRSA, methicillin- or penicillin-sensitive S. aureus (SSA), and CNS by DGGE in the present study may be useful in evolutionary studies and in the development of a specific assay for MRSA from clinical specimens.

Base Sequence↗
PubMed2001

Genomic approaches to typing, taxonomy and evolution of bacterial isolates.

The current literature on bacterial taxonomy, typing and evolution will be critically examined from the perspective of whole-genome structure, function and organization. The following three categories of DNA band pattern studies will be reviewed: (i) random whole-genome analysis; (ii) specific gene variation and (iii) mobile genetic elements. (i) The use of RAPD, PFGE and AFLP to analyse the whole genome will provide a skeleton of polymorphic sites with exact genomic positions as whole-genome sequence data become available. (ii) Different genes provide different levels of evolutionary information for determining isolate relatedness depending on whether they are highly variable (prone to recombination events and horizontal transfer), housekeeping genes with only a small number of single nucleotide differences between isolates or part of the rrn multigene family that is prone to intragenomic recombination and concerted evolution. Comparative analyses of these different gene classes can provide enhanced information about isolate relatedness. (iii) Mobile genetic elements such as insertion sequences, transposons, plasmids and bacteriophages integrate into the bacterial genome at specific (e.g. tRNA genes) or non-specific sites to alter band patterns produced by PFGE, RAPD or AFLP. From the literature it is not clear what level of genetic element duplication constitutes non-relatedness of isolates. A model is presented that incorporates all of the above genomic characteristics for the determination of isolate relatedness in taxonomic, typing and evolutionary studies.

Bacteria↗
PubMed2001

Nocardia veterana sp. nov., isolated from human bronchial lavage.

A nocardioform bacterium was isolated from the bronchoscopic lavage of a 78-year-old man with a past history of tuberculous pleurisy, who presented with bilateral upper lobe lesions at Austin and Repatriation Medical Centre, Heidelberg, Australia. The strain was aerobic, Gram-positive, produced beige substrate mycelium and scant white aerial mycelium. It showed chemotaxonomic markers which were consistent with the classification of Nocardia: i.e. meso-diaminopimelic acid, N-glycolylmuramic acid, arabinose and galactose as diagnostic sugars; phospholipids phosphatidylinositol mannosides, phosphatidylinositol, phosphatidylethanolamine and diphosphatidylglycerol; a menaquinone with a cyclic isoprene side chain, MK-8(H4cycl.); a fatty acid pattern composed of unbranched saturated and monounsaturated fatty acids with a considerable amount of tuberculostearic acid; and mycolic acids composed of 54-62 carbon atoms with three principal mycolic acids which were mono- and polyunsaturated, showing a chain length C56, C58 and C60 and accounting for over 70% of the entire pattern. The 16S rDNA sequence showed the highest similarity to the type strain of Nocardia vaccinii; the DNA-DNA similarity of the two strains was 31%. These data, together with distinct physiological traits and molecular biological analyses, as well as chemotaxonomic results, led to the conclusion that the novel isolate represents a new species within the genus Nocardia for which the name Nocardia veterana sp. nov. is proposed. The type strain is M157222T (DSM 44445T = NRRL B-24136T).

Aged↗
PubMed1999

Use of double gradient denaturing gradient gel electrophoresis to detect (AT)n polymorphisms in the UDP-glucuronosyltransferase 1 gene promoter associated with Gilbert's syndrome.

Gilbert's syndrome, due to reduced hepatic bilirubin glucuronidation is associated with the presence of two extra nucleotides (TA) in the promoter region of the UDP-glucuronosyltransferase 1 (UGT1A1) gene. A rapid method was developed to detect this genetic polymorphism, using double gradient denaturing gradient gel electrophoresis (DG-DGGE). The promoter region of the UGT1A1 gene was amplified with a 40-mer GC-clamp attached to the 5'-end of the reverse primer. The polymerase chain reaction (PCR) product was then separated by DG-DGGE using denaturant concentrations of 15-25% and polyacrylamide concentrations of 6-12%. The (TA)6/(TA)6 homozygotes were clearly distinguished from both (TA)7/(TA)7 homozygotes and (TA)6/(TA)7 heterozygotes. The (TA)7 allele frequency was consistent with that previously reported and elevated bilirubin levels correlated with the presence of the (TA)7 allele. The DG-DGGE method described will make detection for this polymorphism fast, simple, nonradioactive and suitable for a clinical routine diagnostic laboratory, helping to establish the role of this polymorphism in individuals with jaundice due to multiple causes.

Electrophoresis↗
PubMed1998

An Australian isolate of Mycobacterium shimoidei.

A case of Mycobacterium shimoidei in a 75 year old man is reported. He had been a smoker, with a past history of bullous emphysema and a lung abscess. He had a 12 month history of weight loss, night sweats, with increased cough and sputum, and progressive opacification of the left apex with cavity formation. Sputum repeatedly grew M. shimoidei, identification of which was confirmed with high-pressure liquid chromatography (HPLC). He was treated for 45 days with three drugs to which the organism was sensitive, but failed to respond. His death was attributed to mycobacterial infection.

Aged↗
PubMed1998

Isolation of Clostridium tetani from anaerobic empyema.

We report the isolation of Clostridium tetani (along with Fusobacterium mortiferum) from empyema pus. The patient, a 68 year old retired farmer from rural NSW, had recently undergone cholecystectomy, had heart failure and developed an empyema. He improved after drainage of the empyema and penicillin therapy, but died suddenly during convalescence.

Aged↗
PubMed1996

In vitro activity of meropenem compared to nine other antimicrobial agents: importance of its stability when used in agar dilution systems.

The antibacterial activity of meropenem was tested against 426 clinical isolates representing a wide range of aerobic and anaerobic species. The in vitro activity of meropenem was compared with that of iminpenem, ceftazidime, cefotaxime, ciprofloxacin, piperacillin and tobramycin against aerobic isolates, and also compared with that of imipenem, metronidazole, cefoxitin, clindamycin and piperacillin against the anaerobic isolates. Meropenem exhibited an extended spectrum of activity with low minimal inhibitory concentrations (MIC) against Gram negative aerobes, anaerobes, Gram positive anaerobes and most of the Gram positive aerobes. The MIC90 of meropenem against the Enterobacteriaceae ranged from 0.03 mg/l to 0.125 mg/l. Meropenem was very active against extended spectrum beta lactamase producing Klebsiella pneumoniae, most Acinetobacter species, Pseudomonas aeruginosa, Clostridium difficile (MIC90 of 1.0 mg/l), Clostridium perfringens and other Clostridium species. Even though imipenem exhibited better activity against the coagulase negative staphylococci, meropenem still had MIC's which were less than the break point (8.0 mg/l). The stability of meropenem in agar was determined indirectly by plotting the geometric mean MIC of control strains over a period of two weeks. Mean MIC of six control strains for meropenem was 0.05 mg/l and remained constant over 10 days, whereas the mean MIC of imipenem rose to 0.24 mg/l after two days and to 3.4 mg/l after 10 days. Meropenem was therefore far more stable in agar than imipenem. This has implications for laboratories using agar dilution as it requires less frequent plate preparation and decreased labour costs.

Agar↗
PubMed1993

Detection of Clostridium difficile enterotoxin gene in clinical specimens by the polymerase chain reaction.

A rapid assay was developed for detection of the Clostridium difficile enterotoxin gene in stool specimens by means of the polymerase chain reaction (PCR). The PCR primers amplified a 63-bp repetitive sequence of the enterotoxin gene, thereby generating a distinctive ladder pattern of DNA bands following electrophoresis. Crude DNA extracts from stools containing C. difficile produced one (63-bp) or more bands of the characteristic ladder. Of 172 stool specimens from 58 patients, 37 gave positive results by culture (15 specimens) or cytotoxin assay (36 specimens). When 36 available "positive" specimens were tested by the PCR assay, 34 (94%) gave positive results--24 by direct testing, and 10 after extraction of DNA by the Qiagen procedure. Insufficient material of the remaining two specimens was available for DNA extraction. Of 21 stools "negative" for C. difficile by culture or cytotoxin assay, one gave a positive result by PCR and seven produced atypical bands. The rapid PCR detection technique for C. difficile was more sensitive than standard culture, and of a sensitivity similar to cytotoxin testing. The method has the potential for adoption in routine laboratory practice.

Bacterial Toxins↗
PubMed1991

A case of Vibrio vulnificus septicaemia acquired in Victoria.

The clinical features and laboratory findings of a case of Vibrio vulnificus septicaemia are reported. The illness occurred in a previously well 68-year-old man who was accidentally spiked in the buttock by the dorsal spine of a flathead caught in Tamboon Inlet, near Mallacoota, Victoria. The clinical picture of an acute septicaemic illness with shock, associated with metastatic cellulitic lesions on the lower limbs progressing to bulla formation, skin necrosis, necrotising fasciitis and myositis, is characteristic of V. vulnificus septicaemia. It would appear that tetracyclines are the drugs of choice. Surgical debridement may be necessary. Clinical recognition of this rare but characteristic illness will facilitate early effective chemotherapy. To our knowledge this is the southern-most case reported in Australia.

Acute Disease↗
PubMed1991

Classification of medically important clostridia using restriction endonuclease site differences of PCR-amplified 16S rDNA.

Restriction maps were constructed of enzymically amplified 16S rRNA genes (rDNA) isolated from eight Clostridium species. Using maximum parsimony, a dendrogram was constructed from these and published 16S rRNA sequence data. Two distinct clusters were identified: cluster I contained C. difficile, C. sordelli, and C. bifermentans, and showed 30 of 35 restriction sites in common; cluster II contained C. tetani, C. perfringens C. sporogenes and C. botulinum C and G, and showed 20 of 35 restriction sites in common. Further analysis of cluster I organisms revealed that of five HpaII fragments, two were found in equal amounts in all organisms, one was found in varying amounts in all organisms, and two were found, in varying amounts, only in C. sordelli and C. bifermentans. C. sordelli-specific and C. bifermentans-specific HpaII fragments were demonstrated by Southern hybridization of rDNA. One HpaII site within the rDNA was present on most alleles in C. bifermentans, present on a minority of alleles in C. sordelli and absent in C. difficile. This suggested that there were two 16S rRNA alleles with different sequences present within each of the genomes of C. bifermentans and C. sordelli.

Alleles↗
PubMed1987

Quantitative cell-adhesion assay for Clostridium difficile cytotoxin.

A quantitative assay for Clostridium difficile cytotoxin has been developed, based on the observation that suspended fibroblasts exposed to cytotoxin fail to adhere to plastic. A dye-binding technique was used to quantitate adherent cells, in order to obviate microscopy. Adherent BHK cells were fixed with glutaraldehyde and cell protein was stained with Coomassie blue R-250. Cell-bound dye was eluted and estimated spectrophotometrically. The amount of eluted dye was proportional to the number of adherent cells and cell staining was time dependent. Cytotoxin was purified by gel-permeation and ion-exchange chromatography and migrated as a single band on SDS-PAGE. After exposure of suspended BHK cells to purified cytotoxin, their adhesion to plastic was inhibited in a manner which depended on concentration of cytotoxin and on time and temperature of exposure. This study provides the basis for a C. difficile cytotoxin assay that is quantitative, rapid and reproducible and may have wider applicability in the study of other toxins or agents that inhibit cell adhesion.

Animals↗
PubMed1985

Rapid identification of mycobacteria using gas liquid chromatography.

Methyl esters of fatty acids derived from 110 strains of previously identified mycobacteria representing 17 species and a group of unidentified rapid growers, were examined by gas-liquid-chromatography (GLC). Ten species had specific GLC profiles, which enabled accurate identification; but in 2 groups of species strains shared common profiles. M. bovis, and M. xenopi usually had specific profiles but one strain of each could not be distinguished from M. tuberculosis. The group comprising M. terrae, M. fortuitum, M. chelonei, M. flavescens and rapid growers were generally not well separated by GLC; however, 6 of 12 M. terrae strains, 2 of 3 M. flavescens, and all 5 M. fortuitum strains had specific profiles. Other strains of this group had only common peaks and by GLC were indistinguishable from each other. Using a table of specific and characteristic peaks, 34 of 54 (63%) recent isolates were correctly identified, and 18 (33%) were correctly allocated to groups sharing similar GLC profiles: only 2 isolates were wrongly identified. At present, GLC analysis provides easy and rapid identification of a majority of mycobacteria but cannot replace fully biochemical tests in the identification of medical mycobacteria.

Cell Wall↗