Vancomycin-dependent enterococcus.
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Anti-Bacterial Agents↗
Biomedical subjects
A S Rossney
Publications and source records attributed to A S Rossney.
Incidence and detection of multi-drug-resistant enterococci in Dublin hospitals.
In February 1994, an outbreak of vancomycin-resistant Enterococcus faecium (VREM) occurred in the oncology unit of a Dublin hospital. Between February and July 1994, VREM was isolated from 18 patients, one staff member and 14 environmental sites within the unit. The isolates also had high-level aminoglycoside and penicillin resistance. Three pulsed-field gel electrophoresis (PFGE) types were identified, two of them from multiple patients and environmental sites. Plasmid typing allowed subdivision of PFGE types. A retrospective study of enterococci isolated from blood cultures between January 1991 and January 1994 showed that, before the outbreak, fewer than 2% of isolates were vancomycin-resistant but that the incidence of high-level gentamicin resistance had increased from 17% to 60% and ampicillin resistance from 22% to 51%. Among clinically significant non-blood-culture enterococci isolated between September and December 1993, fewer than 1% were vancomycin-resistant, 13% were ampicillin-resistant and 44% highly gentamicin-resistant. None produced beta-lactamase. High-content gentamicin disks (120 micrograms) and low-content vancomycin disks (5 micrograms) allowed simple, reliable detection of resistant enterococci. MICs of vancomycin and teicoplanin determined by agar dilution and E-test agreed well, but values tended to be slightly lower by E-test.
Ampicillin Resistance↗
Staphylococcus aureus phage typing, antimicrobial susceptibility patterns and patient data correlated using a personal computer: advantages for monitoring the epidemiology of MRSA.
Staphylococcus aureus, especially methicillin-resistant S. aureus (MRSA) is an important nosocomial pathogen. A problem encountered in the control of staphylococcal nosocomial infection is the difficulty correlating data available from antimicrobial susceptibility patterns (usually available locally) with phage typing patterns which are generally determined in a reference laboratory. Data problems are exaggerated because many patients have numerous samples taken over long periods of time. This paper describes the use of a database, 'DataEase', on a personal computer to correlate available data with patient demographics and to present the resulting information in whatever format is required. The information might be presented as the phage pattern of each isolate from patients in a particular unit per month or as a combination of the phage types and antimicrobial susceptibility patterns of isolates from a particular unit. The system can be used to generate a list of all isolates for phage typing in a format that allows the phage typing pattern to be recorded directly onto the list worksheet. In addition to providing clinically relevant reports, the system simplifies the collation of epidemiological information, data from which showed that since 1987 the incidence of MRSA has been rising in the group of hospitals served by this laboratory; MRSA of phage type 83A became a problem during 1990 and 1991; the incidence of gentamicin-sensitive phage type non-typable MRSA increased fourfold between 1988 and 1991; and the incidence of gentamicin-resistant MRSA rose sharply in 1992.
Bacteriophage Typing↗
Antibiogram-resistogram typing scheme for methicillin-resistant Staphylococcus aureus.
An antibiogram-resistogram (AR) typing scheme that can simply and rapidly differentiate methicillin-resistant Staphylococcus aureus (MRSA) isolates has been devised. Susceptibility to antibiotics and chemicals was determined by disk diffusion testing. Three disk diffusion methods and three control S. aureus strains were evaluated. A modified Stokes' technique in which S. aureus ATCC 25923 replaced S. aureus NCTC 6571 as the control organism was chosen. Susceptibility patterns against 18 antibiotics and four chemicals were used to determine AR types. AR subtypes were determined with reference to knowledge of the local MRSA population so that plasmid loss would not result in misclassification. AR typing was compared with phage typing and plasmid profiling and found to be more discriminatory than either of these typing methods. Representative isolates of the most frequently occurring AR patterns were further characterised by investigating enterotoxin production, MICs of gentamicin and amikacin, and restriction endonuclease analysis of plasma DNA, to determine whether apparently different strains could have the same AR pattern and to devise confirmatory tests for any such similar patterns. One pattern was shared by two strains but isolates could be differentiated by susceptibility to minocycline. This typing scheme can be used in the diagnostic laboratory and results may be obtained within 24 h.
Anti-Bacterial Agents↗
Evaluation of an antibiogram-resistogram typing scheme for methicillin-resistant Staphylococcus aureus.
Between Dec. 1992 and Aug. 1993, the MRSA population in the Federated Dublin Voluntary Hospitals and St James's Hospital group was studied with an antibiogram-resistogram (AR) typing scheme in which AR patterns were determined by testing susceptibility to 22 antibiotics and chemicals by a modified Stokes' disk diffusion technique. The typing scheme divided this MRSA population into 31 AR types but 90% of isolates belonged to seven types. Isolates belonging to the most frequently occurring types (AR types 13 and 14) differed only in their reaction to lincomycin (or clindamycin) and could not be distinguished by phage typing, plasmid profiling or restriction endonuclease analysis. The AR typing scheme showed that the incidence of different AR types varied in different hospitals and changed during the study period. This typing method differentiated a strain of MRSA responsible for a nosocomial outbreak in an intensive care unit from other MRSA isolated in the unit, and has distinguished imported strains from local ones. In one hospital, AR typing showed that, although a major outbreak occurred with one AR type, there was also a series of smaller outbreaks with other AR types. The technique can be performed in the diagnostic laboratory and results were available within 24 h.
Anti-Bacterial Agents↗
Coagulase testing compared with commercial kits for routinely identifying Staphylococcus aureus.
Five commercial Staphylococcus aureus identification kits--Staphaurex (Wellcome), Staphylase (Oxoid), Staphyslide (bioMèrieux), Biostaph (Medlabs) and Bacto Latex (Difco)--were evaluated for the routine identification of S aureus from primary plates in the routine microbiology laboratory. Comparison was made with two methods of tube coagulase testing and five slide methods for detecting clumping factor (slide coagulase testing). Performances were assessed for two groups of organisms, staphylococcal species alone and a combined staphylococcal and non-staphylococcal species group. The effects of growth on selective media and storage of isolates at room temperature and 4 degrees C were investigated. Selective media cannot be recommended, nor can storage of isolates before testing. Ranked according to efficiency value with the combined staphylococcal and non-staphylococcal species group, the kits and coagulase methods performed as follows (the figures in parentheses are the efficiency values for the staphylococcal group alone): tube coagulase reference method 100% (100%), tube coagulase SJH method 99% (99%), Staphaurex 94% (97%), Staphylase 93% (96%), slide coagulase method No 4 93% (94%), slide coagulase method No 5 93% (93%), Bacto Latex 92% (95%), Staphyslide 92% (95%), and Biostaph 87% (91%). It is concluded that a commercial S aureus identification kit should not replace tube coagulase testing for the routine identification of the organism from primary plates and that, even the kits with the best performances, have little advantage over a good slide coagulase test method.
Bacteriological Techniques↗