J.W. Pearman

Dissemination of New Methicillin-Resistant Staphylococcus aureus Clones in the Community

ABSTRACT Multiple methicillin-resistant Staphylococcus aureus (MRSA) clones carrying type IV staphylococcal cassette chromosome mec were identified in the community-acquired MRSA strains of both the United States and Australia. They multiplied much faster than health-care-associated MRSA and were resistant to fewer non-beta-lactam antibiotics. They seem to have been derived from more diverse S. aureus populations than health-care-associated MRSA strains.

Genetic analysis of community isolates of methicillin-resistant Staphylococcus aureus in Western Australia☆

Methicillin-resistant Staphylococcus aureus (MRSA) obtained from patients who had not been hospitalized outside Western Australia (WA) were studied for antimicrobial resistance and plasmid content and by pulsed-field gel electrophoresis. They were found to be of several types, none of which appeared to be related to MRSA which have been previously studied. It appears that new MRSA strains have emerged in communities in the far north of WA and are being isolated at an increasing frequency in Perth hospitals 2000 km south.

Antimicrobial resistance in Staphylococcus aureus in Australian teaching hospitals, 1989-1999.

An annual survey of antimicrobial resistance in clinical isolates of Staphylococcus aureus was conducted in 21 Australian teaching hospital microbiology laboratories in eight major cities from 1989 to 1999. A total of 19,000 isolates were tested for susceptibility to 18 antimicrobials, with 3795 being methicillin-resistant (MRSA). Resistance to ciprofloxacin in MRSA increased from 4.9% to 75.9%. The proportion of MRSA resistant to erythromycin decreased significantly (99.0%-88.9%), as did that to trimethoprim (98.4%-82.4%) and to tetracycline (96.5%-80.1%). The proportion of MRSA isolated increased in Sydney, Melbourne, Canberra, Adelaide, Perth, and Darwin, but not in Brisbane. The proportion in Hobart peaked in 1994. MRSA in Perth were predominantly non-multiresistant (nmMRSA) throughout the survey (i.e., resistant to less than three of eight indicator antibiotics) due mainly to local strains that originated in the community. The proportion of nmMRSA increased to modest levels in the other cities. In eastern cities, this was due to the appearance of strains closely related to nmMRSA seen in other countries of the southwestern Pacific.

Emergence of high-level mupirocin resistance in methicillin-resistant Staphylococcus aureus in Western Australia

Six mupirocin-resistant Staphylococcus aureus were isolated from patients living in the northern part of Western Australia (WA). They were all resistant to methicillin, tetracycline, trimethoprim and cadmium and harboured similar 41.4 kb plasmids. Transfer and curing experiments with one of the isolates, WBG7569, demonstrated that the 41.4 kb plasmid encoded resistance to mupirocin, tetracycline, trimethoprim and cadmium. The isolates were compared by pulsed-field gel electrophoresis with methicillin-resistant S. aureus (MRSA) previously isolated from the Kimberley region in the northern-most part of WA (WA MRSA). The mupirocin-resistant isolates were found to be closely related to WA MRSA suggesting that they were WA MRSA which had acquired a new multiple-resistance plasmid encoding high-level mupirocin resistance.

Methicillin-resistant Staphylococcus aureus, Western Australia

Endemic MRSA persists in Western Australia despite control measures.

Population dynamics of methicillin-susceptible and -resistant Staphylococcus aureus in remote communities

Objectives Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) was first reported in remote regions of Western Australia (WA) in 1992 and is now the predominant MRSA isolated in the State. To gain insights into the emergence of CA-MRSA, 2146 people living in 11 remote WA communities were screened for colonization with S. aureus. Methods Antibiogram analysis, contour-clamped homogeneous electric field electrophoresis, multilocus sequence typing, Panton–Valentine leucocidin determinant detection and accessory genetic regulator typing were performed to characterize the isolates. MRSA was further characterized by staphylococcal cassette chromosome mec typing. Results The S. aureus population consisted of 13 clonal complexes and two Singleton lineages together with 56 sporadic isolates. Five lineages contained MRSA; however, these were not the predominant methicillin-susceptible S. aureus (MSSA) lineages. There was greater diversity amongst the MSSA while the MRSA appeared to have emerged clonally following acquisition of the staphylococcal cassette chromosome mec. Three MRSA lineages were considered to have been endemic in the communities and have subsequently become predominant lineages of CA-MRSA in the wider WA community. People colonized with MSSA tended to harbour clones of a different genetic lineage at each anatomical site while people colonized with MRSA tended to harbour clones of the same lineage at each site. Overall, the isolates were resistant to few antimicrobials. Conclusions Although the evidence suggests that in WA CA-MRSA strains arose in remote communities and have now disseminated into the wider community, there is no evidence that they arose from the predominant MSSA clones in these communities.

Proteome Analysis of Highly Immunoreactive Proteins of Helicobacter pylori

Background. Identification of the immunoreactive proteins of Helicobacter pylori is important for the development of both diagnostic tests and vaccines relating to the organism. Our aim was to determine whether there are significant differences between human IgG and IgA reactivities to individual H. pylori proteins, and whether patterns of immunoreactivity are sustained across different strains of H. pylori.

Diagnosis of Chlamydia trachomatis and Neisseria gonorrhoeae. Genitourinary infections in males by the Amplicor PCR assay of urine.

The Amplicor CT/NG polymerase chain reaction (PCR) test on urine specimens from males was prospectively evaluated against established specimens and laboratory methods for diagnosing Chlamydia trachomatis and Neisseria gonorrhoeae genitourinary infections, in patients from a remote region of Western Australia. Seventy-three males who were tested for both C. trachomatis and N. gonorrhoeae by both conventional methodology and Amplicor PCR on urine were enrolled in the study. Established testing comprised enzyme immunoassay/immunofluorescence antigen testing (EIA/IF) for C. trachomatis and microscopy and/or culture for N. gonorrhoeae on urethral swabs. Positive test results were confirmed using a set of criteria that included supplemental PCR testing and clinical history. Overall, 13.7% of patients were resolved as positive for C. trachomatis and 52.1% as positive for N. gonorrhoeae. The sensitivity and specificity of the Amplicor CT/NG PCR on male urine specimens for C. trachomatis were 80.0% (8/10) and 95.2% (60/63), compared with 60.0% (6/10) and 100.0% (63/63) for EIA/IF on urethral swabs. For N. gonorrhoeae, the sensitivity and specificity of the Amplicor CT/NG PCR on male urine specimens were both 100% (38/38 and 35/35, respectively) compared with 86.8% (33/38) and 100% (35/35) for microscopy and/or culture on urethral swabs. The results of this study indicate that the Amplicor CT/NG multiplex PCR test for C. trachomatis and N. gonorrhoeae performed on urine in males provides a highly sensitive, specific, and robust method for the diagnosis of both C. trachomatis and N. gonorrhoeae, for the early detection of both symptomatic and asymptomatic infected individuals.

A review of the Royal Perth Hospital Bali experience: an infection control perspective

Abstract Thirty five patients were transferred to Royal Perth Hospital (RPH) after the Bali bombings. The patients had severe burn injuries and were considered to be at high-risk of both the carriage and acquisition of multi-resistant organisms (MROs). Whilst seeking to protect the Bali patients with a comprehensive infection control response, we also sought to protect other high-risk patients from nosocomial acquisition of MROs. MROs were detected from 25 (82%) of the 29 Bali patients admitted to RPH. Bali patients were colonised, or infected, with one or more of the following MROs: multi-resistant Acinetobacter baumannii (MRAB) (19 patients), extended-spectrum ß-lactamase (ESBL) producing Gram-negative bacteria (15 patients), vancomycin-resistant enterococci (VRE) (nine patients), multi-resistant Pseudomonas aeruginosa (MRPA) (six patients), multi-resistant Chryseobacterium sp. (four patients), and methicillin-resistant Staphylococcus aureus (MRSA) (three patients). Five Bali patients developed a total of eight bacteraemic episodes, with MRPA sepsis contributing to death in two patients. Since the Bali bombings horizontal transmission of Bali MROs has occurred in 41 non-Bali patients in RPH. MRPA has had the greatest clinical impact. Eight non-Bali patients developed a total of 11 bacteraemic episodes, with MRPA sepsis contributing to death in four patients. However, apart from MRPA, we have now controlled transmission of the other MROs in RPH. The emergency response to the Bali disaster required strong leadership, good communication and multi-disciplinary teamwork. The infection control strategy contributed to good outcomes for most Bali bombing patients. However, many patients within the Bali cohort were heavily colonised with MROs, and some developed invasive infection. Subsequent nosocomial transmission of these MROs to non-Bali patients has been a legacy of the Bali tragedy.

Genetic analysis of methicillin-resistant Staphylococcus aureus from a Western Australian hospital

The isolates from an outbreak of methicillin-resistant Staphylococcus aureus (MRSA) at Royal Perth Hospital (RPH) during a 3 month period in 1982 have been compared genetically with MRSAs isolated at the same hospital during 1969-1973. The 1982 isolates are genetically similar to isolates from eastern Australia and appear to have been introduced by a patient transferred from a hospital in another Australian state. Methicillin-resistant Staph. aureus isolated during 1969-1973 were genetically distinguishable from the 1982 isolates but were similar to strains reported from elsewhere in the world during these years. This indicates that the MRSA strains currently prevalent in Australia are either a new type or are related to previous MRSAs but have undergone considerable genetic change. These results give further support to suggestions that the strains of MRSA currently being isolated in Australian hospitals have special properties which have facilitated their spread.