Community-Associated Meticillin Resistant Staphylococcus aureus: increased burden of infections in children and young people in Queensland and Australia

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IntroductionThe Gram positive bacterium Staphylococcus aureus, is part of normal human microbiotaand colonises approximately one third of all people at any one time. However, it is also animportant cause of a variety of infections, which can range from minor to life threatening. Arelatively recent development has been the rise of antibiotic resistant clones of S. aureusin the community, in countries around the world. These are collectively known ascommunity-associated meticillin-resistant S. aureus (CA-MRSA). Within this group,particular genotypes and patterns of virulence gene expression have been associated withcharacteristic patterns of infection. There is also evidence that there have been increasesin a variety of staphylococcal infections since the advent of CA-MRSA, the rise of whichhas also led to reconsideration of appropriate antibiotic treatment options. CA-MRSA wasrecognised early (1980s to 1990s) in Australia and has become an established cause ofinfections.StudiesThe studies used Australian hospital admissions coding data for staphylococcal associatedskin infections and information on staphylococcal infection associated admissions inchildren in the state of Queensland and from a Queensland tertiary children’s hospital. Thedata was used to examine the extent, the affected patient groups and timing of the rise ofCA-MRSA in Australia. Levels of antibody to a staphylococcal toxin (Panton ValentineLeukocidin (PVL)) in human sera from persons across the age range, reports on S. aureusbloodstream infections in children from around the world and CA-MRSA causing severeeye infections and S. aureus causing skin infections at the Queensland children’s hospitalwere also studied.OutcomesKey findings of the studies presented, are that national hospital admissions forfurunculosis, a skin infection commonly caused by S. aureus (and CA-MRSA clones) morethan doubled in number per year in the period 1999 to 2014, with particular increases in children and young people. This was at the time when reports of CA-MRSA emerged andbegan to increase in Australia, particularly affecting children and younger adults.Additionally, in Queensland children, admission rates for common skin infections roseapproximately 40% over the period 2000-2011, with infections caused by antibioticresistant bacteria becoming more evident from 2005 onwards and increasing 3 to 4 fold.Data from the tertiary children’s hospital showed that antibiotic (meticillin) resistance roseto approximately one third of all S. aureus isolates causing common community infections(from 2005 onwards), with indigenous children at greater risk. A new finding in Australia, ofCA-MRSA clones causing serious eye infections was described and placed in context ofthe worldwide early reports of such infections. PVL positive S. aureus was identified ascausing skin infections in children in a small scale application of newer technology (wholegenome sequencing) which has become increasingly available for the characterisation ofbacteria.ConclusionCA-MRSA has led to significant increases in skin infections in Australia over a short periodof time, with children and young people particularly affected. Treatments for both minorand more severe infections have had to be reconsidered to take into account increasedCA-MRSA as a cause of infection. The rapidity and potential patient impact of the rise inCA-MRSA highlights the need for ongoing, timely monitoring of changes in S. aureusinfection epidemiology, which can guide appropriate treatment. New applications oftechnology such as bacterial whole genome sequencing are likely to enhance the capacityfor such studies. Identification of methods to better manage and to reduce the burden ofCA-MRSA infections remains a health priority.