CA-MRSA

Community MRSA preys on the poor and deprived

Jon Otter (@jonotter) MRSA , , , , , , ,

deprivation mrsa

As you can probably tell from the title, this post comes with a warning: it presents some rather “un-PC” data, but I’ll do my best to deliver it calmly and dispassionately! My old research team from KCL have just published a paper in PLOS Medicine on the association between social and material deprivation, and MRSA.

I’ve been interested in the dynamic between hospital-associated (HA) and community-associated (CA) MRSA for years (not least because it was the subject of my PhD thesis). I wrote a review several years ago on how community MRSA should be seen as a genotypic phenomenon with epidemiological implications. Using this framework, it is possible to get your head around CA strains of MRSA beginning to cause hospital-acquired infections. The aim of this study was to use a large collection of MRSA from across several regions of London to explore the transmission dynamics and epidemiological associations of HA and CA types of MRSA.

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Inaugural ‘Journal Roundup’ (June 2014)

Jon Otter (@jonotter) Roundup , , , , ,

JHI

I’ve been asked by the Editor of the Journal of Hospital Infection to begin writing a monthly column providing an overview of key updates in the infection prevention and control literature. I’m pleased to say that the first edition (June 2014) is now available on the Journal of Hospital Infection website, and I’m delighted that the Journal Roundup is open access.

I thought it would be useful to outline how I produced this roundup. I began by scanning the tables of contents of the following journals, pulling out articles of interest: AJIC, Ann Intern Med, BMJ, CID, ICHE, JAMA, JAMA Intern Med, JHI, JID, JIP, Lancet, Lancet ID, NEJM. This was easy for the “big five” (Lancet, BMJ, AIM, JAMA and NEJM) because only a handful of articles are directly relevant. It was more tricky for the specialist journals, since all articles are likely to be of interest. I’ve tried to avoid focusing solely on my own research interests, but these doubtless come through. One way to mitigate this in future is for others to provide a Journal Roundup now and then – or at least make some contribution. If you’re interested in this, please do let me know.

Highlights of this inaugural issue include a spike in MERS-CoV cases, coverage of the WHO report on antimicrobial resistance, more evidence that faecal microbiota transplantation works for curing recurrent CDI, the impact of nursing education on patient mortality, individualized antibiotic dosing, CA-MRSA in US Fire Stations, a successful community-based hand hygiene intervention, an outbreak of CRE in Ireland, updated SHEA guidelines for SSI and CDI, the identification of ‘optimum outlier’ (aka ‘positive deviant’) cleaners, a disturbing patient story, an update on the move towards ‘bare below the elbow’ in the US, an overview of the regulatory environment for healthcare apps, conference abstracts from APIC and ECCMID, and the use of Yelp (a customer review website) to identify cases that would otherwise have gone unreported during a foodborne outbreak.

Please feel free to share this with your colleagues, and let me know if you have any thoughts or comments.

 

What is “community-associated” MRSA?

Jon Otter (@jonotter) MRSA , , ,

Community_associated_Methicillin-resistant_Staphylococcus_aureus_b2340183

A study in this month’s ICHE highlights the problems with using epidemiological definitions to designate MRSA as “nosocomial”. The study evaluated the impact of different numerators and denominators on the rate of apparent hospital-onset MRSA across 32 hospitals in California. The time that patients were hospitalized before being considered hospital-onset varied from 48 to more than three days and denominators were also variable. The particular combination of numerator and denominator used resulted in significant differences in the proportion of MRSA cases designated hospital-onset. This has clear implications for comparing rates of hospital-attributable MRSA in the era of public reporting.

The paper raises a wider problem of how to define healthcare- and community-associated MRSA in the era of CA-MRSA strains as a cause of healthcare-associated infections. A recent review in JHI (Otter & French 2012) made the case for a genotypic definition of CA-MRSA. Epidemiological definitions were useful for differentiating CA-MRSA and HA-MRSA strain types in the past. However, although HA-MRSA strain types are rarely transmitted in the community, CA-MRSA strains have now begun to be transmitted in healthcare facilities, so epidemiological definitions are breaking down. CA-MRSA are community strains of S. aureus that have acquired mecA. They are distinct from HA-MRSA and should be defined genetically. Carriage of the Panton-Valentine leukocidin (PVL) or antimicrobial susceptibly profiles can be useful indicators of CA-MRSA but should not be used to define them. For the full assessment of their epidemiology, MRSA infections should now be characterised as (1) caused by HA- or CA-MRSA strain types; (2) acquired in community or healthcare settings; and (3) onset in the community or healthcare facility. (This review made the 10 ten list of the JHI Editors choice and is freely available online here.)

Article citations:

Datta R, Kuo King M, Kim D et al. What Is Nosocomial? Large Variation in Hospital Choice of Numerators and Denominators Affects Rates of Hospital-Onset Methicillin-Resistant Staphylococcus aureus. Infect Control Hosp Epidemiol 2012; 33: 1166-9.

Otter JA, French GL. Community-associated meticillin-resistant Staphylococcus aureus: the case for a genotypic definition. J Hosp Infect 2012; 81: 143-8.