ArtsAutosBooksBusinessEducationEntertainmentFamilyFashionFoodGamesGenderHealthHolidaysHomeHubPagesPersonal FinancePetsPoliticsReligionSportsTechnologyTravel

MRSA in the community

Updated on November 10, 2011
Methicillin resistant Staphylococcus aureus (MRSA)
Methicillin resistant Staphylococcus aureus (MRSA)

Since first reported in 1961 [1] methicillin resistant Staphylococcus aureus (MRSA) has rapidly established itself as one of the most prevalent cause of serious hospital acquired infection becoming endemic in most hospitals in the developed world [2], overtaking methicillin susceptible Staphylococcus aureus (MSSA) in many cases. Until recently MRSA was considered to be almost exclusively a nosocomial pathogen with well defined healthcare related risk factors (e.g. recent surgery, catheters or dialysis) [3]. However, since the early 1990s a growing number of cases of MRSA have been reported in the community, often amongst healthy individuals with no predisposing risk factors [4,5]. This lead to the categorisation of MRSA into community associated (CA-MRSA) and healthcare associated (HA-MRSA) based primarily on epidemiological distribution.

There are several groups considered at higher from CA-MRSA including prison inmates, athletes, children, military recruits and IV drug-users. However, these are not factors in themselves and relate to the CDC’s “5 C’s” - Crowding, skin-to-skin Contact, Compromised skin, Contaminated items and lack of Cleanliness [30].

A number of clinical factors differentiate CA-MRSA, originally an infection in the absence of HA-MRSA associated risk factors [3] sufficed. However, this has become less useful as CA-MRSA strains are increasingly found in hospitals [6,7]. Another difference is the resistance profile of CA-MRSA; most isolates are resistant to ß-lactam antibacterials but susceptible to most other classes. HA-MRSA strains are often resistant to a wider range [3].

Clinical presentations of CA-MRSA also differ with skin and soft tissue infections more common in CA-MRSA and respiratory and urinary tract infections more common in HA-MRSA [3]. There have also been a number of cases which suggest CA-MRSA may be more virulent [8] with manifestations such as necrotizing fasciitis and necrotizing pneumonia [9]. Much research has focused on identifying the virulence factors responsible for these manifestations and a host of toxins and other virulence factors less common in other MRSA strains have been identified [10]. One of these is Panton-Valentine leukocidin (PVL), a pore-forming cytotoxin capable of killing leukocytes. Commonly found in CA-MRSA but almost unheard of in HA-MRSA, PVL was a prime candidate [11]. Whilst epidemiological data suggested a strong correlation between invasive infections, animal studies have produced conflicting results [12,13,14,15]. Recent research does appear to confirm PVL has a role in pathogenesis but this is dependent on species and site [16,17].

The first S. aureus antibacterial resistance was to penicillin soon after its introduction in the 1940s. This was facilitated by the enzyme penicillinase hydrolysing penicillin’s ß-lactam ring [18]. Subsequently, the phage type 80/81 strain of S. aureus reached pandemic proportions in hospitals [19]. The 1960 release of methicillin in which the ß-lactam ring was protected halted this pandemic [1] but success was short-lived. Given the short generation times of bacteria, exposure to antibacterials provides an environment where rapid selection for resistance takes place. Additionally, bacteria possess the ability to (horizontally) transfer genetic material between each other [20] and it is thought that S. aureus acquired methicillin resistance this way from another Staphylococcus species [21].

Unlike penicillin resistance these new strains had a broad spectrum resistance to all ß-lactams as instead of targeting the drug the bacteria’s surface proteins are modified preventing binding [22]. Later molecular studies DNA sequencing MRSA revealed that the gene encoding methicillin resistance (mecA) was carried on highly mobile genetic elements, the staphylococcal chromosomal cassette (SSCmec). SSCmec is a short sequence containing its own recombinases facilitating insertion into the host genome [23]. The first MRSA carried SSCmec I and clones circulated US and European hospitals up to the late 1970s before disappearing [24].

Over the following decade the new SSCmec II and SSCmec III allotypes appeared with MRSA becoming endemic in hospitals throughout the industrialised world. Analysis of the different SSCmec types revealed size differed (34-67Kb), and although all carried the mecA gene, II and III carried additional resistance [28]. This growing resistance has resulted in the reintroduction of vancomycin , the ‘antibacterial of last resort’, however vancomycin resistance has been reported since the late 1990s [25].

CA-MRSA was first reported in remote Western Australia in patients with no recent hospital contact [26]. Between 1997-1999 in Mid-western USA four, otherwise healthy children died from sepsis and necrotizing pneumonia caused by a highly virulent strain [8]. A retrospective study into MRSA cases with no predisposing factors or healthcare contact found evidence of community associated infections dating back to the early 1990s in Chicago [5].

One question to be resolved was the origin of CA-MRSA. In 2002 Ma et al [27] studied a number of CA-MRSA isolates providing evidence that the differences with HA-MRSA were not only clinical but molecular. They identified the novel SCCmec IV element which was much smaller than other SCCmec elements (21-24Kb), and consistent with clinical observations, only ß-lactam resistant. A subsequent study found this was consistent in a sample of 12 diverse CA-MRSA strains tested [29] and suggested that not only where CA-MRSA strains different to HA-MRSA strains, but different to each other, i.e. not evolved from a common ancestor. This in turn provides evidence that the small SCCmec IV has been passed between MSSA strains in a ‘promiscuous’ manner due to increased mobility.

References

  1. Jevons MP. ‘Celbenin’-resistant staphylococci. BMJ 1961; 1: 124–25.
  2. Male, D., Gillman, M. Pathogens and people, 2008, Open University Worldwide, Milton Keynes
  3. Naimi TS, LeDell KH, Como-Sabetti K, et al. Comparison of community and health care-associated methicillin resistant Staphylococcus aureus infection. JAMA 2003; 290: 2976-84.
  4. Klevens RM, Morrison MA, Nadle J, et al. Invasive methicillin resistant Staphylococcus aureus infections in the United States. JAMA 2007; 298: 1763–71.
  5. Herold BC, Immergluck LC, Maranan MC, et al. Community-acquired methicillin-resistant Staphylococcus aureus in children with no identified predisposing risk. JAMA 1998; 279: 593-8
  6. Saiman L, O’Keefe M, Graham PL, et al. Hospital transmission of community-acquired methicillin-resistant Staphylococcus aureus among postpartum women. Clin Infect Dis 2003; 37: 1313-9
  7. De A Trindade P, Pacheco RL, Costa SF, et al. Prevalence of SCCmec Type IV in nosocomial bloodstream isolates of methicillin-resistant Staphylococcus aureus. J Clin Microbiol 2005; 43: 3435-7
  8. Centers for Disease Control and Prevention. Four pediatric deaths from community-acquired methicillin-resistant Staphylococcus aureus—Minnesota and North Dakota, 1997–1999. JAMA 1999; 282: 1123–25.
  9. Gonzalez BE, Hulten KG, Dishop MK, et al. Pulmonary manifestations in children with invasive community-acquired Staphylococcus aureus infection. Clin Infect Dis 2005; 41: 583–90.
  10. Baba T, Takeuchi F, Kuroda M, et al. Genome and virulence determinants of high virulence community-acquired MRSA. Lancet 2002; 359: 1819–27
  11. Lina, G. et al. Involvement of Panton-Valentine leukocidin-producing Staphylococcus aureus in primary skin infections and pneumonia. Clin. Infect. Dis. 1999; 29, 1128–1132.
  12. Labandeira-Rey M, Couzon F, Boisset S, et al. Staphylococcus aureus Panton-Valentine leukocidin causes necrotizing pneumonia. Science 2007; 315: 1130–1133.
  13. Bubeck Wardenburg J, Palazzolo-Ballance AM, Otto M, Schneewind O, DeLeo FR. Panton-Valentine leukocidin is not a virulence determinant in murine models of community-associated methicillin-resistant Staphylococcus aureus disease. J Infect Dis 2008; 198: 1166–70.
  14. Diep, B. A. et al. Contribution of Panton-Valentine leukocidin in community-associated methicillinresistant Staphylococcus aureus pathogenesis. PLoS 2008; ONE 3, e3198.
  15. Brown EL, Dumitrescu O, Thomas D, et al. The Panton-Valentine leukocidin vaccine protects mice against lung and skin infections caused by Staphylococcus aureus USA300. Clin Microbiol Infect 2009; 15: 156–64
  16. Cremieux AC, Dumitrescu O, Lina G, et al. Panton-Valentine leukocidin enhances the severity of community-associated methicillin-resistant Staphylococcus aureus rabbit osteomyelitis. PLoS One 2009; 4: e7204.
  17. Löffler B et al. Staphylococcus aureus panton-valentine leukocidin is a very potent cytotoxic factor for human neutrophils. PLoS Pathog. 2010 Jan 8;6(1):e1000715.
  18. Kirby WM. Extraction of a highly potent penicillin inactivator from penicillin resistant staphylococci. Science 1944; 99: 452–53.
  19. McKenna, Maryn. Superbug : the fatal menace of MRSA. 2010. Free Press, New York
  20. Microbes, S204. 2007. Open University Worldwide, Milton Keynes
  21. Wu, S., Piscitelli, C., de Lencastre, H. & Tomasz, A. Tracking the evolutionary origin of the methicillin resistance gene: cloning and sequencing of a homologue of mecA from a methicillin susceptible strain of Staphylococcus sciuri. Microb. Drug Resist. 1996; 2, 435–441.
  22. Beck 1986
  23. Katayama Y, Ito T, Hiramatsu K. A new class of genetic element, staphylococcus cassette chromosome mec, encodes methicillin resistance in Staphylococcus aureus. Antimicrob Agents Chemother 2000; 44: 1549-55
  24. Crisostomo, M. I. et al. The evolution of methicillin resistance in Staphylococcus aureus: similarity of genetic backgrounds in historically early methicillinsusceptible and -resistant isolates and contemporary epidemic clones. Proc. Natl Acad. Sci. USA 2001; 98: 9865–9870.
  25. Weigel, L. M. et al. Genetic analysis of a high-level vancomycin-resistant isolate of Staphylococcus aureus. Science 2003; 302: 1569–1571.
  26. DeLeo F.R., Otto M., Kreiswirth B.N., Chambers H.F. Community-associated meticillin-resistant Staphylococcus aureus. Lancet 2010; 375: 1557–68.
  27. Ma XX, Ito T, Tiensasitorn C, et al. Novel type of staphylococcal chromosome mec identified in communityacquired methicillin-resistant Staphylococcus aureus strains. Antimicrob Agents Chemother 2002; 46: 1147-52.
  28. Ito, T. et al. Structural comparison of three types of staphylococcal cassette chromosome mec integrated in the chromosome in methicillin-resistant Staphylococcus aureus. Antimicrob. Agents Chemother 2001: 45: 1323–1336.
  29. Daum RS, Ito T, Hiramatsu K, et al. A novel methicillinresistance cassette in community-acquired methicillinresistant Staphylococcus aureus isolates of diverse genetic backgrounds. J Infect Dis 2002; 186: 1344-7.
  30. MRSA and the workplace. Centers for Disease Control and Prevention http://www.cdc.gov/niosh/topics/mrsa/ accessed 19/05/2011.

This article was a summary of a recent dissertation I wrote on CA-MRSA as part of a Life Sciences degree I am doing with the Open University. It's pretty up to date and hopefully reflects the potential severity that MRSA in the community could present and the dangers of antibiotic resistance in general

Comments

    0 of 8192 characters used
    Post Comment

    No comments yet.

    working

    This website uses cookies

    As a user in the EEA, your approval is needed on a few things. To provide a better website experience, hubpages.com uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

    For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at: https://hubpages.com/privacy-policy#gdpr

    Show Details
    Necessary
    HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
    LoginThis is necessary to sign in to the HubPages Service.
    Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
    AkismetThis is used to detect comment spam. (Privacy Policy)
    HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
    HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
    Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
    CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
    Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the googleapis.com or gstatic.com domains, for performance and efficiency reasons. (Privacy Policy)
    Features
    Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
    Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
    Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
    Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
    Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
    VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
    PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
    Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
    MavenThis supports the Maven widget and search functionality. (Privacy Policy)
    Marketing
    Google AdSenseThis is an ad network. (Privacy Policy)
    Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
    Index ExchangeThis is an ad network. (Privacy Policy)
    SovrnThis is an ad network. (Privacy Policy)
    Facebook AdsThis is an ad network. (Privacy Policy)
    Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
    AppNexusThis is an ad network. (Privacy Policy)
    OpenxThis is an ad network. (Privacy Policy)
    Rubicon ProjectThis is an ad network. (Privacy Policy)
    TripleLiftThis is an ad network. (Privacy Policy)
    Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
    Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
    Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
    Statistics
    Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
    ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
    Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)