MRSA: a growing global problem
Karl Pang takes a global look at what different countries are doing to combat this important clinical concern
Methicillin Resistant Staphylococcus aureus (MRSA) causes major morbidity and mortality. Once introduced into an institution it frequently becomes endemic, difficult to control, expensive to treat and often impossible to eradicate.
Staphylococcus aureus (S. aureus), a gram positive coccus is just one of a family of staphylococcal bacteria. 30% of healthy adults are colonized by S. aureus in their nose.
Most strains of S. aureus were sensitive to penicillin when it was introduced in the 1940s, which reduced the rate of S.aureus infection and related morbidity and mortality at the time. By 1959 about 90-95% of S.aureus strains were resistant to penicillin. (1) Methicillin and flucloxacillin were developed from penicillin to treat penicillin-resistant S. aureus. These bacteria were referred as methicillin-sensitive S.aureus (MSSA). Within a year of the introduction of methicillin, in 1961 the first Methicillin Resistant S.aureus (MRSA) was reported in England. (2) MRSA is resistant to many other antibiotics and occasionally is referred to as multiple-resistant S.aureus. The emergence of antibiotic resistance is highly related to the overuse and misuse of antibiotics, and the lack of proper infection control measures. This led to gene mutations and subsequent exchanges of genetic information between bacteria.
There is no specific ‘MRSA disease’. S.aureus infects a range of tissues and body systems causing different types of infection including wound infections, superficial ulcers, intravenous line infections, deep abscesses (lungs, kidneys, bones, liver, and spleen), lung infections, bacteraemia and septic shock.
The incidence of MRSA infections is growing worldwide. UK has the 2nd highest rate of MRSA bacteraemia in Europe, ~45%, Greece has the highest ~55% and Netherlands has the lowest ~1%. (3) (4) The prevalence of MRSA infections in Australia and the USA is similar to UK, ~25-50%. The prevalence of MRSA infection is ~10-25% in Mexico, Trinidad and India, and >50% in Malta, Hong Kong and Singapore. (5)There are ~600,000 MRSA acquisitions each year in English hospitals, leading to ~ 6000 cases of MRSA bacteraemia and several hundred deaths The proportion of MRSA bacteraemia in the UK rose from ~2% in 1992 to ~40% in 2003. (6) Being resistant to many antibiotics, MRSA infection is difficult to eradicate, making it a huge problem in hospitals.
MRSA infection among the healthy public is unusual, but it is an emerging global challenge. MRSA is introduced into the community presumably as a result of cross-infection from colonized staff, visitors and discharged patients. It is an issue that we should be aware of and prepare to manage if MRSA infection becomes endemic in the community.
MRSA infection is much more common in hospital settings (Hospital acquired infection, HAI). The bacteria are transmitted via direct or indirect contact, however, we do not know for sure how MRSA enters the hospital, colonizes staff and patients and causes disease. Patient and staff hand hygiene is the most important issue and poor hygiene could increase the risk of infection.
MRSA is a problem in hospitals because the opportunity they have to induce disease is high. First of all, most patients in the wards are ill and have a degree of immunosuppression either due to drug therapy, chemotherapy or chronic diseases, which makes them prone to infection. Patients with IV lines, catheters or other invasive devices and surgical wounds are at risk of having surface MRSA entering their bodies. Staff/patient hand washing is inadequate, wards are overcrowded, there’s a lack of isolation facilities, the environment is not cleaned sufficiently and the staff to patient ratio is low. All of these factors contribute to the high incidence of cross-infection in hospitals.
In the early 1990’s, the emergence and domination of two particular clones of MRSA coincided with increases in MRSA infection rates in the UK. Epidemic MRSA strains 15 and 16 (EMRSA) are multiple drug resistant and are more effective in colonizing and infecting its host than other strains. (7) EMRSA 15 and 16 account for 93-95% of all MRSA isolates seen in recent years. The evolution of these 2 strains makes MRSA an increasing problem especially in the UK, as these 2 strains are not commonly found elsewhere in the world.
Apart from the morbidity MRSA causes, it also puts a lot of financial pressure on the NHS in the UK, and other health services in the rest of the world. HAI results in increased hospital stay, longer treatment and management, increased infectious control demands and costs the NHS ~1 billion per annum. (8) Actions need to be taken to reduce the problems MRSA brings to the UK.
Much can be done to control MRSA. (9) and previous infectious control methods and surveillance have been shown to decrease MRSA bacteraemias by ~50% since 2003. Vancomycin and teicoplanin are glycopeptide antibiotics used to treat MRSA infections, however, vancomycin-resistant staphylococcus has recently appeared. The most cost-effective method is to prevent infection in the first place and infectious control (IC) is by far the most important. In order for success a large contribution from all members of the IC team is needed. The team consists of microbiologists, senior nurses, Director of Infection Prevention and Control (DIPC), and the IC committee.
Hand washing before and after patient contact is essential. Effective agents are alcohol, soap and water for use on the wards and iodine or chlorhexidine for surgical uses. Gloves and protective clothing (aprons, gowns, hoods and caps) could all reduce contamination and cross-infection. Visitors are also encouraged to clean hands and wear protective clothing. Cleaning the environment; wards, beds, toilet, theatre rooms and sterilizing equipment makes a huge difference in limiting MRSA infection. Accurate disposal of contaminated linen is also important. (9) (10)
Wounds, IV lines, catheters and all other invasive devices should be cleaned and checked regularly to avoid bacterial invasion. (11) Isolation of colonized/infected staff and patients is required to reduce transmission of infection to staff, patients and the community (EMRSA). Some countries, such as Denmark and The Netherlands, have succeeded in maintaining MRSA at very low levels by using control policies based on the prompt isolation of MRSA-positive patients. (12) The screening of MRSA-positive individuals is done by taking swabs from nose (carriers), wounds, skin and sputum and once identified, immediate isolation is needed. Wards should be less busy; the staff to patient ratio should be high and the distance between beds should be at least 3.6m apart in order to keep cross-infection to the minimum. All measures mentioned aim to prevent rather than treat MRSA infection. (9) (10) (11)
To eliminate the reservoir of infection; nasal carriers may be given mupirocin, and skin/hair carriers may be given chlorhexidine or hexachlorophene. This could help to eradicate MRSA colonization and therefore infection. (9)
In order to see whether our control methods are working, continued auditing and surveillance is required. Data collection is essential and regular meetings to discuss epidemiology are necessary to decide on further actions to control or maintain MRSA at low levels.
Karl Pang
4th year medical Student
Glasgow University
Scotland
karlpang@hotmail.co.uk
(1) Barber M, Rozwadowska-Dowzenko M. Infection by penicillin resistant staphylococci. Lancet 1948; ii: 641-4
(2) Jevons MP. Celbenin-resistant staphylococci. BMJ 1961; i: 124-5
(3) European Antimicrobial Resistance Surveillance System (EARSS) data. www.rivm.nl/earss
(4) Department of Health Publications. www.dh.gov.uk/publications
(5) Grundmann H, Aires-de-Sousa M, Boyce J, Tiemersma E. (2006) Emergence and resurgence of meticillin-resistant Staphylococcus aureus as a public-health threat. Lancet. 368(9538):874-85
(6) Health Protection Agency; Staphylococcus aureus bacteraemia laboratory reports and methicillin susceptibility (voluntary reporting scheme): England and Wales, 1990-2003
(7) Johnson AP, Aucken HM, Cavendish S, et al. (2001). “Dominance of EMRSA-15 and -16 among MRSA causing nosocomial bacteraemia in the UK: analysis of isolates from the European Antimicrobial Resistance Surveillance System (EARSS)“. J Antimicrob Chemother 48 (1): 143-4
(8) Gould IM. (2006) Costs of hospital-acquired methicillin-resistant Staphylococcus aureus (MRSA) and its control. Int J Antimicrob Agents. 28(5):379-84
(9) Coia JE, Duckworth GJ, Edwards DI, Farrington M, Fry C, Humphreys H, Mallaghan C, Tucker DR; Joint Working Party of the British Society of Antimicrobial Chemotherapy; Hospital Infection Society; Infection Control Nurses Association. (2006). Guidelines for the control and prevention of meticillin-resistant Staphylococcus aureus (MRSA) in healthcare facilities. J Hosp Infect. 63 Suppl 1:S1-44
(10) Gould IM. (2005) Control of methicillin-resistant Staphylococcus aureus in the UK. Eur J Clin Microbiol Infect Dis. 24(12):789-93
(11) National Institute for Clinical Excellence Prevention of health care associated infections in primary and community care. June 2003
(12) Bootsma MC, Diekmann O, Bonten MJ. (2006) Controlling methicillin-resistant Staphylococcus aureus: quantifying the effects of interventions and rapid diagnostic testing. Proc Natl Acad Sci USA 103 (14): 5620-5
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