What is antimicrobial resistance?
Antimicrobial resistance is resistance of a microorganism to an antimicrobial drug that was originally effective for treatment of infections caused by it. Resistant microorganisms (including bacteria, fungi, viruses and parasites) are able to withstand attack by antimicrobial drugs, such as antibacterial drugs (e.g. antibiotics), antifungals, antivirals, and antimalarials, so that standard treatments become ineffective and infections persist, increasing the risk of spread to others.
During the past four decades, a type of bacteria has evolved from a controllable nuisance into a serious public health concern. This bacterium is known as methicillin-resistant Staphylococcus aureus, or MRSA. About one-third of people in the world have S. aureus bacteria on their bodies at any given time, primarily in the nose and on the skin. The bacteria can be present without causing an active infection. Of the people with S. aureus present, about 1 percent has MRSA, according to the Centers for Disease Control and Prevention (CDC).
MRSA can be categorized according to where the infection was acquired: hospital-acquired MRSA (HA-MRSA) or community-associated MRSA (CA-MRSA).
Hospital-acquired MRSA (HA-MRSA)
HA-MRSA is acquired in the hospital setting and is one of many hospital-acquired infections exhibiting increased antimicrobial resistance. HA-MRSA has increased during the past decade due to a number of factors including an increased number of immunocompromised and elderly patients; an increase in the number of invasive procedures, e.g., advanced surgical operations and life support treatments; and failures in infection control measures such as hand washing prior to patient contact and removal of non-essential catheters.
Community-associated MRSA (CA-MRSA)
CA-MRSA is caused by newly emerging strains unlike those responsible for HA-MRSA and can cause infections in otherwise healthy persons with no links to healthcare systems. CA-MRSA infections typically occur as skin or soft tissue infections, but can develop into more invasive, life-threatening infections. CA-MRSA is occurring with increasing frequency in the United States and around the world and tends to occur in conditions where people are in close physical contact, such as athletes involved in football and wrestling, soldiers kept in close quarters, inmates, childcare workers, and residents of long-term care facilities.
MRSA has attracted the attention of the medical research community, illustrating the urgent need to develop better ways to diagnose and treat bacterial infections.
WHO’s 2014 report on global surveillance of antimicrobial resistance revealed that antibiotic resistance is no longer a prediction for the future; it is happening right now, across the world, and is putting at risk the ability to treat common infections in the community and hospitals. Without urgent, coordinated action, the world is heading towards a post-antibiotic era, in which common infections and minor injuries, which have been treatable for decades, can once again kill.
Staphylococcus aureus continues to be a dangerous pathogen for both community-acquired as well as hospital-associated infections. Methicillin resistant S. aureus (MRSA) is now endemic in India. The growing problem in the Indian scenario is that MRSA prevalence has increased from 12% in 1992 to 80.83% in 1999. The incidence of MRSA varies from 25 per cent in western part of India to 50 per cent in South India. Community acquired MRSA. has been increasingly reported from India. The prolonged hospital stay, indiscriminate use of antibiotics, lack of awareness, receipt of antibiotics before coming to the hospital etc. are predisposing factors of MRSA emergence. Hence, early detection of MRSA and effective antibiotic policy in referral hospitals are of paramount importance from the hospital epidemiological point. Therefore, the knowledge of prevalence of MRSA and their current antimicrobial profile become necessary in the selection of appropriate empirical treatment of these infections.
Among the Gram-positive pathogens, S. aureus continues to cause skin and soft tissue infections (SSTI) in the community as well as invasive infections in the hospitalized patients. In a recent Europe-wide survey, the most common organisms in SSTIs were S. aureus (71% cases) with 22.5 per cent being MRSA. The proportion of MRSA varied among countries ranging from 0.4 per cent in Sweden to 48.4 per cent in Belgium. In a study in US spanning over 10 years, there was an increase in the overall incidence of S. aureus during this period with an increase in community onset MRSA SSTI. The overall MRSA prevalence in our study was 42 per cent in 2008 and 40 per cent in 2009. The prevalence of MRSA in a study from Chennaiwas reported as 40- 50 per cent. S. aureus constituted 17 per cent of catheter related blood stream infections (CRBSIs) in that centre. A high prevalence of MRSA (35% in ward and 43% in ICU was observed from blood culture specimens in a study in Delhi.
The prevalence of MRSA varies between regions and between hospitals in the same region as seen in a study from Delhi where the MRSA prevalence in nosocomial SSTI varied from 7.5 to 41.3 per cent between three tertiary care teaching hospitals
CA-MRSA isolates are now being increasingly reported from India. D’ Souza confirmed cases of MRSA and found that 54 per cent were true CA-MRSA possessing the SCCmec IV and SCC mec V genes. These were mainly isolated from SSTIs. CA-MRSA isolates also showed variable resistance to ciprofloxacin, erythromycin, clindamycin and tetracycline.
In a study from north India, the prevalence of MRSA was 46 per cent and MRSA isolates were found to be more resistant to other antibiotics than MSSA. Significant difference was observed in case of erythromycin, ciprofloxacin, gentamicin and amikacin
Healthcare providers can treat many S. aureus skin infections by draining the abscess or boil and may not need to use antibiotics. Draining of skin boils or abscesses should only be done by a healthcare provider.
For mild to moderate skin infections, incision and drainage by a healthcare provider is the first-line treatment. Before prescribing antibiotics, your provider will consider the potential for antibiotic resistance. Thus, if MRSA is suspected, your provider will avoid treating you with beta-lactam antibiotics, a class of antibiotic observed not to be effective in killing the staph bacteria.
For severe infection, doctors will typically use Vancomycin intravenously.