Staphylococcus aureus

Infectious Diseases Staphylococcus aureus Staphylococcus aureus, often referred to simply as “staph,” are bacteria commonly carried on the skin or in the nose of healthy people. Staph bacteria are one of the most common causes of skin infections in the United States. Most staph infections are minor (such as pimples and boils) and can be treated without antibiotics. However, staph bacteria can also cause serious infections (such as surgical wound infections and pneumonia). In the past, most serious staph bacteria infections were treated with penicillin related antibiotics. Over the past 50 years, however treatment of these infections has become more difficult because staph bacteria have become resistant to various antibiotics, including the commonly used penicillin-related antibiotics.  The emergence of hospital-acquired infections are increasingly becoming a serious healthcare issue. Staphylococcus aureus (Staph. aureus), the most common cause of nosocomial infection, is particularly associated with significant mortality rates and healthcare costs. Methicillin resistant strains of Staph. aureus (MRSA) are increasing in prevalence, and are estimated to account for more than 50% of Staph. aureus hospital isolated strains. Vancomycin is the only available antibiotic that can consistently treat MRSA, and although Staph. aureus strains that are fully resistant to vancomycin do not currently exist, Staph. aureus strains with significantly reduced susceptibility to the usual dose are starting to emerge. If bacterial resistance to vancomycin continues to evolve, the healthcare burden of Staph. aureus is likely to grow in magnitude. MRSA occurs more commonly among persons in hospitals and healthcare facilities. MRSA infection usually develops in hospitalized patients who are elderly , very sick, have an open wound or catheter. MRSA infections acquired in hospitals and healthcare settings can be severe. In addition, certain factors can put some patients at higher risk for MRSA including prolonged hospital stay, receiving broad-spectrum antibiotics, being hospitalized in an intensive care or burn unit, spending time close to other patients with MRSA, having recent surgery, or carrying MRSA in the nose without developing illness Prevalence & Incidence The US CDC states that Staph bacteria are one of the most common causes of skin infection in the US, and are a common cause of pneumonia and bloodstream infections. According to some estimates, as many as 100,000 persons are hospitalized each year with MRSA infections, although only a small proportion of these persons have disease onset occurring in the community. Approximately 25 to 30% of the population is colonized in the nose with staph bacteria at a given time. The numbers who are colonized with MRSA at any one time is not known.   Economic Cost A number of sources (CDC, National Institute of Health, Institute of Medicine) estimate annual medical costs due to Staph. aureus in the USA to be in the region of US$5 billion. However, if other reports are to believed, costs may be even higher. A recent New York study quoted direct medical costs in the region of $34,000 per patient, with an overall cost to the city of $435 million (Rubin et al, 1999). A study in Canadian hospitals found that the total attributable cost to treat MRSA infections was CN$287,200, or CN$14,360 per patient. The cost for isolation and management of colonized patients was CN$128,095, or CN$1,363 per admission, while the costs for MRSA screening in the hospital were CN$109,813. Assuming an infection rate of 10% to 20%, the authors determined the costs associated with MRSA in Canadian hospitals to be $42 million to $59 million annually. In an attempt to curb the increase in infection the UK government released a report in late 2003 detailing those hospitals where patients were most at risk of catching MRSA. The publication estimates that infections occur in as many as 100,000 people a year. Of these, an estimated 5,000 die and the overall cost to the NHS might be £1bn a year.   Potential Total Market Size Due to the lack of availability of a Staph. aureus vaccine, and due to the range of generic antibiotic products used to treat Staph. aureus, it was considered inappropriate to base a market size estimate on sales of current products. Instead, a conservative estimate of market size has been based on the incidence of infection and the potential price that could be charged for a vaccine. The vaccine population is likely to include those at most risk of infection including: those immuno-compromised, surgical, trauma and burn patients, and patients with chronic illnesses such as diabetes, cancer, lung or kidney diseases. The potential population may encompass as many as the 2 million patients estimated by the CDC to contract a nosocomial infection in the USA. A more conservative estimate uses Staph. aureus incidence in developed nations.  Staph. aureus incidence in developed nations = 1.5 million Estimated price of Staph. aureus vaccine = US$100 Potential market size = US$150 million