Fighting MRSA in hospitals: time to restrict the broad use of specific antimicrobial classes?

["Look to Norway"--but for how long?]

Internationally, Norway receives positive attention mainly in the context of Winter Olympics or peace initiatives. However, an Associated Press article recently suggested that the Norwegian health care system had "found the Solution to Killer Superbug". Furthermore, Norway was proclaimed "The Most Infection Free Country in the World". What my be the reality behind such headlines, and how shall we as a nation maintain a favourable situation? Physicians in Scandinavian countries and the Netherlands have a long tradition for modest prescription of antibiotics, and are trained to use agents with a narrow antimicrobial spectre whenever possible. This is probably the main reason why these countries have had less antibiotic resistance than others. The number of antibiotics marketed in a country correlates positively with total drug consumption. Until 1992, Norwegian authorities could reject marketing of new compounds if national experts found no medical need for them. The foresight of senior colleagues has led to the number of marketed antibiotics in Norway, even today, being 10-fold lower than in some other European countries. The national surveillance programme, NORM, reports antimicrobial resistance in human pathogens on an annual basis. For example, national levels of MRSA and ESBL-producing Enterobacteriaceae are still very low whereas ampicillin and ciprofloxacin resistance in E coli and high- level gentamicin resistance in enterococci cause some concern. Norway has well-established epidemiological surveillance systems in the fields of microbiology and infectious diseases. Nevertheless, more knowledge is needed on how antibiotics are used in hospitals. Two national strategic plans (since 2003) have emphasized the explicit importance of antibiotic surveillance to counteract future antibiotic resistance problems. To fulfil national ambitions, there is an urgent need for economic grants to this field; the human resources are there and as eager to start as Olympic performers!

Methicillin-resistant Staphylococcus aureus (MRSA) in food production animals

Until recently, reports on methicillin-resistant Staphylococcus aureus (MRSA) in food production animals were mainly limited to occasional detections in dairy cattle mastitis. However, since 2005 a MRSA clone, CC398, has been reported colonizing pigs, veal calves and broiler chickens and infecting dairy cows. Many aspects of its prevalence in pigs remain unclear. In other livestock, colonizing capacity and reservoir status still require elucidation. MRSA CC398 has also been detected in meat, but, as for other MRSA, the risk this poses is somewhat unclear. Currently, the most worrying aspect of MRSA CC398 appears to be its capacity to spread to humans. This might complicate MRSA control measures in human healthcare, urging research into risk factors and transmission routes. Although infections with MRSA CC398 are much less reported than carriage, more investigation into its pathogenic potential is required. Moreover, the origin and evolution of this clone remain unknown.

Antimicrobial drugs and community-acquired methicillin-resistant Staphylococcus aureus, United Kingdom

We report results of a case-control study of the association between receipt of antimicrobial agents and diagnosis of community-acquired methicillin-resistant Staphylococcus aureus (MRSA) in the United Kingdom. Eligible adults, selected from the General Practice Research Database, had no previous diagnosis of MRSA, no hospitalization in the past 2 years, and > or = 2 years of follow-up recorded in the database. For 2000-2004, we identified 1,981 MRSA case-patients and 19,779 matched control-patients. The odds ratios (ORs) and 95% confidence intervals (CIs) of MRSA diagnosis for patients who were prescribed 1, 2-3, or > or = 4 antimicrobial drugs were 1.57 (CI 1.36-1.80), 2.46 (CI 2.15-2.83), and 6.24 (CI 5.43-7.17), respectively. Risk for community-acquired MRSA increased with number of antimicrobial drug prescriptions, appeared to vary according to antimicrobial drug classes prescribed the previous year, and was highest for quinolones (OR 3.37, CI 2.80-4.09) and macrolides (OR 2.50, CI 2.14-2.91).

MRSA bacteraemia

Methicillin-resistant Staphylococcus aureus (MRSA) has been pandemic for over a decade and is causing a major increase in serious staphylococcal infections. This is reflected in large increases in S. aureus bacteraemia with over 50% in many countries being caused by MRSA. Moreover, in some countries it also seems as though methicillin-susceptible S. aureus (MSSA) bacteraemia is also increasing. MRSA certainly has not replaced MSSA but is an additional burden with significantly higher mortality. Standard treatment of MRSA bacteraemia with glycopeptides is probably suboptimal in the presence of increasing resistance, MIC drift, uncertainties about laboratory susceptibility testing and fears of toxicity. New antibiotics look set to replace glycopeptides as the gold standard for treatment of MRSA bacteraemia, but whether the underlying causes of MRSA bacteraemia can be addressed successfully in order to control this pandemic disease is less certain.

Antibiotic resistance: location, location, location

Antibiotic resistance surveys are published widely, citing percentage resistance rates, sometimes for vast transcontinental regions. Such data seem straightforward, but when one drills deeper, great complexity emerges. Rates for methicillin resistance among Staphylococcus aureus from bacteraemias vary from <1% to 50% among European countries, and vary greatly among both hospitals and hospital units. Methicillin-resistant S. aureus (MRSA) resistance rates are typically higher for tertiary-care hospitals and intensive care units than in general hospitals and wards, and lowest in single specialist centres. The likelihood of resistance also varies according to patient characteristics: those patients from nursing homes and with underlying disease, recent antibiotic treatment and hospitalisation are more likely to harbour resistant pathogens. Percentage rates themselves also may be misleading; they may be high only because the denominator is small or inaccurate; i.e., resistance may be common but the pathogen rare. Measures of disease burden-cases per 1000 bed-days or per 10(5) individuals-overcome this deficiency but are harder to collect, influenced by case mix, and associated with other problems: how to count part days or infections acquired elsewhere; most important, are all cases captured? National or international resistance statistics may illustrate trends and provide benchmarks, but for patient management, good local data are essential. Which units are most affected? Are the resistant infections locally acquired or imported with transferred patients? Are the resistant isolates clonal, indicating cross-infection, or diverse, indicating repeated selection or reflecting antibiotic policy? Unless these aspects of infection are considered, interventions to reduce resistance may be misdirected.