This study represents the first attempt to estimate the burden of HAIs due to multidrug-resistant bacteria in Finland. The annual number of HAIs in acute care hospitals in Finland is at least 50 000. Here we show, that at approximately 2800 (6%) of them may be due to multidrug-resistant bacteria. The HAI morbidity and mortality due to multidrug-resistant bacteria is, in Finland, thus far relatively low and lower than the figures in the EU as a whole, but shows differences depending on the resistant bacterium. The methodology we used was based on the work presented by the ECDC/EMEA and might be applied also by other countries in their burden assessments.
The results we present here are a rough estimate. True figures of the burden of all HAIs due to all resistant microbes cannot directly be achieved through any national surveillance methods generally used. This data cannot easily be collected at a hospital level either: e.g. prevalence surveys are vulnerable for chance, collection of full cover resistance data is laborious in prevalence survey, and often only half of HAIs are microbiologically confirmed. Therefore, an estimate of the burden is practically the best we can achieve to date. In the future, e.g. enhanced on line HAI reporting e.g. by using compulsory computerized reporting of antibiotic prescribing indications (HAI, community-acquired infection or prophylaxis) and automated combination of microbiological data of causative pathogens might improve the data coverage. To get the most applicable data now, we chose national data sources e.g. to cover estimates of HAIs and deaths. The national prevalence data were quite representative of Finnish acute care hospitals: over 8,000 adult inpatients in all five tertiary care hospitals, and all 15 secondary care hospitals as well as 10 (25% of all) other acute care hospitals took part in the voluntary survey. The resistance data from laboratories also well covered the whole country.
There are, however, several limitations in our estimates. Firstly, we included only seven microbes and four infection types. In the national prevalence survey data, the selected microbes, S. aureus, Enterococcus spp., E. coli, K. pneumoniae, Enterobacter spp., P. aeruginosa and Acinetobacter spp., caused 48% of all microbiologically conformed HAIs and comprised 34% of all causative microbes. Selected infection types covered 63% of all HAIs. We excluded coagulase-negative staphylococci, as in the ECDC/EMEA report, due to its various resistance patterns and relatively low virulence, and pneumococci because a majority of these infections are community-acquired. Rice et al. grouped E. faecalis and faecium, S. aureus, K. pneumoniae, A.baumannii, P. auruginosa and the Enterobacter species as the most common nosocomial pathogens that escape the effects of many antibiotics, and used the acronym ESKAPE.
Secondly, we used a prevalence survey, not incidence data, to estimate the HAI numbers and distribution. In the prevalence survey, because HAI prolongs the length of stay, severe HAIs, such as BSIs and pneumonias, are likely to be overrepresented in relation to mild infections, like UTIs. In addition, the prevalence data was from 2005, and lengths of stay may have shortened after that, also affecting the proportions of different HAI.
Thirdly, we applied the same ratio of other infections to BSIs for all microbes. In fact, Enterobacteriaceae are usually more prone to cause UTIs, and MRSA causes SSI. In addition, the NIDR surveillance data included both primary and secondary BSIs, but the prevalence survey included only primary BSI, which can affect the estimated distribution of infection types, leading to an overestimation of the number other infections by approximately 20%.
Fourthly, infections caused by ESBL producing gram-negatives, especially E. coli UTIs, can also be community-acquired, although severe and complicated infections, such as bacteremias, may more likely be healthcare-associated. In reports from different hospital settings from the years 1999–2007, the proportion of community-associated BSIs (i.e. in patients with no previous hospitalizations or healthcare-associated risk factors) among all BSIs due to ESBL producing E. coli has been low but variable: 1.6% in Italy, 3% in Finland, 19% in Spain but reached 42% in Canada[9–12]. This tendency of having the most bacteremic complications during hospital care also applies to MRSA, although community-acquired skin and soft tissue infections are common. Infections due to other multidrug-resistant microbes in our study can mainly be considered healthcare-associated. We estimate that including all BSIs due to multidrug-resistant bacteria as HAIs leads to an overestimation of HAIs due to these bacteria by another 10%. Finally, the average attributable mortality of 3.2% from the Finnish prevalence survey reflects HAI mortality mostly due to sensitive bacteria, which may lead to underestimation of mortality due to multidrug-resistant pathogens even as much as 50%.
Estimates of the burden of HAI due to antibiotic-resistant microbes are important for those who allocate resources or prioritize the work of an infection control team. In countries with low prevalence of antibacterial resistance, a lot of resources of infection control are often allocated to prevent the spread of resistant microbes, i.e. contact tracing, screening patients for colonisation, applying isolation precautions and occasionally also on decolonization. The emergence of carbapenemase-producing Enterobacteriaceae is an example of the importance of timely identifying risk groups for screening and action. However, all infection control resources should not be focused on one microbe or resistance pattern only, such as MRSA or ESBL.
Especially, if the prevalence of antibacterial resistance is high, these narrow spectrum interventions are insufficient to prevent clinical complications. Infection control interventions including evidence-based guidelines, increasingly implemented as “care bundles” and “check lists”, meticulous hand hygiene in all patient care, prudent use of antimicrobials are needed to reduce HAIs in general, along with those caused by multidrug-resistant bacteria. This approach has a greater impact on mortality, morbidity and costs than does screening alone[14, 15].
As most HAIs are due to endogenous bacteria, and because e.g. in Finland, up to 94% of HAIs still stem from non-multidrug-resistant bacteria, we should not forget infection-type specific prevention when allocating resources in low prevalance countries either. This is especially important considering, for example ESBL producing bacteria, which are increasingly prevalent in the community and cause preventable catheter-associated bacteremic UTIs in hospital settings.