Resistance in bacteria of human clinical isolates

Since 2008, different trends have been observed in Gram-positive and Gram-negative bacteria. Methicillin-resistant Staphylococcus aureus MRSA) rates have continued to decrease significantly in invasive isolates, mainly in the western part of Switzerland. This trend was also observed in several other European countries, including the neighboring countries Germany, France and Austria. In contrast, MRSA rates are increasing in wound and abscess samples from outpatients. Penicillin resistance in Streptococcus pneumoniae has also decreased over time. This effect is mainly due to a reduction in the prevalence of more resistant serotypes, due to the introduction of pneumococcal vaccines. Vancomycin resistance in enterococci is still very low, but increasing rates observed during the last months are worrisome.

In contrast, we have observed a steady increase in quinolone resistance and 3rd/4th generation cephalosporin resistance in Escherichia coli and Klebsiella pneumoniae. This increase is observed in most European countries and is consistent with the wide distribution of extended-spectrum-beta-lactamase-(ESBL-)producing isolates. During the last two years, this trend seems to have stabilized in Switzerland, as well as in some other European countries. Fortunately, carbapenem resistance still is rare in E. coli and K. pneumoniae. While carbapenem resistance in E. coli is rare in most European countries as well, increasing carbapenem resistance is observed in Europe in K. pneumoniae; in 2016 resistance rates above 25 % have even been described in Italy, Greece and Romania. To allow a closer monitoring of the distribution of carbapenemase-producing Enterobacteriaceae, an obligation to report these microorganisms was introduced in Switzerland on 1.1.2016.

In Pseudomonas aeruginosa, the increasing resistance rates for piperacillin-tazobactam and ceftazidime peaked in 2015 and have slightly decreased since then, while resistance rates for aminoglycosides are steadily increasing. No significant trends were observed in Acinetobacter spp. and in contrast to Europe, carbapenemase rates were stable. […]