Extended-spectrum β-lactamase (ESBL) -producing Enterobacteriaceae have been notifiable according to the Swedish Communicable Disease Act since 2007. A major increase in the number of cases has been observed, with 2099 cases in 2007 and 7225 cases in 2012. The majority of the isolates are Escherichia coli. Additionally, Swedish data on the prevalence of ESBL-producing invasive isolates of E. coli are available through EARS-Net, and through biannual point prevalence studies, where molecular characterization of isolates from the entire country is carried out. This paper describes major trends in the Swedish epidemiology of ESBL-producing E. coli in the period 2007-2012. Isolates from the point prevalence studies were subjected to antimicrobial susceptibility testing, ESBL genotyping, pulsed-field gel electrophoresis, multi-locus sequence typing and phylogenetic grouping with PCR. The distribution of sequence types, resistance genes and susceptibility levels were all stable over the three study periods. The dominating resistance gene conferring ESBL was blaCTX -M-15 , found in 54-58% of the isolates. ST131 represented 34-38% of the isolates. Other major sequence types were ST38, ST69, ST405, ST617 and ST648, each representing 2-6% of the isolates. Phylogenetic group B2 was the most common, and was observed in 41-47% of the isolates. However, among ST131 isolates the B2 phylogenetic group represented 90-98% of the isolates. The most important epidemiological difference seen over time was that the median age of infected women decreased from 62 to 52 years (p <0.0001) and infected men from 67 to 64 years. A potential explanation might be the shift towards a higher proportion of community-acquired infections in individuals lacking comorbidities.

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Acinetobacter baumannii has emerged as an important opportunistic pathogen equipped with a growing number of antibiotic resistance genes. Our study investigated the molecular epidemiology and antibiotic resistance features of 28 consecutive carbapenem-resistant clinical isolates of A. baumannii collected throughout Sweden in 2012 and 2013. The isolates mainly belonged to clonal complexes (CCs) with an extensive international distribution, such as CC2 (n = 16) and CC25 (n = 7). Resistance to carbapenems was related to blaOXA-23 (20 isolates), blaOXA-24/40-like (6 isolates), blaOXA-467 (1 isolate), and ISAba1-blaOXA-69 (1 isolate). Ceftazidime resistance was associated with blaPER-7 in the CC25 isolates. Two classical point mutations were responsible for resistance to quinolones in all the isolates. Isolates with high levels of resistance to aminoglycosides carried the 16S rRNA methylase armA gene. The isolates also carried a variety of genes encoding aminoglycoside-modifying enzymes. Several novel structures involved in aminoglycoside resistance were identified, including Tn6279, ΔTn6279, Ab-ST3-aadB, and different assemblies of Tn6020 and TnaphA6. Importantly, a number of circular forms related to the IS26 or ISAba125 composite transposons were detected. The frequent occurrence of these circular forms in the populations of several isolates indicates a potential role of these circular forms in the dissemination of antibiotic resistance genes.

VRE increased in Denmark during 2005-15 due to the emergence of several vanA E. faecium clones.

A selection of plasmid-mediated AmpC-producing Escherichia coli isolates carrying blaCMY-2 from Swedish broilers were characterized to establish their relatedness to and a possible overlap with human clinical E. coli isolates. The results showed diversity among the E. coli isolated from broilers, indicating that the spread in the population was not due to one strain. However, only one type of plasmid belonging to replicon type incK was identified. Furthermore, there were no indications of spread of blaCMY-2 E. coli isolates from broilers to human clinical settings, although Swedish broilers may be a source of blaCMY-2 and/or the plasmid carrying blaCMY-2 .

Members of the Enterobacteriaceae with extended-spectrum beta-lactamases (ESBLs) of the CTX-M type have disseminated rapidly in recent years and have become a threat to public health. In parallel with the CTX-M type expansion, the consumption and widespread use of silver-containing products has increased. To determine the carriage rates of silver resistance genes in different Escherichia coli populations, the presence of three silver resistance genes (silE, silP, and silS) and genes encoding CTX-M-, TEM-, and SHV-type enzymes were explored in E. coli isolates of human (n ‫؍‬ 105) and avian (n ‫؍‬ 111) origin. The antibiotic profiles were also determined. Isolates harboring CTX-M genes were further characterized, and phenotypic silver resistance was examined. The silE gene was present in 13 of the isolates. All of them were of human origin. Eleven of these isolates harbored ESBLs of the CTX-M type (P ‫؍‬ 0.007), and eight of them were typed as CTX-M-15 and three as CTX-M-14. None of the silE-positive isolates was related to the O25b-ST131 clone, but 10 out of 13 belonged to the ST10 or ST58 complexes. Phenotypic silver resistance (silver nitrate MIC > 512 mg/liter) was observed after silver exposure in 12 of them, and a concomitant reduced susceptibility to piperacillin-tazobactam developed in three. In conclusion, 12% of the human E. coli isolates but none of the avian isolates harbored silver resistance genes. This indicates another route for or level of silver exposure for humans than that caused by common environmental contamination. Since silE-positive isolates were significantly more often found in CTX-M-positive isolates, it is possible that silver may exert a selective pressure on CTX-M-producing E. coli isolates.

The aim of this study was to investigate the prevalence of extended-spectrum beta-lactamase (ESBL)-producing bacteria in patients at various hospital wards and in a group of relatively healthy volunteers, in order to obtain greater knowledge on how common these bacterial strains are in hospital settings and in the general community. Participants (n = 427) were enrolled at a University Hospital and at Primary Health Care Units (PHCUs) in Sweden in 2008 and 2010. The participants provided rectal swabs, which were tested for the occurrence of ESBL-producing bacteria. Positive samples were analysed with polymerase chain reaction (PCR) methods for bacterial strain typing and ESBL phylogroups. In 2008, the prevalence was 2.1% (2/96) in PHCU subjects and 1.8% (2/113) in hospital patients. In 2010, the prevalence was 3.0% (3/100) in PHCU subjects and 6.8% (8/118) in hospital patients. The dominating phylogroups were CTX-M-1 and CTX-M-9. All ESBL-positive isolates were Escherichia coli. We found a higher prevalence of ESBL faecal carriage than expected, both in the hospital setting and in the PHCU group.