SummaryBackground Gaps in the diagnostic capacity and heterogeneity of national surveillance and reporting standards in Europe make it diffi cult to contain carbapenemase-producing Enterobacteriaceae. We report the development of a consistent sampling framework and the results of the fi rst structured survey on the occurrence of carbapenemaseproducing Klebsiella pneumoniae and Escherichia coli in European hospitals.

Staphylococcus aureus can exemplify better than any other human pathogen the adaptive evolution of bacteria in the antibiotic era, as it has demonstrated a unique ability to quickly respond to each new antibiotic with the development of a resistance mechanism, starting with penicillin and methicillin, until the most recent, linezolid and daptomycin. Resistance mechanisms include enzymatic inactivation of the antibiotic (penicillinase and aminoglycoside-modification enzymes), alteration of the target with decreased affinity for the antibiotic (notable examples being penicillin-binding protein 2a of methicillin-resistant S. aureus and D-Ala-D-Lac of peptidoglycan precursors of vancomycin-resistant strains), trapping of the antibiotic (for vancomycin and possibly daptomycin) and efflux pumps (fluoroquinolones and tetracycline). Complex genetic arrays (staphylococcal chromosomal cassette mec elements or the vanA operon) have been acquired by S. aureus through horizontal gene transfer, while resistance to other antibiotics, including some of the most recent ones (e.g., fluoroquinolones, linezolid and daptomycin) have developed through spontaneous mutations and positive selection. Detection of the resistance mechanisms and their genetic basis is an important support to antibiotic susceptibility surveillance in S. aureus.

Staphylococcus aureus is an important human pathogen, responsible for infections in the community and the healthcare setting. Although much of the attention is focused on the methicillin-resistant "variant" MRSA, the methicillin-susceptible counterpart (MSSA) remains a prime species in infections. The epidemiology of S. aureus, especially of MRSA, showed a rapid evolution in the last years. After representing a typical nosocomial multidrug-resistant pathogen, MRSA has recently emerged in the community and among farmed animals thanks to its ability to evolve and adapt to different settings. Global surveillance has shown that MRSA represents a problem in all continents and countries where studies have been carried out, determining an increase in mortality and the need to use last-resource expensive antibiotics. S. aureus can easily acquire resistance to antibiotics and MRSA is characteristically multidrug resistant. Resistance to vancomycin, the principal anti-MRSA antibiotic is rare, although isolates with decreased susceptibility are recovered in many areas. Resistance to the more recently introduced antibiotics, linezolid and daptomycin, has emerged; however, they remain substantially active against the large majority of MSSA and MRSA. Newer antistaphylococcal drugs have been developed, but since their clinical use has been very limited so far, little is known about the emergence of resistance. Molecular typing techniques have allowed to identify the major successful clones and lineages of MSSA and MRSA, including high-risk clones, and to trace their diffusion. In the face of a continuously evolving scenario, this review depicts the most common clones circulating in different geographical areas and in different settings at present. Since the evolution of S. aureus will continue, it is important to maintain the attention on the epidemiology of S. aureus in the future with a global view.

Predisposing factors, clinical characteristics, and antimicrobial treatment of 37 hematology patients with Stenotrophomonas maltophilia bacteremia who were seen at the department of hematology of the University La Sapienza (Rome) from 1987 to 1996 were evaluated. The results were compared with a control group of patients with Pseudomonas aeruginosa bacteremia. Profound neutropenia was more prolonged in the S. maltophilia group (P=.025), severe cellulitis occurred only in S. maltophilia-infected patients (11 [30%]; P=.0002), and the bacteremia presented as breakthrough infection in 56% of the cases due to S. maltophilia (vs. only 24% of those due to P. aeruginosa; P=.002). Acute mortality rates associated with S. maltophilia and P. aeruginosa bacteremia were 24% and 21%, respectively. In both groups, profound neutropenia and hypotension at the onset of bacteremia, duration of profound neutropenia during bacteremia, severity-of-illness score > or =4, and inappropriate antibacterial treatment were factors significantly associated with death. Most S. maltophilia isolates were resistant to aminoglycosides, beta-lactams, and ciprofloxacin. Cotrimoxazole and ticarcillin-clavulanic acid showed borderline activity. Prompt administration of in vitro-active antibiotics may improve the prognosis of S. maltophilia bacteremia, especially for immunocompromised patients, and novel drug combinations are needed for the treatment of severe infections.

Consecutive non-replicate clinical isolates (n=191) of carbapenem non-susceptible Enterobacteriaceae were collected from 21 hospital laboratories across Italy from November 2013 to April 2014 as part of the European Survey on Carbapenemase-producing Enterobacteriaceae (EuSCAPE) project. Klebsiella pneumoniae carbapenemase-producing K. pneumoniae (KPC-KP) represented 178 (93%) isolates with 76 (43%) respectively resistant to colistin, a key drug for treating carbapenamase-producing Enterobacteriaceae. KPC-KP colistin-resistant isolates were detected in all participating laboratories. This underscores a concerning evolution of colistin resistance in a setting of high KPC-KP endemicity.

We investigated the evolution and epidemiology of a novel livestock-associated methicillin-resistant Staphylococcus aureus strain, which colonizes and infects urban-dwelling Danes even without a Danish animal reservoir. Genetic evidence suggests both poultry and human adaptation, with poultry meat implicated as a probable source.

Methicillin-resistant Staphylococcus aureus (MRSA) Sequence Type (ST)1, Clonal Complex(CC)1, SCCmec V is one of the major Livestock-Associated (LA-) lineages in pig farming industry in Italy and is associated with pigs in other European countries. Recently, it has been increasingly detected in Italian dairy cattle herds. The aim of this study was to analyse the differences between ST1 MRSA and methicillin-susceptible S. aureus (MSSA) from cattle and pig herds in Italy and Europe and human isolates. Sixty-tree animal isolates from different holdings and 20 human isolates were characterized by pulsed-field gel electrophoresis (PFGE), spa-typing, SCCmec typing, and by micro-array analysis for several virulence, antimicrobial resistance, and strain/host-specific marker genes. Three major PFGE clusters were detected. The bovine isolates shared a high (≥90% to 100%) similarity with human isolates and carried the same SCCmec type IVa. They often showed genetic features typical of human adaptation or present in human-associated CC1: Immune evasion cluster (IEC) genes sak and scn, or sea; sat and aphA3-mediated aminoglycoside resistance. Contrary, typical markers of porcine origin in Italy and Spain, like erm(A) mediated macrolide-lincosamide-streptograminB, and of vga(A)-mediated pleuromutilin resistance were always absent in human and bovine isolates. Most of ST(CC)1 MRSA from dairy cattle were multidrug-resistant and contained virulence and immunomodulatory genes associated with full capability of colonizing humans. As such, these strains may represent a greater human hazard than the porcine strains. The zoonotic capacity of CC1 LA-MRSA from livestock must be taken seriously and measures should be implemented at farm-level to prevent spill-over.

Although a trend to a polyclonal evolution of the Italian KPC-KP was noted, this study showed that the KPC-KP population remained largely oligoclonal with the wide diffusion of an ST512 lineage carrying cps-2 capsular type and producing the KPC-3 enzyme.