c Recent reports have revealed the existence of widespread extensively drug-resistant (XDR) P. aeruginosa high-risk clones in health care settings, but there is still scarce information on their specific chromosomal (mutational) and acquired resistance mechanisms. Up to 20 (10.5%) of 190 bloodstream isolates collected from 10 Spanish hospitals met the XDR criteria. A representative number (15 per group) of isolates classified as multidrug-resistant (MDR) (22.6%), resistant to 1 to 2 classes (moderately resistant [modR]) (23.7%), or susceptible to all antibiotics (multiS) (43.2%) were investigated in parallel. Multilocus sequence typing (MLST) analysis revealed that all XDR isolates belonged to sequence type 175 (ST175) (n ‫؍‬ 19) or ST111 (n ‫؍‬ 1), both recognized as international high-risk clones. Clonal diversity was higher among the 15 MDR isolates (4 ST175, 2 ST111, and 8 additional STs) and especially high among the 15 modR (13 different STs) and multiS (14 STs) isolates. The XDR/MDR pattern in ST111 isolates correlated with the production of VIM-2, but none of the ST175 isolates produced acquired ␤-lactamases. In contrast, the analysis of resistance markers in 12 representative isolates (from 7 hospitals) of ST175 revealed that the XDR pattern was driven by the combination of AmpC hyperproduction, OprD inactivation (Q142X), 3 mutations conferring high-level fluoroquinolone resistance (GyrA T83I and D87N and ParC S87W), a G195E mutation in MexZ (involved in MexXY-OprM overexpression), and the production of a class 1 integron harboring the aadB gene (gentamicin and tobramycin resistance). Of particular interest, in nearly all the ST175 isolates, AmpC hyperproduction was driven by a novel AmpR-activating mutation (G154R), as demonstrated by complementation studies using an ampR mutant of PAO1. This work is the first to describe the specific resistance markers of widespread P. aeruginosa XDR high-risk clones producing invasive infections.T he increasing prevalence of nosocomial infections produced by multidrug-resistant (MDR) or extensively drug-resistant (XDR) Pseudomonas aeruginosa strains severely compromises the selection of appropriate treatments and is therefore associated with significant morbidity and mortality (29,36,44). This growing threat results from the extraordinary capacity of this pathogen for developing resistance to nearly all available antibiotics by the selection of mutations in chromosomal genes and from the increasing prevalence of transferable resistance determinants, particularly those encoding class B carbapenemases (metallo-␤-lactamases [MBLs]) or extended-spectrum ␤-lactamases (ESBLs), frequently cotransferred with genes encoding aminoglycosidemodifying enzymes (31,32,45).Among the mutation-mediated resistance mechanisms, particularly noteworthy are those leading to the repression or inactivation of the carbapenem porin OprD, the hyperproduction of the chromosomal cephalosporinase AmpC, or the upregulation of one of the several efflux pumps encoded in the P. aeruginosa genome (20,3...

Rates of IPD among adults increased in Barcelona in the late PCV7 period, coinciding with a clonal expansion of non-PCV7 serotypes. In contrast, rates of IPD caused by PCV7 serotypes decreased among people aged > or = 65 years, which suggests the development of a herd immunity.

Beginning in 1992, a sustained outbreak of multiresistantAcinetobacter baumannii infections was noted in our 1,000-bed hospital in Barcelona, Spain, resulting in considerable overuse of imipenem, to which the organisms were uniformly susceptible. In January 1997, carbapenem-resistant (CR)A. baumannii strains emerged and rapidly disseminated in the intensive care units (ICUs), prompting us to conduct a prospective investigation. It was an 18-month longitudinal intervention study aimed at the identification of the clinical and microbiological epidemiology of the outbreak and its response to a multicomponent infection control strategy. From January 1997 to June 1998, clinical samples from 153 (8%) of 1,836 consecutive ICU patients were found to contain CR A. baumannii. Isolates were verified to be A. baumannii by restriction analysis of the 16S-23S ribosomal genes and the intergenic spacer region. Molecular typing by repetitive extragenic palindromic sequence-based PCR and pulsed-field gel electrophoresis showed that the emergence of carbapenem resistance was not by the selection of resistant mutants but was by the introduction of two new epidemic clones that were different from those responsible for the endemic. Multivariate regression analysis selected those patients with previous carriage of CR A. baumannii(relative risk [RR], 35.3; 95% confidence interval [CI], 7.2 to 173.1), those patients who had previously received therapy with carbapenems (RR, 4.6; 95% CI, 1.3 to 15.6), or those who were admitted into a ward with a high density of patients infected with CR A. baumannii (RR, 1.7; 95% CI, 1.2 to 2.5) to be at a significantly greater risk for the development of clinical colonization or infection with CR A. baumannii strains. In accordance, a combined infection control strategy was designed and implemented, including the sequential closure of all ICUs for decontamination, strict compliance with cross-transmission prevention protocols, and a program that restricted the use of carbapenem. Subsequently, a sharp reduction in the incidence rates of infection or colonization with A. baumannii, whether resistant or susceptible to carbapenems, was shown, although an alarming dominance of the carbapenem-resistant clones was shown at the end of the study.

Virulent hypermucoviscous Klebsiella pneumoniae strains associated with the magA and rmpA genes have mainly emerged in Asia. We analysed the frequency and the clinical and molecular epidemiology of K. pneumoniae bacteraemia isolates obtained over a 7-year period (2007-2013). Fifty-three of 878 K. pneumoniae invasive isolates (5.4%) showed a hypermucoviscous phenotype (by the string test). Of these, 16 (30.2%) were magA(+)/rmpA(+), 12 (22.6%) were magA(-)/rmpA(+), and the remaining 25 (47.2%) were magA(-)/rmpA(-). After multilocus sequence typing and wzi sequencing, all magA(+)/rmpA(+) isolates were serotype K1 and sequence type (ST)23. Of the 12 magA(-)/rmpA(+) isolates, nine were K2 (ST380, ST86, ST65, ST25 and ST493), and three magA(-)/rmpA(+) isolates had the new wzi allele 122, an unknown serotype, and the new ST1013. The remaining isolates, which were magA(-)/rmpA(-), showed different serotypes and STs. Patients with magA(+)/rmpA(+) or magA(-)/rmpA(+)K. pneumoniae bacteraemia more frequently had pyogenic liver abscesses (PLAs) and pneumonia than patients with magA(-)/rmpA(-)K. pneumoniae bacteraemia (respectively: 21.4% vs. 8%, p 0.26; and 17.9% vs. 0%, p 0.05). In fact, magA(-)/rmpA(-) isolates were similar to the those termed 'classic' K. pneumoniae isolates causing bacteraemia, the urinary and biliary tracts being the main foci of infection. In conclusion, hypervirulent clones (CC23K1, CC86K2, CC65K2, and CC380K2) were infrequent among K. pneumoniae isolates causing bacteraemia in our geographical area. A hypermucoviscous phenotype as determined with the string test is not enough to recognize these clones; additional molecular studies are needed. Patients with magA(+) and/or rmpA(+)K. pneumoniae bacteraemia more frequently had PLAs and pneumonia than patients without hypermucoviscosity genes.