Spread of Enterobacter cloacae carrying blaNDM-1, blaCTX-M-15, blaSHV-12 and plasmid-mediated quinolone resistance genes in a surgical intensive care unit in Croatia.

The objective of this study was to describe a hospital cluster of NDM-1-producing Enterobacter cloacae infections observed in the surgical intensive care unit (ICU) of a tertiary-care hospital at Pula, Croatia. NDM-1-producing E. cloacae strains isolated from clinical samples were screened by PCR for the presence of carbapenemases. Genetic relatedness of NDM-1-producing E. cloacae strains was determined by multilocus sequence typing (MLST). During the period October 2013 to April 2014, four patients, with overlapping hospital stay in the surgical ICU, developed severe infections caused by E. cloacae demonstrated to produce carbapenemases. According to MLST, all strains belonged to ST133 and were positive by PCR for the blaNDM-1 carbapenemase gene, for blaCTX-M-15 and blaSHV-12 extended-spectrum ß-lactamase (ESBL) genes, and for blaTEM-1 and blaOXA-1 narrow-spectrum ß-lactamase genes. They were negative for other carbapenemases genes including blaOXA-48, blaVIM and blaKPC as well as for AmpC and the armA and rmtB aminoglycoside resistance genes. All strains were positive for the HI2 replicon, suggesting that an IncHI2 plasmid is likely the plasmid carrying the blaNDM-1 gene. Infection control measures were implemented after the first case although they were not effective in avoiding spread of this organism to other patients in the surgical ICU. In conclusion, the evolving epidemiology of NDM-producing micro-organisms and the interspecies diffusion of this resistance mechanism to emerging pathogens such as E. cloacae necessitate the setting up of strong and urgent joint measures to control the spread of NDM carbapenemase especially in the ICU setting.

[MULTIRESISTANT BACTERIA].

The most important multiresistant bacteria causing treatment failures are extended-spectrum ß-lactamase and/or plasmid-mediated AmpC ß-lactamase positive Enterobacteriaceae, carbapenemase producing Acinetobacter baumannii and Pseudomonas (P.) aeruginosa, methicillin-resistant Staphylococcus (S.) aureus, penicillin-resistant Streptococcus pneumoniae, and van-comycin- resistant Enterococcus spp. Extended-spectrum ß-lactamases hydrolyze oxyimino-caphalosporins and aztreonam, are mostly produced by Enterobacteriaceae, and are encoded on transferable plasmids which often contain resistance genes to non-ô€ -lactam antibiotics. Plasmid-mediated AmpC ß-lactamases descend from the chromosomal ampC gene transferred to the plasmid. Those ô€ -lactamases confer resistance to first, second and third generation of cephalosporins, monobactams, and to ô€ -lactam-ô€ -lactamase inhibitor combinations. Enterobacteriaceae may develop resistance to carbapenems due to the hyperproduction of ESBLs or plasmid-mediated AmpC ß-lactamases in combination with porin loss or due to the production of carbapenemases of class A (KPC, IMI, NMC, SME), B (metallo-ß-lactamases from VIM, IMP or NDM series), and D (OXA-48 ß-lactamase). Carbapenemases found in Acinetobacter spp. belong to molecular class A (KPC), B (metallo-ß-lactamases of IMP, VIM, NDM or SIM family) and D (OXA enzymes). The most frequent mechanism of carbapenem resistance in Acinetobacter spp. is through the production of OXA-enzymes but other various mechanisms including decreased permeability and efflux pump overexpression could also be involved. Carbapenem-resistance in P. aeruginosa is usually mediated by the production of metallo-ß-lactamases of IMP, VIM, GIM, SPM or NDM series, loss of OprD outer membrane protein and/or upregulation of MexAB or MexCD efflux pumps. Methicillin-resistance in S. aureus occurs as the result of the acquisition of mecA gene that encodes novel PBP2a protein. Expression of PBP2a renders bacteria resistant to all ô€ -lactams including cephalosporins (with the exception of ceftaroline and ceftobiprole) and carbapenems. Most strains of penicillin resistant Streptococcus pneumoniae are often resistant to cephalosporins and antibiotics from other classes, presenting a serious problem in treating invasive infections. The most important therapeutic problem in enterococci is development of resistance to vancomycin.

Diversity of carbapenemases in clinical isolates of Enterobacteriaceae in Croatia--the results of a multicentre study.

Since the first carbapenem-resistant Klebsiella pneumoniae strain was isolated in 2008, Enterobacteriaceae with reduced susceptibility to one or more carbapenems have emerged sporadically in different geographical regions in Croatia. These observations gave rise to a multicenter study on carbapenem resistance in Enterobacteriaceae from Croatia. Fifty-seven carbapenem-non-susceptible strains of Enterobacteriaceae were collected during 2011-2012 from four large hospital centres in Croatia. Overall, 36 strains produced VIM-1 ß-lactamase, three produced NDM-1, and one produced KPC-2. A high degree of clonal relatedness was observed in Enterobacter cloacae and Citrobacter freundii strains, in contrast to K. pneumoniae strains. BlaVIM genes were located within class1 integron which contained genes encoding resistance to aminoglycosides (aacA4 ). The study found strong association between blaVIM and qnrB6 and between blaNDM and qnrA6 genes.

Carbapenem resistance and acquired class D beta-lactamases in Acinetobacter baumannii from Croatia 2009-2010.

The molecular epidemiology and the genetic basis of carbapenem resistance was investigated in 185 Acinetobacter baumannii isolates obtained from 13 centers of northern Croatia and Istria during 2009-2010. All isolates were multidrug-resistant, and 35 % (n = 64) were resistant to both imipenem and meropenem. ISAba1-driven overexpression of the intrinsic bla OXA-51-like gene was observed in all carbapenem resistant isolates, and 69 % of these (n = 44) also produced acquired OXA-type carbapenemases. The presence of bla OXA-58-like, bla OXA-24/40-like, and bla OXA-23-like genes was demonstrated in 33 % (n = 21), 27 % (n = 17) and 9 % (n = 6) of carbapenem-resistant isolates, respectively. None of the isolates harbored the bla IMP, bla VIM, bla SIM, bla NDM or bla PER ß-lactamase genes, while bla TEM-1 was detected in five carbapenem- and ampicillin/sulbactam-resistant isolates. Sequence group determination showed a high prevalence (81 %) of isolates belonging to the International clonal lineage (ICL)-I, although the majority (80 %) of isolates carrying acquired carbapenemase genes belonged to the ICL-II. Random amplified polymorphic DNA analysis and multilocus-sequence typing of a subset of carbapenem-resistant isolates revealed a low degree of genetic variability within both ICL-I and ICL-II populations, irrespective of the genetic basis of carbapenem resistance. Overall, an increasing trend toward carbapenem resistance was observed for A. baumannii in Croatia, and the emergence of ICL-II strains producing a variety of acquired carbapenemases.

Local application of mupirocin ointment in the eradication of Staphylococcus aureus from nasal mucosa in patients on chronic hemodialysis.

Efficacy of locally applied mupirocin in the elimination of Staphylococcus aureus (SA) from the nasal mucosa in patients on maintenance hemodialysis was studied. SA was isolated in 27 patients (33.3% of the population of dialysis patients) and trials were carried out in 25 patients by applying a 2% mupirocin ointment for five days. The eradication amounted to 92% immediately upon therapy completion, and to 84%, 56%, 52% and 32% after 1, 2, 3 and 9 months. All SA strains isolated before and after the treatment were sensitive to mupirocin. The authors believe that mupirocin is efficient in the elimination of SA from nasal mucosa, however, control swabs should be periodically taken at two-month intervals.