Changing Characteristics and In Vitro Susceptibility to Ceftazidime/Avibactam of Bloodstream Extensively Drug-Resistant Klebsiella pneumoniae from a Greek Intensive Care Unit.

During 2014-2016, a total of 248 carbapenem-resistant Klebsiella pneumoniae (CARB-R Kp) were recovered in a Greek intensive care unit (ICU), the colistin resistance (COL-R) rates among CARB-R Kp from bloodstream infections (BSIs) were determined, and molecular characterization and the in vitro susceptibility of CARB-R+COL-R Kp to ceftazidime/avibactam were performed. The majority of CARB-R Kp from BSIs (n = 53) were OXA-48 (43.4%) and KPC (33.9%) producers, but no statistically significant differences were observed for the clinical characteristics of ICU patients affected by OXA-48 and other carbapenemase-producing K. pneumoniae. CARB-R+COL-R Kp (n = 28) represented 52.8% of 53 CARB-R Kp recovered from BSIs. The increase in the COL-R rates from 2014 to 2015 was mainly associated with the diffusion of extensively drug-resistant (XDR) OXA-48-co-producing CTX-M-15-like K. pneumoniae, assigned to multilocus-sequence typing ST101, possessing alterations in the mgrB loci. Ceftazidime/avibactam was active against all OXA-48 and KPC producers. Thus, the spread of XDR Kp possessing different types of carbapenemases further complicates the infection control strategies for the management of XDR Kp, whereas ceftazidime/avibactam may be a reasonable alternative to colistin for the treatment of XDR Kp in settings with low prevalence of metallo-ß lactamase-producing K. pneumoniae.

Investigation of Extensively Drug-Resistant blaOXA-23-Producing Acinetobacter baumannii Spread in a Greek Hospital.

A rapid increase was observed in the incidence of extensively drug-resistant Acinetobacter baumannii (XDR Aba) isolates in a Greek hospital during 2014. To investigate the causes of this rise, the antimicrobial resistance profiles of all carbapenem-resistant (CARB-R) Aba isolates recovered during 2014-2015 were determined. Selected XDR Aba isolates (n = 13) were characterized by molecular methods. XDR Aba (48 isolates) represented 21.4% of the 224 CARB-R Aba recovered during the study period. The 13 selected XDR Aba isolates were positive for the blaOXA-23, the intrinsic blaOXA-51, and the adeB gene of the AdeABC efflux pump, and all belonged to the 3LST ST101, corresponding to the international clone II. Three bloodstream isolates possessed two amino acid substitutions (A138T+A226V) in the deduced amino acid sequences of the pmrB gene, which may be implicated in colistin resistance. This study demonstrates that this clone still evolves by obtaining an ever-increasing arsenal of antibiotic resistance mechanisms. The clinical characteristics of the intensive care unit (ICU) patients with XDR Aba were reviewed retrospectively. Infected ICU patients with XDR Aba displayed higher death rates compared with infected ICU patients susceptible to colistin and tigecycline CARB-R Aba, although there were no statistically significant differences. Conclusively, continuous surveillance and molecular characterization of XDR Aba, combined with strict infection control measures are mandatory for combating nosocomial infections caused by this organism.

Characteristics of superinfections during treatment with tigecycline.

Tigecycline has a broad-spectrum in vitro activity against Gram-positive and Gram-negative bacteria, including multidrug-resistant (MDR) strains. However, some Gram-negative bacteria are intrinsically resistant or have reduced susceptibility to tigecycline. We performed a prospective, observational study of 43 patients who received tigecycline as the treatment for serious infections due to MDR Gram-negative microorganisms, to evaluate superinfections. In 60.5% of our patients, tigecycline-resistant (T-R) Gram-negative microorganisms were isolated, representing superinfection in 37.2% and colonization in 23.5%. Pseudomonas aeruginosa was the predominant pathogen (48.4%) followed by Providencia stuartii, Proteus mirabilis and Stenotrophomonas maltophilia. Median time elapsed between tigecycline prescription and isolation of T-R pathogens was 7 days. The 16 superinfections consisted of ventilator-associated pneumonias (43.75%), catheter-related bloodstream infections (37.5%), intra-abdominal infections (12.5%) and urinary tract infection (6.25%). Attributed mortality to superinfections was 31.25%. The comparison of various potential risk factors for isolation of T-R microorganisms did not reveal statistically significant results.

Characterization of ST258 Colistin-Resistant, blaKPC-Producing Klebsiella pneumoniae in a Greek Hospital.

The emergence of colistin resistance may further contribute to treatment failure of infection caused by multidrug-resistant (MDR) Klebsiella pneumoniae. The colistin resistance rates were determined and colistin-resistant carbapenemase-producing K. pneumoniae (COL-R CP-Kp) were characterized over an 18-month period in a Greek hospital. Out of 135 carbapenemase producers, 19 isolates (14%) were categorized as resistant to colistin. Phenotypic and molecular characterization of the COL-R CP-Kp isolates revealed that all were MDR blaKPC producers and, excluding one isolate of MLST ST383, belonged to the international clonal lineage ST258. Furthermore, PCR amplification and sequencing of the mgrB locus revealed nucleotide sequences of different sizes and insertions of IS1- and IS5-like mobile elements. The majority (63%) of the COL-R blaKPC producers was recovered from patients in the intensive care unit (ICU) and clinical data indicated that all patients should have acquired these isolates in the ICU. The findings of the present study underscore a concerning evolution of colistin resistance in a setting of high K. pneumoniae carbapenemase (KPC)-Kp endemicity, such as Greece. Thus, continuous surveillance, molecular characterization, prudent use of antibiotics, and implementation of infection control measures for K. pneumoniae are urgent.

Molecular identification of tigecycline- and colistin-resistant carbapenemase-producing Acinetobacter baumannii from a Greek hospital from 2011 to 2013.

An alarming increase in the resistance rates of tigecycline and colistin among carbapenemase-producing Acinetobacter baumannii recovered from a Greek hospital over a 3-year period (2011-2013) was investigated. The antimicrobial resistance profiles and carbapenemase gene content were determined for a collection of colistin- and/or tigecycline-resistant carbapenemase-producing A. baumannii isolates (n = 42), which were recovered consecutively during the study period. A gradual increase in the incidence of blaOXA-23 producers was observed from 2011 to 2013. A cluster of 21 isolates comprised tigecycline-resistant blaOXA-23 producers displayed a single antimicrobial resistance pattern. The emergence of two blaOXA-23 producers resistant to both tigecycline and colistin was documented. Furthermore, determination of the mechanisms of colistin and tigecycline resistance and molecular typing by the tri-locus sequence typing (3LST) scheme for nine isolates recovered from bloodstream infections were performed. Out of nine isolates, five tigecycline- and two colistin-resistant isolates were blaOXA-23 producers of 3LST ST101 corresponding to the international clone II recovered during 2012-2013. All nine isolates were positive for the presence of the adeB gene of the AdeABC efflux pump. Three colistin-resistant isolates possessed novel substitutions in PmrB, which may be implicated in colistin resistance. To the best of our knowledge, this is the first report of the acquisition of tigecycline and colistin resistance among blaOXA-23-producing A. baumannii of 3LST ST101 in Greece; thus, continuous surveillance and molecular characterization, prudent use of antibiotics and implementation of infection control measures for A. baumannii are urgent.

Carbapenem-resistant Klebsiella pneumoniae infections in a Greek intensive care unit: Molecular characterisation and treatment challenges.

Acquisition of carbapenemase-producing Klebsiella pneumoniae (CP-Kp) strains poses a major threat to critically ill patients. The objectives of this study were to describe the epidemiology of CP-Kp isolates as well as the clinical outcome associated with the corresponding infections and to identify risk factors for mortality of intensive care unit (ICU) patients in a Greek hospital. A prospective, observational study was conducted in a nine-bed general ICU over a 2-year period (April 2010-March 2012). Imipenem-resistant K. pneumoniae isolates recovered from clinical samples of ICU patients were prospectively collected and studied for the presence of carbapenemases. Isolates were submitted to molecular typing using pulsed-field gel electrophoresis (PFGE). In total, 61 CP-Kp isolates (48 KPC-producers and 13 VIM-producers) were recovered from 58 ICU patients. The majority of KPC-producers were classified into a single PFGE type, indicating potent clonal dissemination. Among the 32 infected patients, bacteraemia was diagnosed in 16. Tigecycline+colistin was the most common combination antimicrobial regimen. Infection-attributable mortality was 43.8%. Regarding mortality risk factors, non-survivors were older (P=0.080), all of them presented with septic shock (P=0.010) and they had higher Sepsis-related Organ Failure Assessment (SOFA) scores at infection onset (P=0.004) compared with survivors. Appropriate definitive treatment and combination regimens were not associated with patient survival. In conclusion, CP-Kp infections are associated with limited treatment options and high in-hospital mortality. Effective measures for preventing dissemination of respective isolates in the hospital setting are required.

Tigecycline in the treatment of infections from multi-drug resistant gram-negative pathogens.

OBJECTIVE: This observational retrospective study aims to present early experience with tigecycline (TIG) in the treatment of infections due to multi-drug resistant (MDR) microorganisms. METHODS: Adult patients included, received TIG for >5 days either as monotherapy (M group) or as presumed active monotherapy (PAM group). In the PAM group, all co-administered antimicrobial(s) were resistant in vitro against the targeted pathogen(s) or had been clinically and microbiologically failing after >or=5 days of therapy despite in vitro susceptibility. RESULTS: Forty-five patients (35 in ICU) were treated for 28 Acinetobacter baumannii and 23 Klebsiella pneumoniae infections [21 ventilator-associated and healthcare-acquired pneumonia (VAP/HCAP), 10 bloodstream infections (BSI) and 14 surgical infections (SI)]. Successful overall clinical outcome was 80%, i.e. 81.8% in M group, 78.3% in PAM group, 90.5% in VAP/HCAP, 80% in BSI, 64.3% in SI and 85% in the cases with septic shock. Superinfections from Enterobacteriaceae inherently resistant to tigecycline occurred in 31.8% of M and 13% of PAM group (p<0.001). CONCLUSION: TIG represents a promising option in infections from MDR pathogens, however, further clinical experience is required.