Carbapenem-resistant P. Aeruginosa Research Articles

Metallo-β-lactamase-mediated resistance among clinical carbapenem-resistant Pseudomonas aeruginosa isolates in northern Iran: A potential threat to clinical therapeutics.

Objective:Carbapenems are effective agents to treat multidrug-resistant (MDR) strains of bacteria, including Pseudomonas aeruginosa. However, there is a potential threat of emergence of carbapenem-resistant P. aeruginosa (CRPA). The aim of this study was to determine antibiotic susceptibility patterns and metallo-beta-lactamase (MBL)-mediated resistance in clinical P. aeruginosa isolates.Materials and Methods:Different clinical specimens were subjected to conventional culture-based identification of P. aeruginosa. Antimicrobial susceptibility patterns and MBL production were evaluated using the Kirby-Bauer and combined double-disk synergy test methods, respectively. Multiplex polymerase chain reaction was performed to investigate the presence of the blaIMP, blaVIM, blaNDM, blaSPM, and blaSIM genes.Results:A total of 71 clinical P. aeruginosa isolates were recovered, of which 28.17% were identified as CRPA. The most active antibiotics were colistin and polymyxin B (92.96% susceptibility to each). A total of 35% and 50% of CRPA isolates were MDR and extensively drug-resistant (XDR), respectively. MBL activity was shown in 20% of CRPA. A total of 90%, 40%, and 5% of CRPA isolates harbored the blaIMP, blaVIM, and blaNDM genes, respectively. No correlation was found between the MBL-encoding genes of P. aeruginosa and patient characteristics.Conclusion:Although the prevalence of CRPA in our therapeutic centers was relatively low, this rate of carbapenem resistance reflects a threat limiting treatment choices. A high prevalence of MDR/XDR phenotypes among the MBL-producer isolates suggests the need for continuous assessment of antimicrobial susceptibility and surveillance of antibiotic prescription. In addition, infection control measures are needed to prevent further dissemination of these organisms.

Triton Hodge Test for Detection of Metallo-Β-Lactamases Producing Pseudomonas Aeruginosa Isolates from Egyptian Patients with Infected Diabetic Foot

Background: One of the dreadful complications of diabetes is infected diabetic foot. Accurate detection of carbapenemase-producing Pseudomonas aeruginosa, in the form of metallo-beta-lactamases (MBLs) is necessary to determine the antibiotics for its treatment. Objectives: This study was designed to evaluate the efficacy of Triton Hodge Test (THT) versus MHT for detection of MBLs-producing P. aeruginosa isolates from infected diabetic foot patients. Methodology: Samples were collected from 500 infected diabetic footpatients. They were processed and P. aeruginosa isolates were identified. Then, carbapenem resistant P. aeruginosa (CRPA)isolates weredetected. Modified Hodge test (MHT) and Triton Hodge Test (THT) were used for detectionof MBLs. Furthermore, bla IMP , bla VIM and bla NDM MBLs genes were detected by multiplex and uniplex PCR. Resistance pattern of CRPA isolates was determined. Results: Isolation rate of P. aeruginosa from infected diabetic foot patients was 90/500 (18.00%). CRPA isolates were 16/90 (17.78%). In these isolates, the detection rate of bla NDM , bla VIM and bla IMP genes was (2/16, 12.5%), (10/16,62.5%) and (6/16,37.5%); respectively. The sensitivity, specificity and accuracy of THT in detection of NDM, VIM and IMP carbapenemases are 100 %. On the other hand, the sensitivity of MHT in detection of the studied types are 0.0%, 30.0% and 50.0%; respectively. Its specificity is 100% for all types and its accuracy is 87.5%, 56.3% and 83.1% in detection of these types. No resistance to tigecycline and colistin was detected among CRPA isolates. Conclusion: the THT is a more sensitive and accurate phenotypic test in comparison to MHT for detection of NDM, VIM and IMP carbapenemases in CRPA isolates.

Role of the Outer Membrane Protein OprD2 in Carbapenem-Resistance Mechanisms of Pseudomonas aeruginosa.

We investigated the relationship between the outer membrane protein OprD2 and carbapenem-resistance in 141 clinical isolates of Pseudomonas aeruginosa collected between January and December 2013 from the First Affiliated Hospital of Anhui Medical University in China. Agar dilution methods were employed to determine the minimum inhibitory concentration of meropenem (MEM) and imipenem (IMP) for P. aeruginosa. The gene encoding OprD2 was amplified from141 P. aeruginosa isolates and analyzed by PCR and DNA sequencing. Differences between the effects of IMPR and IMPS groups on the resistance of the P. aeruginosa were observed by SDS-poly acrylamide gel electrophoresis (SDS-PAGE). Three resistance types were classified in the 141 carbapenem-resistant P. aeruginosa (CRPA) isolates tested, namely IMPRMEMR (66.7%), IMPRMEMS (32.6%), and IMPRMEMS (0.7%). DNA sequencing revealed significant diverse gene mutations in the OprD2-encoding gene in these strains. Thirty-four strains had large fragment deletions in the OprD2gene, in 6 strains the gene contained fragment inserts, and in 96 resistant strains, the gene featured small fragment deletions or multi-site mutations. Only 4 metallo-β-lactamase strains and 1 imipenem-sensitive (meropenem-resistant) strain showed a normal OprD2 gene. Using SDS-PAGE to detect the outer membrane protein in 16 CRPA isolates, it was found that 10 IMPRMEMR strains and 5 IMPRMEMS strains had lost the OprD2 protein, while the IMPSMEMR strain contained a normal 46-kDa protein. In conclusion, mutation or loss of the OprD2-encoding gene caused the loss of OprD2, which further led to carbapenem-resistance of P. aeruginosa. Our findings provide insights into the mechanism of carbapenem resistance in P. aeruginosa.

Surveillance and Correlation of Antimicrobial Usage and Resistance of Pseudomonas aeruginosa: A Hospital Population-Based Study

This retrospective study evaluated trends and association between resistance of Pseudomonas aeruginosa isolated from patients with hospital-acquired infections (HAIs) and hospital antimicrobial usage from 2003 through 2011 in a tertiary care hospital in northeast China. HAI was defined as occurrence of infection after hospital admission, without evidence that infection was present or incubating (≦48 h) on admission. In vitro susceptibilities were determined by disk diffusion test and susceptibility profiles were determined using zone diameter interpretive criteria, as recommended by Clinical and Laboratory Standards Institute (CLSI). Data on usage of various antimicrobial agents, expressed as defined daily dose (DDD) per 1,000 patients-days developed by WHO Anatomical Therapeutical Chemical (ATC)/DDD index 2011, were collected from hospital pharmacy computer database. Most of 747 strains of P. aeruginosa were collected from respiratory samples (201 isolates, 26.9%), blood (179, 24.0%), secretions and pus (145, 19.4%) over the years. Time series analysis demonstrated a significant increase in resistance rates of P. aeruginosa to ticarcillin/clavulanic acid, piperacillin/tazobactam, cefoperazone/sulbactam, piperacillin, imipenem, meropenem, ceftazidime, cefepime, ciprofloxacin, and levofloxacin except aminoglycosides over time in the hospital (P<0.001). The rates of carbapenem-resistant P. aeruginosa (CRPA) isolated from patients with HAIs were 14.3%, 17.1%, 21.1%, 24.6%, 37.0%, 48.8%, 56.4%, 51.2%, and 54.1% over time. A significant increase in usage of anti-pseudomonal carbapenems (P<0.001) was seen. ARIMA models demonstrated that anti-pseudomonal carbapenems usage was strongly correlated with the prevalence of imipenem and meropenem-resistant P. aeruginosa (P<0.001). Increasing of quarterly CRPA was strongly correlated at one time lag with quarterly use of anti-pseudomonal carbapenems (P<0.001). Our data demonstrated positive correlation between anti-pseudomonal antimicrobial usage and P. aeruginosa resistance to several classes of antibiotics, but not all antimicrobial agents in the hospital.

Karbapeneme Dirençli Pseudomonas aeruginosa’ya Bağlı Bir Hastane Enfeksiyonu Salgınının İncelenmesi

Pseudomonas aeruginosa is an important nosocomial pathogen that causes opportunistic infections and hospital outbreaks. During October 2012, carbapenem-resistant P.aeruginosa strains with similar antibiotic resistance patterns, were isolated from specimens sent from the intensive care and plastic surgery units in our hospital. Thus a hospital outbreak was suspected. The microbiology laboratory database was retrospectively searched and all strains of P.aeruginosa isolated during the four month period, starting with the initial carbapenem-resistant strain in August 2012, was evaluated as a hospital outbreak. The aim of this study was to define the outbreak by investigating the clonal relationship between the strains, to detect the potential environmental sources and to evaluate the period of the outbreak, risk factors and the efficiency of infection control measures. The study was conducted between August-November 2012. Twenty patients with carbapenem-resistant P.aeruginosa (CRPA) positive cultures were included in the study. The control group consisted of 22 patients with carbapenem-susceptible P.aeruginosa (CSPA) positive cultures. The clonal relationship between 26 CRPA strains was studied by pulsed-field gel electrophoresis (PFGE). The PFGE results indicated that CRPA strains in our hospital were not related to a single clone, however, there were four major clones composed of four to eight strains. Logistic regression analysis indicated that the risk increased 15.7 fold (95% CI: 1.19-207.76) by the use of carbapenem, 76.8 fold (95% CI: 2.03-2901.30) by surgical procedures and 0.787 fold (95% CI: 0.63-0.97) by the duration of hospital stay. Surveillance cultures from health-care personel and the environment performed in course of the outbreak, yielded no growth of a strain with the similar antibiotic resistance pattern. The spread of CRPA has been controlled by the use of effective precautionary measures, regressing the isolate number to 0-1 strain/month. Since CRPA infections have high mortality and lack therapeutic alternatives, they should be regarded among the priorities of the infection control programmes. This study has enabled to test the effectiveness of the infection control program, to make plans for the possible future outbreaks and to train the staff.

Selective advantages of two major clones of carbapenem-resistant Pseudomonas aeruginosa isolates (CC235 and CC641) from Korea: antimicrobial resistance, virulence and biofilm-forming activity

The characteristics of carbapenem-resistant P. aeruginosa (CRPA) isolates from Korea were investigated. Two major clones, clonal complex (CC) 235 and CC641, were identified. CC235, an important international clone, might have been imported recently in Korea as this clone displayed a homogeneous genotype, oprD mutation and antimicrobial resistance profile. While 13 ST235 isolates harboured the blaIMP-6 gene, which conferred high-level meropenem resistance, CC641 isolates showed high biofilm-forming activity. CC235 and CC641 isolates showed distinct distribution of ferripyoverdine receptor type and virulence markers. While all CC235 isolates were of the fpvAIIb type and exoS(-)/exoU(+), CC641 isolates were exoS(+)/exoU(-), and all but one showed the fpvAIII type. CC235 and CC641 isolates were also characterized by different extracellular protease activity: staphylolysin and elastase activities in CC235 and CC641, respectively. Two major CRPA clones in Korea seem to be predominant, reflecting their selective advantage by virtue of antimicrobial resistance, virulence and biofilm-forming activity.

Influence of carbapenem resistance on mortality and the dynamics of mortality in Pseudomonas aeruginosa bloodstream infection

ObjectiveWe aimed to study the influence of carbapenem resistance on attributable mortality in a cohort of patients with Pseudomonas aeruginosa bacteremia. MethodsData on 121 episodes of P. aeruginosa bacteremia occurring between January and December 2005 were retrospectively analyzed. ResultsThirty-three episodes were caused by carbapenem-resistant P. aeruginosa (CRPA) strains and 88 by carbapenem-susceptible P. aeruginosa (CSPA) strains. There was no significant difference in mortality between the groups (33% in CRPA vs. 30% in CSPA; p = 0.69). However, a Kaplan–Meier survival analysis showed that in the first 48h after the onset of bacteremia, there was a lower cumulative mortality proportion in the CRPA group than in the CSPA group (13% vs. 50%; p = 0.026). The independent risk factors associated with death in P. aeruginosa bacteremia were clinical presentation with severe sepsis (odds ratio (OR) 38, 95% confidence interval (CI) 10.2–142.2) and bacteremia of high-risk origin (OR 6.6, 95% CI 1.6–26.9). ConclusionsAccording to our data, carbapenem resistance was not associated with higher mortality in patients with P. aeruginosa bacteremia. The slower initial mortality in the CRPA group might have implications in the design of the optimal antibiotic policy strategy.

Carbapenem-resistant Pseudomonas aeruginosa: factors influencing multidrug-resistant acquisition in non-critically ill patients

A cohort study was carried out on hospitalized adult non-critically ill patients (January 2003-December 2004) to identify factors associated with the acquisition of multidrug-resistant Pseudomonas aeruginosa (MDR-PA). A total of 246 non-critically patients were included, 162 (66%) who revealed MDR-PA in the first isolate and 84 (34%) who had carbapenem-resistant P. aeruginosa (CR-PA) isolates. Multivariate analysis identified nosocomial acquisition (odds ratio [OR] 2.7, 95% confidence interval [CI] 1.1-6.3), urinary catheter (OR 2.1, 95%CI 1.1-4.3), and the prior use of fluoroquinolones (OR 2.6, 95%CI 1.0-6.7) as independent risk factors associated with MDR-PA acquisition. Our results show that antibiotics, most notably, fluoroquinolones, may play a major role in the emergence of MDR-PA.

Outbreak of carbapenem-resistant Pseudomonas aeruginosa producing SPM-1 metallo-β-lactamase in a teaching hospital in southern Brazil

To describe the first nosocomial outbreak of Pseudomonas aeruginosa producing SPM-1 metallo-beta-lactamase (MBL) in southern Brazil. From January to October 2004, carbapenem-resistant P. aeruginosa (CRPA) were recovered from hospitalized patients. Mortality, site of infection/colonization, patient location and susceptibility profiles were analysed. A sample of CRPA was screened for MBL production, evaluated for the presence of bla(SPM-1), bla(IMP-1) and bla(VIM-2) genes by PCR and submitted for molecular typing by DNA macrorestriction. A total of 135 CRPA (one isolate per patient) were recovered. Two major antibiotic susceptibility profiles comprised 63.7% of the isolates (susceptibility to polymyxin B and aztreonam, and susceptibility only to polymyxin B). Thirty-five CRPA were screened for MBL production (10 isolates from April, June and July, and 25 from September and October) and 27 (77.1%) proved to be positive for MBL production. Twenty-one of the 24 CRPA tested carried the bla(SPM-1) gene. The mortality of patients with CRPA was 48.1% and no variable was associated with death. Molecular typing revealed the presence of a clone with four related subtypes among the bla(SPM-1)-positive CRPA. The prevalence of MBL production by CRPA is high and horizontal transmission is a major determinant for the spread of SPM-1 CRPA among patients in this institution. As infection control measures failed to control the spread of CRPA, continuous surveillance for MBL production is warranted.