Assessment of Silver Levels in a Closed-Incision Negative Pressure Therapy Dressing: In Vitro and In Vivo Study.

Objective: In recent years, reticulated open-cell foam-based closed-incision negative pressure therapy (ROCF-ciNPT) has shown effectiveness in management of various postoperative incisions. These dressings consist of a skin interface layer that absorbs fluid from the skin surface and reduces the potential for microbial colonization within the dressing by means of ionic silver. This study examines the ability of silver to reduce the bioburden within the dressing as well as the localized effect due to potential silver mobility. Approach: Ability of silver to reduce bioburden within the ROCF-ciNPT dressing was assessed using Staphylococcus aureus, Pseudomonas aeruginosa, and Candida spp. Furthermore, silver mobility was assessed using an in vitro skin model to study the zone of inhibition along with released silver quantification. Using a porcine model, diffusion of silver into blood and tissue was studied using emission spectrometry and histology. Results: Microbial growth in the ROCF-ciNPT dressing was significantly reduced (∼2.7-4.9 log reduction) compared to a silver-free negative control. No zone of inhibition was observed for microbial colonies for up to 7 days with minimal localized silver release (<5.5 ppm release). In vivo studies demonstrated no measurable concentration (<0.2 µg/g) of silver in the blood, urine, feces, kidney, and liver tissue biopsy. Innovation: This study provides an important insight into silver concentration and mobility within the ROCF-ciNPT dressing, given emerging concerns associated with potential silver cytotoxicity. Conclusion: These results indicate the concentration of silver (0.019% silver by weight) in the ROCF-ciNPT dressings has been adequate to reduce bioburden within the skin interface layer, while severely limiting the amount of silver leaching out.

Occurrence of intI1-associated VIM-5 carbapenemase and co-existence of all four classes of ß-lactamase in carbapenem-resistant clinical Pseudomonas aeruginosa DMC-27b.

OBJECTIVES: Emergence of carbapenem-resistant Pseudomonas aeruginosa is limiting current treatment options. Carbapenemases and their association with integrons can cause rapid dissemination of resistance traits. We report here the co-existence and chromosomal inheritance of all four classes of ß-lactamase and the presence of a unique class 1 integron (intI1) harbouring blaVIM-5 within a single isolate of P. aeruginosa, DMC-27b. METHODS: DMC-27b, isolated from urine, was characterized for carbapenem resistance both phenotypically and genotypically. The orientation of gene cassette structures of class 1 integrons was determined using referenced and designed overlapping primers and complete genome sequence (CGS) data. The antimicrobial resistance profile, porin protein mutations and the presence of active efflux activity were studied from the CGS. RESULTS: P. aeruginosa DMC-27b was resistant to a total of 20 antibiotics, with imipenem and meropenem MIC90s of >512 mg/L. The isolate harboured all four classes of ß-lactamase: VEB-1 (class A), VIM-5 (class B), PDC-35 (class C) and OXA-2 and OXA-50 (both class D). Chromosomal harbouring of blaVIM-5 was associated with the intI1 gene cassette as the sole gene, a unique cassette so far reported. A total of 11 mutations, among them some mutations causing extra folds and changes in binding sites, in porin protein OprD might also affect its functionality regarding the transportation of antibiotics. CONCLUSIONS: This is one of the earliest reports of its kind on the co-existence of all four ß-lactamase classes in P. aeruginosa DMC-27b. Acquisition of multiple resistance determinants is paving the way for the development of MDR. This superbug is a model for rapid dissemination of resistance traits both horizontally and vertically.

A novel enzyme-free electrochemical biosensor for rapid detection of Pseudomonas aeruginosa based on high catalytic Cu-ZrMOF and conductive Super P.

Pseudomonas aeruginosa (P. aeruginosa) is one of the most intractable multidrug-resistant bacteria of nosocomial infections. The conventional detection methods for P. aeruginosa are time-consuming or low detection sensitivity. Here, a novel enzyme-free electrochemical biosensor was constructed to detect P. aeruginosa rapidly and sensitively. Firstly, the ZrMOF with large surface area was synthesized, which offers excellent adsorption. Further, it was connected with a specific amount of Cu2+ to synthesize Cu-ZrMOF with high catalytic activity. Then the Cu-ZrMOF@Aptamer@DNA nanocomposite was composed and served as the signal probe to catalyse the decomposition of H2O2. Moreover, high conductive Super P was introduced to increase the electron transfer for satisfactory detection sensitivity. The proposed biosensor was constructed and used to quantify P. aeruginosa with a wide linearity range of 10-106 CFU mL-1 and a low limit of detection of 2 CFU mL-1 (S/N = 3). Compared with conventional methods, the new method of present biosensor is more sensitive, and less time-consuming (only within 120 min). The analytical performance evaluation indicated that the biosensor exhibits good reproducibility and specificity. Finally, the biosensor was successfully applied to quantify P. aeruginosa in spiked urine samples. These results show that the proposed electrochemical biosensor might be a potential laboratory tool for detecting P. aeruginosa in the clinic.

Genotypic identification of Pseudomonas aeruginosa strains isolated from patients with urinary tract infection.

BACKGROUND: Numerous nosocomial infections including urinary tract infection (UTI) have been reported to be linked to Pseudomonas aeruginosa (P. aeruginosa). This bacterium is one of the most common pathogen colonized in the urinary tract. The main purpose of this study was to evaluated the presence of antibiotic resistance genes and also the most frequent genotype patterns of P. aeruginosa in the patients with UTI hospitalized in different wards of hospitals. MATERIALS AND METHODS: In this study, 70 strains of P. aeruginosa isolated of urine samples from the patients with UTI were assessed. The isolated strains were genotyped using Multiple-Locus Variable Number Tandem Repeat Analysis (MLVA) method. We have also analyzed the presence of TEM and SHV resistant genes in the isolates. RESULTS: A total of 70 P. aeruginosa strains was isolated from the UTI patients. Based on MLVA method, 61 various genotypes of P. aeruginosa were identified which grouped into two main clusters and 4 sub-clusters. Moreover, approximately 80% and 70% of isolated strains carried the TEM and SHV resistance genes, respectively. CONCLUSION: Our findings showed that the majority of patients hospitalized in different wards of hospitals have experienced the urinary tract infection caused by P. aeruginosa. According to the genotyping results, a high diversity of the P. aeruginosa population was observed in the patients with UTI. Our results can provide a better understanding of the P. aeruginosa genotype distribution and epidemiology of infection, which can be applied as basic data for future antibiotic therapies.

Bacteremia complicating urinary tract infection by Pseudomonas aeruginosa: Mortality risk factors.

OBJECTIVES: To examine the clinical risk factors for death within 30 days of diagnosis of Pseudomonas aeruginosa-causing bacteremia after a urinary tract infection. METHODS: A total of 62 patients with Pseudomonas aeruginosa isolated from both urine and blood at the same episode from January 2009 to December 2016 were enrolled in the present study. We retrospectively investigated clinical risk factors for death by comparison between surviving patients and those who died within 30 days after diagnosis of P. aeruginosa bacteremia. The comparison for risk factors for bacteremia-related death included 31 categories, such as age, laboratory data, underlying diseases, clinical history, history of surgery, care in the intensive care unit, P. aeruginosa susceptibility to the antibiotics used at the time of bacteremia diagnosis and consultation with urological department. RESULTS: The study included 48 men and 14 women aged 71.3 ± 10.4 years. Nine patients (14.5%) died of P. aeruginosa bacteremia. Statistical analysis showed that non-survivors had significantly lower albumin levels than survivors (2.07 ± 0.62 vs 2.62 ± 0.65; P = 0.023). The non-survivors had significantly higher rates of ventilator use, history of heart disease, septic shock and lower rates of consultation with urological departments after diagnosis (P < 0.05). CONCLUSIONS: Patients with bacteremia complicating urinary infection by P. aeruginosa have a low death rate. Earlier intervention by urologists might improve patients' outcome. Lower albumin levels, ventilator use, history of heart disease and septic shock are factors associated with higher mortality rate.

Complement depletion and Coombs positivity in pneumococcal hemolytic uremic syndrome (pnHUS). Case series and plea to revisit an old pathogenetic concept.

Hemolytic uremic syndrome is a rare complication of invasive pneumococcal infection (pnHUS). Its pathogenesis is poorly understood, and treatment remains controversial. The emerging role of complement in various forms of HUS warrants a new look at this "old" disease. We performed a retrospective analysis of clinical and laboratory features of three sequential cases of pnHUS since 2008 associated with pneumonia/pleural empyema, two due to Streptococcus pneumoniae serotype 19 A. Profound depletion of complement C3 (and less of C4) was observed in two patients. One patient was Coombs test positive. Her red blood cells (RBCs) strongly agglutinated with blood group compatible donor serum at 0 °C, but not at 37 °C. All three patients were treated with hemodialysis, concentrated RBCs, and platelets. Patient 2 received frozen plasma for hepatic failure with coagulation factor depletion. Intravenous immunoglobulin infusion, intended to neutralize pneumococcal neuraminidase in patient 3, was associated with rapid normalization of platelets and cessation of hemolysis. Two patients recovered without sequelae or disease recurrence. Patient 2 died within 2½ days of admission due to complicating Pseudomonas aeruginosa sepsis and multiorgan failure. Our observations suggest that pnHUS can be associated with dramatic, transient complement consumption early in the course of the disease, probably via the alternative pathway. A critical review of the literature and the reported cases argue against the postulated pathological role of preformed antibodies against the neuraminidase-exposed Thomsen-Friedenreich neoantigen (T antigen) in pnHUS. The improved understanding of complement regulation and bacterial strategies of complement evasion allows to propose a testable, new pathogenetic model of pnHUS. This model shifts emphasis from the action of natural anti-T antibodies toward impaired Complement Factor H (CFH) binding and function on desialylated membranes. Removal of neuraminic acid residues converts (protected) self to non-self surfaces that supports membrane attack complex (MAC) assembly. Complement activation is potentially exacerbated by decreased CFH availability following tight CFH binding to pneumococcal evasion proteins and/or by the presence of genetic variants of complement regulator proteins. Detailed clinical and experimental investigations are warranted to better understand the role of unregulated complement activation in pnHUS. Instead of avoidance of plasma, a new, integrated model is evolving, which may include short-term therapeutic complement blockade, particularly where genetic or functional APC dysregulation is suspected, in addition to bacterial elimination and, potentially, neuraminidase neutralization.

KPC-2 carbapenemase-producing Pseudomonas aeruginosa reaching Germany.

Background: Antimicrobial resistance due to carbapenemase expression poses a worldwide threat in healthcare. Inter-genus exchange of genetic information is of utmost importance in this context. Objectives: Here, to the best of our knowledge, we describe the first detection and characterization of a KPC-2-producing Pseudomonas aeruginosa in Germany. Methods: Characterization of the isolate was performed using MALDI-TOF MS, automated microdilution and MLST. Carbapenemase detection was performed using phenotypic and genotypic assays. The blaKPC-2-carrying plasmid was transformed into Escherichia coli NEB® 10-beta. The purified plasmid DNA was sequenced using the Illumina technique. Results: The isolate expressed ST235 and was resistant to carbapenems. Antimicrobial susceptibility testing revealed colistin to be the only antimicrobial agent active in vitro. The blaKPC-2 gene was located on a replicon type lncHI1 plasmid as part of Tn4401. Conclusions: The first detection (to the best of our knowledge) of plasmid-encoded KPC-2 in P. aeruginosa in Germany may point to a currently underestimated spread of carbapenemases among clinically relevant Gram-negative bacteria. Here, to the best of our knowledge, we also provide the first report of blaKPC-2 associated with the IncHI1 plasmid.

Progressive increase of resistance in Enterobacteriaceae urinary isolates from kidney transplant recipients over the past decade: narrowing of the therapeutic options.

BACKGROUND: Antibiotic resistance is an emerging phenomenon in kidney transplantation (KT). METHODS: We compared species distribution and antimicrobial susceptibility patterns in 1052 isolates from urine cultures obtained in 2 different cohorts of kidney transplant recipients in a single center (Cohort A: 189 patients undergoing KT between January 2002 and December 2004 [336 isolates]; Cohort B: 115 patients undergoing KT between January 2011 and December 2013 [716 isolates]). RESULTS: Asymptomatic bacteriuria accounted for most of the isolates (86.9% in Cohort A and 92.3% in Cohort B). Klebsiella pneumoniae (9.5% vs. 15.6%), Pseudomonas aeruginosa (1.8% vs. 7.9%), and Enterobacter cloacae (0.6% vs. 3.1%) were significantly more common in Cohort B. The isolation of K. pneumoniae in Cohort B was associated with the occurrence of acute pyelonephritis (9.8% of all K. pneumoniae isolates vs. 2.8% of the remaining uropathogens; P = 0.001). Non-susceptibility rates among Enterobacteriaceae in Cohort B were higher for every class of antibiotics (P ≤ 0.003) with the exception of fosfomycin. Compared to Cohort A, significant increases were seen in isolates from Cohort B for multidrug-resistant (MDR) (43.9% vs. 67.8%, respectively; P = 0.001), extended-spectrum beta-lactamase (ESBL)-producing (6.6% vs. 26.1%; P = 0.001), and carbapenemase-producing Enterobacteriaceae strains (0.0% vs. 5.0%; P = 0.001). Such differences were mostly attributable to K. pneumoniae (as 54.5% and 13.4% of isolates in Cohort B were ESBL-producing and carbapenemase-producing, respectively). MDR isolates were responsible for 69.1% of episodes of symptomatic urinary tract infection in Cohort B. CONCLUSION: The increase in resistance rates among Enterobacteriaceae uropathogens is significant and may have an effect on KT programs.

Catheter-associated urinary tract infection in a surgical intensive care unit.

BACKGROUND/AIM: Because patients in intensive care units usully have an urinary catheter, the risk of urinary tract infection for these patients is higher than in other patients. The aim of this study was to identify risk factors and causative microrganisms in patients with catheter-associated urinary tract infection (CAUTI) in the Surgical Intensive Care Unit (SICU) during a 6-year period. METHODS: All data were collected during prospective surveillance conducted from 2006 to 2011 in the SICU, Military Medical Academy, Belgrade, Serbia. This case control study was performed in patients with nosocomial infections recorded during surveillance. The cases with CAUTIs were identified using the definition of the Center for Disease Control and Prevention. The control group consisted of patients with other nosocomial infections who did not fulfill criteria for CAUTIs according to case definition. Results. We surveyed 1,369 patients representing 13,761 patient days. There were a total of 226 patients with nosocomial infections in the SICU. Of these patients, 64 had CAUTIs as defined in this study, and 162 met the criteria for the control group. Multivariate logistic regression analysis identified two risk factors independently associated to CAUTIs: the duration of having an indwelling catheter (OR = 1.014; 95% CI 1.005-1.024; p = 0.003) and female gender (OR = 2.377; 95% CI 1.278-4.421; p = 0.006). Overall 71 pathogens were isolated from the urine culture of 64 patients with CAUTIs. Candida spp. (28.2%), Pseudomonas aeruginosa (18.3%) and Klebsiella spp. (15.5%) were the most frequently isolated microorganisms. CONCLUSIONS: The risk factors and causative microrganisms considering CAUTIs in the SICU must be considered in of planning CAUTIs prevention in this setting.

Pseudomonas aeruginosa quorum sensing molecules correlate with clinical status in cystic fibrosis.

Pseudomonas aeruginosa produces quorum sensing signal molecules that are potential biomarkers for infection.A prospective study of 60 cystic fibrosis patients with chronic P. aeruginosa, who required intravenous antibiotics for pulmonary exacerbations, was undertaken. Clinical measurements and biological samples were obtained at the start and end of the treatment period. Additional data were available for 29 of these patients when they were clinically stable.Cross-sectionally, quorum sensing signal molecules were detectable in the sputum, plasma and urine of 86%, 75% and 83% patients, respectively. They were positively correlated between the three biofluids. Positive correlations were observed for most quorum sensing signal molecules in sputum, plasma and urine, with quantitative measures of pulmonary P. aeruginosa load at the start of a pulmonary exacerbation. Plasma concentrations of 2-nonyl-4-hydroxy-quinoline (NHQ) were significantly higher at the start of a pulmonary exacerbation compared to clinical stability (p<0.01). Following the administration of systemic antibiotics, plasma 2-heptyl-4-hydroxyquinoline (p=0.02) and NHQ concentrations (p<0.01) decreased significantly.In conclusion, quorum sensing signal molecules are detectable in cystic fibrosis patients with pulmonary P. aeruginosa infection and are positively correlated with quantitative measures of P. aeruginosa. NHQ correlates with clinical status and has potential as a novel biomarker for P. aeruginosa infection.

Virulence and Antibiotic Resistance of Pseudomonas aeruginosa Isolated from Patients with Urinary Tract Infections in Southern Poland.

BACKGROUND: The aim of this study was to analyze the resistance and virulence of Pseudomonas aeruginosa strains causing urinary tract infections in in- and outpatients in Southern Poland. METHODS: The study included 83 inpatients and 66 outpatients; 36.9% were female. RESULTS: Monomicrobial infections accounted for 74.5%; polymicrobial infections occurred more frequently among inpatients (odds ratio, OR = 4.32, p = 0.0008). exoS and lasB were detected in 90 and 74% of isolates, respectively. aprA was present in 66%, pilB in 5% and pilA in 23% of isolates. Isolates from adults were more frequently resistant to fluoroquinolones (OR = 0.37, p = 0.029). Twenty-nine isolates were classified as multidrug resistant and 12 as extremely drug resistant, which occurred less frequently in patients <17 years (OR = 0.18, p = 0.024). Nine metallo-ß-lactamase-positive isolates were identified. blaSHV was present in 10, blaTEM in 6, blaOXA-10 in 3 and blaVIM-2 in 3 isolates. CONCLUSION: Antibiotic selection should be based on the knowledge of local antimicrobial susceptibilities to maximize the benefit for patients and minimize the risk of drug resistance.

Renal abscess due to Pseudomonas aeruginosa: report of two cases.

We report two cases of renal abscess due to Pseudomonas aeruginosa in previously healthy children. The first patient was a nine-year old girl with a three-week history of intermittent fever and the second was a three-year old boy with a four-day history of fever. Pseudomonas aeruginosa was isolated from the urine cultures of both children. In both cases ultrasound and CT/MRI scans revealed the formation of a renal abscess. The patients were successfully treated with administration of antipseudomonal drugs for seven and five weeks, respectively. In both children no surgical intervention was required and the follow-up revealed no impact on the overall renal function or arterial pressure.

Bacteriophage therapy for refractory Pseudomonas aeruginosa urinary tract infection.

We describe the success of adjunctive bacteriophage therapy for refractory Pseudomonas aeruginosa urinary tract infection in the context of bilateral ureteric stents and bladder ulceration, after repeated failure of antibiotics alone. No bacteriophage-resistant bacteria arose, and the kinetics of bacteriophage and bacteria in urine suggest self-sustaining and self-limiting infection.

Identification of nonclonal Pseudomonas aeruginosa isolates with reduced colistin susceptibility in Korea.

The in vitro activity of colistin was evaluated against 215 nonduplicated Pseudomonas aeruginosa isolates, including 53 multidrug-resistant isolates, which were collected between 2006 and 2007 from nine tertiary care hospitals in Korea. Colistin-nonsusceptible P. aeruginosa (CNPA) isolates were genotyped using multilocus sequence typing. Sixteen (7.4%) CNPA isolates (minimum inhibitory concentration [MIC], >2 mg/l) were identified, including three resistant isolates. All but one of the MDR P. aeruginosa isolates was susceptible to colistin. Multilocus sequence typing analysis identified 12 sequence types (STs) among 16 CNPA isolates, indicating that colistin nonsusceptibility might arise independently. However, ST244 and ST292, which may be international clones, were found in multiple CNPA isolates. Our data indicate an increase of P. aeruginosa isolates with reduced colistin susceptibility, suggesting the need for continuous surveillance of P. aeruginosa.

[Nitrite test in Pseudomonas aeruginosa urinary tract infections].

UNLABELLED: Pseudomonas aeruginosa (PA) is considered to be bacteria with a low capability to produce nitrite. OBJECTIVE: To investigate the incidence of a positive urine nitrite test in community-acquired urinary tract infections (UTI) in children, caused by PA. METHODS: The medical records of 38 children (18 females) admitted for febrile PA UTI during a period of 7 years were reviewed. Urine nitrite tests were carried out using dipstrips, and results were reported as positive or negative. RESULTS: Of the 38 patients, 17 had a positive nitrite test and 21 had a negative test (proportion of positive 0.45, 95% confidence interval 0.29 to 0.61). Pyuria was detected in 13/17 patients with a positive nitrate test vs. 5/21 with a negative test (p=0.003). Data regarding renal ultrasound (US) were available for 35 patients, and in 20 abnormalities were detected, 14/17 in the positive vs. 6/18 in negative nitrite group (p = 0.001). CONCLUSION: The urine nitrite test may be positive in PA UTI, therefore, a positive test does not rule out Pseudomonas UTI.