An Assessment of Siderophore Production, Mucoviscosity, and Mouse Infection Models for Defining the Virulence Spectrum of Hypervirulent Klebsiella pneumoniae.

Hypervirulent Klebsiella pneumoniae (hvKp) bacteria are more virulent than classical K. pneumoniae (cKp) with resultant differences in clinical manifestations and management. It is unclear whether all hvKp isolates share a similar pathogenic potential. This report assessed the utility of siderophore production, mucoviscosity, and murine infection for defining the virulence spectrum of hvKp. Three strain cohorts were identified and defined based on the CD1 mouse subcutaneous (SQ) challenge model: (i) fully virulent hvKp strains (fvhvKp), lethal at a challenge inoculum (CI) of ≤103 CFU; (ii) partially virulent hvKp strains (pvhvKp), lethal at a CI of >103 to 107 CFU; (iii) classical K. pneumoniae, not lethal at a CI of 107 CFU. Quantitative siderophore and mucoviscosity assays differentiated fvhvKp and pvhvKp strains from cKp strains but were unable to differentiate between the fvhvKP and pvhvKP strain cohorts. However, SQ challenge of CD1 mice and intraperitoneal (IP) challenge of CD1 and BALB/c mice, but not C57BL/6 mice, were able to discriminate between an fvhvKp and a pvhvKp strain; SQ challenge of CD1 mice may have the greatest sensitivity. cKp was differentiated from hvKp both by SQ challenge of CD1 mice and IP challenge of all three mouse strains. These data identify a means to define the relative virulence of hvKP strains. It remains unclear whether the observed differences of hvKp virulence in mice translates to human infection. However, these data can be used to sort random collections of K. pneumoniae strains into fvhvKp and pvhvKp strain cohorts and assess for differences in clinical manifestations and outcomes.IMPORTANCE The pathogenic potential of hvKp strains is primarily mediated by a large virulence plasmid. The minimal set of genes required for the full expression of the hypervirulent phenotype is undefined. A number of reports describe hvKp strains possessing only a portion of the virulence plasmid; the clinical consequences of this are unclear. Therefore, the goal of this report was to determine whether virulence among hvKp strains varied and, if so, how to best identify the relative virulence of hvKp isolates. Data demonstrate hvKp pathogenic potential varies in CD1 and BALB/c murine infection models. In contrast, measurements of siderophore production and mucoviscosity were unable to discriminate the differences in hvKp isolate virulence observed in mice. This information can be used in future studies to determine the mechanisms responsible for differences between fully virulent hvKp and partially virulent hvKp and whether the differences observed in mice translate to disease in humans.

Low antimicrobial resistance in general practice patients in Rotterdam, the city with the largest proportion of immigrants in the Netherlands.

Antimicrobial resistance (AMR) is an increasing problem. The prevalence of antimicrobial resistance in general practice patients is expected to be relatively high in Rotterdam, the Dutch city with the largest proportion non-Western immigrants. The aim of this study was to assess the prevalence of antibiotic-resistant uropathogens (Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis) in general practices in Rotterdam, and to find a possible association between the prevalence of antibiotic-resistant E. coli and age, gender, and socioeconomic status (SES). A retrospective analysis was performed of urine samples from general practice patients in 2016. The prevalence of AMR in uropathogens was compared with national resistance data, as was the prevalence of highly and multidrug resistant and extended spectrum ß-lactamase (ESBL) producing E. coli and K. pneumoniae. Univariate logistic regression was used to study associations between antibiotic-resistant E. coli and age, gender, and SES area score. No clinically relevant differences were observed in the prevalence of antibiotic-resistant uropathogens in Rotterdam compared with the national prevalence. For E. coli and K. pneumoniae, the prevalence was 3.6% for ESBL production (both pathogens together), while the prevalence ranged between 4.2%-5.0% for high resistance and between 1.2%-3.3% for multidrug resistance. Ciprofloxacin-resistant E. coli was significantly associated with higher age. Although Rotterdam has a high percentage of non-western immigrants and a low SES, AMR is low among general practice patients. This indicates that adherence to national guidelines in general practice enables maintenance of low AMR, even in high-risk populations.

Comparison of equal doses of continuous venovenous haemofiltration and haemodiafiltration on ciprofloxacin population pharmacokinetics in critically ill patients.

OBJECTIVES: Whilst commonly performed in ICUs, renal replacement therapies (RRTs) differ in their solute clearances. There is a paucity of data on ciprofloxacin clearances in different RRT techniques. The aim of this study was to compare the population pharmacokinetics of ciprofloxacin during equal doses of continuous venovenous haemofiltration (CVVHF) and continuous venovenous haemodiafiltration (CVVHDF) in septic patients. METHODS: Patients receiving 400 mg of ciprofloxacin intravenously 8 or 12 hourly and undergoing either CVVHF or CVVHDF were eligible. Up to 10 blood samples were collected over one dosing interval and analysed by a validated chromatographic method. Population pharmacokinetic analysis and Monte Carlo simulation was undertaken using Pmetrics. RESULTS: Eighteen sampling intervals were included (8 CVVHDF and 10 CVVHF) from 11 patients (6 patients having sampling during both RRT modes). A two-compartment linear model best described the data. Increasing patient weight was the only covariate associated with increasing drug clearance. The mean (SD) parameter estimates were: clearance, 10.7 (5.3) L/h; volume of distribution of the central compartment, 21.3 (11.3) L; rate constant for drug distribution from the central compartment to the peripheral compartment, 10.9 (4.3) L/h; and rate constant for drug distribution from the peripheral compartment to the central compartment, 2.3 (1.8) L/h. After accounting for patient weight, the mean ciprofloxacin clearance was not statistically different between CVVHF and CVVHDF [11.8 (9.9) and 10.3 (7.4) L/h, respectively, P = 0.43]. CONCLUSIONS: The present study indicates a high pharmacokinetic variability of ciprofloxacin during CVVHF and CVVHDF with no significant differences in clearance apparent. Based on patient weight, higher ciprofloxacin dosing regimens should be used in critically ill patients when difficult-to-treat pathogens are suspected.

[Assessment of persistent potential dominant pathogens of acute intestinal infections].

To determine the prevalence,and etiological structure of acute intestinal infections, to investigate the dominant agents' persistence factors. According with materials of statistical reports we did the retrospective epidemiological analysis of acute intestinal infections incidence in Sumy region from 2006 till 2011. Biological properties of 40 strains of Klebsiella pneumonia, 40 strains of Enterobacter cloacae and 50 strains of Staphylococcus aureus were investigated. Moderate trend of acute intestinal infections incidence increase was indicated. Bacteria of genera Klebsiella, Enterobacter, Staphylococcus were predominated in etiological structure. Incidence of acute diarrheal infections caused by Klebsiella and Enterobacter was reached the maximum in the spring-summer period. The incidence of staphylococcal etiology was discrete. The strains of Klebsiella pneumonia, Staphylococcus aureus and Enterobacter cloacae were remarkable for different frequency and intensity of persistence factors. Аnti-interferon activity was detected in 100% of clinical isolates of microorganisms, anti-lysozym activity was detected in 87.3 ± 2.9% of clinical isolates of microorganisms, anti-complementary activity was detected in 72.3 ± 3.9% of clinical isolates of microorganisms. Biological properties of opportunistic pathogens that cause acute intestinal infections can be used as epidemiological factors for differentiation of microorganisms pathogenicity.

Assessment of hypermucoviscosity as a virulence factor for experimental Klebsiella pneumoniae infections: comparative virulence analysis with hypermucoviscosity-negative strain.

BACKGROUND: Klebsiella pneumoniae displaying the hypermucoviscosity (HV) phenotype are considered more virulent than HV-negative strains. Nevertheless, the emergence of tissue-abscesses-associated HV-negative isolates motivated us to re-evaluate the role of HV-phenotype. RESULTS: Instead of genetically manipulating the HV-phenotype of K. pneumoniae, we selected two clinically isolated K1 strains, 1112 (HV-positive) and 1084 (HV-negative), to avoid possible interference from defects in the capsule. These well-encapsulated strains with similar genetic backgrounds were used for comparative analysis of bacterial virulence in a pneumoniae or a liver abscess model generated in either naïve or diabetic mice. In the pneumonia model, the HV-positive strain 1112 proliferated to higher loads in the lungs and blood of naïve mice, but was less prone to disseminate into the blood of diabetic mice compared to the HV-negative strain 1084. In the liver abscess model, 1084 was as potent as 1112 in inducing liver abscesses in both the naïve and diabetic mice. The 1084-infected diabetic mice were more inclined to develop bacteremia and had a higher mortality rate than those infected by 1112. A mini-Tn5 mutant of 1112, isolated due to its loss of HV-phenotype, was avirulent to mice. CONCLUSION: These results indicate that the HV-phenotype is required for the virulence of the clinically isolated HV-positive strain 1112. The superior ability of the HV-negative stain 1084 over 1112 to cause bacteremia in diabetic mice suggests that factors other than the HV phenotype were required for the systemic dissemination of K. pneumoniae in an immunocompromised setting.

Effects of the USA PATRIOT Act and the 2002 Bioterrorism Preparedness Act on select agent research in the United States.

A bibliometric analysis of the Bacillus anthracis and Ebola virus archival literature was conducted to determine whether negative consequences of the Uniting and Strengthening America by Providing Appropriate Tools Required to Intercept and Obstruct Terrorism" (USA PATRIOT) Act and the 2002 Bioterrorism Preparedness Act on US select agent research could be discerned. Indicators of the health of the field, such as number of papers published per year, number of researchers authoring papers, and influx rate of new authors, indicated an overall stimulus to the field after 2002. As measured by interorganizational coauthorships, both B. anthracis and Ebola virus research networks expanded after 2002 in terms of the number of organizations and the degree of collaboration. Coauthorship between US and non US scientists also grew for Ebola virus but contracted for the subset of B. anthracis research that did not involve possession of viable, virulent bacteria. Some non-US institutions were dropped, and collaborations with others intensified. Contrary to expectations, research did not become centralized around a few gatekeeper institutions. Two negative effects were detected. There was an increased turnover rate of authors in the select agent community that was not observed in the control organism (Klebsiella pneumoniae) research community. However, the most striking effect observed was not associated with individual authors or institutions; it was a loss of efficiency, with an approximate 2- to 5-fold increase in the cost of doing select agent research as measured by the number of research papers published per millions of US research dollars awarded.

Identification of a conserved chromosomal region encoding Klebsiella pneumoniae type 1 and type 3 fimbriae and assessment of the role of fimbriae in pathogenicity.

Type 3 fimbriae are expressed by most clinical Klebsiella pneumoniae isolates and mediate adhesion to host structures in vitro. However, the role of type 3 fimbriae in K. pneumoniae virulence has not been evaluated by use of in vivo infection models. In this study, the type 3 fimbrial gene cluster (mrk) of the clinical isolate C3091 is described in detail. The mrk gene cluster was revealed to be localized in close proximity to the type 1 fimbrial gene cluster. Thus, a 20.4-kb fimbria-encoding region was identified and found to be highly conserved among different K. pneumoniae isolates. Interestingly, a homologue to PecS, known as a global regulator of virulence in Erwinia chrysanthemi, was identified in the fimbria-encoding region. Comparison to the previously characterized plasmid encoded mrk gene cluster revealed significant differences, and it is established here that the putative regulatory gene mrkE is not a part of the chromosomally encoded type 3 fimbrial gene cluster. To evaluate the role of type 3 fimbriae in virulence, a type 3 fimbria mutant and a type 1 and type 3 fimbria double mutant was constructed. Type 3 fimbria expression was found to strongly promote biofilm formation. However, the fimbria mutants were as effective at colonizing the intestine as the wild type, and their virulence was not attenuated in a lung infection model. Also, in a urinary tract infection model, type 3 fimbriae did not influence the virulence, whereas type 1 fimbriae were verified as an essential virulence factor. Thus, type 3 fimbriae were established not to be a virulence factor in uncomplicated K. pneumoniae infections. However, since type 3 fimbriae promote biofilm formation, their role in development of infections in catheterized patients needs to be elucidated.

Attributable costs and length of stay of an extended-spectrum beta-lactamase-producing Klebsiella pneumoniae outbreak in a neonatal intensive care unit.

OBJECTIVES: To determine the costs of the interventions aimed at controlling the 4-month outbreak and to determine the attributable length of stay (LOS) associated with infection and colonization with extended-spectrum beta-lactamase-producing Klebsiella pneumoniae. DESIGN: A retrospective cost analysis was conducted from the hospital perspective. A micro-costing approach was employed. The LOS of four groups of hospitalized patients were compared with each other. National Perinatal Information Center criteria were used to stratify infants for severity of risk. The LOS of each group was compared with that of a national sample of similarly stratified infants. SETTING: A level III-IV, 45-bed neonatal intensive care unit. PATIENTS: Infant groups were infected (n = 8), colonized (n = 14), concurrent cohort (n = 54), and prior cohort (n = 486). RESULTS: The cost of the outbreak totaled 341,751 dollars. The largest proportion of costs was related to healthcare worker time providing direct patient care (2,489 hours at a cost of 146,331 dollars). Infected and colonized neonates had longer LOS than either the concurrent cohort or the prior cohort (P < .001). Compared with the national sample, infected infants had a 48.5-day longer mean LOS (95% confidence interval [CI95], 1.7 to 95.2), whereas the prior cohort's mean LOS was 6 days shorter (CI95, -9.4 to -2.9). CONCLUSIONS: This study increases the understanding of the burden of these multidrug-resistant organisms. Further research is needed to estimate the societal costs of these infections and the cost-effectiveness of preventive interventions.

The cost of antibiotic resistance: effect of resistance among Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudmonas aeruginosa on length of hospital stay.

To assess the effect of antimicrobial resistance on length of hospital stay, a case-control study compared infections due to four nosocomial pathogens. Significantly increased lengths of stay were associated with infections due to methicillin-resistant Staphylococcus aureus, extended-spectrum beta-lactamase-producing Klebsiella pneumoniae, and carbapenem-resistant Acinetobacter baumannii or Pseudomonas aeruginosa. Infections with resistant pathogens are associated with prolonged hospitalization.