Nosocomial Infection With Cephalosporin-ResistantKlebsiella pneumoniaeIs Not Associated With Increased Mortality

Impact of infection with extended-spectrum β-lactamase-producing Escherichia coli or Klebsiella species on outcome and hospitalization costs

BACKGROUND

Extended-spectrum β-lactamase (ESBL)-producing bacteria are important sources of infection; however, Canadian data evaluating the impact of ESBL-associated infection are lacking.

AIM

To determine whether patients infected with ESBL-producing Escherichia coli or Klebsiella species (ESBL-EcKs) exhibit differences in clinical outcome, microbiological outcome, mortality, and/or hospital resource use compared to patients infected with non-ESBL-producing strains.

METHODS

A retrospective case-control study of 75 case patients with ESBL-EcKs matched to controls infected with non-ESBL-EcKs who were hospitalized from June 2010 to April 2013 was conducted. Patient-level cost data were provided by the institution's business office. Clinical data were collected using the electronic databases and paper charts.

FINDINGS

Median infection-related hospitalization costs per patient were greater for cases than controls (C$10,507 vs C$7,882; median difference: C$3,416; P = 0.04). The primary driver of increased costs was prolonged infection-related hospital length of stay (8 vs 6 days; P = 0.02) with patient location (ward, ICU) and indirect care costs (including costs associated with infection prevention and control) as the leading cost categories. Cases were more likely to experience clinical failure (25% vs 11%; P = 0.03), with a higher all-cause mortality (17% vs 5%; P = 0.04). Less than half of case patients were prescribed appropriate empiric antimicrobial therapy, whereas controls received adequate initial treatment in nearly all circumstances (48% vs 96%; P < 0.01).

CONCLUSION

Patients with infection caused by ESBL-EcKs are at increased risk for clinical failure and mortality, with additional cost to the Canadian healthcare system of C$3,416 per patient.

Hypermucoviscosity as a virulence factor in experimental Klebsiella pneumoniae endophthalmitis

PURPOSE

Klebsiella pneumoniae is a common cause of endogenous bacterial endophthalmitis, a disease that frequently results in a poor visual outcome. Hypermucoviscosity has been identified as a virulence factor among clinical bacteremia isolates of K. pneumoniae. In this study, an experimental murine model of K. pneumoniae endophthalmitis was established, and the role of hypermucoviscosity in its pathogenesis was analyzed.

METHODS

C57BL/6J mice were intravitreously injected with 100 CFU of hypermucoviscous (HMV+) or nonhypermucoviscous (HMV-) K. pneumoniae. Intraocular bacterial growth, retinal function, gross pathology, and inflammatory responses were monitored every 3 hours until the eyes lost significant (>90%) retinal function, or the infection appeared to clear.

RESULTS

The HMV+ strain grew logarithmically in eyes until approximately 15 hours postinfection (PI), reaching a stationary phase of growth at approximately 8.0 log(10) CFU/eye. The HMV- strain grew logarithmically to approximately 7.6 log(10) by 18 hours, but bacterial count declined to approximately 6.4 log(10) CFU/eye by 21 hours PI. Eyes infected with the HMV+ strain retained approximately 35% a-wave and <10% b-wave function by 18 hours PI. These eyes also had a cumulative clinical score of 14+ by 18 hours and underwent phthisis between 21 and 24 hours. Eyes infected with the HMV- strain had a cumulative clinical score of <6 and retained >60% a-wave and >50% b-wave function throughout 21 hours. Five of 7 eyes had <100 CFU HMV- K. pneumoniae at 27 hours PI.

CONCLUSIONS

The findings demonstrate the site-threatening consequences of K. pneumoniae endophthalmitis and the importance of the hypermucoviscosity phenotype in the pathogenesis of experimental K. pneumoniae endophthalmitis.

Measuring the impact of multidrug resistance in nosocomial infection

PURPOSE OF REVIEW

The review examines potential confounders hampering measurement of the impact of multidrug resistance in nosocomial infections. Methodological techniques dealing with the problem of confounding are discussed and current findings in how multidrug resistance affects outcome in patients with nosocomial infection are highlighted.

RECENT FINDINGS

Outcome comparisons between patients infected with multidrug-resistant pathogens and patients infected with susceptible microorganisms are hampered by confounders such as differences in disease severity, prolonged hospitalization prior to onset of infection (exposure time), the causative pathogen, the type of infection, and the rate of appropriate empirical antimicrobial therapy. The confounding effect can be countered by means of either multivariable regression techniques or matched cohort studies, or a combination of both. Recent literature on the impact of multidrug resistance (methicillin-resistant Staphylococcus aureus, vancomycin-resistant enterococci, extended-spectrum beta-lactamase producing Enterobacteriaceae, etc) is conflicting and highly dependable on the way disturbing variables are accounted for.

SUMMARY

Recent data underscore that the impact of multidrug resistance on the outcome of nosocomial infection might differ depending on the study population, type of infection, type of pathogen and appropriateness of therapy, and hence, that any conclusion drawn prior to accurate accounting for imbalanced confounders is premature and potentially false.