P. Rocco LaSala

Emergence of linezolid-resistant coagulase-negative Staphylococcus in a cancer centre linked to increased linezolid utilization

OBJECTIVES The prevalence of linezolid-resistant coagulase-negative Staphylococcus (CoNS) in the MD Anderson Cancer Center rose from 0.6% in 2007 to 5.5% in 2009. The aim of our study was to analyse the relationship between linezolid use and an outbreak of linezolid-resistant CoNS. PATIENTS AND METHODS We retrospectively identified 27 infection or colonization events. Eleven isolates were available for supplemental investigation; species identification, clonal relatedness and linezolid resistance mutation analysis. The medical records of the affected patients were reviewed and linezolid utilization data were obtained from the pharmacy. RESULTS Available isolates were confirmed as clonally related Staphylococcus epidermidis. Partial 23S rRNA gene sequencing found a G2576T mutation in all of the isolates tested. All patients received linezolid within 3 months prior to an event. Patients without a prior hospitalization had a longer time from admission to event; 29 versus 3.5 days (P = 0.002). The outbreak was preceded by a 51% increase in inpatient linezolid utilization and 64% of affected patients belonged to the leukaemia service, which had a utilization rate 3.1 times that of the other services (95% confidence interval: 2.96-3.23). CONCLUSIONS Increased linezolid utilization preceded the appearance of a linezolid-resistant CoNS clone. Patients probably acquired the clonal strain nosocomially, given the longer time from admission to event among patients with no previous admission to the MD Anderson Cancer Center. Linezolid administration then selected this strain, since all patients received linezolid prior to an event. A linezolid utilization rate of >or=13 defined daily doses/100 patient-days was similar to that reported in two other outbreaks and may be the threshold required to generate an outbreak.

Tick-borne flaviviruses.

There has been a remarkable increase in tick-borne flaviviral disease incidence throughout the past 2 decades. Transmission of tick-borne viruses, like other vector-borne agents, is impacted by a very broad set of factors, both natural (eg, climate and ecology) and man-made (eg, human mobility and agricultural patterns). As our encroachment into areas of virus endemicity intensifies, and as changes in global economic and environmental conditions continue to promote the expansion of tick populations, we will undoubtedly continue to observe attendant increases in rates of disease attributable to these vector-borne pathogens. This article focuses on a some of the major tick-borne flaviviral diseases, caused in particular by tick-borne encephalitis virus, louping ill virus, Powassan virus, Kyasanur Forest disease virus, and Omsk hemorrhagic fever virus, as well as their subtypes.

Quantitative fecal lactoferrin in toxin-positive and toxin-negative Clostridium difficile specimens

ABSTRACT Quantitative fecal lactoferrin was measured in 112 patients tested for toxigenic Clostridium difficile using glutamate dehydrogenase (GDH) and toxin immunoassays combined with tcdB PCR. Lactoferrin levels were higher in the GDH-positive/toxin-positive group (79 μg/ml) than in the GDH-positive/toxin-negative/PCR-positive (21 μg/ml) and the GDH-negative groups (13 μg/ml). Differences in fecal lactoferrin levels suggest variable presence or severity of C. difficile infection among toxin-positive and toxin-negative patients.

Aspergillus Collagen-Like Genes (acl): Identification, Sequence Polymorphism, and Assessment for PCR-Based Pathogen Detection

ABSTRACT The genus Aspergillus is a burden to public health due to its ubiquitous presence in the environment, its production of allergens, and wide demographic susceptibility among cystic fibrosis, asthmatic, and immunosuppressed patients. Current methods of detection of Aspergillus colonization and infection rely on lengthy morphological characterization or nonstandardized serological assays that are restricted to identifying a fungal etiology. Collagen-like genes have been shown to exhibit species-specific conservation across the noncollagenous regions as well as strain-specific polymorphism in the collagen-like regions. Here we assess the conserved region of the Aspergillus collagen-like (acl) genes and explore the application of PCR amplicon size-based discrimination among the five most common etiologic species of the Aspergillus genus, including Aspergillus fumigatus, A. flavus, A. nidulans, A. niger, and A. terreus. Genetic polymorphism and phylogenetic analysis of the aclF1 gene were additionally examined among the available strains. Furthermore, the applicability of the PCR-based assay to identification of these five species in cultures derived from sputum and bronchoalveolar fluid from 19 clinical samples was explored. Application of capillary electrophoresis on nanogels was additionally demonstrated to improve the discrimination between Aspergillus species. Overall, this study demonstrated that Aspergillus acl genes could be used as PCR targets to discriminate between clinically relevant Aspergillus species. Future studies aim to utilize the detection of Aspergillus acl genes in PCR and microfluidic applications to determine the sensitivity and specificity for the identification of Aspergillus colonization and invasive aspergillosis in immunocompromised subjects.

Candida dubliniensis endophthalmitis: first case in North America

To report an unusual case of endogenous fungal endophthalmitis due to Candida dubliniensis. Interventional case report of a 27-year-old immunocompetent male with loss of vision, dense vitritis, and chorioretinal infiltrates, who underwent a diagnostic pars plana vitrectomy. Microbiology cultures obtained by a diagnostic vitrectomy were positive for the growth of C. dubliniensis. This infectious process was then appropriately treated with intravitreal amphotericin B and systemic fluconazole with resolution of the endophthalmitis. Endogenous fungal endophthalmitis is a condition that can masquerade other more common causes of endophthalmitis. Atypical cases of endophthalmitis may benefit from diagnostic pars plana vitrectomy for prompt diagnosis and treatment.

Comparison of Analytical and Clinical Performance of Three Methods for Detection of Clostridium difficile

CONTEXT Diagnostic laboratory testing for Clostridium difficile infection has undergone considerable and rapid evolution during the last decade. The ideal detection method(s), which should exhibit high analytical and clinical sensitivity and specificity, remains undefined. OBJECTIVE We sought to evaluate the analytical and clinical performance characteristics of three methods for the laboratory detection of C difficile. DESIGN This study used 114 consecutive stool samples to compare three methods of C difficile detection: an enzyme immunoassay (EIA) for toxins A/B, a lateral flow membrane immunoassay for glutamate dehydrogenase (GDH), and a qualitative real-time polymerase chain reaction (PCR) assay. Medical records of all patients having ≥1 positive test result were reviewed to estimate the clinical likelihood of C difficile infection. RESULTS Based upon laboratory result consensus values, analytical sensitivity was significantly higher for GDH (94%) and PCR (94%) assays than for toxin EIA (25%). Analytical specificity was significantly higher for PCR (100%) and EIA (100%) than for GDH assay (93%). In contrast, assay performance based upon clinical probability of C difficile infection suggested lower discriminatory power (ie, clinical specificity) of the more analytically sensitive methods. CONCLUSIONS Higher rates of C difficile detection will be realized upon implementation of GDH assay and/or real-time PCR-based testing algorithms than by testing with EIA alone. Further study is required to elucidate potential downstream costs for higher detection rates.

Pathology consultation on detection of Clostridium difficile.

Laboratory methods for detecting Clostridium difficile have undergone considerable evolution since the organisms etiologic association with antibiotic-associated diarrhea and colitis was established. Clearly, familiarity with the advantages and shortcomings of the various assays is essential for the laboratory director when choosing among these tests. For the consulting pathologist, furthermore, an understanding of the laboratorys role in securing a diagnosis of C difficile infection (CDI) is also required to identify requests for unnecessary testing that may be costly and potentially misleading. The purpose of this article is to highlight the major differences in laboratory test methods for CDI and to review a few commonly encountered provider ordering scenarios.

Multidisciplinary performance improvement team for reducing health care–associated Clostridium difficile infection

Clostridium difficile is the most frequent cause of health care-associated diarrhea and is a significant cause of morbidity and mortality. It is also associated with a considerable financial burden. A concerted multidisciplinary approach is required for prevention.

Topical Adjuvants Incompletely Remove Adherent Staphylococcus aureus from Implant Materials

Adjuvant treatments including Betadine, Dakins solution (sodium hypochlorite), or hydrogen peroxide (H2O2) have been attempted to eradicate prosthetic joint infection caused by biofilm or intracellular bacteria. The purpose of this study was to evaluate the in vitro abilities of chemical adjuvants to decrease Staphylococcus aureus (S. aureus) biofilm presence on orthopaedic implant grade materials, including titanium, stainless steel, and cobalt chrome. S. aureus biofilms were grown for 48 h and evaluated for baseline colony forming units/centimeter squared (CFU/cm2) and compared to treatments with Betadine, Dakins solution, H2O2, or 1% chlorine dioxide (ClO2). Control discs (n = 18) across all metals had an average of 4.2 × 107 CFU/cm2. All treatments had statistically significant reductions in CFU/cm2 when compared to respective control discs (p < 0.05). For all metals combined, the most efficacious treatments were Betadine and H2O2, with an average 98% and 97% CFU/cm2 reduction, respectively. There were no significant differences between reductions seen with Betadine and H2O2, but both groups had statistically greater reductions than Dakins solution and ClO2. There was no change in antibiotic resistance patterns after treatment. Analysis of S. aureus biofilms demonstrated a statistically significant reduction in biofilm after a five‐minute treatment with the modalities, with an average two log reduction in CFU/cm2. Statement of clinical significance: While statistically significant reductions in CFU/cm2 were accomplished with chemical adjuvant treatments, the overall concentration of bacteria never fell below 105 CFU/cm2, leading to questionable clinical significance. Further techniques to eradicate biofilm should be investigated.