Exhibition of antifungal resistance by sterol-auxotrophic strains of Candida glabrata with intact virulence.

Background: Candida glabrata is an emerging fungal pathogen in immune-compromised hosts. Previously undetected C. glabrata isolates were successfully recovered from clinical specimens by adding sterols to the growth medium. The clinical isolates are unable to synthesize ergosterol but can take up exogenous sterols under aerobic conditions. Objectives: This study characterizes the sterol-auxotrophic C. glabrata strains, examines the mutation(s) in sterol synthesis genes, characterizes the drug susceptibility and evaluates the virulence in a mouse infection model. Methods: Drug susceptibility of the C. glabrata strains was evaluated in a sterol-supplemented medium. The coding sequences of the sterol synthesis genes were analysed in six sterol-auxotrophic strains of C. glabrata. The fungal burden of mice infected with C. glabrata strain was determined. Results: The sterol-auxotrophic strains showed high-level resistance to both azoles and amphotericin B when sterols were supplied in the test medium. Additionally, the strains harbour missense mutations in either ERG1 or ERG7. Significant differences in fungal burden were not observed between the sterol-auxotrophic strain and the sterol-competent strain with the mice infection models. Conclusions: The sterol-auxotrophic C. glabrata strain investigated in this study seemed to maintain intact virulence, probably due to the supply of exogenous sterols from host organ(s). This suggests that exogenous sterol uptake develops antifungal resistance during infection.

Microbiology of Bloodstream Infections in Children After Hematopoietic Stem Cell Transplantation: A Single-Center Experience Over Two Decades (1997-2017).

BACKGROUND: Bloodstream infections (BSIs) occur frequently after hematopoietic stem cell transplantation (HSCT). We examined the microbiology of BSI in pediatric HSCT recipients over a 2-decade period at our institution to inform empirical antimicrobial prescribing and infection prevention strategies. METHODS: We conducted a retrospective cohort study of children (<18 years) who underwent HSCT at Duke University between 1997 and 2015. We used recurrent-event gap-time Cox proportional hazards models to determine the hazards of all-cause and cause-specific BSI according to HSCT year. We compared the median time to BSI by causative organism type and evaluated for temporal trends in the prevalence of antibiotic resistance among causative organisms. RESULTS: A total of 865 BSI occurred in 1311 children, including 412 (48%) Gram-positive bacterial, 196 (23%) Gram-negative bacterial, 56 (6%) fungal, 23 (3%) mycobacterial, and 178 (21%) polymicrobial BSI. The hazard of all BSIs did not change substantially over time during the study period, but the hazard of fungal BSIs declined over time during the study period (P = .04). Most fungal BSIs (82%) occurred in the first 100 days after HSCT, whereas mycobacterial BSIs occurred later after HSCT than BSIs caused by other organisms (P < .0001). The prevalence of vancomycin resistance among BSIs caused by Enterococcus faecium increased during the study period (P = .0007). The risk of 2-year mortality in children was increased with BSI (P = .02), Gram-negative bacterial BSI (P = .02), and fungal BSI (P < .0001). CONCLUSIONS: Despite expanded practices for BSI prevention over the past several decades, the incidence of BSI remains high in pediatric HSCT recipients at our institution. Additional strategies are urgently needed to effectively prevent BSIs in this high-risk population.

Microbiology and Risk Factors for Hospital-Associated Bloodstream Infections Among Pediatric Hematopoietic Stem Cell Transplant Recipients.

BACKGROUND: Children undergoing hematopoietic stem cell transplantation (HSCT) are at high risk for hospital-associated bloodstream infections (HA-BSIs). This study aimed to describe the incidence, microbiology, and risk factors for HA-BSI in pediatric HSCT recipients. METHODS: We performed a single-center retrospective cohort study of children and adolescents (<18 years of age) who underwent HSCT over a 20-year period (1997-2016). We determined the incidence and case fatality rate of HA-BSI by causative organism. We used multivariable Poisson regression to identify risk factors for HA-BSI. RESULTS: Of 1294 patients, the majority (86%) received an allogeneic HSCT, most commonly with umbilical cord blood (63%). During the initial HSCT hospitalization, 334 HA-BSIs occurred among 261 (20%) patients. These were classified as gram-positive bacterial (46%), gram-negative bacterial (24%), fungal (12%), mycobacterial (<1%), or polymicrobial (19%). During the study period, there was a decline in the cumulative incidence of HA-BSI (P = .021) and, specifically, fungal HA-BSIs (P = .002). In multivariable analyses, older age (incidence rate ratio [IRR], 1.03; 95% confidence interval [CI], 1.01-1.06), umbilical cord blood donor source (vs bone marrow; IRR, 1.69; 95% CI, 1.19-2.40), and nonmyeloablative conditioning (vs myeloablative; IRR, 1.85; 95% CI, 1.21-2.82) were associated with a higher risk of HA-BSIs. The case fatality rate was higher for fungal HA-BSI than other HA-BSI categories (21% vs 6%; P = .002). CONCLUSIONS: Over the past 2 decades, the incidence of HA-BSIs has declined among pediatric HSCT recipients at our institution. Older age, umbilical cord blood donor source, and nonmyeloablative conditioning regimens are independent risk factors for HA-BSI among children undergoing HSCT.

Performance of the Accelerate Diagnostics PhenoTM system with resin-containing BacT/ALERT® Plus blood culture bottles.

Bacteremia and septicemia require rapid identification (ID) and antimicrobial susceptibility testing (AST) to start targeted, appropriate therapy. To answer this need, Accelerate Diagnostics, Inc., developed the Accelerate Pheno™ system (AXDX), a fast ID and phenotypic AST platform. Performance of a pre-FDA clearance version of AXDX was evaluated using 261 positive BacT/ALERT® Plus bottles and compared with standard of care (SOC). Average time to ID was reduced by 24.9±6.9 h and AST by 36.7±18.9 h compared with SOC. AXDX reports ID and AST of blood pathogens in 1.9 and 7.1 h. Positive percent agreement and negative percent agreement of AXDX ID were 94.5% and 98.9%, respectively. AXDX AST had an essential agreement of 96.5% and categorical agreement of 94.6% with 4 major errors and 7 very major errors. AXDX performance was acceptable for all 3 bottle types. Rapid ID and AST with AXDX could impact patient care and antimicrobial stewardship.

Multicenter Clinical Evaluation of BacT/Alert Virtuo Blood Culture System.

BacT/Alert Virtuo is an advanced, automated blood culture system incorporating improved automation and an enhanced detection algorithm to shorten time to detection. A multicenter study of the investigational Virtuo system (bioMérieux, Inc., Durham, NC) compared to BacT/Alert 3D (BTA3D) for detection of bacteremia/fungemia in four bottle types, SA and FA Plus (aerobic) and SN and FN Plus (anaerobic), was performed in a clinical setting with patient samples in a matched system design clinical trial. Blood was added to paired aerobic or anaerobic bottles, with the volume in each bottle in each pair required to be ≤10 ml and with the volumes required to be within 30% of each other. Of 5,709 bottle sets (52.5% aerobic pairs and 47.5% anaerobic pairs), 430 (7.5%) were positive for bacterial or fungal growth, with 342 (6.0%) clinically significant and 83 (1.5%) contaminated. A total of 3,539 sets (62.0%) were volume compliant, with 203 sets (5.7%) clinically significant. The positivity rates for volume-compliant bottle pairs determined by the two systems were comparable, with 68.7% of clinically significant isolates detected by both instruments, 15.7% by Virtuo only, and 15.7% by BTA3D only. Virtuo detected microbial growth nearly 2 h sooner overall than BTA3D (mean, 15.9 h versus 17.7 h). Shorter time to detection by Virtuo was related to organism group, with the time to detection being significantly shorter for enteric Gram-negative bacilli and enterococci (means, 3.6 h and 2.3 h shorter, respectively). This large clinical study demonstrated that the Virtuo blood culture system produced results comparable to those seen with the long-established BTA3D system, with significantly shorter time to detection.

Two-Phase Hospital-Associated Outbreak of Mycobacterium abscessus: Investigation and Mitigation.

BACKGROUND: Nontuberculous mycobacteria (NTM) commonly colonize municipal water supplies and cause healthcare-associated outbreaks. We investigated a biphasic outbreak of Mycobacterium abscessus at a tertiary care hospital. METHODS: Case patients had recent hospital exposure and laboratory-confirmed colonization or infection with M. abscessus from January 2013 through December 2015. We conducted a multidisciplinary epidemiologic, field, and laboratory investigation. RESULTS: The incidence rate of M. abscessus increased from 0.7 cases per 10000 patient-days during the baseline period (January 2013-July 2013) to 3.0 cases per 10000 patient-days during phase 1 of the outbreak (August 2013-May 2014) (incidence rate ratio, 4.6 [95% confidence interval, 2.3-8.8]; P < .001). Thirty-six of 71 (51%) phase 1 cases were lung transplant patients with positive respiratory cultures. We eliminated tap water exposure to the aerodigestive tract among high-risk patients, and the incidence rate decreased to baseline. Twelve of 24 (50%) phase 2 (December 2014-June 2015) cases occurred in cardiac surgery patients with invasive infections. Phase 2 resolved after we implemented an intensified disinfection protocol and used sterile water for heater-cooler units of cardiopulmonary bypass machines. Molecular fingerprinting of clinical isolates identified 2 clonal strains of M. abscessus; 1 clone was isolated from water sources at a new hospital addition. We made several water engineering interventions to improve water flow and increase disinfectant levels. CONCLUSIONS: We investigated and mitigated a 2-phase clonal outbreak of M. abscessus linked to hospital tap water. Healthcare facilities with endemic NTM should consider similar tap water avoidance and engineering strategies to decrease risk of NTM infection.

Evaluation of a Fully Automated Research Prototype for the Immediate Identification of Microorganisms from Positive Blood Cultures under Clinical Conditions.

UNLABELLED: A clinical laboratory evaluation of an intrinsic fluorescence spectroscopy (IFS)-based identification system paired to a BacT/Alert Virtuo microbial detection system (bioMérieux, Inc., Durham, NC) was performed to assess the potential for fully automated identification of positive blood cultures. The prototype IFS system incorporates a novel method combining a simple microbial purification procedure with rapid in situ identification via spectroscopy. Results were available within 15 min of a bottle signaling positive and required no manual intervention. Among cultures positive for organisms contained within the database and producing acceptable spectra, 75 of 88 (85.2%) and 79 of 88 (89.8%) were correctly identified to the species and genus level, respectively. These results are similar to the performance of existing rapid methods. IMPORTANCE: A fully automated research platform was developed to identify microbial growth from positive blood cultures in <15 min. Because of the automated format, results can be generated during all shifts, with or without staffing, which in turn could promote more timely administration of target antimicrobial therapy.

Challenges in Preparation of Cumulative Antibiogram Reports for Community Hospitals.

Knowledge of local antimicrobial resistance is critical for management of infectious diseases. Community hospitals' compliance with Clinical and Laboratory Standards Institute (CLSI) guidance for creation of cumulative antibiograms is uncertain. This descriptive cohort study of antibiogram reporting practices included community hospitals enrolled in the Duke Infection Control Outreach Network. Cumulative antibiograms from 2012 were reviewed for criteria on reporting practices and compliance with CLSI guidelines. Microbiology personnel were sent a voluntary, electronic survey on antibiogram preparation practices. Data were compiled using descriptive statistics. Thirty-two of 37 (86%) hospitals provided antibiograms; 26 of 37 (70%) also provided survey responses. Twelve (38%) antibiograms specified methods used for compiling data and exclusion of duplicates. Eight (25%) reported only species with >30 isolates. Of the 24 that did not follow the 30-isolate rule, 3 (13%) included footnotes to indicate impaired statistical validity. Twenty (63%) reported at least 1 pathogen-drug combination not recommended for primary or supplemental testing per CLSI. Thirteen (41%) separately reported methicillin-resistant and -susceptible Staphylococcus aureus. Complete compliance with CLSI guidelines was observed in only 3 (9%) antibiograms. Survey respondents' self-assessment of full or partial compliance with CLSI guidelines was 50% and 15%, respectively; 33% reported uncertainty with CLSI guidelines. Full adherence to CLSI guidelines for hospital antibiograms was uncommon. Uncertainty about CLSI guidelines was common. Alternate strategies, such as regional antibiograms using pooled data and educational outreach efforts, are needed to provide reliable and appropriate susceptibility estimates for community hospitals.

The Incidence of Propionibacterium acnes in Open Shoulder Surgery: A Controlled Diagnostic Study.

BACKGROUND: Propionibacterium acnes has arisen as the most common microorganism identified at the time of revision shoulder arthroplasty. There is limited evidence to suggest how frequently false-positive cultures occur. The purpose of this prospective controlled study was to evaluate culture growth from specimens obtained during open shoulder surgery. METHODS: Patients undergoing an open deltopectoral approach to the shoulder were prospectively enrolled. Patients with a history of shoulder surgery or any concern for active or previous shoulder infection were excluded. Three pericapsular soft-tissue samples were taken from the shoulder for bacterial culture and were incubated for fourteen days. A sterile sponge was also analyzed in parallel with the tissue cultures. In addition, similar cultures were obtained from patients who had undergone previous shoulder surgery. RESULTS: Overall, 20.5% of surgeries (twenty-four of 117) yielded at least one specimen removed for culture that was positive for bacterial growth, and 13.0% of sterile control specimens (seven of fifty-four) had positive culture growth (p = 0.234). P. acnes represented 83.0% of all positive cultures (thirty-nine of forty-seven) at a median incubation time of fourteen days. Among the subjects who had not undergone previous surgery, 17.1% (fourteen of eighty-two) had at least one positive P. acnes culture. Male sex was univariably associated with a greater likelihood of bacterial growth (p < 0.01), and patients who had not undergone previous surgery and had received two or more preoperative corticosteroid injections had a higher likelihood of bacterial growth (p = 0.047). CONCLUSIONS: The clinical importance of positive P. acnes cultures from specimens obtained from open shoulder surgery remains uncertain. Male sex and preoperative corticosteroid injections were associated with a higher likelihood of bacterial growth on culture and are risk factors that merit further investigation. Previously reported incidences of positive P. acnes culture results from specimens from primary and revision shoulder arthroplasty may be overestimated because of a substantial level of culture contamination. CLINICAL RELEVANCE: P. acnes is isolated via culture at a substantial rate from shoulders undergoing a deltopectoral approach. The clinical importance of culture growth by this low-virulence organism still remains uncertain. Further study is necessary to more specifically characterize culture growth by P. acnes as an infection, commensal presence, or contaminant.

Rising rates of carbapenem-resistant enterobacteriaceae in community hospitals: a mixed-methods review of epidemiology and microbiology practices in a network of community hospitals in the southeastern United States.

OBJECTIVE: Describe the epidemiology of carbapenem-resistant Enterobacteriaceae (CRE) and examine the effect of lower carbapenem breakpoints on CRE detection. DESIGN: Retrospective cohort. SETTING: Inpatient care at community hospitals. PATIENTS: All patients with CRE-positive cultures were included. METHODS: CRE isolated from 25 community hospitals were prospectively entered into a centralized database from January 2008 through December 2012. Microbiology laboratory practices were assessed using questionnaires. RESULTS: A total of 305 CRE isolates were detected at 16 hospitals (64%). Patients with CRE had symptomatic infection in 180 cases (59%) and asymptomatic colonization in the remainder (125 cases; 41%). Klebsiella pneumoniae (277 isolates; 91%) was the most prevalent species. The majority of cases were healthcare associated (288 cases; 94%). The rate of CRE detection increased more than fivefold from 2008 (0.26 cases per 100,000 patient-days) to 2012 (1.4 cases per 100,000 patient-days; incidence rate ratio (IRR), 5.3 [95% confidence interval (CI), 1.22-22.7]; P = .01). Only 5 hospitals (20%) had adopted the 2010 Clinical and Laboratory Standards Institute (CLSI) carbapenem breakpoints. The 5 hospitals that adopted the lower carbapenem breakpoints were more likely to detect CRE after implementation of breakpoints than before (4.1 vs 0.5 cases per 100,000 patient-days; P < .001; IRR, 8.1 [95% CI, 2.7-24.6]). Hospitals that implemented the lower carbapenem breakpoints were more likely to detect CRE than were hospitals that did not (3.3 vs 1.1 cases per 100,000 patient-days; P = .01). CONCLUSIONS: The rate of CRE detection increased fivefold in community hospitals in the southeastern United States from 2008 to 2012. Despite this, our estimates are likely underestimates of the true rate of CRE detection, given the low adoption of the carbapenem breakpoints recommended in the 2010 CLSI guidelines.

Control of simultaneous outbreaks of carbapenemase-producing enterobacteriaceae and extensively drug-resistant Acinetobacter baumannii infection in an intensive care unit using interventions promoted in the Centers for Disease Control and Prevention 2012 carbapenemase-resistant Enterobacteriaceae Toolkit.

OBJECTIVE: We describe the efficacy of enhanced infection control measures, including those recommended in the Centers for Disease Control and Prevention's 2012 carbapenem-resistant Enterobacteriaceae (CRE) toolkit, to control concurrent outbreaks of carbapenemase-producing Enterobacteriaceae (CPE) and extensively drug-resistant Acinetobacter baumannii (XDR-AB). DESIGN: Before-after intervention study. SETTING: Fifteen-bed surgical trauma intensive care unit (ICU). METHODS: We investigated the impact of enhanced infection control measures in response to clusters of CPE and XDR-AB infections in an ICU from April 2009 to March 2010. Polymerase chain reaction was used to detect the presence of blaKPC and resistance plasmids in CRE. Pulsed-field gel electrophoresis was performed to assess XDR-AB clonality. Enhanced infection-control measures were implemented in response to ongoing transmission of CPE and a new outbreak of XDR-AB. Efficacy was evaluated by comparing the incidence rate (IR) of CPE and XDR-AB before and after the implementation of these measures. RESULTS: The IR of CPE for the 12 months before the implementation of enhanced measures was 7.77 cases per 1,000 patient-days, whereas the IR of XDR-AB for the 3 months before implementation was 6.79 cases per 1,000 patient-days. All examined CPE shared endemic blaKPC resistance plasmids, and 6 of the 7 XDR-AB isolates were clonal. Following institution of enhanced infection control measures, the CPE IR decreased to 1.22 cases per 1,000 patient-days (P = .001), and no more cases of XDR-AB were identified. CONCLUSIONS: Use of infection control measures described in the Centers for Disease Control and Prevention's 2012 CRE toolkit was associated with a reduction in the IR of CPE and an interruption in XDR-AB transmission.

Respiratory fungal infections: molecular diagnostic tests.

Fungal infection of the respiratory tract can take several forms, the most common of which is pneumonia. Fungal infection can occur in the immunocompetent typically as a result of inhalation of a large inoculum of fungal elements. However, the number of etiologic agents attacking immunocompetent individuals and causing significant infection is limited. Molecular assays are a potential additional and sensitive weapon that can be added to the diagnostic arsenal used by physicians to determine whether a fungus is definitively, probably, or possibly causing infection in a patient.

Successful treatment of osseous blastomycosis without pulmonary or disseminated disease and review of the literature.

Blastomycosis commonly occurs following inhalation of Blastomyces dermatitidis conidia causing a pulmonary infection and can disseminate to extrapulmonary sites. Osseous involvement primarily results from hematogenous spread, but in rare cases, direct inoculation can occur. We describe a case of osseous blastomycosis without pulmonary or disseminated disease successfully treated with posaconazole.

More serious infectious morbidity and mortality associated with simultaneous candidemia and coagulase-negative staphylococcal bacteremia in neonates and in vitro adherence studies between Candida albicans and Staphylococcus epidermidis.

BACKGROUND: Candida species and coagulase-negative staphylococci (CoNS) are common etiologies of hospital acquired bloodstream infection in the neonatal intensive care unit (NICU). Sepsis with either organism may result in serious infectious sequelae and along with other staphylococci are the most common causes of abscess formation in preterm infants. This increased incidence of abscess formation may be in part due to adherence factors of both pathogens. METHODS: All cases of concurrent positive blood cultures for both Candida species and CoNS were identified from the microbiology database in NICU patients from January 1998 to December 2000 and analyzed for risk factors and outcomes. In vitro co-aggregation studies between Candida albicans and Staphylococcus epidermidis were also performed. RESULTS: Six premature infants were identified as having concurrent Candida and CoNS bloodstream infections during this time period. Four of the six patients developed end-organ dissemination with abscess or infected thrombus formation. Three of the six patients expired during or after their infection. In vitro, co-aggregation studies did not demonstrate reproducible direct adherence between C. albicans and S. epidermidis. CONCLUSIONS: Simultaneous bloodstream infection with Candida and CoNS, compared to either one alone, is more likely to predispose to abscess formation, septic thrombophlebitis and mortality. Further studies are needed to examine the pathogenesis of these complex infections.

Clinical microbiology costs for methods of active surveillance for Klebsiella pneumoniae carbapenemase-producing Enterobacteriaceae.

OBJECTIVE: To compare direct laboratory costs of different methods for perirectal screening for carbapenemase-producing Enterobacteriaceae (CPE) colonization. DESIGN: Cost-benefit analysis. SETTING: A university hospital and affiliated long-term acute care hospital (LTACH). PARTICIPANTS: Inpatients from the hospital or LTACH. METHODS: Perirectal samples were collected from inpatients at risk for exposure to CPE. In 2009, we compared the accuracy of the Centers for Disease Control and Prevention (CDC)-recommended CPE screening method with similar methods incorporating a chromogenic agar (CA). We then performed a cost projection analysis using 2012 screening results for the CA method, the CDC method, and a molecular assay with wholesale pricing based on the 2009 analysis. Comparisons of turnaround and personnel time were also performed. RESULTS: A total of 185 (2.7%) of 6,860 samples were confirmed as CPE positive during 2012. We previously found that the CDC protocol had a lower sensitivity than the CA method and predicted that the CDC protocol would have missed 92 of the CPE-positive screening results, whereas the modified protocol using CA would have missed 26, assuming similar prevalence and performance. Turnaround time was 3 days using the CDC and CA-modified protocols compared with 1 day for molecular testing. The estimated annual total program cost and total technologist's hours would be the following: CA-modified protocol, $37,441 and 376 hours; CDC protocol, $22,818 and 482 hours; and molecular testing, $224,596 and 343 hours. CONCLUSIONS: The CDC screening protocol appeared to be the least expensive perirectal screening method. However, expense must be weighed against a lower sensitivity and extra labor needed for additional work-up of non-CPE isolates. The molecular test has the shortest turnaround time but the greatest expense.

Outbreak of bacteremia due to Burkholderia contaminans linked to intravenous fentanyl from an institutional compounding pharmacy.

IMPORTANCE Many health care facilities compound medications on site to fulfill local demands when customized formulations are needed, national supply is critically low, or costs for manufactured pharmaceuticals are excessive. Small, institutional compounding facilities may perform the same high-risk procedures as large distributors of compounded medications. OBJECTIVES To investigate an outbreak related to contamination of compounded sterile preparations and to determine processes to prevent future outbreaks. DESIGN, SETTING, AND PARTICIPANTS We performed an outbreak investigation of inpatients at Duke University Hospital from August 31 through September 6, 2012. The investigation included a case-control study, compounding facility inspection and environmental sampling, observation of a mock compounding demonstration, and microbiologic and molecular testing of sequestered medication. EXPOSURES Intravenous fentanyl prepared by an institutional compounding pharmacy. MAIN OUTCOMES AND MEASURES Microbiologic and molecular evidence of contamination of a compounded sterile preparation and failure of routine sterility testing. RESULTS Blood cultures of 7 patients during a 7-day period at Duke University Hospital yielded pan-susceptible Burkholderia cepacia complex bacteria. The risk factor common to all patients was receipt of continuous fentanyl infusion prepared by our institutional compounding pharmacy (odds ratio, 11.22; 95% CI, 2.09-∞; P = .01). The outbreak was terminated after sequestration of compounded fentanyl. An intensive evaluation of the compounding facility, its practice, and its procedures was completed. Investigators evaluated the clean room, collected targeted microbiologic samples within the compounding pharmacy environment, and observed a mock demonstration of compounding practice. The B cepacia complex was found in the anteroom sink drain and pH probe calibration fluid from the compounding clean room. Multiple microbiologic analyses of sequestered fentanyl initially failed. Ultimately, a batched, vacuum-assisted filtration method produced B cepacia complex from a single lot. Molecular analyses using repetitive element polymerase chain reaction and pulsed-field gel electrophoresis confirmed a clonal Burkholderia contaminans strain from patients, fentanyl, and environmental samples. CONCLUSIONS AND RELEVANCE An outbreak of B contaminans bacteremia was linked to contamination of locally compounded intravenous fentanyl. Health care facilities that house institutional compounding facilities must be vigilant in efforts to prevent, recognize, and terminate medication-related outbreaks.

Modified Hodge test versus indirect carbapenemase test: prospective evaluation of a phenotypic assay for detection of Klebsiella pneumoniae carbapenemase (KPC) in Enterobacteriaceae.

The currently recommended phenotypic test for the detection of carbapenemase-producing members of the family Enterobacteriaceae is the modified Hodge test (MHT). However, the MHT lacks specificity. Here we demonstrate an alternative phenotypic test, the indirect carbapenemase test, for the detection of blaKPC-producing isolates that has specificity superior to that of the MHT for non-Klebsiella Enterobacteriaceae.

Influence of DMSO on antifungal activity during susceptibility testing in vitro.

Dimethylsulfoxide (DMSO) binds within the plasma membrane of cells and increases membrane permeability. DMSO is used in antifungal (AF) susceptibility assays for water insoluble agents. DMSO was observed to cause Candida albicans to express enhanced, diminished, or no change in growth compared to control medium, suggesting DMSO could influence the efficacy of water-insoluble AF agents. The activity of 4 water soluble AF agents against 6 yeast species was tested under conditions similar to the CSLI M27-A3 method. Growth response to 0.5% and 1% DMSO was variable. In 15 of 67 AF assays, DMSO resulted in a different MIC-2 (substantial inhibition of growth) value compared to control. Two of these involved differences of two doubling dilutions. The results imply that, in some cases of water-insoluble AF drug-yeast combinations, the MIC-2 may be skewed from the more clinically relevant MIC, providing one reason for possible discordance between MIC results and clinical outcomes.