Mechanism of action and initial evaluation of a membrane active all-D-enantiomer antimicrobial peptidomimetic.

Development of therapy against infections caused by antibiotic-resistant pathogens is a major unmet need in contemporary medicine. In previous work, our group chemically modified an antimicrobial peptidomimetic motif for targeted applications against cancer and obesity. Here, we show that the modified motif per se is resistant to proteolytic degradation and is a candidate antiinfective agent. We also show that the susceptibility of microorganisms to the drug is independent of bacterial growth phase. Moreover, this peptidomimetic selectively interferes with the integrity and function of the microbial surface lipid bilayer, data indicative that bacterial death results from membrane disruption followed by dissipation of membrane potential. Finally, we demonstrate two potential translational applications: use against biofilms and synergy with antibiotics in use. In summary, we introduce the mechanism of action and the initial evaluation of a prototype drug and a platform for the development of D-enantiomer antimicrobial peptidomimetics that target bacterial membranes of certain gram-negative problem pathogens with promising translational applications.

FKS mutant Candida glabrata: risk factors and outcomes in patients with candidemia.

BACKGROUND: Echinocandins are recommended for Candia glabrata candidemia. Mutations in the FKS1 and FKS2 genes are associated with echinocandin resistance. Few studies have assessed risk factors for FKS mutant isolates and outcomes in patients receiving micafungin treatment. METHODS: Patients with C. glabrata bloodstream infection admitted to a large, tertiary care hospital between 2009 and 2012 were included in this study. For each isolate, FKS1 and FKS2 genes were sequenced to identify mutations. Risk factors for FKS mutations and treatment outcomes in patients receiving an echinocandin were assessed using multivariate logistic regression. RESULTS: Seventy-two patients were included in the study of which 13 (18%) had an FKS mutant isolate. The only significant predictor for FKS mutations was prior echinocandin exposure (odds ratio [OR], 19.9; 95% confidence interval [CI], 4.7-84.7; P ≤ .01). Treatment failure occurred in 17 (30%) of 57 patients who received an echinocandin and was more common in patients with FKS mutants (6 of 10; 60%) compared with non-FKS mutants (11 of 47; 23%). Underlying gastrointestinal disorder (OR, 4.7; 95% CI, 1.1-20.9; P = .04) and prior echinocandin exposure (OR, 8.3; 95% CI, 1.7-40.4; P ≤ .01) were independent predictors of echinocandin treatment failure. Treatment response and echinocandin minimum inhibitory concentrations varied among specific FKS mutations. CONCLUSIONS: FKS mutations were identified in 18% of 72 patients with C. glabrata candidemia. Common risk factors for FKS mutant isolates included previous echinocandin exposure, which also influenced response rates.

Clinical practice patterns in hospitalized patients at risk for invasive candidiasis: role of antifungal stewardship programs in an era of rapid diagnostics.

BACKGROUND: Rapid diagnostic tests for Candida are becoming available that may supplement traditional microbiological identification. OBJECTIVE: Assess clinical practice patterns in patients with or at risk of candidiasis who may benefit from the use of rapid diagnostic tests. METHODS: This was a prospective cohort study of patients with candidemia or receiving systemic antifungals conducted at a university-affiliated tertiary care hospital. Time to initiation of therapy, Candida species, time to identification, and indications for antifungal use were assessed. RESULTS: A total of 162 patients with candidemia aged 58 ± 17 years were identified. Average time to yeast identification yeast was 2.2 ± 1.3 days and varied by Candida species (range = 0.6-7.9 days). Average time for patient to start antifungal therapy was 3.5 ± 2.1 days. In Monte Carlo simulations, average time to initiation of antifungal therapy was 0.6 ± 0.2 days for T2Candida, 2.6 ± 1.3 days for PNA-FISH (fluorescence in situ hybridization using peptide nucleic acid probes), and 2.5 ± 1.4 days for MALDI-TOF (matrix-assisted laser desorption/ionization time of flight). Use of T2Candida on the day of the blood culture collection resulted in 3136 to 6078 fewer doses of echinocandins annually per 5000 patients. CONCLUSION: Many interventions are possible for antifungal stewardship programs to improve care of patients at risk for systemic candidiasis, including rapid identification of yeast species and limiting unnecessary antifungal agents. Technology enabling rapid diagnosis of Candida will be paramount to appropriate, cost-effective treatment of patients with or at risk for candidiasis.

An evaluation of multiple phenotypic screening methods for Klebsiella pneumoniae carbapenemase (KPC)-producing Enterobacteriaceae.

Klebsiella pneumoniae carbapenemase (KPC)-producing Enterobacteriaceae may display MICs to carbapenems within susceptible or intermediate ranges, prompting confirmatory testing. Four phenotypic methods to detect KPC producers were evaluated against a collection of clinical Enterobacteriaceae isolates. Meropenem-phenylboronic acid double disk synergy testing demonstrated the best performance with 100% sensitivity and specificity.

The impact of direct inoculation of ascites into blood culture bottles on ascites culture positivity.

Objective: Assess whether direct inoculation of ascites into blood culture bottles would improve ascites culture yield. Design: Pre-post-study. Setting: The study was performed at a quaternary academic medical center in Houston, Texas, including all inpatient and emergency department encounters. Patients: Ascites cultures collected from November 2020 to December 2022 were reviewed and screened for spontaneous bacterial peritonitis. Patients were excluded if a prior ascites culture from the same patient was already included in the study or if there was evidence of secondary bacterial peritonitis. Intervention: In the pre-intervention period, ascites cultures were collected into a sterile container and inoculated onto/into solid and liquid media. In the post-intervention period, ascites cultures were instead directly inoculated into bioMérieux© blood culture bottles at the bedside. Results: 114 patients met inclusion and exclusion criteria, 61 pre-intervention and 53 post-intervention. Overall ascites culture positivity was 15.8% (18/114), 11.5% (7/61) pre-intervention vs 20.8% (11/53) post-intervention. After adjusting for confounders, the intervention had a trend toward a significant effect on ascites culture positivity (P = 0.077). No significant differences were seen in time to positivity, hospital length of stay, or 30-day readmission. Conclusions: Direct inoculation of ascitic fluid into blood culture bottles led to a small increase in culture yield but lacked statistical significance. This lack of significance may be due to the study being underpowered. Further studies are required to investigate if this is due to procedural inefficiencies (eg, inadequate inoculation volumes) or pragmatic clinical practice considerations (ie, high rates of pre-culture antibiotics).

Detection of invasive Bartonella infections with next-generation sequencing of microbial cell-free DNA.

We report 9 patients with invasive Bartonella infections, including 5 with endocarditis, who were diagnosed with microbial cell-free DNA next-generation sequencing and Bartonella serology studies. Diagnosis with plasma mcfDNA NGS enabled a faster clinical and laboratory diagnosis in 8 patients. Prompt diagnosis impacted antibiotic management in all 9 patients.

Discontinuation of contact precautions in patients with hospital-acquired MRSA and VRE infections during the COVID-19 pandemic: A multi-center experience.

Variations in the literature support the benefit of contact precautions for methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE) infections in the hospital setting. During personal protective equipment shortages throughout the COVID-19 pandemic, contact precautions were discontinued for MRSA and VRE-infected patients. Rates of hospital-acquired MRSA and VRE infections were compared before and after this intervention, along with hand hygiene proportions. Contact precaution discontinuation did not lead to an increase in hospital-acquired MRSA or VRE infections.

The impact of a blood-culture diagnostic stewardship intervention on utilization rates and antimicrobial stewardship.

Blood-culture overutilization is associated with increased cost and excessive antimicrobial use. We implemented an intervention in the adult intensive care unit (ICU), combining education based on the DISTRIBUTE algorithm and restriction to infectious diseases and ICU providers. Our intervention led to reduced blood-culture utilization without affecting safety metrics.

Use of rifamycin drugs and development of infection by rifamycin-resistant strains of Clostridium difficile.

The relationship between rifamycin drug use and the development of resistant strains of Clostridium difficile was studied at a large university hospital in Houston, TX, between May 2007 and September 2011. In 49 of 283 (17.3%) patients with C. difficile infection (CDI), a rifamycin-resistant strain of C. difficile was identified that compares to a rate of 8% using the same definitions in 2006-2007 (P = 0.59). The 49 patients infected by a resistant organism were matched by date of admission to 98 control patients with CDI from whom a rifamycin-susceptible C. difficile strain was isolated. Cases and controls did not differ according to demographic and clinical characteristics and showed similar but low rates of prior rifamycin use. Similar rates of rifamycin resistance were seen in cases of hospital-acquired CDI (38/112 [34%]) versus community-acquired CDI (7/20 [35%]). At a university hospital in which rifaximin was commonly used, infection by rifamycin-resistant strains of C. difficile was not shown to relate to prior use of a rifamycin drug or to acquiring the infection in the hospital, although the rate of overall resistance appeared to be rising.

The Impact of Initial Specimen Diversion Systems on Blood Culture Contamination.

Blood culture contamination is associated with increased antimicrobial use, length of stay, and hospital cost. To address this problem, blood culture diversion has been developed as an additional measure to reduce contamination to targeted goals. Three different versions were proposed, including an open technique and 2 commercially available devices. This study aims to review the existing literature and analyze evidence for these 3 techniques.

Micafungin pharmacodynamics predict clinical outcomes in hospitalized patients with candidemia caused by certain Candida species.

STUDY OBJECTIVE: Echinocandins are guideline-preferred therapies for invasive candidiasis (IC). Fixed dosing of echinocandins is commonly used despite variations in body mass index and echinocandin susceptibility. The purpose of this study was to evaluate clinical outcomes of micafungin based on population-predicted pharmacokinetic/pharmacodynamic (PK/PD) factors and susceptibility. DESIGN AND SETTING: Candida isolate results were screened from bloodstream or intraabdominal cultures of hospitalized patients admitted to a quaternary-care teaching hospital. Patients with a first episode of IC who received micafungin for at least 48 h were included. Patients with mixed cultures or Candida species with no minimum inhibitory concentration (MIC) differences were excluded. Breakpoints for micafungin MIC and area under the curve (AUC)/MIC ratio were calculated using classification and regression tree (CART) analysis and related to clinical outcomes. Primary efficacy outcome was candida-contributable mortality, defined as mortality within 28 days of positive culture with concomitant micafungin treatment failure; secondary outcome was micafungin treatment failure within 28 days, MAIN RESULTS: Seventy-two patients were included of whom 15 (21%) had Candida-contributable mortality and 34 (47%) experienced micafungin treatment failure. C. albicans and C. tropicalis did not have differing MICs and these patients were excluded from the study. Mortality using a CART-derived MIC breakpoint of ≥1.0 mg/L was 38% compared to 9% in patients infected with lower MIC strains (p = 0.003). Patients with a CART-derived AUC/MIC value >138.5 had a mortality rate of 9% compared to 41% for patients with AUC/MIC values below the breakpoint (p = 0.0013). Results were similar for treatment failure rates, and both were confirmed using multivariable models. CONCLUSIONS: CART-derived micafungin MIC and AUC/MIC breakpoints predicted patient mortality and treatment failure for certain Candida species. These results support the need for further PK/PD studies to optimize echinocandin dosing and improve patient outcomes.

The effect of a plasma next-generation sequencing test on antimicrobial management in immunocompetent and immunocompromised patients-A single-center retrospective study.

Objective: To describe the use of next-generation sequencing (NGS) and to determine whether NGS leads to changes in antimicrobial management. Design and setting: This retrospective cohort study included patients aged ≥18 years admitted to a single tertiary-care center in Houston, Texas, with an NGS test performed between January 1, 2017, and December 31, 2018. Patients: In total, 167 NGS tests were performed. Most patients were of non-Hispanic ethnicity (n = 129), white (n = 106), and male (n = 116), with a mean age of 52 years (SD, 16). Moreover, 61 patients were immunocompromised: solid-organ transplant (n = 30), patients with human immunodeficiency virus (n = 14), and rheumatology patients on immunosuppressive therapy (n = 12). Results: Of the 167 NGS tests performed, 118 (71%) were positive. Test results associated with a change in antimicrobial management were found in 120 (72%) of 167 cases, with an average of 0.32 (SD, 1.57) fewer antimicrobials after the test. The largest change in antimicrobial management was in glycopeptide use (36 discontinuations) followed by antimycobacterial drug use (27 additions among 8 patients). Also, 49 patients had negative NGS results, but only 36 patients had their antibiotics discontinued. Conclusions: Plasma NGS testing is associated with a change in antimicrobial management in most cases. We observed a decrease in glycopeptide use after NGS results, which highlights physicians' comfort in withdrawing methicillin-resistant Staphylococcus aureus (MRSA) coverage. In addition, antimycobacterial coverage increased, corresponding with early mycobacterial detection by NGS. Further studies are needed to determine effective ways to use NGS testing as an antimicrobial stewardship tool.

Impact of gastrointestinal polymerase chain reaction panels on antibiotic utilization in hospitalized adult patients.

Multiplex stool polymerase chain reaction (PCR) panels offer rapid comprehensive testing for patients with infectious diarrhea. We compared antibiotic utilization among hospitalized patients with suspected infectious diarrhea who underwent diagnostic testing with either a stool culture or stool PCR panel. No significant differences in antibiotic utilization were identified.

Impact of prior inappropriate fluconazole dosing on isolation of fluconazole-nonsusceptible Candida species in hospitalized patients with candidemia.

Prior use of fluconazole is a modifiable risk factor for the isolation of fluconazole-nonsusceptible Candida species. Optimization of the use of fluconazole by appropriate dose or duration may be able to minimize the risk of resistance. The objective of this study was to evaluate the effects of prior fluconazole therapy, including the dose and duration, on fluconazole susceptibility among Candida species isolated from hospitalized patients with candidemia. A retrospective cohort study of hospitalized patients with a first occurrence of nosocomial candidemia, from 2006 to 2009, was carried out. The relationships between the initial dose and duration of prior fluconazole therapy and the isolation of fluconazole-nonsusceptible Candida species were assessed. An initial fluconazole dose greater than 2 mg/kg and less than 6 mg/kg of body weight was considered suboptimal. A total of 177 patients were identified, of whom 133 patients aged 61 ± 16 years (56% male, 51% Caucasian, 51% with an APACHE II score of ≥ 15) had candidemia more than 2 days after the hospital admission day. Nine of 107 (8%) patients with fluconazole-susceptible Candida species and 9 of 26 (35%) patients with fluconazole-nonsusceptible Candida species had prior fluconazole exposure (risk ratio [RR], 3.03; 95% confidence interval [95% CI], 1.57 to 5.86; P, 0.0022). Preexposure with an initial dose of fluconazole greater than 2 mg/kg and less than 6 mg/kg occurred in 3 of 9 (33%) and 8 of 9 (89%) patients with fluconazole-susceptible and fluconazole-nonsusceptible Candida species, respectively (P, 0.0498). We conclude that patients with candidemia due to fluconazole-nonsusceptible Candida species were more likely to have received prior fluconazole therapy. Suboptimal initial dosing of prior fluconazole therapy was associated with candidemia with fluconazole-nonsusceptible Candida species.

An integrated approach to evaluate different tetracycline derivatives for formulary decisions.

PURPOSE: Stenotrophomonas maltophilia has emerged as a critical opportunistic pathogen associated with significant morbidity and mortality. Tetracycline derivatives have been recognized as alternative treatment options, but they have varied pharmacokinetic properties. An integrated approach to different tetracycline derivatives for formulary decisions is reported. METHODS: The minimum inhibitory concentration (MIC) data from clonally diverse bloodstream S. maltophilia isolates were examined, along with the pharmacokinetic profiles of 4 tetracycline derivatives, to predict achievable pharmacodynamic exposures with standard intravenous dosing regimens. Antimicrobial therapy was assessed using the ratio of daily drug acquisition cost relative to the ratio of the free-drug area under the time-concentration curve (fAUC) to minimum inhibitory concentration (MIC) for 90% of isolates (fAUC/MIC90). RESULTS: In our analysis, minocycline had the greatest fAUC/MIC90. Doxycycline was the most financially preferred agent, as calculated using 2020 average wholesale price for base-case estimates of drug acquisition cost. CONCLUSION: An integrated evaluation for antimicrobial formulary decision-making addressed local susceptibility data, pharmacokinetics, pharmacodynamics, dosing regimens, and drug acquisition costs. This comprehensive method is more objective than the conventional approach and warrants validation.

Characteristics of Rickettsia typhi Infections Detected with Next-Generation Sequencing of Microbial Cell-Free Deoxyribonucleic Acid in a Tertiary Care Hospital.

We present 10 patients with Rickettsia typhi infection in whom next-generation sequencing of microbial cell-free deoxyribonucleic acid (mcfDNA) was used as a diagnostic tool. Rickettsia typhi mcfDNA was detected in all cases and was more rapid and specific than rickettsial serology. Rickettsia typhi mcfDNA impacted antibiotic management in 50% of patients.

Association between universal face shield in a quaternary care center and reduction of SARS-COV2 infections among healthcare personnel and hospitalized patients.

We implemented universal face shield use for all healthcare personnel upon entry to facility in order to counter an increase in SARS-COV2 cases among healthcare personnel and hospitalized patients. There was a marked reduction of infections in both healthcare personnel and hospitalized patients between pre and post intervention. Our results support universal face shield use as part of a multifaceted approach in areas of high SARS-COV2 community transmission.

Using clinical decision support to improve urine culture diagnostic stewardship, antimicrobial stewardship, and financial cost: A multicenter experience.

OBJECTIVE: Despite evidence to the contrary, many practitioners continue to inappropriately screen for and treat bacteria in the urine of clinically asymptomatic patients. The purpose of this study was to evaluate the impact of a new order set on the number of urine culture performed, antibiotic days of therapy (DOT), catheter-associated urinary tract infections (CAUTI), and associated financial impact. DESIGN: A quasi-experimental before-and-after intervention. SETTING: We conducted this study at 5 Catholic Health Initiative (CHI) hospitals in Texas that use the same electronic health record (EHR) system. PATIENTS: The study populations included adult patients who had urine culture performed from June 2017 to June 2019. INTERVENTION: The intervention (implemented June 25, 2018) was the addition of a new order set in the electronic health record that required practitioners to choose an indication for the type of urine study. The primary outcome was number of urine cultures performed adjusted for the number of total patient days. RESULTS: Following implementation of the new order set, the number of urine cultures performed among the 5 sites decreased from 1,175.8 tests per 10,000 patient days before the intervention to 701.4 after the intervention (40.4% reduction; P < .01). Antibiotic DOT for patients with a urinary tract infection indication decreased from 102.5 to 86.9 per 1,000 patient days (15.2% reduction; P < .01). The CAUTI standardized infection ratio was 1.0 before the intervention and 0.8 after the intervention (P = .23). The estimated yearly savings following the intervention was US$535,181. CONCLUSIONS: The addition of a new order set resulted in decreases in the number of urine cultures performed and the antibiotic DOT, as well as substantial financial savings.

MIC profiling of ceftazidime/avibactam against two carbapenemase-producing Klebsiella pneumoniae isolates.

OBJECTIVES: The aim of this study was to correlate the results of a modified susceptibility testing method with outcomes of ceftazidime/avibactam (CAZ/AVI) therapy. METHODS: Two bloodstream K. pneumoniae isolates (CAZ/AVI-susceptible) from an abdominal source were recovered from two unrelated patients. Both patients were treated with CAZ/AVI but had discordant outcomes: KP118 (eradication within 24 h) and KP286 (persistent bacteraemia for over 30 days). Carbapenemase production in the two isolates was confirmed by Carba NP test. The CAZ minimum inhibitory concentration (MIC) was determined with escalating AVI concentrations (0-16 mg/L). The concentration-response was characterised by the sigmoid inhibitory maximum effect model. The best-fit parameter values were used to predict %T > MICi associated with CAZ/AVI exposures expected in peritoneal fluid after standard dosing (2.5 g every 8 h). These CAZ/AVI exposures were simulated in a hollow-fibre infection model (HFIM), and the bacterial responses were correlated with observed clinical outcomes. RESULTS: The AVI-dependent reduction in CAZ MIC was well characterised in both bacterial isolates (r2 ≥ 0.98). In the HFIM, sustained suppression of KP118 (T > MICi = 100%) was observed over 5 days, but not with KP286 (T > MICi < 100%). These observations are consistent with the clinical course of the patients. CONCLUSIONS: The discordant patient outcomes could be potentially explained by MIC profiling of CAZ/AVI. This method appears to be more robust than conventional susceptibility testing in predicting positive clinical outcome of CAZ/AVI therapy, and the clinical utility of this approach should be further investigated.