Exploring colistin pharmacodynamics against Klebsiella pneumoniae: A need to revise current susceptibility breakpoints

Objectives: Because the pharmacokinetic/pharmacodynamic (PK/PD) characteristics of colistin against Enterobacteriaceae are not well explored, we studied the activity of colistin against K. pneumoniae in an in vitro PK/PD model simulating different dosing regimens. Methods: Three clinical isolates of K. pneumoniae with MICs of 0.5, 1 and 4mg/L were tested in an in vitro PK/PD model following a dose-fractionation design over a period of 24h. A high and low inoculumof 107 and 104 cfu/mL with and without a heteroresistant subpopulation, respectively, were used. PK/PD indices associated with colistin activity were explored and Monte Carlo analysis was performed in order to determine the PTA for achieving a bactericidal effect (2 log kill). Results: The fAUC/MIC (R2"0.64-0.68) followed by fCmax/MIC (R2=0.55-0.63) best described colistin's 24 h log10 cfu/mL reduction for both low and high inocula. Dosing regimens with fCmax/MIC≥6 were always associated with a bactericidal effect (P=0.0025). However, at clinically achievable concentrations, usually below fCmax/MIC=6, an fAUC/MIC ≤25 was more predictive of a bactericidal effect. Using a dosing regimen of 9 MU/ day, the PTA for this pharmacodynamic target was 100%, 5%-70%and 0%, for isolates with MICs of ≤0.5, 1 and ≥2 mg/L, respectively. Dosing regimens that aim for a trough level of 1 mg/L achieve coverage of strains up to 0.5 mg/L (target trough/MIC=2 mg/L). Conclusions: Characterization of the pharmacodynamics of colistin against Enterobacteriaceae in an in vitro model of infection indicates that a revision of current susceptibility breakpoints is needed. Therapeutic drug monitoring of colistin to achieve pharmacodynamic targets in individual patients is highly recommended

Assessing Clinical Potential of Old Antibiotics against Severe Infections by Multi-Drug-Resistant Gram-Negative Bacteria Using In Silico Modelling

In the light of increasing antimicrobial resistance among gram-negative bacteria and the lack of new more potent antimicrobial agents, new strategies have been explored. Old antibiotics, such as colistin, temocillin, fosfomycin, mecillinam, nitrofurantoin, minocycline, and chloramphenicol, have attracted the attention since they often exhibit in vitro activity against multi-drug-resistant (MDR) gram-negative bacteria, such as Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii. The current review provides a summary of the in vitro activity, pharmacokinetics and PK/PD characteristics of old antibiotics. In silico modelling was then performed using Monte Carlo simulation in order to combine all preclinical data with human pharmacokinetics and determine the probability of target (1-log kill in thigh/lung infection animal models) attainment (PTA) of different dosing regimens. The potential of clinical efficacy of a drug against severe infections by MDR gram-negative bacteria was considered when PTA was >95% at the epidemiological cutoff values of corresponding species. In vitro potent activity against MDR gram-negative pathogens has been shown for colistin, polymyxin B, temocillin (against E. coli and K. pneumoniae), fosfomycin (against E. coli), mecillinam (against E. coli), minocycline (against E. coli, K. pneumoniae, A. baumannii), and chloramphenicol (against E. coli) with ECOFF or MIC90 ≤ 16 mg/L. When preclinical PK/PD targets were combined with human pharmacokinetics, Monte Carlo analysis showed that among the old antibiotics analyzed, there is clinical potential for polymyxin B against E. coli, K. pneumoniae, and A. baumannii; for temocillin against K. pneumoniae and E. coli; for fosfomycin against E. coli and K. pneumoniae; and for mecillinam against E. coli. Clinical studies are needed to verify the potential of those antibiotics to effectively treat infections by multi-drug resistant gram-negative bacteria

Detection of KPC, NDM and VIM-Producing Organisms Directly from Rectal Swabs by a Multiplex Lateral Flow Immunoassay

We report a preliminary evaluation of the NG-Test CARBA 5 immunochromatographic assay for detecting carbapenemases directly from rectal swabs on the same day of sampling. Thirty fecal swabs were examined for carbapenemase-producing organisms (CPOs) by conventional culture, PCR, and NG-Test CARBA 5. Each sample was tested by the immunochromatographic assay five times, including direct testing and incubation in trypticase soy broth for 1, 2, 3, and 4 h. Twenty patients yielded CPOs by culture. Immunochromatographic and PCR results were concordant and detected the same 25 carbapenemases (11 KPC, 8 VIM, and 6 NDM). In five cases, we detected co-carriage of KPC and VIM. Compared with PCR, the sensitivity of NG-Test CARBA 5 for the detection of KPC, VIM, and NDM was 80% without incubation, 88% with one hour, 92% with two, and 100% with three hours incubation, while specificity was 100% for all time points. All samples containing adequate fecal content were detected by NG-Test CARBA 5 concordantly with PCR, without incubation. NG-Test CARBA 5 is a reliable test that rapidly detects the presence of carbapenemases at the same day of sampling, directly from rectal swabs. It thus provides early information to guide antimicrobial treatment and infection control interventions

Epidemiology and Incidence of COVID-19-Associated Pulmonary Aspergillosis (CAPA) in a Greek Tertiary Care Academic Reference Hospital

Introduction Invasive pulmonary aspergillosis is an emerging complication among intensive care unit (ICU) patients with COVID-19 (CAPA). In the present study, all CAPA cases during the first year of the pandemic were reviewed in critically ill patients at a 650-bed tertiary Greek COVID-19 reference hospital. Methods Data regarding patients admitted to the ICU of Attikon Hospital in Athens, Greece, between 22 March 2020 and 28 February 2021 with a positive PCR for SARS-CoV-2 infection were reviewed. Clinical and microbiological records were analysed including demographic, clinical, laboratory and radiological features, treatment and outcomes. CAPA was determined according to the recent 2020 ECMM/ISHAM definitions. Results A total of 179 patients were admitted in the ICU and 6 (3.3%) patients were diagnosed with CAPA (4 probable and 2 possible CAPA) with 5/6 with co-infection with multidrug-resistant (MDR) gram-negative pathogens. No patient had a history of immunosuppression. All suffered from acute respiratory distress syndrome. The median (range) time from intubation to diagnosis was 6 (1-14) days. Five patients had positive Aspergillus cultures in bronchial secretions (1 A. fumigatus, 1 A. flavus, 1 A. fumigatus + A. flavus, 1 A. fumigatus + A. terreus and 1 A. terreus) while culture was negative in one patient. All isolates were susceptible to antifungal drugs. Serum galactomannan (GM), pan-Aspergillus PCR and (1,3)-beta-d-glucan (BDG) were positive in 4/6 (67%), 5/6 (83%, 3/5 in two consecutive samples) and 4/6 (67%, in consecutive samples) patients, respectively. GM and PCR positive bronchial secretions had GM indices > 9.95 and PCR C-t < 34. All were treated with antifungal drugs with 5 out of 6 receiving isavuconazole. Mortality was 67% (4/6) with 1/4 attributed to CAPA (two died as a result of bacterial septic shock and one as a result of multiorgan failure). Conclusion The incidence of CAPA in ICU patients was 3.3% and it was associated with approximately a 17% attributable mortality in the setting of MDR gram-negative pathogen co-infections

Pharmacokinetic–pharmacodynamic modelling of meropenem against VIM-producing Klebsiella pneumoniae isolates: clinical implications

VIM-producing Klebsiella pneumoniae isolates are usually associated with high MICs to carbapenems. Preclinical studies investigating the pharmacokinetic-pharmacodynamic (PK-PD) characteristics of carbapenems against these isolates are lacking. The in vitro antibacterial activity of meropenem against one WT and three VIM-producing K. pneumoniae clinical isolates (median MICs 0.031, 8, 16 and 128 mg l(-1)) was studied in a dialysis-diffusion PK-PD model and verified in a thigh infection neutropenic animal model by testing selected strains and exposures. The in vitro PK-PD target associated with bactericidal activity was estimated and the target attainment for different dosing regimens was calculated with Monte Carlo analysis. The in vitro model was correlated with the in vivo data, with log(10)CFU/ml reduction of 2 for the WT (MIC 0.031 mg l(-1)) isolates, with %fT >MIC 25 and 100 %, respectively. The in vitro bactericidal activity for all isolates was associated with 40 % fT>MIC and attained in >90 % of cases with the standard 1 g q8 0.5 h infusion dosing regimen only for isolates with MICs up to 1 mg l(-1). For isolates with MICs of 2-8 mg l(-1), prolonged infusion regimens (4 h infusion q8 or 2 h infusion q4) of standard (1 g) and higher (2 g) doses or continuous infusion regimens (3-6 g) are required. For isolates with a MIC of 16 mg l(-1) the unconventional dosing regimen of 2 g as 2 h infusion q4 or 12 g continuous infusion will be required. Prolonged and continuous infusion regimens of meropenem may increase efficacy against VIM-producing K. pneumoniae isolates

Phenotypic/Genotypic Profile of OXA-10-Like-Harboring, Carbapenem-Resistant Pseudomonas aeruginosa: Using Validated Pharmacokinetic/Pharmacodynamic In Vivo Models To Further Evaluate Enzyme Functionality and Clinical Implications

In vitro MICs and in vivo pharmacodynamics of ceftazidime and cefepime human-simulated regimens (HSR) against modified carbapenem inactivation method (mCIM)-positive Pseudomonas aeruginosa isolates harboring different OXA-10-like sub-types were described. The murine thigh model assessed ceftazidime (2 g every 8 h [q8h] HSR) and cefepime (2 g and 1 g q8h HSR). Phenotypes were similar despite possessing OXA-10-like subtypes with differing spectra. Ceftazidime produced >= 1-log(10) killing in all isolates. Cefepime activity was dose dependent and MIC driven. This approach may be useful in assessing the implications of beta-lactamase variants

A multicentre evaluation of the NG-test DetecTool OXA-23 for the rapid detection of OXA-23 carbapenemase directly from blood cultures

Objectives A multicentre study evaluating NG-Test DetecTool OXA-23 for the detection of OXA-23 carbapenemase directly from positive blood cultures (PBCs). Methods The NG-Test DetecTool OXA-23 is an immunoassay that integrates a sample preparation device. We evaluated NG-Test DetecTool OXA-23 on 189 spiked and 126 clinical PBCs. The clinical samples’ standard-of-care procedure consisted of bacterial identification from the first day of positivity by MALDI-TOF MS, conventional culture and antimicrobial susceptibility testing. The immunoassay results were verified molecularly. The strains used for the spiked samples consisted of well-characterized Acinetobacter baumannii and Proteus mirabilis strains. Results The NG-Test DetecTool OXA-23 was evaluated on 315 PBCs and revealed sensitivity of 100% (95% CI: 98.21%–100.00%) and specificity of 100% (95% CI: 96.73%–100.00%). It provided 204 true-positive results for OXA-23 in 196 bottles with carbapenem-resistant A. baumannii (CRAB) and 8 bottles with carbapenem-resistant P. mirabilis and also provided 111 true-negative results. There were no false-positive and no false-negative results. Among the 315 PBCs studied, 83 clinical blood cultures collected in the ICU of a Greek university hospital, which were tested prospectively, all yielded CRAB, and OXA-23 was correctly detected in all samples from the first day of positivity using the NG-Test DetecTool OXA-23. Conclusions The NG-Test DetecTool OXA-23 has exhibited excellent sensitivity and specificity for OXA-23 detection in PBCs and can provide valuable information for appropriate selection of antibiotic therapy and early implementation of infection control measures