Less Is More: When to Repeat Antimicrobial Susceptibility Testing.

This study investigated the frequency of change of the antimicrobial susceptibility pattern when the same isolate was found in the same patient in various situations. We used laboratory data collected over a period of 8 years (January 2014 to December 2021) at the clinical microbiology laboratory of a tertiary hospital for Escherichia coli, Klebsiella pneumoniae, Enterobacter spp., Pseudomonas aeruginosa, and Staphylococcus aureus. Antimicrobial susceptibility tests (AST) were performed using Vitek 2 automated system. We determined essential agreement and categorical agreement, and introduced the new terms essential MIC increase and change from nonresistant to resistant to present changes in antimicrobial susceptibility over time. During the study period, 18,501 successive AST were included. The risk for S. aureus to be resistant to any antibiotic upon repeated culture was <10% during a follow-up of 30 days. For Enterobacterales, this risk was approximately 10% during a follow-up of 7 days. For P. aeruginosa, this risk was higher. The longer the follow-up period, the higher the risk that the bacteria would show phenotypic resistance. We also found that some drug-bug combinations were more likely to develop phenotypical resistance (i.e., E. coli/amoxicillin-clavulanic acid and E. coli/cefuroxime). A potential consequence of our finding is that if we regard a risk of resistance below 10% as acceptable, it may be feasible to omit follow-up AST within 7 days for the microorganisms investigated in this study. This approach saves money, time, and will reduce laboratory waste. Further studies are needed to determine whether these savings are in balance with the small possibility of treating patients with inadequate antibiotics.

Frequency of Positive Aspergillus Tests in COVID-19 Patients in Comparison to Other Patients with Pulmonary Infections Admitted to the Intensive Care Unit.

The aim of this study was to describe the frequency of positive Aspergillus tests in COVID-19 patients and investigate the association between COVID-19 and a positive Aspergillus test result. We compared the proportion of positive Aspergillus tests in COVID-19 patients admitted to the intensive care unit (ICU) for >24 h with two control groups: patients with community-acquired pneumonia with (i) a PCR-confirmed influenza infection (considered a positive control since the link between influenza and invasive aspergillosis has been established) and (ii) Streptococcus pneumoniae pneumonia (in whom positive Aspergillus tests are mostly considered as colonization). During the study period, 92 COVID-19 patients (mean [standard deviation] age, 62 [14] years; 76.1% males), 48 influenza patients (55 [14]; 56.2% males), and 65 pneumococcal pneumonia patients (58 [15], 63,1% males) were identified. Any positive Aspergillus test from any respiratory sample was found in 10.9% of the COVID-19 patients, 6.2% of the patients with pneumococcal pneumonia, and 22.9% of those infected with influenza. A positive culture or PCR or galactomannan test on bronchoalveolar lavage (BAL) fluid only was found in 5.4% of COVID-19 patients, which was lower than in patients with influenza (18.8%) and comparable to that in the pneumococcal pneumonia group (4.6%). Using logistic regression analysis, the odds ratio (OR) (95% confidence interval) for a positive Aspergillus test on BAL fluid for COVID-19 patients was 1.2 (0.3 to 5.1; P = 0.8) compared to the pneumococcal pneumonia group, while it was 0.2 (0.1 to 0.8; P = 0.02) compared to the influenza group. This difference remained significant when corrected for age and sex. In conclusion, in COVID-19 patients, the prevalence of a positive Aspergillus test was comparable to that in patients admitted for pneumococcal pneumonia but substantially lower than what we observed in patients with influenza.

Antimicrobial susceptibility to last-resort antibiotics in carbapenemase-producing bacteria from Ukrainian patients.

Since March 2022, an increase was observed in multidrug-resistant microorganisms (MDRO), associated with the hospital transfer of Ukrainian patients. The goal was to collect phenotypic susceptibility data and assess clinical implications. Carbapenemase-producing Enterobacterales (CPE, n = 96), Pseudomonas aeruginosa (CPPA, n = 20), and carbapenem-resistant Acinetobacter baumannii-calcoaceticus (CRAB, n = 6) from Ukrainian patients were obtained from March to December 2022 from the Dutch MDRO surveillance. Antimicrobial susceptibility testing was performed using broth microdilution (BMD) when available, fosfomycin agar dilution, disk diffusion (DD) for cefiderocol, and diverse gradient strips. All isolates were sequenced with Illumina next-generation sequencing. For meropenem, aminoglycosides, ceftazidime-avibactam, ceftolozane-tazobactam, and imipenem-relebactam, susceptibility rates were low (0%-30%), due to the high number of blaNDM-positive isolates (79/122; 65%). For cefiderocol, results depended on reading with or without microcolonies, applying EUCAST or CLSI breakpoints, and whether DD or BMD was used; e.g., for Klebsiella pneumoniae, 30%-97% were susceptible. For colistin, 103/111 (93%) non-intrinsically resistant CPE/CPPA/CRAB isolates were susceptible. For most CPE, a low minimal inhibitory concentration (MIC) of <0.5 mg/L was measured for tigecycline and ceftazidime-avibactam-aztreonam. For CPPA, cefiderocol tested susceptible in 65%-100% of isolates. For CRAB, ampicillin-sulbactam MICs were ≥128 mg/L; for sulbactam-durlobactam, 1-2 mg/L. Admission in a Ukrainian hospital in the last year was a risk factor for MDRO, and majority were screening isolates (79%). There is extensive phenotypic resistance to last-resort antibiotics in MDRO from Ukrainian patients. Interpretation of cefiderocol susceptibility results depends on several variables. When treating patients recently admitted in Ukraine, suspected for Gram-negative bacterial infection, this should be taken into consideration. IMPORTANCE: Since March 2022, multidrug-resistant microorganisms associated with Ukrainian patients have been detected in national surveillance systems of several European countries. We studied the phenotypic antimicrobial susceptibility to last-resort antibiotics of multidrug-resistant microorganisms from Ukrainian patients in the Netherlands and assessed clinical implications. Our research revealed that there was extensive phenotypic resistance to last-resort antibiotics. Healthcare professionals should be aware of multidrug-resistant microorganisms when treating patients recently admitted in Ukraine, suspected for Gram-negative bacterial infection.

Automated Patch Clamp Meets High-Throughput Screening: 384 Cells Recorded in Parallel on a Planar Patch Clamp Module.

We have developed an automated patch clamp module for high-throughput ion channel screening, recording from 384 cells simultaneously. The module is incorporated into a laboratory pipetting robot and uses a 384-channel pipettor head for application of cells and compounds. The module contains 384 amplifier channels for fully parallel recordings using a digital amplifier. Success rates for completed experiments (1- to 4-point concentration-response curves for cells satisfying defined quality control parameters) of greater than 85% have been routinely achieved with, for example, HEK, CHO, and RBL cell lines expressing hNaV1.7, hERG, Kir2.1, GABA, or glutamate receptors. Pharmacology experiments are recorded and analyzed using specialized software, and the pharmacology of hNaV1.7 and hERG is described. Fast external solution exchange rates of <50 ms are demonstrated using Kir2.1. Short exposure times are achieved by stacking the external solutions inside the pipette of the robot to minimize exposure of the ligand on the receptor. This ensures that ligand-gated ion channels, for example, GABA and glutamate described in this report, can be reproducibly recorded. Stem cell-derived cardiomyocytes have also been used with success rates of 52% for cells that have a seal resistance of >200 MΩ, and recordings of voltage-gated Na+ and Ca2+ are shown.