DOI: 10.5061/dryad.1ns1rn907
title: Aztreonam-induced filamentation in Pseudomonas aeruginosa

description: Objectives: The proliferation of metallo-beta-lactamase-producing
 Pseudomonas aeruginosa represents a significant public health threat. P.
 aeruginosa can undergo significant phenotypic changes that can drastically
 impair antibiotic efficacy. This study’s objectives were (1) to quantify
 the time course of killing of VIM-2-producing P. aeruginosa in response to
 aztreonam-based therapies, and (2) to document the capacity of P.
 aeruginosa to undergo morphological transformations that facilitate
 persistence. Methods: A well-characterized, clinical
 VIM-2-producing P. aeruginosa was studied in the Hollow Fiber
 Infection Model (HFIM) over 9 days (7 days of active antibiotic therapy, 2
 days treatment withdrawal) at a 107.5 CFU/mL starting inoculum. HFIM
 treatment arms included: growth control, aztreonam, ceftazidime/avibactam,
 aztreonam/‌ceftazidime/‌avibactam, polymyxin B, and
 aztreonam/‌ceftazidime/‌avibactam/‌polymyxin B. In addition, real-time
 imaging studies were conducted under static conditions to determine the
 time course of the reversion of persister cells.  Results: A
 pronounced discrepancy was observed between OD620 and bacterial counts
 obtained from plating methods (hereafter referred to as ‘OD-count
 discrepancy’). For aztreonam monotherapy, observed counts were 0 CFU/mL by
 120 h. Despite this, there was a significant OD-count discrepancy as
 compared to the pre-treatment 0h. Between therapy withdrawal at 168h and
 216h, all arms with suppressed counts had re-grown to the system carrying
 capacity. Real-time imaging of the P. aeruginosa filaments after drug
 removal showed rapid reversion from a long, filamentous phenotype to many
 individual rods within 2 h. Conclusion: Managing MBL-producing P.
 aeruginosa will require a multi-faceted approach, focused on maximizing
 killing and minimizing proliferation of resistant and persistent
 subpopulations, which will involve eliminating drug-induced phenotypic
 transformers.
description: # Aztreonam-induced filamentation in Pseudomonas aeruginosa --- Author:
 Nicholas M. Smith, PharmD, PhD Contact:
 [nmsmith2@buffalo.edu](mailto:nmsmith2@buffalo.edu) Last Update:
 2023-07-20 These videos were generated through timelapse microscopy of a
 clinical VIM-2-producing P. aeruginosa under selective pressure by
 aztreonam and after drug removal. ## Description of the data file and
 structure 2020_20_31_782_Exponential Growth_MHB.wmv
 2020_20_31_782_Filamentation_AZT_67.wmv 2020_20_31_782_Reversion_6hr.wmv
 2020_20_31_782_Reversion_18hr.wmv 2020_20_31_782_Reversion_24hr.wmv
 2020_20_31_782_Reversion_48hr.wmv 2020_20_31_782_Exponential
 Growth_MHB.wmv -This timelapse video is of P. aeruginosa in exponential
 growing phase without drug pressure
 2020_20_31_782_Filamentation_AZT_67.wmv -This timelapse video is of P.
 aeruginosa in expoenntial growing phase under drug pressure (aztreonam
 66mg/L, static conditions), which shows bacterial filamentation
 2020_20_31_782_Reversion_6hr.wmv * This time-lapse video is of P.
 aeruginosa after gently washing drug off of cells after 6 hours of drug
 exposure. Filaments are shown to revert back to rod shapes then divide
 normally 2020_20_31_782_Reversion_18hr.wmv * This time-lapse video is of
 P. aeruginosa after gently washing drug off of cells after 18 hours of
 drug exposure. Filaments are shown to revert back to rod shapes then
 divide normally 2020_20_31_782_Reversion_24hr.wmv * This time-lapse video
 is of P. aeruginosa after gently washing drug off of cells after 24 hours
 of drug exposure. Filaments are shown to revert back to rod shapes then
 divide normally 2020_20_31_782_Reversion_48hr.wmv * This time-lapse video
 is of P. aeruginosa after gently washing drug off of cells after 48 hours
 of drug exposure. Filaments are shown to revert back to rod shapes then
 divide normally Fig1_SEM_10k.7z SEM Images for Figure 1 are also provided
 in full resolution with scale bars