Formic acid, an organic acid food preservative, induces viable-but-non-culturable state, and triggers new Antimicrobial Resistance traits in Acinetobacter baumannii and Klebsiella pneumoniae

Abstract

Numerous human pathogens, especially Gram-negative bacteria, are able to enter the viable-but-non-culturable (VBNC) state when they are exposed to environmental stressors and pose the risk of being resuscitated and causing infection after the removal of the trigger. Widely used food preservatives like weak organic acids are potential VBNC inducers in food processing and packaging facilities but have only been reported for food-borne pathogens. In the present study, it is demonstrated for the first time that one such agent, formic acid (FA), can induce a VBNC state at food processing, storage, and distribution temperatures (4, 25, and 37°C) with a varied time of treatment (days 4–10) in pathogenic Gram-negative bacteria Acinetobacter baumannii and Klebsiella pneumoniae. The use of hospital-associated pathogens is critical based on the earlier reports that demonstrated the presence of these bacteria in hospital kitchens and commonly consumed foods. VBNC induction was validated by multiple parameters, e.g., non-culturability, metabolic activity as energy production, respiratory markers, and membrane integrity. Furthermore, it was demonstrated that the removal of FA was able to resuscitate VBNC with an increased expression of multiple virulence and Antimicrobial Resistance (AMR) genes in both pathogens. Since food additives/preservatives are significantly used in most food manufacturing facilities supplying to hospitals, contamination of these packaged foods with pathogenic bacteria and the consequence of exposure to food additives emerge as pertinent issues for infection control, and control of antimicrobial resistance in the hospital setting.

An Azomethine-H-Based Fluorogenic Sensor for Formic Acid

“…By contrast, a signal at δ H = 8.23 ppm, assigned to the naphthalene phenolic group, showed a downfield shift of Δδ = 0.24 ppm due to increasing amounts of [HCO 2 H], possibly indicating that FA forms a hydrogen-bonded complex with Az-H, which promotes (Z)-to-(E) isomerization (Scheme 2). Further strengthening this argument, exposure of Az-H to 25 equiv of HCl resulted in no observable change, as witnessed by 1 H NMR spectroscopy (Figure S2 in the Supporting Information).…”

“…On a biological level, FA is used as part of a defense mechanism, e.g., in insect stings. From an agriculture and food perspective, FA has been targeted as an industrial preservative . From an environmental standpoint, FA has garnered broad interest, serving as a liquid-organic hydrogen carrier (LOHC), − where dehydrogenation of FA delivers CO 2 and H 2 , enabling liquid storage and transport.…”

“…From an agriculture and food perspective, FA has been targeted as an industrial preservative. 1 From an environmental standpoint, FA has garnered broad interest, serving as a liquid-organic hydrogen carrier (LOHC), 2−4 where dehydrogenation of FA delivers CO 2 and H 2 , enabling liquid storage and transport. In this vein, FA can then either be used directly in formate fuel cells (FFCs) or converted into CO 2 and H 2 �the latter finding utility in H 2 oxidation or as a substrate for direct combustion; both opportunities present a carbon-neutral fuel source.…”

“…Solution-based kinetics and all-solid-state fluorescent measurements were obtained on a Wilson Analytical Open Platform Fluorometer (Wilson Analytical, St. Albert, Alberta, Canada) using OceanView 2.0 software (Ocean Insight, Orlando, FL, USA). 1 H NMR studies were performed using a Bruker Avance 300 NMR spectrometer (Milton, Ontario, Canada). Scanning electron microscopy (SEM) was performed on a FEI Quanta 200 Environmental Scanning Electron Microscopy system (ESEM) equipped with an EDAX Octane Plus SDD detector and TEAM software.…”

Targeted metagenomics using bait-capture to detect antibiotic resistance genes in retail meat and seafood

“…It may be possible that some of the positives detected by bait-capture may have been due to the presence of DNA in the sample, rather than from viable cells. It is also possible that the sensitivity of bait-capture is higher than plating on selective agar due to the presence of viable but non-culturable cells, silent (unexpressed) AMR genes, or other technical reasons ( Deekshit and Srikumar, 2022 ; Yadav et al, 2022 ). One notable discrepancy between the culture method and sequencing was the underrepresentation of the bla CTX-M gene family in the sequenced datasets.…”