Genetic organization of an Acinetobacter baumannii chromosomal region harbouring genes related to siderophore biosynthesis and transport

The Acinetobacter baumannii 8399 clinical isolate secretes dihydroxybenzoic acid (DHBA) and a high-affinity catechol siderophore, which is different from other bacterial iron chelators already characterized. Complementation assays with enterobactin-deficient Escherichia coli strains led to the isolation of a cosmid clone containing A. baumannii 8399 genes required for the biosynthesis and activation of DHBA. Accordingly, the cloned fragment harbours a dhbACEB polycistronic operon encoding predicted proteins highly similar to several bacterial proteins required for DHBA biosynthesis from chorismic acid. Genes encoding deduced proteins related to the E. coli Fes and the Bacillus subtilis DhbF proteins, and a putative Yersinia pestis phosphopantetheinyl transferase, all of them involved in the assembly and utilization of catechol siderophores in other bacteria, were found next to the dhbACEB locus. This A. baumannii 8399 gene cluster also contained the om73, p45 and p114 predicted genes encoding proteins potentially involved in transport of ferric siderophore complexes. The deduced products of the p114 and p45 genes are putative membrane proteins that belong to the RND and MFS efflux pump proteins, respectively. Interestingly, P45 is highly related to the E. coli P43 (EntS) protein that participates in the secretion of enterobactin. Although P114 is similar to other bacterial efflux pump proteins involved in antibiotic resistance, its genetic arrangement within this A. baumannii 8399 locus is different from that described in other bacteria. The product of om73 is a Fur- and iron-regulated surface-exposed outer-membrane protein. These characteristics together with the presence of a predicted TonB box and its high similarity to other siderophore receptors indicate that OM73 plays such a role in A. baumannii 8399. The 184 nt om73–p114 intergenic region contains promoter elements that could drive the expression of these divergently transcribed genes, all of which are in close proximity to almost perfect Fur boxes. This arrangement explains the iron- and Fur-regulated expression of om73, and provides strong evidence for a similar regulation for the expression of p114.

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Biofilm Formation Caused by Clinical Acinetobacter baumannii Isolates Is Associated with Overexpression of the AdeFGH Efflux Pump

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00877-15 ◽

2015 ◽

Vol 59 (8) ◽

pp. 4817-4825 ◽

Cited By ~ 58

Author(s):

Xinlong He ◽

Feng Lu ◽

Fenglai Yuan ◽

Donglin Jiang ◽

Peng Zhao ◽

...

Keyword(s):

Acinetobacter Baumannii ◽

Gene Transcription ◽

Biofilm Formation ◽

Efflux Pump ◽

Outer Membrane Proteins ◽

Content Type ◽

Potential Association ◽

Genes Encoding ◽

Clinical Environments

ABSTRACTChronic wound infections are associated with biofilm formation, which in turn has been correlated with drug resistance. However, the mechanism by which bacteria form biofilms in clinical environments is not clearly understood. This study was designed to investigate the biofilm formation potency ofAcinetobacter baumanniiand the potential association of biofilm formation with genes encoding efflux pumps, quorum-sensing regulators, and outer membrane proteins. A total of 48 clinically isolatedA. baumanniistrains, identified by enterobacterial repetitive intergenic consensus (ERIC)-PCR as types A-II, A-III, and A-IV, were analyzed. Three representative strains, which were designatedA. baumanniiABR2, ABR11, and ABS17, were used to evaluate antimicrobial susceptibility, biofilm inducibility, and gene transcription (abaI,adeB,adeG,adeJ,carO, andompA). A significant increase in the MICs of different classes of antibiotics was observed in the biofilm cells. The formation of a biofilm was significantly induced in all the representative strains exposed to levofloxacin. The levels of gene transcription varied between bacterial genotypes, antibiotics, and antibiotic concentrations. The upregulation ofadeGcorrelated with biofilm induction. The consistent upregulation ofadeGandabaIwas detected in A-III-typeA. baumanniiin response to levofloxacin and meropenem (1/8 to 1/2× the MIC), conditions which resulted in the greatest extent of biofilm induction. This study demonstrates a potential role of the AdeFGH efflux pump in the synthesis and transport of autoinducer molecules during biofilm formation, suggesting a link between low-dose antimicrobial therapy and a high risk of biofilm infections caused byA. baumannii. This study provides useful information for the development of antibiofilm strategies.

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Tigecycline efflux in Acinetobacter baumannii is mediated by TetA in synergy with RND-type efflux transporters

Journal of Antimicrobial Chemotherapy ◽

10.1093/jac/dkaa015 ◽

2020 ◽

Vol 75 (5) ◽

pp. 1135-1139 ◽

Cited By ~ 4

Author(s):

Wuen Ee Foong ◽

Jochen Wilhelm ◽

Heng-Keat Tam ◽

Klaas M Pos

Keyword(s):

Acinetobacter Baumannii ◽

Efflux Pump ◽

Gene Knockout ◽

Drug Susceptibility ◽

Major Facilitator Superfamily ◽

Rt Pcr ◽

E Coli ◽

Rnd Efflux Pump ◽

Major Facilitator

Abstract Objectives To investigate the role of Major Facilitator Superfamily (MFS)-type transporters from Acinetobacter baumannii AYE in tigecycline efflux. Methods Two putative tetracycline transporter genes of A. baumannii AYE (tetA and tetG) were heterologously expressed in Escherichia coli and drug susceptibility assays were conducted with tigecycline and three other tetracycline derivatives. The importance of TetA in tigecycline transport in A. baumannii was determined by complementation of tetA in WT and Resistance Nodulation cell Division (RND) gene knockout strains of A. baumannii ATCC 19606. Gene expression of the MFS-type tetA gene and RND efflux pump genes adeB, adeG and adeJ in A. baumannii AYE in the presence of tigecycline was analysed by quantitative real-time RT–PCR. Results Overproduction of TetA or TetG conferred resistance to doxycycline, minocycline and tetracycline in E. coli. Cells expressing tetA, but not those expressing tetG, conferred resistance to tigecycline, implying that TetA is a determinant for tigecycline transport. A. baumannii WT and RND-knockout strains complemented with plasmid-encoded tetA are significantly less susceptible to tigecycline compared with non-complemented strains. Efflux pump genes tetA and adeG are up-regulated in A. baumannii AYE in the presence of subinhibitory tigecycline concentrations. Conclusions TetA plays an important role in tigecycline efflux of A. baumannii by removing the drug from cytoplasm to periplasm and, subsequently, the RND-type transporters AdeABC and AdeIJK extrude tigecycline across the outer membrane. When challenged with tigecycline, tetA is up-regulated in A. baumannii AYE. Synergy between TetA and the RND-type transporters AdeABC and/or AdeIJK appears necessary for A. baumannii to confer higher tigecycline resistance via drug efflux.

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EFFLUX PUMP OVEREXPRESSION PROFILING IN ACINETOBACTER BAUMANNII AND STUDY OF NEW 1-(1-NAPHTHYLMETHYL)-PIPERAZINE ANALOGS AS POTENTIAL EFFLUX INHIBITORS

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00710-21 ◽

2021 ◽

Author(s):

Morgane Choquet ◽

Elodie Lohou ◽

Etienne Pair ◽

Pascal Sonnet ◽

Catherine Mullie

Keyword(s):

Antibiotic Resistance ◽

Acinetobacter Baumannii ◽

Inhibitory Activity ◽

Efflux Pump ◽

Parent Compound ◽

Efflux Pumps ◽

Quinoline Derivative ◽

Genes Encoding ◽

Efflux Pump Inhibitors ◽

Therapeutic Alternatives

Overexpression of efflux pumps extruding antibiotics currently used for the treatment of Acinetobacter baumannii infections has been described as an important mechanism causing antibiotic resistance. The first aim of this work was to phenotypically evaluate the overexpression of efflux pumps on a collection of 124 ciprofloxacin resistant A. baumannii strains. An overexpression of genes encoding one or more efflux pumps was obtained for 19 out of the 34 strains with a positive phenotypic efflux (56%). The most frequent genes overexpressed were those belonging to the RND family, with adeJ being the most prevalent (50%). Interestingly, efflux pump genes coding for MATE and MFS families were also overexpressed quite frequently: abeM (32%) and abaQ (26%). The second aim was to synthesize 1-(1-NaphthylMethyl)-Piperazine analogs as potential new efflux pump inhibitors and biologically evaluate them against strains with a positive phenotypic efflux. Quinoline and pyridine analogs were found to be more effective than their parent compound 1-(1-NaphthylMethyl)-Piperazine. Stereochemistry also played an important part in the inhibitory activity as quinoline derivative ( R )-3a was identified as being the most effective and less cytotoxic. Its inhibitory activity was also correlated to the number of efflux pumps expressed by a strain. The results obtained in this work suggest that quinoline analogs of 1-(1-NaphthylMethyl)-Piperazine are promising leads in the development of new anti- Acinetobacter baumannii therapeutic alternatives, in combination with antibiotics for which an efflux-mediated resistance is suspected.

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Overexpression and functional characterization of an ABC (ATP-binding cassette) transporter encoded by the genes drrA and drrB of Mycobacterium tuberculosis

Biochemical Journal ◽

10.1042/bj20020615 ◽

2002 ◽

Vol 367 (1) ◽

pp. 279-285 ◽

Cited By ~ 90

Author(s):

Baisakhee Saha CHOUDHURI ◽

Sanjib BHAKTA ◽

Rajib BARIK ◽

Joyoti BASU ◽

Manikuntala KUNDU ◽

...

Keyword(s):

Mycobacterium Tuberculosis ◽

Abc Transporters ◽

Efflux Pump ◽

Functional Characterization ◽

Atp Binding ◽

E Coli ◽

Neutral Compound ◽

Genes Encoding ◽

Simultaneous Expression ◽

Atp Binding Cassette

The genes encoding ATP-binding cassette (ABC) transporters occupy 2.5% of the genome of Mycobacterium tuberculosis. However, none of these putative ABC transporters has been characterized so far. We describe the development of expression systems for simultaneous expression of the ATP-binding protein DrrA and the membrane integral protein DrrB which together behave as a functional doxorubicin efflux pump. Doxorubicin uptake in Escherichia coli or Mycobacterium smegmatis expressing DrrAB was inhibited by reserpine, an inhibitor of ABC transporters. The localization of DrrA to the membrane depended on the simultaneous expression of DrrB. ATP binding was positively regulated by doxorubicin and daunorubicin. At the same time, DrrB appeared to be sensitive to proteolysis when expressed alone in the absence of DrrA. Simultaneous expression of the two polypeptides was essential to obtain a functional doxorubicin efflux pump. Expression of DrrAB in E. coli conferred 8-fold increased resistance to ethidium bromide, a cationic compound. 2′,7′-bis-(2-Carboxyethyl)-5(6)-carboxyfluorescein (BCECF), a neutral compound, also behaved as a substrate of the reconstituted efflux pump. When expressed in M. smegmatis, DrrAB conferred resistance to a number of clinically relevant, structurally unrelated antibiotics. The resistant phenotype could be reversed by verapamil and reserpine, two potent inhibitors of ABC transporters.

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The Asp20-to-Asn Substitution in the Response Regulator AdeR Leads to Enhanced Efflux Activity of AdeB in Acinetobacter baumannii

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.02413-15 ◽

2015 ◽

Vol 60 (2) ◽

pp. 1085-1090 ◽

Cited By ~ 12

Author(s):

Jennifer Nowak ◽

Thamarai Schneiders ◽

Harald Seifert ◽

Paul G. Higgins

Keyword(s):

Acinetobacter Baumannii ◽

Antimicrobial Susceptibility ◽

Efflux Pump ◽

Response Regulator ◽

Two Component System ◽

Content Type ◽

Susceptibility Data ◽

Genes Encoding ◽

Induced Changes

ABSTRACTOverexpression of the resistance-nodulation-cell division-type efflux pump AdeABC is often associated with multidrug resistance inAcinetobacter baumanniiand has been linked to mutations in the genes encoding the AdeRS two-component system. In a previous study, we reported that the Asp20→Asn amino acid substitution in the response regulator AdeR is associated withadeBoverexpression and reduced susceptibility to the antimicrobials levofloxacin, tigecycline, and trimethoprim-sulfamethoxazole. To further characterize the effect of the Asp20→Asn substitution on antimicrobial susceptibility, the expression of the efflux genesadeB,adeJ, andadeG, and substrate accumulation, four plasmid constructs [containingadeR(Asp20)S,adeR(Asn20)S,adeR(Asp20)SABC, andadeR(Asn20)SABC] were introduced into theadeRSABC-deficientA. baumanniiisolate NIPH 60. NeitheradeRSconstruct induced changes in antimicrobial susceptibility or substrate accumulation from that for the vector-only control. TheadeR(Asp20)SABCtransformant showed reduced susceptibility to 6 antimicrobials and accumulated 12% less ethidium than the control, whereas the Asn20 variant showed reduced susceptibility to 6 of 8 antimicrobial classes tested, and its ethidium accumulation was only 72% of that observed for the vector-only construct.adeBexpression was 7-fold higher in theadeR(Asn20)SABCtransformant than in its Asp20 variant. No changes inadeGoradeJexpression or in acriflavine or rhodamine 6G accumulation were detected. The antimicrobial susceptibility data suggest that AdeRS does not regulate any resistance determinants other than AdeABC. Furthermore, the characterization of the Asp20→Asn20 substitution proves that the reduced antimicrobial susceptibility previously associated with this substitution was indeed caused by enhanced efflux activity of AdeB.

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The Escherichia coli multiple antibiotic resistance activator protein represses transcription of the lac operon

Biochemical Society Transactions ◽

10.1042/bst20180498 ◽

2019 ◽

Vol 47 (2) ◽

pp. 671-677

Author(s):

Anna Lankester ◽

Shafayeth Ahmed ◽

Lisa E. Lamberte ◽

Rachel A. Kettles ◽

David C. Grainger

Keyword(s):

Escherichia Coli ◽

Antibiotic Resistance ◽

Efflux Pump ◽

Regulatory Region ◽

Lac Operon ◽

Multiple Antibiotic Resistance ◽

E Coli ◽

Genes Encoding ◽

Response Systems ◽

A Site

AbstractIn Escherichia coli, the marRAB operon is a determinant for antibiotic resistance. Such phenotypes require the encoded transcription factor MarA that activates efflux pump expression. To better understand all genes controlled by MarA, we recently mapped binding of the regulator across the E. coli genome. As expected, many MarA targets were adjacent to genes encoding stress response systems. Surprisingly, one MarA-binding site overlapped the lac operon regulatory region. Here, we show that MarA specifically targets this locus and can block transcription of the lac genes. Repression is mediated by binding of MarA to a site overlapping the lacP1 promoter −35 element. Control of the lac operon by MarA does not impact antibiotic resistance.

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AdeIJK, a Resistance-Nodulation-Cell Division Pump Effluxing Multiple Antibiotics in Acinetobacter baumannii

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00732-07 ◽

2008 ◽

Vol 52 (2) ◽

pp. 557-562 ◽

Cited By ~ 193

Author(s):

Laurence Damier-Piolle ◽

Sophie Magnet ◽

Sylvie Brémont ◽

Thierry Lambert ◽

Patrice Courvalin

Keyword(s):

Cell Division ◽

Acinetobacter Baumannii ◽

Efflux Pump ◽

Sodium Dodecyl ◽

Northern Blotting ◽

E Coli ◽

Reverse Transcription Pcr ◽

Membrane Components ◽

Derivatives Of

ABSTRACT We have identified a second resistance-nodulation-cell division (RND)-type efflux pump, AdeIJK, in clinical isolate Acinetobacter baumannii BM4454. The adeI, adeJ, and adeK genes encode, respectively, the membrane fusion, RND, and outer membrane components of the pump. AdeJ belongs to the AcrB protein family (57% identity with AcrB from Escherichia coli). mRNA analysis by Northern blotting and reverse transcription-PCR indicated that the genes were cotranscribed. Overexpression of the cloned adeIJK operon was toxic in both E. coli and Acinetobacter. The adeIJK genes were detected in all of the 60 strains of A. baumannii tested. The two latter observations suggest that the AdeIJK complex might contribute to intrinsic but not to acquired antibiotic resistance in Acinetobacter. To characterize the substrate specificity of the pump, we have constructed derivatives of BM4454 in which adeIJK (strain BM4579), adeABC (strain BM4561), or both groups of genes (strain BM4652) were inactivated by deletion-insertion. Determination of the antibiotic susceptibility of these strains and of BM4652 and BM4579, in which the adeIJK operon was provided in trans, indicated that the AdeIJK pump contributes to resistance to β-lactams, chloramphenicol, tetracycline, erythromycin, lincosamides, fluoroquinolones, fusidic acid, novobiocin, rifampin, trimethoprim, acridine, safranin, pyronine, and sodium dodecyl sulfate. The chemical structure of these molecules suggests that amphiphilic compounds are the preferred substrates. The AdeABC and AdeIJK efflux systems contributed in a more than additive fashion to tigecycline resistance.

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Roles of Efflux Pumps from Different Superfamilies in the Surface-Associated Motility and Virulence of Acinetobacter baumannii ATCC 17978

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.02190-18 ◽

2019 ◽

Vol 63 (3) ◽

Cited By ~ 3

Author(s):

María Pérez-Varela ◽

Jordi Corral ◽

Jesús Aranda ◽

Jordi Barbé

Keyword(s):

Acinetobacter Baumannii ◽

Efflux Pump ◽

Efflux Pumps ◽

Major Facilitator Superfamily ◽

Content Type ◽

Small Multidrug Resistance ◽

Genes Encoding ◽

Resistance Nodulation Division ◽

Major Facilitator ◽

Reported Data

ABSTRACT Although the relationship between Acinetobacter baumannii efflux pumps and antimicrobial resistance is well documented, less is known about the involvement of these proteins in the pathogenicity of this nosocomial pathogen. In previous work, we identified the AbaQ major facilitator superfamily (MFS) efflux pump and demonstrated its participation in the motility and virulence of A. baumannii. In the present study, we examined the role in these processes of A. baumannii transporters belonging to different superfamilies of efflux pumps. Genes encoding known or putative permeases belonging to efflux pump superfamilies other than the MFS were selected, and the corresponding knockouts were constructed. The antimicrobial susceptibilities of these mutants were consistent with previously reported data. In mutants of A. baumannii strain ATCC 17978 carrying inactivated genes encoding the efflux pumps A1S_2736 (resistance nodulation division [RND]), A1S_3371 (multidrug and toxic compound extrusion [MATE]), and A1S_0710 (small multidrug resistance [SMR]), as well as the newly described ATP-binding cassette (ABC) permeases A1S_1242 and A1S_2622, both surface-associated motility and virulence were reduced compared to the parental strain. However, inactivation of the genes encoding the known ABC permeases A1S_0536 and A1S_1535, the newly identified putative ABC permeases A1S_0027 and A1S_1057, or the proteobacterial antimicrobial compound efflux (PACE) transporters A1S_1503 and A1S_2063 had no effects on bacterial motility or virulence. Our results demonstrate the involvement of antimicrobial transporters belonging at least to five of the six known efflux pump superfamilies in both surface-associated motility and virulence in A. baumannii ATCC 17978.

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Mechanisms Accounting for Fluoroquinolone Resistance in Escherichia coli Clinical Isolates

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00665-08 ◽

2008 ◽

Vol 53 (1) ◽

pp. 235-241 ◽

Cited By ~ 95

Author(s):

Sonia K. Morgan-Linnell ◽

Lauren Becnel Boyd ◽

David Steffen ◽

Lynn Zechiedrich

Keyword(s):

Escherichia Coli ◽

Antimicrobial Agents ◽

Efflux Pump ◽

Resistance Mechanisms ◽

Clinical Isolates ◽

Fluoroquinolone Resistance ◽

Multidrug Efflux Pump ◽

Topoisomerase Iv ◽

E Coli ◽

Genes Encoding

ABSTRACT Fluoroquinolone MICs are increased through the acquisition of chromosomal mutations in the genes encoding gyrase (gyrA and gyrB) and topoisomerase IV (parC and parE), increased levels of the multidrug efflux pump AcrAB, and the plasmid-borne genes aac(6′)-Ib-cr and the qnr variants in Escherichia coli. In the accompanying report, we found that ciprofloxacin, gatifloxacin, levofloxacin, and norfloxacin MICs for fluoroquinolone-resistant E. coli clinical isolates were very high and widely varied (L. Becnel Boyd, M. J. Maynard, S. K. Morgan-Linnell, L. B. Horton, R. Sucgang, R. J. Hamill, J. Rojo Jimenez, J. Versalovic, D. Steffen, and L. Zechiedrich, Antimicrob. Agents Chemother. 53:229-234, 2009). Here, we sequenced gyrA, gyrB, parC, and parE; screened for aac(6′)-Ib-cr and qnrA; and quantified AcrA levels in E. coli isolates for which patient sex, age, location, and site of infection were known. We found that (i) all fluoroquinolone-resistant isolates had gyrA mutations; (ii) ∼85% of gyrA mutants also had parC mutations; (iii) the ciprofloxacin and norfloxacin MICs for isolates harboring aac(6′)-Ib-cr (∼23%) were significantly higher, but the gatifloxacin and levofloxacin MICs were not; (iv) no isolate had qnrA; and (v) ∼33% of the fluoroquinolone-resistant isolates had increased AcrA levels. Increased AcrA correlated with nonsusceptibility to the fluoroquinolones but did not correlate with nonsusceptibility to any other antimicrobial agents reported from hospital antibiograms. Known mechanisms accounted for the fluoroquinolone MICs of 50 to 70% of the isolates; the remaining included isolates for which the MICs were up to 1,500-fold higher than expected. Thus, additional, unknown fluoroquinolone resistance mechanisms must be present in some clinical isolates.

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Amotosalen is a bacterial multidrug efflux pump substrate potentially affecting its pathogen inactivation activity

10.1101/2021.03.15.435562 ◽

2021 ◽

Author(s):

Alex B. Green ◽

Katelyn E. Zulauf ◽

Katherine A. Truelson ◽

Lucius Chiaraviglio ◽

Meng Cui ◽

...

Keyword(s):

Acinetobacter Baumannii ◽

Efflux Pump ◽

Efflux Pumps ◽

Multidrug Resistant ◽

Pathogen Inactivation ◽

Multidrug Efflux ◽

Multidrug Efflux Pump ◽

Minimal Inhibitory Concentrations ◽

E Coli ◽

Rnd Efflux Pumps

AbstractPathogen inactivation is a strategy to improve the safety of transfusion products. The Cerus Intercept technology makes use of a psoralen compound called amotosalen in combination with UVA light to inactivate bacteria, viruses and protozoa. Psoralens have structural similarity to bacterial multidrug-efflux pump substrates. As these efflux pumps are often overexpressed in multidrug-resistant pathogens and with recent reported outbreaks of transfusion-associated sepsis with Acinetobacter, we tested whether contemporary drug-resistant pathogens might show resistance to amotosalen and other psoralens based on multidrug efflux mechanisms through microbiological, biophysical and molecular modeling analysis. The main efflux systems in Enterobacterales and Acinetobacter baumannii, tripartite RND (resistance-nodulation-cell division) systems which span the inner and outer membranes of Gram-negative pathogens and expel antibiotics from the bacterial cytoplasm into the extracellular space, were specifically examined. We found that amotosalen was an efflux substrate for the TolC-dependent RND efflux pumps in E. coli and the AdeABC efflux pump from Acinetobacter baumannii, and that minimal inhibitory concentrations for contemporary bacterial isolates in vitro approached and exceeded the concentration of amotosalen used in the approved platelet and plasma inactivation procedures. These findings suggest that otherwise safe and effective inactivation methods should be further studied to exclude possible gaps in their ability to inactivate contemporary, multidrug-resistant bacterial pathogens.ImportancePathogen inactivation is a strategy to enhance the safety of transfused blood products. We identify the compound, amotosalen, widely used for pathogen inactivation, as a bacterial multidrug efflux substrate. Specifically, experiments suggest that amotosalen is pumped out of bacteria by the major TolC-dependent RND efflux pumps in E. coli and the AdeABC efflux pump in Acinetobacter baumannii. Such efflux pumps are often overexpressed in multidrug-resistant pathogens. Importantly, the minimal inhibitory concentrations for contemporary multidrug-resistant Enterobacterales, Acinetobacter baumannii, Pseudomonas aeruginosa, Burkholderia spp., and Stenotrophomonas maltophilia isolates approached or exceeded the amotosalen concentration used in approved platelet and plasma inactivation procedures, potentially as a result of efflux pump activity. Although there are important differences in methodology between our experiments and blood product pathogen inactivation, these findings suggest that otherwise safe and effective inactivation methods should be further studied to exclude possible gaps in their ability to inactivate contemporary, multidrug-resistant bacterial pathogens.

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