{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,29]],"date-time":"2026-07-29T20:21:20Z","timestamp":1785356480755,"version":"3.55.0"},"reference-count":33,"publisher":"MDPI AG","issue":"1","license":[{"start":{"date-parts":[[2026,1,15]],"date-time":"2026-01-15T00:00:00Z","timestamp":1768435200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Department of Medical, Oral and Biotechnological Sciences, University of Chieti-Pescara","award":["ex-60%, FAR 2023"],"award-info":[{"award-number":["ex-60%, FAR 2023"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Antibiotics"],"abstract":"<jats:p>Background\/Objectives: Stenotrophomonas maltophilia is an opportunistic pathogen causing severe infections, particularly in patients with cystic fibrosis (CF). Its intrinsic multidrug resistance and biofilm-forming capacity complicate treatment. Although biofilms are generally associated with antimicrobial tolerance, the relationship between biofilm formation and planktonic antibiotic resistance in S. maltophilia remains poorly understood. This study investigated the association between antibiotic resistance profiles and biofilm production in clinical isolates from CF and non-CF patients. Methods: A total of 86 clinical isolates (40 from CF airways and 46 from non-CF patients) were analyzed. Susceptibility to seven antibiotics was assessed by disk diffusion, and multidrug resistance profiles were defined using standard criteria. Biofilm formation was quantified after 24 h using a crystal violet microtiter plate assay and categorized by using a semiquantitative scale. Results: High resistance rates were observed, particularly to meropenem (87.2%), ciprofloxacin (80.2%), and rifampicin (72.1%). CF isolates exhibited significantly higher resistance to piperacillin\/tazobactam and a greater prevalence of multidrug resistance. Biofilm formation was detected in 94.2% of isolates, with strong or powerful producers predominating. However, CF isolates formed significantly less biofilm than non-CF isolates. Notably, resistance to piperacillin\/tazobactam and meropenem was associated with reduced biofilm biomass and a lower proportion of high biofilm producers. Across all isolates, an inverse correlation was observed between the number of antibiotic resistances and biofilm biomass. These trends persisted after stratification by clinical origin, although some comparisons did not reach statistical significance. Conclusions: This study reveals an unexpected inverse relationship between planktonic antibiotic resistance and biofilm-forming capacity in S. maltophilia. Enhanced biofilm production may represent an alternative persistence strategy in more antibiotic-susceptible strains, with important implications for infection management and therapeutic failure.<\/jats:p>","DOI":"10.3390\/antibiotics15010085","type":"journal-article","created":{"date-parts":[[2026,1,15]],"date-time":"2026-01-15T08:26:36Z","timestamp":1768465596000},"page":"85","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":3,"title":["An Unexpected Inverse Relationship Between Biofilm Formation and Antibiotic Resistance in Stenotrophomonas\u00a0maltophilia"],"prefix":"10.3390","volume":"15","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-6309-6981","authenticated-orcid":false,"given":"Arianna","family":"Pompilio","sequence":"first","affiliation":[{"name":"Department of Medical, Oral, and Biotechnological Sciences, \u201cG. d\u2019Annunzio\u201d University of Chieti-Pescara, 66100 Chieti, Italy"},{"name":"Center of Advanced Studies and Technology, \u201cG. d\u2019Annunzio\u201d University of Chieti-Pescara, 66100 Chieti, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5850-2810","authenticated-orcid":false,"given":"Giovanni","family":"Di Bonaventura","sequence":"additional","affiliation":[{"name":"Department of Medical, Oral, and Biotechnological Sciences, \u201cG. d\u2019Annunzio\u201d University of Chieti-Pescara, 66100 Chieti, Italy"},{"name":"Center of Advanced Studies and Technology, \u201cG. d\u2019Annunzio\u201d University of Chieti-Pescara, 66100 Chieti, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,1,15]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"e0003019","DOI":"10.1128\/CMR.00030-19","article-title":"Advances in the Microbiology of Stenotrophomonas maltophilia","volume":"34","author":"Brooke","year":"2021","journal-title":"Clin. Microbiol. Rev."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"S3","DOI":"10.1093\/jpids\/piac052","article-title":"Opportunistic Pathogens in Cystic Fibrosis: Epidemiology and Pathogenesis of Lung Infection","volume":"11","author":"Blanchard","year":"2022","journal-title":"J. Pediatr. Infect. Dis. Soc."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"1291","DOI":"10.1016\/j.cmi.2025.04.031","article-title":"How do I manage a patient with Stenotrophomonas maltophilia infection?","volume":"31","author":"Monardo","year":"2025","journal-title":"Clin. Microbiol. Infect."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"151","DOI":"10.1128\/AAC.48.1.151-160.2004","article-title":"Biofilm formation by Stenotrophomonas maltophilia: Modulation by quinolones, trimethoprim-sulfamethoxazole, and ceftazidime","volume":"48","author":"Spedicato","year":"2004","journal-title":"Antimicrob. Agents Chemother."},{"key":"ref_5","doi-asserted-by":"crossref","unstructured":"Pompilio, A., Crocetta, V., Confalone, P., Nicoletti, M., Petrucca, A., Guarnieri, S., Fiscarelli, E., Savini, V., Piccolomini, R., and Di Bonaventura, G. (2010). Adhesion to and biofilm formation on IB3-1 bronchial cells by Stenotrophomonas maltophilia isolates from cystic fibrosis patients. BMC Microbiol., 10.","DOI":"10.1186\/1471-2180-10-102"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"365","DOI":"10.1016\/j.bjid.2016.04.002","article-title":"Antimicrobial susceptibility of hospital acquired Stenotrophomonas maltophilia isolate biofilms","volume":"20","author":"Sun","year":"2016","journal-title":"Braz. J. Infect. Dis."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"36","DOI":"10.1038\/s41522-019-0109-2","article-title":"Biofilms facilitate cheating and social exploitation of \u03b2-lactam resistance in Escherichia coli","volume":"5","author":"Amanatidou","year":"2019","journal-title":"NPJ Biofilms Microbiomes"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"27","DOI":"10.1038\/s44259-024-00046-3","article-title":"Mechanisms of antimicrobial resistance in biofilms","volume":"2","author":"Liu","year":"2024","journal-title":"NPJ Antimicrob. Resist."},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Michaelis, C., and Grohmann, E. (2023). Horizontal Gene Transfer of Antibiotic Resistance Genes in Biofilms. Antibiotics, 12.","DOI":"10.3390\/antibiotics12020328"},{"key":"ref_10","doi-asserted-by":"crossref","unstructured":"Zhao, A., Sun, J., and Liu, Y. (2023). Understanding bacterial biofilms: From definition to treatment strategies. Front. Cell. Infect. Microbiol., 13.","DOI":"10.3389\/fcimb.2023.1137947"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"322","DOI":"10.1016\/j.ijantimicag.2009.12.011","article-title":"Antibiotic resistance of bacterial biofilms","volume":"35","author":"Bjarnsholt","year":"2010","journal-title":"Int. J. Antimicrob. Agents"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"7116","DOI":"10.1128\/AEM.02636-13","article-title":"Bacterial persister cell formation and dormancy","volume":"79","author":"Wood","year":"2013","journal-title":"Appl. Environ. Microbiol."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"2735","DOI":"10.1128\/AAC.01774-09","article-title":"Antimicrobial susceptibilities of a worldwide collection of Stenotrophomonas maltophilia isolates tested against tigecycline and agents commonly used for S. maltophilia infections","volume":"54","author":"Farrell","year":"2010","journal-title":"Antimicrob. Agents Chemother."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"e364","DOI":"10.1093\/infdis\/jiae451","article-title":"Population Pharmacokinetic Modeling of Cefepime, Meropenem, and Piperacillin-Tazobactam in Patients with Cystic Fibrosis","volume":"231","author":"Rolsma","year":"2025","journal-title":"J. Infect. Dis."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"57","DOI":"10.1038\/ng.3148","article-title":"Convergent evolution and adaptation of Pseudomonas aeruginosa within patients with cystic fibrosis","volume":"47","author":"Marvig","year":"2015","journal-title":"Nat. Genet."},{"key":"ref_16","first-page":"62","article-title":"Mutation-driven evolution of Pseudomonas aeruginosa in the presence of either ceftazidime or ceftazidime\/avibactam","volume":"10","author":"Martinez","year":"2018","journal-title":"Antimicrob. Agents Chemother."},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Duan, Z., Qin, J., Liu, Y., Li, C., and Ying, C. (2020). Molecular epidemiology and risk factors of Stenotrophomonas maltophilia infections in a Chinese teaching hospital. BMC Microbiol., 20.","DOI":"10.1186\/s12866-020-01985-3"},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Bostanghadiri, N., Ardebili, A., Ghalavand, Z., Teymouri, S., Mirzarazi, M., Goudarzi, M., Ghasemi, E., and Hashemi, A. (2021). Antibiotic resistance, biofilm formation, and biofilm-associated genes among Stenotrophomonas maltophilia clinical isolates. BMC Res. Notes, 14.","DOI":"10.1186\/s13104-021-05567-y"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"285","DOI":"10.3947\/ic.2016.48.4.285","article-title":"Current Situation of Antimicrobial Resistance and Genetic Differences in Stenotrophomonas maltophilia Complex Isolates by Multilocus Variable Number of Tandem Repeat Analysis","volume":"48","author":"Rhee","year":"2016","journal-title":"Infect. Chemother."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"102537","DOI":"10.1016\/j.mib.2024.102537","article-title":"Biofilms as more than the sum of their parts: Lessons from developmental biology","volume":"82","author":"Squyres","year":"2024","journal-title":"Curr. Opin. Microbiol."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"28","DOI":"10.15698\/mic2021.02.741","article-title":"Biofilms by bacterial human pathogens: Clinical relevance\u2014Development, composition and regulation\u2014Therapeutical strategies","volume":"8","author":"Schulze","year":"2021","journal-title":"Microb. Cell"},{"key":"ref_22","doi-asserted-by":"crossref","unstructured":"Pompilio, A., Ranalli, M., Piccirilli, A., Perilli, M., Vukovic, D., Savic, B., Krutova, M., Drevinek, P., Jonas, D., and Fiscarelli, E.V. (2020). Biofilm Formation among Stenotrophomonas maltophilia Isolates Has Clinical Relevance: The ANSELM Prospective Multicenter Study. Microorganisms, 9.","DOI":"10.3390\/microorganisms9010049"},{"key":"ref_23","doi-asserted-by":"crossref","unstructured":"Mikhailovich, V., Heydarov, R., Zimenkov, D., and Chebotar, I. (2024). Stenotrophomonas maltophilia virulence: A current view. Front. Microbiol., 15.","DOI":"10.3389\/fmicb.2024.1385631"},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"Esposito, A., Pompilio, A., Bettua, C., Crocetta, V., Giacobazzi, E., Fiscarelli, E., Jousson, O., and Di Bonaventura, G. (2017). Evolution of Stenotrophomonas maltophilia in Cystic Fibrosis Lung over Chronic Infection: A Genomic and Phenotypic Population Study. Front. Microbiol., 8.","DOI":"10.3389\/fmicb.2017.01590"},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Qi, L., Li, H., Zhang, C., Liang, B., Li, J., Wang, L., Du, X., Liu, X., Qiu, S., and Song, H. (2016). Relationship between Antibiotic Resistance, Biofilm Formation, and Biofilm-Specific Resistance in Acinetobacter baumannii. Front. Microbiol., 7.","DOI":"10.3389\/fmicb.2016.00483"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"68","DOI":"10.1016\/j.ijantimicag.2008.02.009","article-title":"Higher biofilm formation in multidrug-resistant clinical isolates of Staphylococcus aureus","volume":"32","author":"Kwon","year":"2008","journal-title":"Int. J. Antimicrob. Agents"},{"key":"ref_27","first-page":"301","article-title":"Differences in biofilm development and antibiotic susceptibility among Streptococcus pneumoniae isolates from cystic fibrosis samples and blood cultures","volume":"59","author":"Morosini","year":"2007","journal-title":"J. Antimicrob. Chemother."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"126","DOI":"10.1016\/j.ijantimicag.2009.09.015","article-title":"Multidrug resistance in clinical isolates of Stenotrophomonas maltophilia: Roles of integrons, efflux pumps, phosphoglucomutase (SpgM), and melanin and biofilm formation","volume":"35","author":"Liaw","year":"2010","journal-title":"Int. J. Antimicrob. Agents"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"106367","DOI":"10.1016\/j.ijantimicag.2021.106367","article-title":"Clinical outcomes of Stenotrophomonas maltophilia infection treated with trimethoprim\/sulfamethoxazole, minocycline, or fluoroquinolone monotherapy","volume":"58","author":"Junco","year":"2021","journal-title":"Int. J. Antimicrob. Agents"},{"key":"ref_30","unstructured":"EUCAST (2025, September 15). Disk Diffusion Method for Antimicrobial Susceptibility Testing. Version 13.0 (January 2025). Available online: www.eucast.org."},{"key":"ref_31","unstructured":"(2024). Performance Standards for Antimicrobial Disk Susceptibility Tests (Standard No. CLSI M02)."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"268","DOI":"10.1111\/j.1469-0691.2011.03570.x","article-title":"Multidrug-resistant, extensively drug-resistant and pandrug-resistant bacteria: An international expert proposal for interim standard definitions for acquired resistance","volume":"18","author":"Magiorakos","year":"2012","journal-title":"Clin. Microbiol. Infect."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"891","DOI":"10.1111\/j.1600-0463.2007.apm_630.x","article-title":"Quantification of biofilm in microtiter plates: Overview of testing conditions and practical recommendations for assessment of biofilm production by staphylococci","volume":"115","author":"Hola","year":"2007","journal-title":"APMIS"}],"container-title":["Antibiotics"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2079-6382\/15\/1\/85\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,1,15]],"date-time":"2026-01-15T09:53:57Z","timestamp":1768470837000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2079-6382\/15\/1\/85"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,1,15]]},"references-count":33,"journal-issue":{"issue":"1","published-online":{"date-parts":[[2026,1]]}},"alternative-id":["antibiotics15010085"],"URL":"https:\/\/doi.org\/10.3390\/antibiotics15010085","relation":{},"ISSN":["2079-6382"],"issn-type":[{"value":"2079-6382","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,1,15]]}}}