TABLE 1.
Examples of biofilms exposed to low antibiotic concentrations.
| Antibiotic | Low AB concentration | Description | ARGs | MGEs | Polymicrobial biofilm | References |
| Trimethoprim | 1.2–10.4 ng/g | Exposure to the discharge from WWTPs | Class 1, 2, 3 integrons | Yes | Aubertheau et al., 2017 | |
| Sulfamethoxazole | 1.3–20.1 ng/g | |||||
| Levofloxacin + ofloxacin | 10–276 ng/g | |||||
| Ofloxacin | 421–649 ng/L | Natural biofilms exposed to a pressurized sewage pipe. | qnrS, sul1, sul2, blaTEM, blaKPC, ermB, tetM, tetW | intI1 | Yes | Auguet et al., 2017 |
| Ciprofloxacin | 2905–1379 ng/L | |||||
| Norfloxacin | 652–731 ng/L | |||||
| Tobramycin | 1 mg/ml; 1–5 μg/ml | In vitro Pseudomonas aeruginosa biofilms. MBEC used for antimicrobial assay. | MexAB-OprM efflux pump | No | Brooun et al., 2000 | |
| Ciprofloxacin | 0.001–100 μg/ml | |||||
| Ofloxacin | 0.1–100 μg/ml | |||||
| Erythromycin | 6 μg/L | Biofilms of P. aeruginosa isolates, including multi-drug resistant strains recovered from urban sewage plants. | sul1, mexD (efflux pump), pilH (viruelnce gene) | (rhlR, lasI) quorum sensing genes | No | Bruchmann et al., 2013 |
| Roxithromycin | 1 μg/L | |||||
| Sulfamethoxazole | 2 μg/L | |||||
| Kanamycin | 0.8, 25.6 mg/L | P. aeruginosa and P. protegens, bacterial isolates grown in agar colonies | No | Chow et al., 2015 | ||
| Tetracycline | 25.6 mg/L | |||||
| Ciprofloxacin | 0.0125, 0.025 mg/L | |||||
| Sulfadiazine | 0.74–1.63 ng/g | ARGs occurrence and Abundance in natural biofilms in comparison to sediment, water column in estuarines influenced by WWTPs. | sul1, sul2, sul3, sulA, tetA, tetB, tetC, tetG, tetL, tetM, tetO, tetQ, tetS, tetT, tetW, tetX, ermB, Chl, qnrS, qnrB, aac(6′)-Ib, zntA, zntB | intI1 | Yes | Guo et al., 2018 |
| Sulfapyridine | 0.44–11.46 ng/g | |||||
| Sulfathiazole | 0.44–12.04 ng/g | |||||
| Sulfamethazine | 1.24 ng/g | |||||
| Norfloxacin | 16.26–129 ng/g | |||||
| Ciprofloxacin | 11.73–66.27 ng/g | |||||
| Enrofloxacin | 6.42–25.07 ng/g | |||||
| Ofloxacin | 2.23–45.01 ng/g | |||||
| Tetracycline | 1.51–7.80 ng/g | |||||
| Oxytetracycline | 0.37–54.40 ng/g | |||||
| Doxycyclinehyclate | 1.68–8.78 ng/g | |||||
| Chorotetracycline | 0.85–7.76 ng/g | |||||
| Chloramphenicol | 1.20–27.27 ng/g | |||||
| Eythromycin | 1.33–4.68 ng/g | |||||
| Roxithromycin | 0.41–3.35 ng/g | |||||
| Gentamicin streptomycin amikacin tobramycin | 0.3 μg/ml | P. aeruginosa and E. coli in vitro biofilm formation assays. | arr (aminoglycoside response regulator) | Yes (2 spp) | Hoffman et al., 2005 | |
| Methicillin ampicillin amoxicillin cloxacillin | 1 to 3 μg/ml | In vitro biofilms of 15 strains of methicillin-resistant Staphylococcus aureus (MRSA). | agr (quorum sensing system) | No | Kaplan et al., 2012 | |
| Triclosan | 10 μg/L | River biofilms grown in bioreactors, algae and cyanobacteria effects were also tested. | Yes | Lawrence et al., 2009 | ||
| Triclocarban | 10 μg/L | |||||
| Sewage effluent | 2.5 ppm | Addition of sewage effluent to river biofilms | intI1 | Yes | Lehmann et al., 2016 | |
| Ciprofloxacin | 461–1922 ng/L | Staphylococcus spp. and Enterococcus spp. from WWTP influent and effluent. | Yes (2spp) | Lépesová et al., 2018 | ||
| Tetracycline | < 2–16 ng/L | |||||
| Erythromycin | 22–102 ng/L | |||||
| Penicillin | < 1.3– < 2 ng/L | |||||
| Erythromycin | 1 μg/L | River biofilms grown in artificial streams were exposed to a mixture of antibiotics and a combination of nutrient low to high concentrations | sul1, sul2 | intI1 | Yes | Subirats et al., 2018 |
| Sulfamethozaxole | ||||||
| Ciprofloxacin | ||||||
| Erythromycin | 1–4 μg/L | River biofilms grown in bioreactors. Biofilm thickness, bacterial biomass, and EPS volume against AB exposure was tested. | Yes | Waiser et al., 2016 | ||
| Trimethoprim | 4 μg/L | |||||
| Clindamycin | 4 μg/L | |||||
| Kanamycin | 25–100 μg/ml | P. chloraphis in vitro assays | No | Wang et al., 2016 | ||
| Piperacillin | 25–100 μg/ml | |||||
| Tobramycin | 0.05, 0.1 and 0.3 mg/L | Geobacter sulfurreducens biofilms | acrA, acrB, ccpA, omcB, omcC, omcS, omcT, omcE, ppcA and ppcD | pilA-C, pilA-N, pilS, and pilC (pilus genes) | No | Zhou et al., 2017 |
AB, Antibiotic; ARGs, Antibiotic Resistant Genes; MGEs, Mobile Genetic Elements; WWTP, Wastewater Treatment Plant; MBEC, minimum biofilm eradication concentration, EPS, Extracellular Polymeric Substance.