Abstract
Purpose
Tolerance to antibiotics may occur due to changes in bacterial growth patterns and
can be a precursor to development of resistance. However, there is a lack of information
on the ability of ocular bacteria isolates to develop tolerance. This paper explores
the tolerance to 8 different antibiotics of 61 microbial keratitis isolates of Pseudomonas aeruginosa from Australia and India using the MBC/MIC ratio, with tolerance defined by a ratio
32, and tolerance to ciprofloxacin by an agar diffusion assay.
Methods
Antibiotics used were ciprofloxacin, levofloxacin, gentamicin, tobramycin, piperacillin,
imipenem, ceftazidime and polymyxin B. Isolates were sourced from microbial keratitis
infections in Australia and India. Minimum bactericidal and minimum inhibitory concentration
(MBC and MIC) were obtained using broth microdilution and compared to breakpoints
from the Clinical Laboratory Standards Institute (CLSI) and European Committee on
Antimicrobial Susceptibility Testing (EUCAST) to determine bacterial susceptibility.
Tolerance was assessed as MBC/MIC ≥ 32. An alternative method for tolerance detection
(TD) was assessed with 13P. aeruginosa sensitive isolates by agar disk diffusion assay of ciprofloxacin followed by application
of glucose to the agar and observation of re-growth of colonies.
Results
Thirty-three isolates were resistant to imipenem, 20 to ciprofloxacin, 14 to tobramycin
and piperacillin, 12 to levofloxacin and ceftazidime, 8 to gentamicin, and 5 to polymyxin
B. The percentage of strains resistant to levofloxacin (7 vs 30 %; p = 0.023), gentamicin
(0 vs 24 %; p = 0.005) and tobramycin (4 vs 33 %; p = 0.004) was significantly greater
in isolates from India. On average, strains from India exhibited notably greater MIC and MBC values compared
to strains obtained from Australia. Out of 61 isolates, none displayed an MBC/MIC
ratio 32. However, three sensitive isolates had low tolerance, nine had medium tolerance
and one had high tolerance to ciprofloxacin with the TDtest.
Conclusions
This study used two methods to determine whether P. aeruginosa strains could show tolerance to antibiotics. Using the MBC/MIC criteria no strain
was considered tolerant to any of the eight antibiotics used. When 13 strains were
tested for tolerance against ciprofloxacin, the most commonly used monotherapy for
keratitis, one had high tolerance and nine had medium tolerance. This demonstrates
the capacity of P. aeruginosa to develop tolerance which may result in therapeutic failures if inappropriate dosing
regimens are used to treat keratitis.
Keywords
To read this article in full you will need to make a payment
Purchase one-time access:
Academic & Personal: 24 hour online accessCorporate R&D Professionals: 24 hour online accessOne-time access price info
- For academic or personal research use, select 'Academic and Personal'
- For corporate R&D use, select 'Corporate R&D Professionals'
Subscribe:
Subscribe to Contact Lens and Anterior EyeAlready a print subscriber? Claim online access
Already an online subscriber? Sign in
Register: Create an account
Institutional Access: Sign in to ScienceDirect
References
- Collective antibiotic tolerance: mechanisms, dynamics and intervention.Nat Chem Biol. 2015; 11: 182-188https://doi.org/10.1038/nchembio.1754
- Microbial keratitis – A review of epidemiology, pathogenesis, ocular manifestations, and management.Niger J Ophthalmol. 2018; 26: 13-23
- Diagnosing and managing microbial keratitis.Community Eye Health. 2015; 28: 3-6
- Contact lens-related corneal infection in Australia.Clin Exp Optom. 2020; 103: 408-417https://doi.org/10.1111/cxo.13082
- Contact lens –related keratitis and ocular microbiology: a review of the latest research related to the microbiota of the ocular surface.Contact Lens Spectrum. 2017; 32: 2
- Microbial keratitis predisposing factors and morbidity.Ophthalmology. 2006; 113: 109-116https://doi.org/10.1016/j.ophtha.2005.08.013
- Management and treatment of contact lens-related Pseudomonas keratitis.Clin Ophthalmol. 2012; 6: 919-924https://doi.org/10.2147/OPTH.S25168
- Empirical treatment of bacterial keratitis: an international survey of corneal specialists.BMJ Open Ophthalmol. 2017; 2https://doi.org/10.1136/bmjophth-2016-000047
- Risk factors and causative organisms in microbial keratitis.Cornea. 2008; 27: 22-27https://doi.org/10.1097/ICO.0b013e318156caf2
- In vitro antibiotic susceptibility of Pseudomonas aeruginosa corneal ulcer Isolates.Ocul Immunol Inflamm. 2015; 23: 252-255https://doi.org/10.3109/09273948.2014.883545
- Fluoroquinolone-resistant Pseudomonas aeruginosa: risk factors for acquisition and impact on outcomes.J Antimicrob Chemother. 2005; 55: 535-541https://doi.org/10.1093/jac/dki026
- Antibiotic tolerance leads to antibiotic resistance.Nat Med. 2020; 26: 163https://doi.org/10.1038/s41591-020-0778-7
- Distinguishing between resistance, tolerance and persistence to antibiotic treatment.Nat Rev Microbiol. 2016; 14: 320-330https://doi.org/10.1038/nrmicro.2016.34
- Persisters and beyond: mechanisms of phenotypic drug resistance and drug tolerance in bacteria.Crit Rev Biochem Mol Biol. 2014; 49: 91-101https://doi.org/10.3109/10409238.2013.869543
- Role of nutrient limitation and stationary-phase existence in Klebsiella pneumoniae biofilm resistance to ampicillin and ciprofloxacin.Antimicrob Agents Chemother. 2003; 47: 1251-1256https://doi.org/10.1128/AAC.47.4.1251-1256.2003
- Long-term survival during stationary phase: evolution and the GASP phenotype.Nat Rev Microbiol. 2006; 4: 113-120https://doi.org/10.1038/nrmicro1340
- Optimization of lag time underlies antibiotic tolerance in evolved bacterial populations.Nature. 2014; 513: 418-421https://doi.org/10.1038/nature13469
- Universal antibiotic tolerance arising from antibiotic-triggered accumulation of pyocyanin in Pseudomonas aeruginosa.PLoS Biol. 2019; 17: e3000573
- Molecular mechanisms of biofilm-based antibiotic resistance and tolerance in pathogenic bacteria.FEMS Microbiol Rev. 2017; 41: 276-301https://doi.org/10.1093/femsre/fux010
- Biofilms and planktonic cells of Pseudomonas aeruginosa have similar resistance to killing by antimicrobials.J Bacteriol. 2001; 183: 6746-6751https://doi.org/10.1128/JB.183.23.6746-6751.2001
- Nonmultiplying bacteria are profoundly tolerant to antibiotics.Handb Exp Pharmacol. 2012; 211: 99-119https://doi.org/10.1007/978-3-642-28951-4_7
- Contributions of antibiotic penetration, oxygen limitation, and low metabolic activity to tolerance of Pseudomonas aeruginosa biofilms to ciprofloxacin and tobramycin.Antimicrob Agents Chemother. 2003; 47: 317-323https://doi.org/10.1128/AAC.47.1.317-323.2003
- TDtest: easy detection of bacterial tolerance and persistence in clinical isolates by a modified disk-diffusion assay.Sci Rep. 2017; 7: 41284https://doi.org/10.1038/srep41284
- Susceptibility of Contact Lens-Related Pseudomonas aeruginosa Keratitis Isolates to Multipurpose Disinfecting Solutions, Disinfectants, and Antibiotics.Transl Vis Sci Technol. 2020; 9: 2https://doi.org/10.1167/tvst.9.5.2
- CLSI M100-ED30: 2020 Performance Standards for Antimicrobial Susceptibility Testing.30th Ed. Clinical & Laboratory Standards Institute, 2020
Breakpoint tables for interpretation of MICs and zone diameters. 10th ed.: European Committee on Antimicrobial Susceptibility Testing (EUCAST). 2020.
- Bactericidal activity of oxacillin and glycopeptides against Staphylococcus aureus in patients with endocarditis: looking for a relationship between tolerance and outcome.Ann Clin Microbiol Antimicrob. 2011; 10: 26https://doi.org/10.1186/1476-0711-10-26
- Evaluation of TD test for analysis of persistence or tolerance in clinical isolates of Staphylococcus aureus.J Microbiol Methods. 2019; 167105705https://doi.org/10.1016/j.mimet.2019.105705
- Infectious keratitis: A review.Clin Exp Ophthalmol. 2022; https://doi.org/10.1111/ceo.14113
- Antibiotic tolerance among clinical isolates of bacteria.Antimicrob Agents Chemother. 1986; 30: 521-527https://doi.org/10.1128/AAC.30.4.521
- Glycopeptide tolerance in Staphylococcus aureus.J Antimicrob Chemother. 1998; 42: 189-197https://doi.org/10.1093/jac/42.2.189
- Clinical significance of carbapenem-tolerant Pseudomonas aeruginosa isolated in the respiratory tract.Antibiotics (Basel). 2020; 9https://doi.org/10.3390/antibiotics9090626
- Problems in in vitro determination of antibiotic tolerance in clinical isolates.Antimicrob Agents Chemother. 1986; 30: 633-637https://doi.org/10.1128/AAC.30.5.633
- The clinical treatment of bacterial keratitis: A review of drop instillation regimes.Cont Lens Anterior Eye. 2022; 101725https://doi.org/10.1016/j.clae.2022.101725
- The development of ciprofloxacin resistance in Pseudomonas aeruginosa involves multiple response stages and multiple proteins.Antimicrob Agents Chemother. 2010; 54: 4626-4635https://doi.org/10.1128/AAC.00762-10
- Antibiotic tolerance facilitates the evolution of resistance.Science. 2017; 355: 826-830https://doi.org/10.1126/science.aaj2191
- Antibiotic resistance characteristics of Pseudomonas aeruginosa isolated from keratitis in Australia and India.Antibiotics (Basel). 2020; 9https://doi.org/10.3390/antibiotics9090600
- Role of topical high concentration levofloxacin 1.5% in bacterial keratitis.Indian Journal of Ophthalmology Case Reports. 2021; 1: 643-647
- Delhi Infectious Keratitis Study: Update on clinico-microbiological profile and outcomes of infectious keratitis.J Curr Ophthalmol. 2020; 32: 249-255https://doi.org/10.4103/JOCO.JOCO_113_20
Article info
Publication history
Published online: February 01, 2023
Accepted:
January 27,
2023
Received in revised form:
December 18,
2022
Received:
July 17,
2022
Publication stage
In Press Corrected ProofIdentification
Copyright
© 2023 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.
