Microbioassay of Antimicrobial Agents

Simon, Harold J.; Yin, Elaine Jong

doi:10.1128/aem.19.4.573-579.1970

Cited by 120 publications

(44 citation statements)

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“…The disks, impregnated with NPs, drug, or NP-drug conjugates were then placed on top of the agar. A previous method of impregnation, the dip method, in which dry disks were dipped into known concentrations by forceps and then placed onto the agar cultures was found to produce inconsistent results because it was shown that the disks can absorb different amounts of liquid, introducing variability in the absorbed concentrations [179]. Instead, the more accurate drop method described by Sabath [180] was used.…”

Section: Antimicrobial Susceptibility Testsmentioning

confidence: 99%

Antibacterial activity of iron oxide, iron nitride, and tobramycin conjugated nanoparticles against Pseudomonas aeruginosa biofilms

Armijo¹,

Wawrzyniec²,

Kopciuch³

et al. 2020

J Nanobiotechnol

128

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Background: Novel methods are necessary to reduce morbidity and mortality of patients suffering from infections with Pseudomonas aeruginosa. Being the most common infectious species of the Pseudomonas genus, P. aeruginosa is the primary Gram-negative etiology responsible for nosocomial infections. Due to the ubiquity and high adaptability of this species, an effective universal treatment method for P. aeruginosa infection still eludes investigators, despite the extensive research in this area. Results:We report bacterial inhibition by iron-oxide (nominally magnetite) nanoparticles (NPs) alone, having a mean hydrodynamic diameter of ~ 16 nm, as well as alginate-capped iron-oxide NPs. Alginate capping increased the average hydrodynamic diameter to ~ 230 nm. We also investigated alginate-capped iron-oxide NP-drug conjugates, with a practically unchanged hydrodynamic diameter of ~ 232 nm. Susceptibility and minimum inhibitory concentration (MIC) of the NPs, NP-tobramycin conjugates, and tobramycin alone were determined in the PAO1 bacterial colonies. Investigations into susceptibility using the disk diffusion method were done after 3 days of biofilm growth and after 60 days of growth. MIC of all compounds of interest was determined after 60-days of growth, to ensure thorough establishment of biofilm colonies. Conclusions:Positive inhibition is reported for uncapped and alginate-capped iron-oxide NPs, and the corresponding MICs are presented. We report zero susceptibility to iron-oxide NPs capped with polyethylene glycol, suggesting that the capping agent plays a major role in enabling bactericidal ability in of the nanocomposite. Our findings suggest that the alginate-coated nanocomposites investigated in this study have the potential to overcome the bacterial biofilm barrier. Magnetic field application increases the action, likely via enhanced diffusion of the iron-oxide NPs and NP-drug conjugates through mucin and alginate barriers, which are characteristic of cystic-fibrosis respiratory infections. We demonstrate that iron-oxide NPs coated with alginate, as well as alginate-coated magnetite-tobramycin conjugates inhibit P. aeruginosa growth and biofilm formation in established colonies. We have also determined that susceptibility to tobramycin decreases for longer culture times. However, susceptibility to the iron-oxide NP © The Author(s) 2020. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article' s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article'

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Section: Antimicrobial Susceptibility Testsmentioning

confidence: 99%

Antibacterial activity of iron oxide, iron nitride, and tobramycin conjugated nanoparticles against Pseudomonas aeruginosa biofilms

Armijo¹,

Wawrzyniec²,

Kopciuch³

et al. 2020

J Nanobiotechnol

128

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“…Antibiotic concentrations in serum and urine were assayed by a modified agar diffusion method 12 using paper discs as a reservoir for each sample. 13,14 Known concentrations of doxycycline hydrochloride or tetracycline hydrochloride (Fluka, Buchs, Switzerland) were added to either pooled urine or serum of clinically normal untreated dogs and cats as standard solutions, and pooled serum or urine containing no antimicrobial agent were used as negative controls.…”

Section: Antibiotic Assay Techniquementioning

confidence: 99%

Susceptibility of bacteria from feline and canine urinary tract infections to doxycycline and tetracycline concentrations attained in urine four hours after oral dosage

et al. 2006

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Objectives To measure urinary concentrations of doxycycline in cats and dogs and tetracycline in dogs 4 h after conventional oral dosing and determine whether these antibiotics were present in sufficient concentrations to be effective against common feline and canine urinary tract pathogens as assessed in vitro by Epsilometer and disc diffusion antimicrobial susceptibility methods. Design A prospective study involving oral administration to clinically normal cats and dogs of doxycycline or tetracycline (dogs only) and culture of bacteria from dogs and cats with urinary tract infections to determine their susceptibility to both doxycycline and tetracycline in vitro. Procedure In the first study, nine cats and eight dogs were administered doxycycline monohydrate (5 mg/kg every 12 h) and a further eight dogs were administered tetracycline hydrochloride (20 mg/kg every 8 h) for 72 h. Blood was collected at 2 and 4 h, and urine at 4 h, after the last dose. The concentration of each agent in serum and urine was determined by modified agar diffusion. In the second study, 45 urine samples from cats and dogs with urinary tract infections were cultured. Every bacterial isolate was tested in vitro using both Epsilometer (doxycycline and tetracycline) and disc diffusion (doxycycline, tetracycline or amoxycillin‐clavulanate) tests. Results Serum doxycycline concentrations in sera of cats and dogs at 2 h were 4.2±1.0 mg/mL and 3.4±1.1 mg/mL, respectively. The corresponding concentrations at 4 h were 3.5±0.7 mg/mL and 2.8±0.6 mg/mL. Urinary doxycycline concentrations at 4 h (53.8±24.4 mg/mL for cats and 52.4±24.1 mg/mL for dogs) were substantially higher than corresponding serum values. Serum tetracycline concentrations in dogs at 2 and 4 h, and in urine at 4 h, were 6.8±2.8, 5.4±0.8, 144.8±39.4 mg/mL, respectively. Most of the urinary tract pathogens (35/45) were susceptible to urinary concentrations of doxycycline and 38/45 were susceptible to tetracycline. In contrast 41/45 of all isolates were susceptible to amoxycillin‐clavulanate. Conclusion This is the first report of urinary concentrations of doxycycline after conventional oral administration. Concentrations attained in the urine of normal cats and dogs were sufficient to inhibit the growth of a significant number of urinary tract pathogens and thus doxycycline may be a useful antimicrobial agent for some urinary tract infections.

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“…The concentrations of cefepime equivalent in plasma were estimated by employing the microbiological assay technique (Simon & Jongyin, 1970;Arret et al, 1971) using Escherichia coli (MTCC 739) as the test organism. The bioassay method used in this work could not distinguish between the parent compound and its active metabolites, if they exist.…”

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confidence: 99%