Guidelines and recommendations for antimicrobial minimum inhibitory concentration (MIC) testing against veterinary mycoplasma species

Abstract

-The absence of standardised procedures for minimum inhibitory concentration (MIC) testing of antimicrobial agents against veterinary mycoplasma and ureaplasma species (Mollicutes) has made it difficult to compare results originating from different laboratories. This report, prepared on behalf of the International Research Programme on Comparative Mycoplasmology (IRPCM), offers guidelines and recommendations for veterinary MIC testing of these organisms in an effort to rectify this problem. The subjects discussed include suitable media for broth and agar MIC assays, storage and preparation of antimicrobial agents, standardisation of mycoplasma inocula for MIC tests, validation of equipment, incubation conditions, and determination of MIC end points. A standard medium for all veterinary mycoplasma MIC tests cannot currently be recommended, owing to the diversity of nutritional requirements of different mycoplasma species. Instead mycoplasma broths or agars giving optimal growth of specific mycoplasmas or ureaplasmas are recommended, as suboptimal growth may lead to falsely low MIC results. The importance of using standardised mycoplasma inocula, for assays using either solid or liquid media is stressed. The growth phase may be less important as lag phase and logarithmic phase cultures of Mycoplasma gallisepticum, M. synoviae, M. bovis and M. hyopneumoniae have given very similar results in liquid MIC assays. The liquid method of Tanner and Wu and the agar method described by Hannan et al. are compared and described in detail. Methods for calculating MIC 50 s and MIC 90 s are described and the interpretation of results discussed. Methods for assessing mycoplasmacidal (MMC) activity of antimicrobial agents are also described. Adoption of these guidelines should lead to more consistent MIC results being obtained between laboratories. MIC

<i>In Vitro</i> Susceptibility of <i>Mycoplasma hyopneumoniae</i> Field Isolates and Occurrence of Fluoroquinolone, Macrolides and Lincomycin Resistance

“…Focusing on M. hyopneumoniae infection, the primary isolation was carried out in BHL broth and BHL agar medium as described previously [23]. Cultures identified as M. hyopneumoniae by colony characterization and by specific PCR [13] were stocked at −80°C until use.The following 12 antimicrobial agents generally applied in pig industry in Thailand were used; Chlortetracycline (CTC) [Sigma, St. Louis, MO, U.S.A.] Minimal inhibitory concentration (MIC) test was carried out by broth microdilution method with some modifications [5,16] using flat bottomed microplates with 96 wells. Tests were read after incubation of 7 days at 37°C, and the lowest concentration of a drug inhibiting any detectable color change of the medium was regarded as MIC of the drug.…”

“…The following 12 antimicrobial agents generally applied in pig industry in Thailand were used; Chlortetracycline (CTC) [ Minimal inhibitory concentration (MIC) test was carried out by broth microdilution method with some modifications [5,16] using flat bottomed microplates with 96 wells. Tests were read after incubation of 7 days at 37°C, and the lowest concentration of a drug inhibiting any detectable color change of the medium was regarded as MIC of the drug.…”

A study of in vitro antibacterial activity of lanthanides complexes with a tetradentate Schiff base ligand

“…The MIC values were determined following the methods used by other investigators and essentially followed the guidelines described by Hannan PCT [18] . Although a limited number of isolates were tested, some prediction can be made about possible outcome of treatment efficacy since, in hospitals, treatment is based on tests on one clinical isolate.…”

Development of a reproducible method to determine minimum inhibitory concentration (MIC) of plant extract against a slow-growing mycoplasmas organism

“…This medium has been found to be effective for in vitro antimicrobial susceptibility testing (Hannan, 2000). Filter-sterilized, amoxycillin-clavulanic acid was added at a concentration of 5×10 5 IU/l growth medium.…”