Susceptibilities of Mycoplasma bovis, Mycoplasma dispar, and Ureaplasma diversum strains to antimicrobial agents in vitro

Abstract

The purpose of this study was to determine the susceptibility of various strains of Mycoplasma bovis, Mycoplasma dispar, and Ureaplasma diversum, which are prevalent causes of pneumonia in calves, to 16 antimicrobial agents in vitro. The MICs of the antimicrobial agents were determined by a serial broth dilution method for 16 field strains and the type strain of M. bovis, for 19 field strains and the type strain of M. dispar, and for 17 field strains of U. diversum. Final MICs for M. bovis and M. dispar were read after 7 days and final MICs for U. diversum after 1 to 2 days. All strains tested were susceptible to tylosin, kitasamycin, and tiamulin but were resistant to nifuroquine and streptomycin. Most strains of U. diversum were intermediately susceptible to oxytetracycline but fuly susceptible to chlortetracycline; most strains of M. bovis and M. dispar, however, were resistant to both agents. Strains of M. dispar and U. diversum were susceptible to doxycycline and minocycline, but strains of M. bovis were only intermediately susceptible. Susceptibility or resistance to chloramphenicol, spiramycin, spectinomycin, lincomycin, or enrofloxacin depended on the species but was not equal for the three species. The type strains of M. bovis and M. dispar were more susceptible to various antimicrobial agents, including tetracyclines, than the field strains. This finding might indicate that M. bovis and M. dispar strains are becoming resistant to these agents. Antimicrobial agents that are effective in vitro against all three mycoplasma species can be considered for treating mycoplasma infections in pneumonic calves. Therefore, tylosin, kitasamycin, and tiamulin may be preferred over oxytetracycline and chlortetracycline.Several mycoplasma species, of the many that have been isolated from cattle, are pathogenic. Mycoplasma bovis is regarded as the most pathogenic, with the exception of Mycoplasma mycoides subsp. mycoides small-colony biotype, the agent of contagious bovine pleuropneumonia. M. bovis causes mastitis in dairy cattle, respiratory tract infections in calves, and arthritis in all age groups of cattle, and it is prevalent worldwide (5). In addition, Mycoplasma dispar and Ureaplasma diversum have frequently been isolated from the respiratory tracts of pneumonic calves, and their prevalence is assumed to be worldwide also (16). Their pathogenic significance in calf respiratory disease has been proven (7). U. diversum can also be isolated from the genital tracts of cows and bulls. M. bovis, M. dispar, and U. diversum are prevalent in the Netherlands (23, 25).Because bacteria and mycoplasmas are involved in calf pneumonia, calves are often treated with antimicrobial agents. The massive and timely use of macrolide antibiotics, singly or in combination with other drugs, contributed to the recovery of more than 90% of calves affected by pneumonia (12). Although antimicrobial agents cause calves to recover from the clinical signs of respiratory disease (12), they do not eliminate mycoplasmas from the herd. Although t...

Naturally OccurringMycoplasma Bovis—Associated Pneumonia and Polyarthritis in Feedlot Beef Calves

“…If this occurs, then M. bovis infection might persist because many strains are resistant to the antibiotics commonly used to treat pneumonia in feedlot cattle 4,31,33 and because the variability of the immunodominant surface lipoproteins could allow evasion of the immune response. 15 Thus, although M. bovis commonly colonizes normal bovine lungs without ill effect, it might be able to proliferate and express virulence genes within the lesions of fibrinosuppurative bronchopneumonia, leading to a self-perpetuating, antibiotic-resistant, chronic disease.…”

“…1,2,7,8,23,25,28 Many strains of M. bovis are resistant to the antibiotics that are commonly used in feedlots, consistent with observations that natural disease often persists despite antibiotic therapy. 4,31,33 Mycoplasma bovis has the ability to undergo antigenic variation by phenotypic alteration of the immunodominant surface lipoproteins 5,15,26 and modulates the host immune response. 11,35,37,38 In addition, M. bovis can adhere to, invade, and survive in epithelial and inflammatory cells.…”

In Vitro Antimicrobial Inhibition Profiles ofMycoplasma BovisIsolates Recovered from Various Regions of the United States from 2002 to 2003

“…Methods of measuring growth endpoint are varied because of the characteristic lack of acid production from sugars by M. bovis. They range from a redox indicator, 18 to growth pellet formation, 2 to acid production from pyruvate. 19 Stabilized resazurin (alamarBlue) is used as growth indicator for MIC studies with mycobacteria, 20 as well as gram-negative and gram-positive bacteria.…”

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

“…Once these plates were cooled a bacterial lawn was prepared by spreading 100 μL from the above prepared bacterial suspension using sterile swabs. Wells of 6 mm in diameter were punched into the agar and filled with 100 μL of the antimicrobial under investigation at a concentration of 1 μg/mL [16]. The plates were then incubated at 37 °C for 24 h before zones of inhibition were measured using a caliper [15] .…”

“…Antimicrobial activities of the ligand L and its Ln (III) complexes were estimated by the determination of minimum inhibitory concentration (MIC, μg/mL) using a micro-broth dilution method and following the guidelines of Hannan [16] . A stock solution of each antimicrobial in dimethylsulfoxide was prepared according to National Committee for Clinical Laboratory Standards guidelines [17] .…”