In vitro activity of tylvalosin against Spanish field strains of Mycoplasma hyopneumoniae

Mycoplasma hyopneumoniae is involved in the porcine enzootic pneumonia and respiratory disease complex; therefore, the search for new treatment options that contribute to the control of this organism is relevant. The minimal inhibitory concentrations (MICs) and minimal bactericidal concentrations of tylvalosin and 19 other antimicrobial agents against 20 Spanish field isolates of M. hyopneumoniae were determined using the broth microdilution method, with the type strain (J) as a control strain. Tylvalosin had MIC50 and MIC90 values of 0.016 and 0.06 µg/ml, respectively, and was the second-most effective of the assayed antibiotics, after valnemulin. Tiamulin, tylosin and lincomycin were also among the antibiotics with the lowest MIC50 and MIC90 values against the 20 field isolates (0.06-0.25 µg/ml). However, resistance to tylosin and spiramycin, which like tylvalosin, are 16-membered macrolides, was observed. The MIC50 and MIC90 values for ciprofloxacin and enrofloxacin ranged from 0.125 to 1 µg/ml; the corresponding values ranged from 2 to 4 µg/ml for oxytetracyline, which was the most active tetracycline. Furthermore, tylvalosin and valnemulin exhibited the highest bactericidal activities. In conclusion, the macrolide tylvalosin and the pleuromutilin valnemulin exhibited the highest in vitro antimicrobial activities against M. hyopneumoniae field isolates in comparison with the other tested antibiotics.

In vitro susceptibilities of field isolates of Mycoplasma agalactiae

In order to determine how widespread antibiotic resistance has become to standard treatments, the in vitro susceptibilities of 28 Mycoplasma agalactiae Spanish field isolates to 16 antimicrobial agents were determined using a broth microdilution method. The most effective antimicrobials based on minimum inhibitory concentration (MIC)(90) values were fluoroquinolones, tetracyclines and macrolides. Two strains were tetracycline resistant. Streptomycin, erythromycin and nalidixic acid resistance was observed in all strains.

Application of flow cytometry for the determination of minimal inhibitory concentration of several antibacterial agents on Mycoplasma hyopneumoniae

AIM

In this study, flow cytometry was evaluated for the determination of the minimal inhibitory concentrations (MICs) of nine antibacterial agents (enrofloxacin, ciprofloxacin, oxytetracycline, chloramphenicol, tylosin, lincomycin, gentamycin, spectinomycin and streptomycin) against M. hyopneumoniae.

METHODS AND RESULTS

Flow cytometry was able to detect Mycoplasma hyopneumoniae inhibition at 12 h postincubation, whereas the results obtained by the traditional method were only obtained at 48 h, when a visible change in the medium had occurred. At 48 h, both methods gave the same result for eight antibacterial agents, whereas flow cytometry gave slightly higher MIC values for one antibacterial agent (tylosin). This was attributed to the fact that the M. hyopneumoniae growth that had occurred in those tubes was not enough to visibly change the colour of the medium. A good relationship was found between the flow cytometry and the traditional method.

CONCLUSION

Flow cytometry was found to be a good method for the determination of antimicrobial MICs in M. hyopneumoniae.

SIGNIFICANCE AND IMPACT OF THE STUDY

The flow cytometric method allows the determination of the response of M. hyopneumoniae to each of the antibacterial agents in near real time, and has potential for the identification and study of resistant subpopulations.

In vitro susceptibilities of Mycoplasma putrefaciens field isolates

MICs were determined for 15 antimicrobial agents against 37 Mycoplasma putrefaciens isolates. The most effective antimicrobial drug classes were the fluoroquinolones, the tetracyclines, the lincosamide lincomycin, and the macrolides. The susceptibility profile of the isolates correlated with the geographic origin. This is the first report of decreased susceptibility to the macrolides, lincomycin, and the tetracyclines in M. putrefaciens strains.

First isolation of Mycoplasma capricolum subsp. capricolum, one of the causal agents of caprine contagious agalactia, on the island of Lanzarote (Spain)

During an unusually long period of bad weather, several outbreaks of caprine contagious agalactia (CCA) were reported in a number of flocks on the island of Lanzarote (Canary Islands, Spain). Clinical and subclinical mastitis in lactating goats and some cases of arthritis and pneumonia in kids were observed in the affected flocks. Mycoplasma capricolum subsp. capricolum was isolated as the main causal agent of the outbreaks, associated with M. mycoides subsp. mycoides "large colony type" (Mmm LC) in two flocks. This is the first report of an isolation of M. capricolum subsp. capricolum on the island of Lanzarote. The finding is of epidemiological importance and could complicate plans to control the disease. The significance of this mycoplasma species in association with CCA must now be studied in detail.

In vitro susceptibilities of field isolates of Mycoplasma mycoides subsp. mycoides large colony type to 15 antimicrobials

In vitro susceptibilities of 16 Mycoplasma mycoides subsp. mycoides large colony type field isolates to 15 antimicrobial agents were determined using a broth microdilution method. The most effective antimicrobials were fluoroquinolones, tetracyclines and macrolides, with MIC values under 2 microg/ml. Resistance to nalidixic acid, gentamicin, streptomycin and spectinomycin was observed.

Use of flow cytometry for enumeration of Mycoplasma mycoides subsp. mycoides large-colony type in broth medium

AIMS

The potential of using flow cytometry (FC) in combination with a fluorescent dye (SYBR green-I) for rapidly estimating Mycoplasma mycoides subSPS. mycoides large-colony type (MmmLC) in broth culture was examined.

METHODS AND RESULTS

The FC analysis was performed by staining the MmmLC cells with a fluorescent dye, SYBR green-I (SYBR), and the results were compared with plate count method (colony forming units, - CFUs). There was a good correlation (linear regression, r(2) = 0.93) between mycoplasma counts determined by FC (cells ml(-1)) and by traditional plate count method (CFU ml(-1)). The lowest bacterial concentration detected by FC and traditional plate count was of the order of 10(4) cells ml(-1) and 10(3) CFU ml(-1), respectively. FC method allowed results in 20-30 min, whereas at least 24 h were necessary to obtain results with the traditional plate count method (CFU).

CONCLUSION

Growth rates of MmmLC in broth medium determined by FC were highly reproducible and correlated well with mycoplasma counts assessed by the plate count method.

SIGNIFICANCE AND IMPACT OF THE STUDY

These findings suggest that FC could be a good alternative to replace other time-consuming techniques that are currently used to enumerate mycoplasma in broth medium, such as plate count method (CFU).

Characterisation of protein and antigen variability among Mycoplasma mycoides subsp. mycoides (LC) and Mycoplasma agalactiae field strains by SDS-PAGE and immunoblotting

Mycoplasma mycoides subsp. mycoides (LC) (Mmm LC) and Mycoplasma agalactiae are the most important mycoplasma species involved in the contagious agalactia syndrome. A total of 25 field strains from Spain and the two type strains were analysed by SDS-PAGE and immunoblotting. Two polyclonal antisera (PAbs) raised against a pool of strains of each mycoplasma species were used. The results revealed a high degree of protein variability among the field strains. The type strain of Mmm LC appeared to be representative of the field strains of this species, whereas this was not the case with the M. agalactiae type strain. Whereas M. agalactiae is known to possess a gene family regulating surface antigen diversity, there is a need to study the mechanisms used byMmm LC to generate antigenic variability in more detail.

Protein and Antigenic Variability among Mycoplasma hyopneumoniae Strains by SDS-PAGE and Immunoblot

Porcine enzootic pneumonia (PEP), with Mycoplasma hyopneumoniae as the primary agent, is a chronic respiratory disease that causes major economic losses to the pig industry worldwide. The aim of this work was to analyse 18 field strains of M. hyopneumoniae isolated in Gran Canaria (Spain) and the reference M. hyopneumoniae strain by SDS-PAGE and immunoblot. A monoclonal antibody (MAb) against the membrane protein p46 reacted with all the strains in this study. In contrast, a purified polyclonal antibody (PAb) against the cytoplasmic protein p36 reacted with this protein in only 10 strains. A MAb against the adhesin protein p97 stained multiple proteins of different sizes and with different intensities. Different antigenic patterns in the same M. hyopneumoniae strains were also observed after different numbers of passages in culture medium. Furthermore, variability in the staining of the 36 kDa protein was observed, depending on whether the p36 PAb or the antiserum against M. hyopneumoniae reference strain was used. It is concluded that local M. hyopneumoniae field isolates in Gran Canaria are characterized by protein diversity.

Microbiological survey for Mycoplasma spp. in a contagious agalactia endemic area

In this work, we report a microbiological survey for Mycoplasma spp. undertaken between 2001 and 2002 in 28 goat herds in Gran Canaria, Spain, an area where contagious agalactia is endemic. All herds were randomly selected and represented approximately 15.5% of the total goat population of the island. A variable number of milk, articular and auricular swab samples were collected from each flock and cultured in specific mycoplasma culture media. There was a total of 38.5% positive flocks from which 37 mycoplasma isolates were obtained. In contrast with previous data obtained in Spain, our results showed that the large colony variant of M. mycoides subsp. mycoides (Mmm LC) was the most commonly isolated agent associated with contagious agalactia. This species was isolated from 90% of the positive herds and accounted for 54.1% of all isolations. M. agalactiae was isolated from 40% of the positive herds (27% of all isolations) and in six herds M. arginini was isolated (18.7% of all isolations). No M. capricolum or M. putrefaciens strains were isolated. Mycoplasmas were isolated from 21 milk samples, 15 ear canals swabs and one articular sample. The association of several species was reported in several herds. These results are at variance with previous serological studies, which indicated a higher disease prevalence, and suggest that it could be necessary to use detection techniques such PCR to confirm the existence of contagious agalactia in goats.

The Occurrence of Mycoplasmas in the Lungs of Swine in Gran Canaria (Spain)

The study was conducted to investigate the mycoplasmal flora in the lungs of pigs with enzootic pneumonia at Gran Canaria (Spain). From 54 pneumonic lungs collected at an abattoir, 85 isolates were cultivated. On the basis of cultural and biochemical characteristics, the isolates were preliminarily identified as Mycoplasma species. Using different species-specific PCRs, 40, 27, 11 and 7 of the isolates were identified as M. hyorhinis, M. hyopneumoniae, M. hyosynoviae and M. flocculare, respectively. Nine of the M. hyopneumoniae cultures were found to be in mixed culture with M. flocculare as demonstrated by PCR. By use of a M. flocculare antiserum it was possible to eliminate M. flocculare from M. hyopneumoniae mixed cultures. This study is the first report on isolation of porcine mycoplasmas at Gran Canaria (Spain).

Evaluation of Mycoplasma hyopneumoniae growth by flow cytometry

AIMS

In the present study we evaluated the potential application of the flow cytometry (FC) technique to determine the growth rates of Mycoplasma hyopneumoniae in a broth medium.

METHODS AND RESULTS

The FC analysis was performed using the fluorochromes Syto 9, propidium iodide (PI) or a combination of both dyes and results were compared with those obtained by colour-changing units (CCU) and pH measurements. While CCU counts ml(-1) were higher than those obtained from the FC technique, a good relation between M. hyopneumoniae growth rates was observed in the different phases of the growth curve (logarithmic, stationary and senescence phases). Labelling with Syto 9 alone was sufficient to differentiate M. hyopneumoniae cells with different amounts of nucleic acids, in the stationary and senescence phase of the M. hyopneumoniae growth curve. PI labelling did not detect cell death in the end phase of M. hyopneumoniae growth.

CONCLUSIONS

These data show that FC is a very useful, practical and fast technique to study the growth rates of M. hyopneumoniae in broth medium.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is to our knowledge the first application of FC to the study of M. hyopneumoniae growth in broth culture.

Serological study of contagious agalactia in herds of goats in the Canary Islands

An indirect ELISA, using local strains of Mycoplasma agalactiae and Mycoplasma mycoides subspecies mycoides large colony (MmmLC), was applied to evaluate the seroprevalence of M agalactiae and MmmLC in flocks of goats on each of the Canary Islands. In total 3890 samples of serum were collected from 204 flocks. The results indicated that the seroprevalence of both organisms is high on all the islands; average values of 55 per cent and 67 per cent were recorded, respectively, for M agalactiae and MmmLC.