Genotyping of Mycoplasma hyopneumoniae in wild boar lung samples.

Mycoplasma hyopneumoniae is the etiologic agent of enzootic pneumonia (EP), an important cause of disease-associated losses in swine production and a role of wild boar in recurrent infections can be supposed. Genotypes of M. hyopneumoniae from wild boar are unknown but could indicate its role as a potential reservoir. Therefore, 34 lung samples being PCR-positive for M. hyopneumoniae from wild boar from the Geneva region in Switzerland were assayed by genotyping using the p146 and multi-locus sequence typing (MLST) approaches and compared to data from outbreak cases from domestic swine in Switzerland. Successful genotyping was dependent on a sufficiently high concentration of M. hyopneumoniae DNA in the samples as assessed by different real-time PCR assays. The p146 genotyping was more successful with 24 samples (70.5%) being typeable whereas only 6 samples (17.6%) could be genotyped using the MLST approach. Variability of genotypes was high but identical types were found in geographically related animals. Genotypes from wild boar showed phylogenetic relatedness to those from domestic pigs but no matching types could be identified. Results show that direct genotyping from wild boar lung samples is possible and provides a promising approach to investigate future EP outbreak related samples from wild boar.

Distribution of Paenibacillus larvae spores inside honey bee colonies and its relevance for diagnosis.

One of the most important factors affecting the development of honey bee colonies is infectious diseases such as American foulbrood (AFB) caused by the spore forming Gram-positive bacterium Paenibacillus larvae. Colony inspections for AFB clinical symptoms are time consuming. Moreover, diseased cells in the early stages of the infection may easily be overlooked. In this study, we investigated whether it is possible to determine the sanitary status of a colony based on analyses of different materials collected from the hive. We analysed 237 bee samples and 67 honey samples originating from 71 colonies situated in 13 apiaries with clinical AFB occurrences. We tested whether a difference in spore load among bees inside the whole hive exists and which sample material related to its location inside the hive was the most appropriate for an early AFB diagnosis based on the culture method. Results indicated that diagnostics based on analysis of honey samples and bees collected at the hive entrance are of limited value as only 86% and 83%, respectively, of samples from AFB-symptomatic colonies were positive. Analysis of bee samples collected from the brood nest, honey chamber, and edge frame allowed the detection of all colonies showing AFB clinical symptoms. Microbiological analysis showed that more than one quarter of samples collected from colonies without AFB clinical symptoms were positive for P. larvae. Based on these results, we recommend investigating colonies by testing bee samples from the brood nest, edge frame or honey chamber for P. larvae spores.

Combined effect of volatile antimicrobial agents on the growth of Penicillium notatum.

Widely used antimicrobial volatile organic compounds, such as sulphur dioxide and ethanol but also selected aroma compounds such as carvacrol, allyl isothiocyanate (AITC) and cinnamaldehyde, were tested single and in binary combination for their effect on Penicillium notatum growth in vapour phase at 30 degrees C. Aroma compounds were more efficient compared to sulphur dioxide and ethanol. AITC and cinnamaldehyde had the highest inhibition activity on the growth of P. notatum with minimum inhibitory concentration (MIC) of 3.8 and 3.9 micromol/L of air, respectively. The impact of agents combined two by two was assessed using two criteria, the increase of growth delay and the reduction of growth rate. A synergistic activity was identified for six combinations; ethanol/carvacrol, sulphur dioxide/carvacrol, sulphur dioxide/AITC, sulphur dioxide/cinnamaldehyde, AITC/cinnamaldehyde and cinnamaldehyde/carvacrol. The advantage of these combinations is to reduce the concentration of each agent and their relative impact in organoleptic properties.

Antimicrobial activity of carvacrol related to its chemical structure.

AIMS: To investigate the relation between the chemical structure and the antimicrobial activity of carvacrol, eugenol, menthol and two synthesized carvacrol derivative compounds: carvacrol methyl ether and carvacryl acetate against bacteria, Escherichia coli, Pseudomonas fluorescens, Staphylococcus aureus, Lactobacillus plantarum, Bacillus subtilis, a yeast Saccharomyces cerevisiae and one fungi Botrytis cinerea. METHODS AND RESULTS: The antimicrobial activity was tested in liquid and vapour phases, by both broth liquid and microatmosphere methods, respectively. The same classification of the compound's antimicrobial efficiency was found with both methods. Eugenol and menthol exhibited a weaker antimicrobial activity than carvacrol, the most hydrophobic compound. Carvacryl acetate and carvacrol methyl ether were not efficient, indicating that the presence of a free hydroxyl group is essential for antimicrobial activity. CONCLUSIONS: The different extents of antimicrobial aroma compounds' efficiency showed that hydrophobicity is an important factor and the presence of a free hydroxyl group and a delocalized system allows proton exchange. SIGNIFICANCE AND IMPACT OF THE STUDY: This study has identified the importance of the hydrophobicity and the chemical structure of phenolic aroma compounds for antimicrobial activity and may contribute to a most rational use of these compounds as antimicrobial agent.

Lactic acid bacteria biomass monitoring in highly conductive media by permittivity measurements.

Recent technological improvements have extended the application range of permittivity biomass measurements to bacterial fermentations in highly conductive media. With Lactobacillus casei, the effective biomass detection sensitivity of the FOGALE Biomass System is around 0.2 g/l (0.01 pF/cm). Fermentations growth kinetics of Lactobacillus casei can be recorded with good reproducibility and accuracy despite the high medium conductivity varying between 15 and 75 mS/cm, and the low cell concentration (<6 g/l).

Dielectric monitoring of growth and sporulation of Bacillus thuringiensis.

On-line permittivity and optical density measurements have been used to monitor biomass concentration and sporulation status during growth of a spore-forming bacterium, Bacillus thuringiensis, in fed-batch culture. The correlation between permittivity, optical density and other observations showed three distinct phases of growth: growth itself, transition and sporulation. The permittivity variations during the transition and sporulation phases could be related to the sporulation development: the evolution pattern of the ratio of optical density to permittivity was representative of the culture state, and during the sporulation phase, a permittivity index could be build to measure the extend of spore liberation.

Infectious keratoconjunctivitis of ibex, chamois and other Caprinae.

Infectious keratoconjunctivitis (IKC) caused by Mycoplasma conjunctivae is a highly contagious ocular infection which is common in domestic sheep and goats. In the European Alps, IKC is often observed in Alpine chamois (Rupicapra r. rupicapra) and in Alpine ibex (Capra i. ibex), but the disease has also been described in other wild Caprinae in the Pyrenees and in New Zealand. The infection is characterised by inflammation of the conjunctiva and cornea, and in the most advanced stages, the cornea is opaque or even perforated. In IKC outbreaks in chamois and ibex, spontaneous recovery is the most prevalent outcome of the disease. However, mortality can occasionally reach 30%. Recent studies in eastern Switzerland indicated that M. conjunctivae infection is not self-maintained in chamois. In contrast, the disease is endemic and self-maintained in the domestic sheep population. Spillover of the agent from sheep living in proximity during summer may be the origin of point-source epidemics in wild Caprinae. Flies are likely to play a central role in interspecific transmission of M. conjunctivae on alpine meadows. When outbreaks of IKC occur in wildlife, a special effort should be made to avoid unnecessary human disturbance in affected areas. However, animals presenting irreversible ocular lesions should be shot by professional gamekeepers to prevent suffering. Prevention of IKC in wild Caprinae should focus on preventing the spillover of M. conjunctivae from livestock. However, studies are required to evaluate the distribution of M. conjunctivae infection in domestic sheep in several countries and to assess the risk of IKC spillover from domestic animals to wildlife. In addition, immunological studies should be performed to develop tools which could lead to the control of M. conjunctivae infection in domestic sheep.

Mycoplasma conjunctivae infection is self-maintained in the Swiss domestic sheep population.

Bacteriological and serological investigations were performed to assess whether the domestic sheep population is a reservoir of Mycoplasma conjunctivae in Switzerland. Among a sample of 69 sheep showing clinical signs of infectious keratoconjunctivitis (IKC) in three Swiss cantons, M. conjunctivae was identified 53 times (76.8%). A commercially prepared indirect ELISA was used to detect M. conjunctivae antibodies in 674 sera of adult sheep. We analysed a stratified random sample of 123 sheep herds from 25 out of the 26 Swiss cantons. At least one positive animal was detected in 89.4% of the herds. In positive herds (n=110), 57.1% of the individual animals tested positive. To assess the importance of sheep's age in the spread of M. conjunctivae, 209 sera of adult sheep and 93 lamb sera among eight sheep herds were analysed using the indirect ELISA. Seroprevalence in 2-6-month-old lambs was 50.5%, indicating that the IKC agent is spread in sheep flocks during raising. Lambs experimentally infected with M. conjunctivae carried the agent for 8 and 23 weeks, respectively, depending on the strain used for challenge. We conclude that the M. conjunctivae-infection is endemic and self-maintained in the domestic sheep population in Switzerland.

Detection of specific Mycoplasma conjunctivae antibodies in the sera of sheep with infectious keratoconjunctivitis.

The serological cross reactions between Mycoplasma conjunctivae, the etiological agent of infectious keratoconjunctivitis (IKC), and the antigenetically and phylogenetically closely related Mycoplasma ovipneumoniae, which is often found in sheep, were analysed. Cross reacting antigens were identified using sera from sheep with IKC and from sheep of herds known to be free of IKC, as well as rabbit hyperimmune serum specific to the two Mycoplasma species. Cross reactions were predominantly due to the strongly antigenic proteins of 42 kDa and 83 kDa. Serospecific antigens of M. conjunctivae could be separated from cross-reacting antigens by the extraction of Tween 20-soluble membrane proteins. The Tween 20-extracted proteins of the M. conjunctivae strain HRC/581T were used for the development of an indirect ELISA test. This ELISA test was shown to be a useful serological method for the diagnosis of M. conjunctivae infections and to identify infected sheep herds.