The moderate drift towards less tetracycline-susceptible isolates of contagious agalactia causative agents might result from different molecular mechanisms.

Contagious agalactia is a mycoplasmosis that affects small ruminants, is associated with loss of milk production and high morbidity rates, and is highly deleterious to dairy industries. The etiological agents are four mycoplasma (sub)species, of which the relative importance depends on the countries and the animal host. Tetracyclines are non-expensive, broad-spectrum antimicrobials and are often used to control mastitis in dairy herds. However, the in vitro efficiency of tetracyclines against each of the etiological agents of contagious agalactia has been poorly assessed. The aims of this study were i) to compare the tetracycline susceptibilities of various field isolates, belonging to different mycoplasma (sub)species and subtypes, collected over the years from different clinical contexts in France or Spain, and ii) to investigate the molecular mechanisms behind the decreased susceptibility of some isolates to tetracyclines. The Minimum Inhibitory Concentrations (MICs) of tetracyclines were determined in vitro on a set of 120 isolates. Statistical analyses were run to define the significance of any observed differences in MICs distribution. As mutations in the genes encoding the tetracycline targets (rrs loci) are most often associated with increased tetracycline MICs in animal mycoplasmas, these genes were sequenced. The loss of susceptibility to tetracyclines after year 2010 is not significant and recent MICs are higher in M. agalactiae, especially isolates from mastitis cases, than in other etiological agents of contagious agalactia. The observed increases in MICs were not always associated with mutations in the rrs alleles which suggests the existence of other resistance mechanisms yet to be deciphered.

In vitro assessment of the antimicrobial susceptibility of caprine isolates of Mycoplasma mycoides subsp. capri.

The minimum inhibitory concentration (MIC) and minimum mycoplasmacidal concentration (MMC) of 17 antimicrobials against 41 Spanish caprine isolates of Mycoplasma mycoides subsp. capri (Mmc) obtained from different specimens (milk, external auricular canal and semen) were determined using a liquid microdilution method. For half of the isolates, the MIC was also estimated for seven of the antimicrobials using an epsilometric test (ET), in order to compare both methods and assess the validity of ET. Mutations in genes gyrA, gyrB, parC and parE conferring fluoroquinolone resistance, which have been recently described in Mmc, were investigated using PCR. The anatomical origin of the isolate had no effect on its antimicrobial susceptibility. Moxifloxacin and doxycycline had the lowest MIC values. The rest of the fluoroquinolones studied (except norfloxacin), together with tylosin and clindamycin, also had low MIC values, although the MMC obtained for clindamycin was higher than for the other antimicrobials. For all the aminoglycosides, spiramycin and erythromycin, a notable level of resistance was observed. The ET was in close agreement with broth microdilution at low MICs, but not at intermediate or high MICs. The analysis of the genomic sequences revealed the presence of an amino acid substitution in codon 83 of the gene gyrA, which has not been described previously in Mmc.

Epidemiological role of birds in the transmission and maintenance of zoonoses. / Papel epidemiológico de las aves en la transmisión y mantenimiento de zoonosis.

The risk of zoonoses spreading from birds to humans is lower, quantitatively speaking, than the risk of transmission between other host groups, because the two taxonomic groups share fewer pathogens. Nevertheless, birds have a number of epidemiological characteristics that make them extremely important hosts in the transmission and maintenance of zoonoses, including their susceptibility to pathogens that are extremely hazardous to humans (such as highly pathogenic avian influenza virus, West Nile virus and Chlamydia psittaci) and their ability to travel long distances, especially in the case of migratory birds. The fact that the human diet includes poultry products (meat, eggs and their by-products) also means that most human cases of foodborne zoonoses are infections of avian origin. Lastly, close contact between humans and pet birds or urban birds leads to interactions of public health concern. This article sets out to describe the main factors that determine the role of birds in the epidemiology of zoonotic infections.

Le risque que les oiseaux transmettent des zoonoses à l'homme est moins élevé, au plan quantitatif, qu'entre hôtes d'autres catégories, car le nombre d'agents pathogènes affectant à la fois ces deux groupes taxonomiques est moindre. Cependant, certaines particularités épidémiologiques des oiseaux leur font jouer un rôle d'hôtes importants dans la persistance et la transmission de zoonoses : d'une part, leur sensibilité à des agents pathogènes dangereux pour l'homme (par exemple, le virus de l'influenza aviaire hautement pathogène, le virus de West Nile, Chlamydia psittaci) et, d'autre part, leur capacité à se déplacer sur de longues distances, notamment dans le cas des oiseaux migrateurs. En outre, les produits avicoles faisant partie des denrées alimentaires consommées par l'homme (viande de volaille, oeufs et produits dérivés), la majorité des cas de zoonoses d'origine alimentaire diagnostiqués chez l'homme sont d'origine aviaire. Enfin, les contacts étroits entre les humains et leurs oiseaux de compagnie ou avec des oiseaux des villes entraînent des interactions qui sont à prendre en compte en santé publique. Les auteurs décrivent les principales caractéristiques épidémiologiques des oiseaux jugées déterminantes par rapport aux infections zoonotiques.

El riesgo de transmisión de zoonosis de aves a humanos es menor, cuantitativamente hablando, que el que tiene lugar entre otros grupos de hospedadores, debido a que estos dos grupos taxonómicos comparten un menor número de agentes patógenos. No obstante, algunas particularidades epidemiológicas de las aves las convierten en hospedadores de gran importancia en el mantenimiento y la transmisión de zoonosis, como su capacidad de contraer infecciones por agentes patógenos peligrosos para los humanos (como el virus de la influenza aviar altamente patógena, el virus del Nilo Occidental o Chlamydia psittaci, entre otros) así como su gran capacidad de desplazamiento, especialmente en el caso de las aves migratorias. Además, el hecho de que la alimentación humana incluya productos avícolas (carne y huevos y productos derivados) hace que la mayoría de casos de zoonosis de origen alimentario diagnosticados en humanos sean infecciones de origen aviar. Por último, el estrecho contacto entre humanos y mascotas aviares o aves urbanas conlleva interacciones de interés para la salud pública. Este trabajo pretende describir los principales determinantes epidemiológicos de las aves en relación con las infecciones zoonósicas.

Sensitivity of two methods to detect Mycoplasma agalactiae in goat milk.

BACKGROUND: Laboratory diagnostic techniques able to detect Mycoplasma agalactiae are essential in contagious agalactia in dairy goats. This study was designed: 1) to determine the detection limits of PCR and culture in goat milk samples, 2) to examine the effects of experimental conditions including the DNA extraction method, PCR technique and storage conditions (fresh versus frozen stored milk samples) on these methods and 3), to establish agreement between PCR and culture techniques using milk samples from goats with mastitis in commercial dairy herds. The study was conducted both on artificially inoculated and field samples. RESULTS: Our findings indicate that culture is able to detect M. agalactiae in goat milk at lower concentrations than PCR. Qualitative detection of M.agalactiae by culture and PCR was not affected by sample freezing, though the DNA extraction method used significantly affected the results of the different PCR protocols. When clinical samples were used, both techniques showed good agreement. CONCLUSIONS: The results from this study indicate that both culture and PCR are able to detect M. agalactiae in clinical goat mastitis samples. However, in bulk tank milk samples with presumably lower M. agalactiae concentrations, culture is recommended within the first 24 h of sample collection due to its lower limit of detection. To improve the diagnostic sensitivity of PCR in milk samples, there is a need to increase the efficiency of extracting DNA from milk samples using protocols including a previous step of enzymatic digestion.