Rosangela Estel Ziech

Lippia alba essential oil promotes survival of silver catfish (Rhamdia quelen) infected with Aeromonas sp.

In vitro and in vivo activity of the Lippia alba essential oil (EO) against Aeromonas sp. was evaluated. In the in vitro assay the minimum inhibitory concentration (MIC) and a minimum bactericidal concentration (MBC) of EO for Aeromonas cells were determined using the microdilution method. Twenty five strains of Aeromonas sp. isolated from infected fish obtained from local fish farms were used. MIC and MBC values were 2862 and 5998 µg mL-1 for L. alba EO and 0.5 and 1.2 µg mL-1 for gentamicin, respectively. In the in vivo assay silver catfish juveniles (Rhamdia quelen) (7.50 ± 1.85 g and 10.0 ± 1.0 cm) with typical injuries associated to Aeromonas infection were divided into four treatments (in triplicate n=10): untreated fish (negative control), 10 mg L-1 of gentamicin, and 20 or 50 µL L-1 of EO. Fish were maintained in aerated 20 L plastic boxes. After 10 days survival of silver catfish infected with Aermonas sp. and treated with essential oil (50 µL L-1) was greater than 90%.

Clostridium chauvoei, an Evolutionary Dead-End Pathogen

Full genome sequences of 20 strains of Clostridium chauvoei, the etiological agent of blackleg of cattle and sheep, isolated from four different continents over a period of 64 years (1951–2015) were determined and analyzed. The study reveals that the genome of the species C. chauvoei is highly homogeneous compared to the closely related species C. perfringens, a widespread pathogen that affects human and many animal species. Analysis of the CRISPR locus is sufficient to differentiate most C. chauvoei strains and is the most heterogenous region in the genome, containing in total 187 different spacer elements that are distributed as 30 – 77 copies in the various strains. Some genetic differences are found in the 3 allelic variants of fliC1, fliC2 and fliC3 genes that encode structural flagellin proteins, and certain strains do only contain one or two alleles. However, the major virulence genes including the highly toxic C.chauvoei toxin A, the sialidase and the two hyaluronidases are fully conserved as are the metabolic and structural genes of C. chauvoei. These data indicate that C. chauvoei is a strict ruminant-associated pathogen that has reached a dead end in its evolution.

Corrigendum: Clostridium chauvoei, an Evolutionary Dead-End Pathogen

[This corrects the article on p. 1054 in vol. 8, PMID: 28649238.].

Antimicrobial Susceptibility and Biofilm Production by Salmonella sp. Strains Isolated from Frozen Poultry Carcasses

The objectives of this study were to evaluate the antimicrobial resistance and the biofilm-producing ability of Salmonella sp. strains isolated from frozen poultry carcasses. Antimicrobial susceptibility was tested by the disk-diffusion method. Biofilm-producing ability was determined in 96-well polystyrene microplates stained with crystal violet at 1%. Out of the 22 strains tested, all were multiresistant, that is, resistant to more than three antimicrobial classes, and 72.7% were able to form biofilms. The highest resistance rates obtained were against sulfonamides, tetracycline, and quinolones. On the other hand, 100% of the strains were sensitive to chloramphenicol. According to the rate of biofilm formation, 3 (13.6%) and 13 (59.1%) strains were classified as moderate and weak biofilm-producers, respectively, and 27.3% did not form biofilms. Biofilms increase the tolerance of microorganisms to stress, reducing their sensitivity to disinfectants and antimicrobials; favor equipment corrosion; and act as substrates for the adhesion of bacteria with lower biofilm-producing capacity. The results of the present study stress the importance of cleaning procedures in food processing plants and highlight the public health risks related to the emergence of multiresistant strains.

Campylobacter fetus em bovinos no estado do Rio Grande do Sul

Bovine genital campylobacteriosis (BGC) is an infectious disease caused by Campylobacter fetus, which determines temporary infertility, mild endometritis, miscarriage in females and also increases the calving interval. The occurrence of BGC in the Brazilian herds has varied widely among regions. The aim of this study was to identify by polymerase chain reaction (PCR) the occurrence of C. fetus in bovines from Rio Grande do Sul (RS), Brazil using samples collected from1999 to 2010. A total of 816 samples from 37 counties localized predominantly in the Southwest and Central Western regions of the RS state were analyzed. Four hundred eighty preputial aspirated samples (92 from artificial insemination centers and 388 from farms that use natural mating) and 324 cervical aspirates and abomasal contents of 12 aborted fetuses were analyzed. As result, 10.9% (89/816) were positive for C. fetus. When the results were analyzed in relation to its origin, 6.5% (6/92) of the males samples from insemination centers were positive, and the ones from natural mating 9% (35/388) were positives. For the females, this percentage was 13.6% (44/324) of positivity, and the samples from the aborted fetuses 33.3% (4/12) were positive. When the 91 farms that used natural mating and the 37 counties were analyzed, it showed a positivity rate of 44.0% (40/91) and 63.2% (24/37), respectively. This study shows the importance of BGC for bovine herds, and a larger occurrence of positive samples among females when compared to male.