Prevalence and antibiotic resistance in bacterial isolates of dogs with ulcerative keratitis in São Paulo State, Brazil.

OBJECTIVE: Identify microorganisms present in canine eyes affected by ulcerative keratitis and assess its resistance profile to available antimicrobial drugs. METHODS: Samples were collected from 88 canine eyes that exhibited ulcerative keratitis. They were identified using MALDI-TOF and subjected to antimicrobial susceptibility testing by disk diffusion. RESULTS: Among the assessed subjects, brachycephalic dogs accounted for 74.48% (50/83) of the evaluated canines. Among the 88 evaluated eyes, 90.9% (80/88) showed positive cultures, with 11.33% (10/88) of the samples isolating more than one species of bacteria. Of all bacterial isolates identified (90), Gram-positive bacteria accounted for 63.33% (57/90), while Gram-negative bacteria constituted 36.66% (33/90), with predominance of Staphylococcus spp. at 35.55% (32/90) being, Staphylococcus pseudintermedius at 68.75% (22/32), and Pseudomonas aeruginosa at 15.55% (14/90), respectively. Staphylococcus spp. exhibited resistance to penicillin (89.29%), sulfadiazine and trimethoprim (60.71%), and tetracycline (67.86%), while doxycycline (88.89%), cefotaxime (85.71%), chloramphenicol (82.14%), gentamicin, and moxifloxacin (78.57%) showed the highest sensitivity rates. Pseudomonas aeruginosa displayed sensitivity (100%) to gentamicin and imipenem, and resistance (8.33%) to norfloxacin, ciprofloxacin, and cefepime. Similarly, the Enterobacteriaceae family showed higher sensitivity to amikacin and gentamicin (88.89%), imipenem (88.24%), and levofloxacin (87.5%), with pronounced resistance to amoxicillin-clavulanate (50%) and cefazolin (47.06%). This highlights multiresistance in 23.33% (21/90) of the isolates. CONCLUSIONS: The most isolated species in canine ulcerative keratitis are S. pseudintermedius and P. aeruginosa. However, other species were also isolated, demonstrating diversity in ocular microbiota infection. There is a high-rate multidrug resistance associated with canine ulcerative keratitis. Nevertheless, these strains exhibited sensitivity to antimicrobials commonly used in veterinary ophthalmology.

Thermal hydrolysis of sewage sludge partially removes organic micropollutants but does not enhance their anaerobic biotransformation.

Pretreatment technologies prior to anaerobic digestion (AD) have been developed with the aim of enhancing biogas productivity and reducing the presence of pathogens in digested sludge. Among them, thermal hydrolysis (TH) appears as the most promising one. In wastewater treatment plants (WWTPs) sludge is the end point of many organic micropollutants (OMPs), which was proved to lead to important environmental and human risks since sludge is commonly used in agriculture. The objective of this work is to determine the fate OMPs in TH and subsequent AD. Sewage sludge was pretreated in a TH pilot plant at 170 °C for 20 min. Afterwards, two anaerobic digesters with a working volume of 14 L fed with fresh and pretreated sludge were operated in parallel in mesophilic conditions. TH proved to be an effective technology to partially or totally remove the dissolved fraction of OMPs as well as the fraction sorbed into those suspended solids that are solubilised after this pretreatment. However, it did not affect the OMPs sorbed concentration into solids that are not solubilised. Globally, the OMPs removal efficiency during TH appears to be linked to the solids solubilisation during this process. Afterwards, the OMPs biotransformation efficiency in AD of fresh and pretreated sludge was determined. Noticeable differences between the microbiome of both reactors was determined, but the anaerobic biotransformation was not substantially different for most of the OMPs. However, it affected musk fragrances, which presented considerably lower biotransformation efficiency in the reactor fed with pretreated sludge. Therefore, TH was proved effective in partially removing OMPs but not in enhancing their bioavailability and subsequent anaerobic biotransformation.

Organic overloading affects the microbial interactions during anaerobic digestion in sewage sludge reactors.

There is still a lack of information about microbial interactions of anaerobic digestion microbiome during process disturbance which limits our ability to predict the mechanisms that drive community dynamics on these events. This paper aims to determine how an organic overloading affects these interactions and to characterize in detail the microbiome structure and diversity in sewage sludge anaerobic reactors during an acidosis event. Two identical sewage sludge anaerobic reactors were subjected to an organic loading shock by adding glycerol waste. As consequence, volatile fatty acids accumulated after only 24 h (up to 2.5 g/L) while Bacteroidales and Methanomicrobiales became displaced by Firmicutes and Methanosaeta sp, showing that reactor acidosis can occur without an immediate decline of this methanogen. Network analysis revealed 9 clusters of co-occurring microorganisms with different behaviors during overloading. At first, Veillonellaceae family, the main glycerol degrading, associated with Candidatus Cloacimonetes, volatile fatty acids fermenters, increased their relative abundance in detriment of the syntrophic bacteria; although as conditions become more acidic, these groups were displaced by other fermenters like Porphyromonadaceae and Chitinophagaceae. Eventually, the methanogenesis failed 72 h after organic overloading, when pH reached values lower than 6. Overall, our results showed a succession of functionally redundant microorganisms, most likely because of niche specialization during organic overloading. The detailed temporal analysis elucidated the processes governing the dynamics anaerobic digestion microbiome, a knowledge required to develop anaerobic digestion management strategies based on its microbiome during process disturbances.