Identification and antimicrobial susceptibility of obligate anaerobic bacteria from clinical samples of animal origin

Antimicrobial resistance and virulence profiles of Enterobacterales isolated from two-finger and three-finger sloths (Choloepus hoffmanni and Bradypus variegatus) of Costa Rica

Background

Wildlife has been recently recognized as an environmental reservoir for antimicrobial resistance (AMR). However, less information on this topic is available in animals released back into the wild after rehabilitation in wildlife facilities, compared with studies performed exclusively in captive or free-ranging wildlife. This study aimed to evaluate the potential influence of captivity and/or treatment while in captivity of wild sloths on the AMR and virulence profiles of sloths' Enterobacterales.

Methods

Oral and rectal swab samples were collected from 39 two-finger (Choloepus hoffmanni) and three-finger sloths (Bradypus variegatus) of Costa Rica (n = 78) and analyzed using conventional bacteriological techniques. A generalized linear mixed model was applied to estimate the isolates' multiple antimicrobial resistance and virulence indices as a function of animal status.

Results

A considerable level of resistance was detected, especially for Citrobacter youngae and Escherichia coli, with 17.5% of isolates classified as multidrug-resistant. Virulence indices of isolates from rehabilitated sloths were significantly higher than the ones from sloths being hand-reared for shorter periods.

Conclusions

To our knowledge, this is the first description of sloths' antimicrobial resistant Enterobacterales, suggesting that sloths' rehabilitation and consequent exposure to humans, may promote the selection of bacteria with higher virulence. Ultimately, these bacteria may represent a threat to human and animal health due to their zoonotic potential and AMR and virulence profiles.

The Concentration of Metronidazole in the Distal Interphalangeal Joint following Intravenous Regional Limb Perfusion via the Cephalic Vein in Standing Horses

OBJECTIVE

 The aim of this study was to determine the concentration of metronidazole in the distal interphalangeal joint (DIPJ) of the thoracic limb after administering metronidazole to standing horses by intravenous regional limb perfusion (IVRLP).

METHODS

 Eleven healthy horses had a wide rubber tourniquet applied to the proximal aspect of the antebrachium for 0.5 hours and 500 mg of metronidazole diluted in physiologic saline solution to a total volume of 108 mL was administered by cephalic IVRLP. Synovial fluid samples were collected from the DIPJ before perfusion and at 0.25, 0.5, 2, 12 and 24 hours. Blood samples were obtained at the same time points for serum analysis. Concentrations of metronidazole were determined by liquid chromatography/tandem mass spectrometry.

RESULTS

 Four horses were excluded due to low synovial fluid concentrations and not completing the full tourniquet application time. The C _max in the synovial fluid was 327 ± 208 µg/mL, and the t _max was 26 ± 7 minutes. Only the concentrations of metronidazole at time points 0.25 and 0.5 hours were significantly different (p < 0.001) from synovial concentration before perfusion. The serum C _max was 1.78 ± 0.93 µg/mL, and the t _max was 76 ± 52min.

CONCLUSION

 Metronidazole administered by IVRLP reached high concentrations in the synovial fluid at 0.5 hours. However, the concentrations rapidly decreased below the minimum inhibitory concentration of potential target pathogens. Effectiveness of metronidazole administered by IVRLP as a sole therapy against anaerobic infections of synovial structures of the distal limb cannot be determined by a pharmacokinetic study. However, the present study serves as the basis for future carefully planned clinical trials.

Antimicrobial susceptibility patterns of anaerobic bacteria identified from clinical specimens of diseased dogs and cats

We aimed to clarify antimicrobial susceptibility patterns of anaerobes from diseased companion animals. Bacterial identification was based on the Japanese 2012 guidelines for the testing of anaerobic bacteria. AST was performed using the broth microdilution method. The anaerobe-containing samples collected from 2014 to 2018 included blood (anaerobe recovery rate, 5.0%), bile (9.4%), joint fluids (0.6%), pleural effusions (42.6%), ascites (64.1%), cerebrospinal fluids (3.0%), and punctures (75.0%). The anaerobes identified included Bacteroides spp. (33.2%), Peptostreptococcus spp. (19.6%), Prevotella spp. (13.6%), Propionibacterium spp. (10.3%), Clostridium spp. (9.3%), and Fusobacterium spp. (7.5%). Bacteroides fragilis group isolates were resistant to penicillin G (100%), ampicillin (100%), cefmetazole (63.6%), ceftizoxime (90.0%), and clindamycin (40.0%). Our observations demonstrated antimicrobial susceptibility in anaerobes isolated from Japanese companion animals.

High-throughput sequencing reveals microbial communities in drinking water treatment sludge from six geographically distributed plants, including potentially toxic cyanobacteria and pathogens

The microbial community structures of drinking water treatment sludge (DWTS) generated for raw water (RW) from different locations and with different source types - including river water, lake water and reservoir water -were investigated using high-throughput sequencing. Because the unit operations in the six DWTPs were similar, community composition in fresh sludge may be determined by microbial community in the corresponding RW. Although Proteobacteria, Cyanobacteria, Bacteroidetes, Firmicutes, Verrucomicrobia, and Planctomycetes were the dominant phyla among the six DWTS samples, no single phylum exhibited similar abundance across all the samples, owing to differences in total phosphorus, chemical oxygen demand, Al, Fe, and chloride in RW. Three genera of potentially toxic cyanobacteria (Planktothrix, Microcystis and Cylindrospermopsis), and four potential pathogens (Escherichia coli, Bacteroides ovatus, Prevotella copri and Rickettsia) were found in sludge samples. Because proliferation of potentially toxic cyanobacteria and Rickettsia in RW was mainly affected by nutrients, while growth of Escherichia coli, Bacteroides ovatus and Prevotella copri in RW may be influenced by Fe, control of nutrients and Fe in RW is essential to decrease toxic cyanobacteria and pathogens in DWTS.

Rectal administration of metronidazole with and without rectal evacuation prior to use in horses

In a randomized crossover design study, 10 adult horses were administered crushed metronidazole tablets rectally at 20 mg/kg. Horses' rectums were either evacuated (E) or not evacuated (NE) of manure prior to the administration of the drug. Serum samples were taken over 24 hr and plasma concentrations were determined via high pressure liquid chromatography. At 15 min post-administration, group E had a significantly higher plasma concentration (p = 0.027), but there were no concentration differences at any other time points. There was large variability in relative bioavailability in the NE group, with a median of 86.7%. Based on our results, there is no advantage to manually evacuating a horse's rectum prior to rectal administration of metronidazole. Further study at higher dosages as well as examination of clinical efficacy is warranted.

Prevalence and dissemination of antibiotic resistance genes and coselection of heavy metals in Chinese dairy farms

This study aims to explore prevalence and dissemination of antibiotic resistance genes (ARGs) in dairy farms. A variety of ARGs conferring resistance to most classes of antibiotics were detected in feces and soil samples obtained from dairy farms, using a high-throughput metagenomic sequencing approach. The ARGs observed in the feces and the soil samples were significantly correlated (p<0.01). The abundance of mobile genetics elements, such as transposase, was also examined to evaluate the potential risk of horizontal ARGs transfer. The positive correlation (p<0.001) between the total abundance of transposase genes and ARGs in the soil samples suggested strong dissemination capacity of ARGs in soil. In addition, the ARGs and metal resistance genes (MRGs) were significantly correlated with heavy metals in the feces (p<0.01), suggesting that the heavy metals promoted the emergence of metal resistance, and participated in the coselection processes for ARGs. The prevalence of ARGs with high levels of genetic mobile elements in the dairy farms suggests that cattle excrement is a major reservoir of ARGs with a high risk of dissemination, which increases the potential risk of environmental pollution and threatens public health.