Characteristics of Aerococcus viridans isolated from porcine fetuses in Korean farms

Remodelling of the healthy foal's conjunctival microbiome in the first two months of life

Introduction

The aim of the study was to explore and characterise healthy foals' eye microbiomes in the first two months of life.

Material and Methods

Conjunctival swabs were collected three times, not later than 12 h after delivery and again at the end of the first and the second months of life from six clinically healthy foals of the Polish Konik breed. The average interval between the first and second samplings was 33.3 days and between the second and third was 35.6 days. Next-generation sequencing performed on a MiSeq sequencer in paired-end technology was used to analyse the composition of the conjunctival microbiota.

Results

Paired one-sided t-tests revealed that conjunctival microbiota diversity was the lowest in the first 24 h of life and significantly increased between birth and the first month. The most prevalent family throughout the study was Micrococcaceae and the most prevalent genus was Corynebacterium. Sequences of potentially pathogenic bacteria such as Pseudomonas, Acinetobacter and Streptococcus spp. that may be involved in inflammatory processes were identified. Ocular commensals such as Corynebacterium and Lactobacillaceae that were found in the ocular surface microbiome of the foals are believed to be capable of restoring the ocular microbiome and maintaining balance.

Conclusion

A healthy ocular surface microbiota in the early period of a foal's life develops dynamically and changes its composition.

First isolation of Aerococcus viridans from clinical specimens collected on a pig farm in Poland

Introduction

Successful retrieval of Aerococcus viridans from porcine clinical specimens has been rarely described, and data has only been obtained from a few swine-producing countries. Therefore, the aim of this study was the isolation of A. viridans recovered from a specimen originating from a commercial pig farm located in Poland.

Material and Methods

Seven dead 12-week-old pigs weighing 24-26 kg with joint swelling of the hind legs were selected on a modern farrow-to-nursery farm in Poland in October 2023. The research material was joint swabs from one affected limb amputated through the proximal part of the femur. Bacteria were isolated using matrix-assisted laser desorption/ionisation-time-of-flight mass spectrometry. Antimicrobial susceptibility testing of isolates of Staphylococcus aureus, A. viridans and Trueperella pyogenes was performed by disc diffusion and also by minimal inhibitory concentration evaluation in the case of A. viridans. Two pooled samples were screened by PCR for Streptococcus suis, Actinobacillus pleuropneumoniae, Actinobacillus suis, Mycoplasma hyorhinis, M. hyosynoviae and Glaesserella parasuis.

Results

Five samples were positive for bacteria by culture and five isolates were recovered. Staphylococcus aureus was identified in three samples and T. pyogenes and A. viridans in one each. Pooled samples were G. parasuis-, M. hyorhinis-, M. hyosynoviae-, Actinobacillus pleuropneumoniae-, Actinobacillus suis- and S. suis-negative in the PCR. The A. viridans isolated was susceptible to beta-lactams and gentamicin. Ten representative nucleotide contigs from the 500 obtained showed similarity as high as 97.5% to GenBank reference strains.

Conclusion

To the best of our knowledge, this is the first identification of A. viridans in clinically affected Polish pigs. It elevates the importance of uncommon pathogens, including A. viridans, in the development of lameness in pigs. This research emphasises the role of modern diagnostic tools for accurate identification of swine pathogens. Further research would prove beneficial to elucidate the mechanisms of A. viridans infection, its prevalence, pathogenicity and virulence factors.

Antimicrobial susceptibility rates in gram-positive catalase-negative cocci from sheep and goat genital microbiota

Gram-positive catalase-negative cocci (GPCNCs) are significant components of the genital microbiota in sheep and goats. However, characterizing them can be difficult due to overlapping culture features and the limited information on their susceptibility to antibiotics. In this study, 97 foreskin and 13 vaginal swabs were investigated using a culturomic approach. Of 110 animals, 76 (69.09 %) hosted GPCNCs, including strains from Streptococcaceae (37, 33.64 %), Aerococcaceae (30, 27.27 %), Enterococcaceae (6, 5.45 %) and other minor species. With increasing antimicrobial resistance rates in livestock, surveillance programs are globally required, so we conducted a pilot study on GPCNCs isolated from the genital mucosa surfaces of sheep and goats using the minimal inhibitory concentration assay (MIC). Due to gaps in interpretative standard breakpoints, normalized resistance interpretation was used for setting epidemiological susceptibility cut-off values (COWTs). Of 57 suitable strains, the majority (80.71 %) showed high COWTs with decrease susceptibility to at least one antimicrobial class, with 22.81 % displaying multiresistant profiles. Of interest, combined resistances to beta-lactams, macrolides, lincosamides, and tetracyclines were detected in strains of Streptococcus plurianimalium. Further combinations, including resistance to beta-lactams, pleuromutilins, aminoglycosides, and lincosamides, were also recorded in both Streptococcus uberis and Enterococcus spp. strains. Being beta-lactams, macrolides, and tetracyclines the most used antibiotics in livestock worldwide, our results highlight the need for their prudent use. Collectively, our findings highlight that small ruminant genital microbiota can serve as reservoirs for opportunistic severe pathogens, often zoonotic, carrying multidrug resistances, thus standing for high risks for both animals and humans.

Biological characterization of the phage lysin AVPL and its efficiency against Aerococcus viridans-induced mastitis in a murine model

Aerococcus viridans (A. viridans) is an important opportunistic zoonotic pathogen that poses a potential threat to the animal husbandry industry, such as cow mastitis, due to the widespread development of multidrug-resistant strains. Phage lysins have emerged as a promising alternative antibiotic treatment strategy. However, no lysins have been reported to treat A. viridans infections. In this study, the critical active domain and key active sites of the first A. viridans phage lysin AVPL were revealed. AVPL consists of an N-terminal N-acetylmuramoyl-L-alanine amidase catalytic domain and a C-terminal binding domain comprising two conserved LysM. H40, N44, E52, W68, H147, T157, F60, F64, I77, N92, Q97, H159, V160, D161, and S42 were identified as key sites for maintaining the activity of the catalytic domain. The LysM motif plays a crucial role in binding AVPL to bacterial cell wall peptidoglycan. AVPL maintains stable activity in the temperature range of 4-45°C and pH range of 4-10, and its activity is independent of the presence of metal ions. In vitro, the bactericidal effect of AVPL showed efficient bactericidal activity in milk samples, with 2 µg/mL of AVPL reducing A. viridans by approximately 2 Log10 in 1 h. Furthermore, a single dose (25 µg) of lysin AVPL significantly reduces bacterial load (approximately 2 Log10) in the mammary gland of mice, improves mastitis pathology, and reduces the concentration of inflammatory cytokines (TNF-α, IL-1β, and IL-6) in mammary tissue. Overall, this work provides a novel alternative therapeutic drug for mastitis induced by multidrug-resistant A. viridans.

IMPORTANCE

A. viridans is a zoonotic pathogen known to cause various diseases, including mastitis in dairy cows. In recent years, there has been an increase in antibiotic-resistant or multidrug-resistant strains of this pathogen. Phage lysins are an effective approach to treating infections caused by multidrug-resistant strains. This study revealed the biological properties and key active sites of the first A. viridans phage lysin named AVPL. AVPL can effectively kill multidrug-resistant A. viridans in pasteurized whole milk. Importantly, 25 μg AVPL significantly alleviates the symptoms of mouse mastitis induced by A. viridans. Overall, our results demonstrate the potential of lysin AVPL as an antimicrobial agent for the treatment of mastitis caused by A. viridans.

Copper exposure causes alteration in the intestinal microbiota and metabolites in Takifugu rubripes

Copper is an environmental pollutant, and copper in aquatic environments mainly comes from soil and water. It enters the environment through atmospheric deposition, sewage discharge, and industrial production, and enters aquatic organisms, causing toxicity. Takifugu rubripes (T. rubripes) is a marine fish with high economic value. Due to the toxic effects of heavy metals on aquatic organisms such as fish, it can affect the gut community and metabolites of fish. The gut is an important channel for fish to communicate with the outside world and a necessary pathway for the metabolism of nutrients and toxic substances in the fish body. Studies have shown that due to changes in global water emissions and the high sensitivity of aquatic organisms to the environment, copper may pose greater potential hazards to aquatic organisms. Copper poses a greater risk to aquatic species than other heavy metals and metal/metal like pollutants (such as cadmium, lead, mercury, arsenic, etc.) . In order to elucidate the effects of copper exposure on the gut of T. rubripes. In this study, we exposed T. rubripes to 0, 50, 100, or 500 μg/L of copper for three days, the effects of copper exposure on the gut microbiota structure and metabolites of the T. rubripes were investigated using 16 S rRNA gene and metabolomics techniques. The research results indicate that with the increase copper concentration, the intestinal tissue of T. rubripes undergoes significant damage. 16 S rRNA sequencing results show that copper exposure alters the structure and metabolites of intestinal microbiota. Copper exposure of 100 and 500 μg/L inhibited the colonization of the bacterial gut, disrupted the intestinal barrier, and made the fish susceptible to the pathogens. Liquid chromatography-mass spectrometry analysis showed that copper regulated the production of metabolites such as L-histidine, arachidonic acid, and L-glutamic acid, which are related to energy and immunity. Microbiome-metabolome correlation analysis showed that Subdoligranulum, Family_XIII_AD3011_group, and Clostridium_sensu_stricto_1 were the key bacteria for copper ion intervention, and they might up-regulate the levels of metabolites such as indole-3-acetic acid, 3-indoleacrylic acid, and 5-hydroxyindole in the tryptophan metabolism pathway. In summary, our research has demonstrated that copper exposure can cause pathological changes in the intestinal tissue of the T. rubripes. High concentrations of copper ions can affect the colonization of the T. rubripes microbiota in the intestine, damage the fish's immune system, and alter the structure and metabolites of the intestinal microbiota, this can lead to intestinal metabolic dysfunction. providing a reference for the evaluation of the biological toxicity effects of heavy metal elements in the marine environment. This study provides a reference for evaluating the biological toxicity effects of heavy metal elements in marine environments.

Aerococcus viridans and Public Health: Oral Carriage and Antimicrobial Resistance in Stray Dogs and Cats in Algeria

The current study aimed to determine the occurrence and antimicrobial resistance of oral Aerococcus viridans in stray dogs and cats in Algeria. Oral swabs from 200 stray animals (100 dogs and 100 cats) were collected and cultured on Columbia agar medium supplemented with 5% defibrinated sheep blood. Isolates were identified using analytical profile index Rapid 20 Strep commercial kits, and antibiotic susceptibility was determined using the disk diffusion method. Of the 200 animals sampled, 34 carried A. viridans in their oral cavities, with 26 isolates (76.47%) resistant to at least 2 drugs. Multidrug resistance profiles (to more than three different antimicrobials) were observed only in cats (26.08% of isolates). More isolates were resistant to erythromycin and tetracycline (71% and 65%, respectively) than to other antimicrobials. This is the first research study in Algeria detecting antimicrobial resistance in oral A. viridans isolated from dogs and cats and highlights potential public health concerns. Clinical trials registration number: 01/2018.

Effect of the Presence of Antibiotic Residues on the Microbiological Quality and Antimicrobial Resistance in Fresh Goat Meat

A total of 11 fresh goat legs were collected at the retail level. Mesophiles, Pseudomonas spp., Enterobacteriaceae, staphylococci, enterococci, Clostridium perfringens, Campylobacter spp., and Listeria monocytogenes counts were determined. Nine samples were free of antibiotic residues, while in the other two samples the presence of sulfadiazine and doxycycline was detected. The antimicrobial resistance of E. coli, staphylococci, Macrococcus spp., and enterococci isolates was also evaluated. Clostridium perfringens was found in two samples. Methicillin-resistant Staphylococcus aureus was detected in one sample. S. epidermidis isolated from one sample containing doxycycline residues showed resistance to mupirocin. Moreover, multi-resistant S. epidermidis and M. caseolyticus were found. Most of the isolated Enterococcus faecium were multi-resistant. Neither extended-spectrum β-lactamase -producing E. coli nor vancomycin-resistant enterococci were detected in any sample. The presence of doxycycline or sulfadiazine could affect the goat meat microbiota since less microbial diversity was found in these samples compared to those free of antibiotics. The presence of antibiotic residues could increase the antimicrobial resistance of enterococci in fresh goat meat. The presence of multidrug-resistant bacteria in goat meat could be considered a potential threat and should be monitored. Special measures should be taken at the farm level and during slaughter to reduce antimicrobial resistance.

Characteristics of Aerococcus viridans isolated from porcine fetuses in Korean farms

Swine abortion caused by viruses as well as bacteria has caused many economic losses in domestic farms over the years; however, bacterial abortion has not yet been studied in Korea. Several bacterial species were isolated from aborted fetuses (n = 103) for which the cause of death was not viral abortion. Among them, we focused on Aerococcus viridans, which had the highest positive rate within three provinces (Gangwon, Jeonnam and Gyeongnam). A total of 16 isolates were identified as A. viridans by matrix‐assisted laser desorption ionization‐time of flight mass spectrometry (MALDI‐TOF MS), and 13 were characterized by both antibiotic resistance and 16S rRNA gene analysis. Based on antibiotic susceptibility testing result, eight antimicrobials could not effectively eliminate the present isolation (more than 40% of isolates can resist these antibiotics), while all except two strains were susceptible to trimethoprim/sulfamethoxazole. Molecular analysis indicated genetic variation among these strains. This study is the first report detecting A. viridans from aborted fetuses in Korean domestic farms.