Virulence Plasmids of Rhodococcus equi Isolates From Cuban Patients With AIDS

Bifidobacterium longum subsp. longum XZ01 delays the progression of colon cancer in mice through the interaction between the microbial spatial distribution and tumour immunity

Studies have shown that the colonisation of active microorganisms is more conducive to the development of tumour immunotherapy, but intuitive evidence regarding shaping of the tumour immune microenvironment is lacking. In this study, we used Bifidobacterium longum subsp. longum (XZ01) to intervene in a colon cancer mouse model and found that its mechanism may be related to the interaction between the spatial distribution of microorganisms and tumour immunity. Through the visualisation method we established, for the first time, we showed that harmful active bacteria such as Streptococcus and Rhodococcus specifically accumulate in the middle and upper layers of tumour tissue. These bacteria likely participate in signalling pathways that affect macrophages by directly contacting or invading the macrophages, leading to a nondifferentiated state in macrophages and the loss of some immune functions. Furthermore, the accumulation of Streptococcus and Rhodococcus fragments in the deep layer of tumour tissue likely upregulates the expression of IL-10 in tumour tissue and inhibits other immune cells, such as CD8+ T cells, DC and NK cells. In contrast, XZ01 can specifically compete for the growth sites of Streptococcus and Rhodococcus in the middle and upper layers of tumour tissue and probably protects macrophages from being invaded by harmful bacteria. XZ01 directly regulates the polarisation of M0 macrophages towards the M1 phenotype by upregulating IFN-γ, thus activating tumour immunity to inhibit the growth of tumour cells. This study revealed that the influence of active microorganisms on the tumour immune microenvironment is crucial for effective immunotherapy intervention, potentially offering new targets for improving patient prognosis.

In vitro susceptibility pattern of Rhodococcus equi isolated from patients to antimicrobials recommended exclusively to humans, to domestic animals and to both

Rhodococcus equi is an opportunistic soil-borne bacterium that is eliminated in feces of multi-host animals. An increase in multidrug-resistant R. equi isolates has been reported in humans and domestic animals, and it has been hypothesized that the treatment of R. equi in foals could increase the selective pressure on multidrug-resistant isolates and favor human infections by resistant isolates. We investigated the in vitro antimicrobial susceptibility/resistance of 41 R. equi strains from humans, which were isolated from patients with pulmonary signs, using 19 antimicrobials from 10 distinct classes, recommended exclusively to humans, recommended exclusively to domestic animals and used in both. All isolates were subjected to mass spectrometry and identified as R. equi. Among the antimicrobials used exclusively in humans, tigecycline and vancomycin showed 100% efficacy. Amikacin, amoxicillin/clavulanic acid, imipenem, levofloxacin, clarithromycin, rifampin, ciprofloxacin, and gentamicin, used in both humans and animals, revealed high efficacy (97-100%). Conversely, a higher frequency of isolates was resistant to penicillin (87.8%) and trimethoprim/sulfamethoxazole (43.9%), which are used in both humans and animals. Among the antimicrobials used only in animals, isolates were resistant to florfenicol (46.4%), ceftiofur (17.1%), and enrofloxacin (2.5%). Multidrug resistance was observed in 34% of isolates. The identification of drug-resistant R. equi isolated from humans used exclusively in animals is circumstantial evidence of the pathogen transmission from domestic animals to humans. This study contributes to the molecular identification of Rhodococcus species from humans and to the epidemiological vigilance of the multidrug-resistant isolates.

Fatal Infection in an Alpaca (Vicugna pacos) Caused by Pathogenic Rhodococcus equi

Simple Summary

Serious consequences of septicemic bacterial infections include the formation of purulent and pyogranulomatous inflammation resulting in abscesses in inner organs. Different bacteria are known to cause these infections in livestock. In this study, we report in detail on a case of a fatal Rhodococcus (R.) equi infection in an alpaca (Vicugna pacos), to our knowledge, for the first time. R. equi is a member of the actinomycetes, a bacterial group known to contain several pathogenic bacteria. R. equi primarily affects equine foals and other domestic animals, but also humans, which renders this bacterium a zoonotic agent. The rhodococcal infection of the alpaca reported herein caused septicemia, resulting in emaciation and severe lesions in the lungs and heart. The onset of infection was presumably caused by aspiration pneumonia, resulting in abscesses exclusively in the lungs. The R. equi isolate proved to be pathogenic, based on the virulence gene vapA encoding the virulence-associated protein A. Antibiotic susceptibility testing revealed a susceptibility to doxycycline, erythromycin, gentamycin, neomycin, rifampicin, trimethoprim/sulfamethoxazole, tetracycline and vancomycin. This report of an R. equi infection in an alpaca makes clear that we still have knowledge gaps about bacterial infectious diseases in alpacas and potential zoonotic impacts. Therefore, the determination of pathogenic, zoonotic bacteria in alpacas is essential for treatment and preventive measures with respect to sustaining the health, welfare and productivity of this camelid species.

Abstract

Rhodococcus (R.) equi is a pathogen primarily known for infections in equine foals, but is also present in numerous livestock species including New World camelids. Moreover, R. equi is considered an emerging zoonotic pathogen. In this report, we describe in detail a fatal rhodococcal infection in an alpaca (Vicugna pacos), to our best knowledge, for the first time. The alpaca died due to a septicemic course of an R. equi infection resulting in emaciation and severe lesions including pyogranulomas in the lungs and pericardial effusion. The onset of the infection was presumably caused by aspiration pneumonia. R. equi could be isolated from the pyogranulomas in the lung and unequivocally identified by MALDI-TOF MS analysis and partial sequencing of the 16S rRNA gene, the 16S-23S internal transcribed spacer (ITS) region and the rpoB gene. The isolate proved to possess the vapA gene in accordance with tested isolates originating from the lungs of infected horses. The R. equi isolates revealed low minimal inhibitory concentrations (MIC values) for doxycycline, erythromycin, gentamycin, neomycin, rifampicin, trimethoprim/sulfamethoxazole, tetracycline and vancomycin in antibiotic susceptibility testing. Investigations on the cause of bacterial, especially fatal, septicemic infections in alpacas are essential for adequately addressing the requirements for health and welfare issues of this New World camelid species. Furthermore, the zoonotic potential of R. equi has to be considered with regard to the One Health approach.

Genomic Characteristics Revealed Plasmid-Mediated Pathogenicity and Ubiquitous Rifamycin Resistance of Rhodococcus equi

Rhodococcus equi is a zoonotic pathogen that can cause fatal disease in patients who are immunocompromised. At present, the epidemiology and pathogenic mechanisms of R. equi infection are not clear. This study characterized the genomes of 53 R. equi strains from different sources. Pan-genome analysis showed that all R. equi strains contained 11481 pan genes, including 3690 core genes and 602 ~ 1079 accessory genes. Functional annotation of pan genome focused on the genes related to basic lifestyle, such as the storage and expression of metabolic and genetic information. Phylogenetic analysis based on pan-genome showed that the R. equi strains were clustered into six clades, which was not directly related to the isolation location and host source. Also, a total of 84 virulence genes were predicted in 53 R. equi strains. These virulence factors can be divided into 20 categories related to substance metabolism, secreted protein and immune escape. Meanwhile, six antibiotic resistance genes (RbpA, tetA (33), erm (46), sul1, qacEdelta 1 and aadA9) were detected, and all strains carried RbpA related to rifamycin resistance. In addition, 28 plasmids were found in the 53 R. equi strains, belonging to Type-A (n = 14), Type-B (n = 8) and Type-N (n = 6), respectively. The genetic structures of the same type of plasmid were highly similar. In conclusion, R. equi strains show different genomic characteristics, virulence-related genes, potential drug resistance and virulence plasmid structures, which may be conducive to the evolution of its pathogenesis.

Cellulitis-related Rhodococcus equi in a cat harboring VAPA-type plasmid pattern

Rhodococcus equi is a well-known intracellular facultative bacterium that is opportunistic in nature, and a contagious disease-causing agent of pyogranulomatous infections in humans and multihost animals. Feline rhodococcosis is an uncommon or unnoticed clinical condition, in which the organism is usually refractory to conventional antimicrobial therapy. The pathogenicity of the agent is intimately associated with plasmid-governed infectivity, which is attributed to the presence of plasmid-encoded virulence-associated proteins (Vap). Three host-adapted virulence plasmid types (VAPs) have been distinguished to date: pVAPA, pVAPB, and pVAPN, whose infections are related to equine, pig, and bovine or caprine origin, respectively, while humans are infected by all three VAP types. Most virulence studies with R. equi plasmid types in animals involve livestock species. Conversely, data on the pathogenicity and human relevance of the virulence plasmid profile of R. equi isolated from cats remains unclear. This report describes a case of cellulitis-related R. equi that harbors the pVAPA-type in a cat with cutaneous lesion. Long-term therapy of the cat using marbofloxacin, a broad-spectrum third-generation fluoroquinolone, resulted effectiveness. pVAPA is a host-adapted virulent type that has been associated predominantly with pulmonary foal infections. Our cat had a history of contact with other cats, livestock (including horses), and farm environment that could have favored the transmission of the pathogen. Besides no clear evidence of cat-to-humans transmission of the pathogen, the identification of R. equi harboring pVAPA-type in a cat with cutaneous abscessed lesion represent relevance in human health because this virulent type has been described in people worldwide with clinical rhodococcal disorders.

Rhodococcus equi-Occurrence in Goats and Clinical Case Report

Background: Rhodococcus equi infection is commonly known in equine medicine to cause frequently fatal rhodococcosis. Infections in other species and people are also reported. Clinical manifestation in goats is relatively similar to horses and humans, but data regarding bacterium prevalence are scarce. Thus, the study aimed to estimate the occurrence of R. equi in goats. Methods: During post mortem examination, submandibular, mediastinal, and mesenteric lymph nodes were collected. Standard methods were used for bacteria isolation and identification. Results: A total of 134 goats were examined, and 272 lymph node samples were collected. R. equi was isolated from four animals. All four isolates carried the choE gene, and one also had traA and pVAPN plasmid genes. Conclusions: To the authors’ best knowledge, this is the first report of R. equi occurrence and genetic diversity in goats. The results may help create a model for treating rhodococcosis in other animal species and assessing the role of meat contamination as a potential source of human infection. This research should be considered a pilot study for further application of the goat as a model of R. equi infection in horses and humans.