Biofilm formation and determination of minimum biofilm eradication concentration of antibiotics in Mycoplasma hyopneumoniae

Effective biofilm eradication in MRSA isolates with aminoglycoside-modifying enzyme genes using high-concentration and prolonged gentamicin treatment

Bone and soft tissue infections caused by biofilm-forming bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA), remain a significant clinical challenge. While the control of local infection is necessary, systemic treatment is also required, and biofilm eradication is a critical target for successful management. Topical antibiotic treatments, such as antibiotic-loaded bone cement (ALBC), have been used for some time, and continuous local antibiotic perfusion therapy, a less invasive method, has been developed by our group. However, the optimal antibiotics and concentrations for biofilms of clinical isolates are still not well understood. We examined the efficacy of high concentrations of gentamicin against MRSA biofilms and the role of gentamicin resistance genes in biofilm eradication. We collected 101 MRSA samples from a hospital in Japan and analyzed their gene properties, including methicillin and gentamicin resistance, and their minimum biofilm eradication concentration (MBEC) values. Our results showed that high concentrations of gentamicin are effective against MRSA biofilms and that even concentrations lower than the MBEC value could eliminate biofilms after prolonged exposure. We also identified three aminoglycoside/gentamicin resistance genes [aac(6')-aph(2″), aph(3')-III, and ant(4')-IA] and found that the presence or absence of these genes may inform the selection of treatments. It was also found that possession of the aac(6')-aph(2″) gene correlated with the minimum inhibitory concentration/MBEC values of gentamicin. Although this study provides insight into the efficacy of gentamicin against MRSA biofilms and the role of gentamicin resistance genes, careful selection of the optimal treatment strategy is needed for clinical application.

IMPORTANCE

Our analysis of 101 MRSA clinical isolates has provided valuable insights that could enhance treatment selection for biofilm infections in orthopedics. We found that high concentrations of gentamicin were effective against MRSA biofilms, and even prolonged exposure to concentrations lower than the minimum biofilm eradication concentration (MBEC) value could eliminate biofilms. The presence of the aac(6')-aph(2″) gene, an aminoglycoside resistance gene, was found to correlate with the minimum inhibitory concentration (MIC) and MBEC values of gentamicin, providing a potential predictive tool for treatment susceptibility. These results suggest that extended high concentrations of local gentamicin treatment could effectively eliminate MRSA biofilms in orthopedic infections. Furthermore, testing for gentamicin MIC or the possession of the aac(6')-aph(2″) gene could help select treatment, including topical gentamicin administration and surgical debridement.

Continuous local antibiotic perfusion technique for surgical site infections after shoulder surgery

Background

Continuous local antibiotic perfusion (CLAP) is a method for preserving tissue and function against surgical site infections (SSIs) after shoulder surgery.

Methods

To describe the application of the novel CLAP technique to 10 patients with SSIs after shoulder surgery that were not controlled with repeated surgical débridement or elderly patients who are insufficient physical resilience for further surgeries.

Results

CLAP, consisting of gentamicin, was performed for 2 weeks, after which the infection was well-controlled. The white blood cell count and C-reactive protein level improved rapidly within 1 week of initiating CLAP, after which the patients were switched to oral antibiotics for 3 months. None of the patients experienced any adverse events.

Conclusion

CLAP for SSIs after shoulder surgery was successful in preserving implants and grafts. The SSIs were controlled with no adverse events. CLAP may be an important treatment option for SSIs after shoulder surgery.

Research Progress on Immune Evasion of Mycoplasma hyopneumoniae

As the main pathogen associated with enzootic pneumonia (EP), Mycoplasma hyopneumoniae (Mhp) is globally prevalent and inflicts huge financial losses on the worldwide swine industry each year. However, the pathogenicity of Mhp has not been fully explained to date. Mhp invasion usually leads to long-term chronic infection and persistent lung colonization, suggesting that Mhp has developed effective immune evasion strategies. In this review, we offer more detailed information than was previously available about its immune evasion mechanisms through a systematic summary of the extant findings. Genetic mutation and post-translational protein processing confer Mhp the ability to alter its surface antigens. With the help of adhesins, Mhp can achieve cell invasion. And Mhp can modulate the host immune system through the induction of inflammation, incomplete autophagy, apoptosis, and the suppression of immune cell or immune effector activity. Furthermore, we offer the latest views on how we may treat Mhp infections and develop novel vaccines.

Poly-Gamma-Glutamic Acid Nanopolymer Effect against Bacterial Biofilms: In Vitro and In Vivo Study

In this study, a biodegradable poly-gamma-glutamic-acid nanopolymer (Ɣ-PGA NP) was investigated for its activity against clinical strains of Gram-positive (Staphylococcus aureus and Streptococcus pyogenes) and Gram-negative (Klebsiella pneumoniae and Escherichia coli), and reference strains of S. aureus ATCC 6538, S. pyogenes ATCC 19615 (Gram-positive), and Gram-negative E. coli ATCC 25922, and K. pneumoniae ATCC 13884 bacterial biofilms. The minimum inhibitory concentration (MIC) effect of Ɣ-PGA NP showed inhibitory effects of 0.2, 0.4, 1.6, and 3.2 μg/mL for S. pyogenes, S. aureus, E. coli, and K. pneumoniae, respectively. Also, MIC values were 1.6, 0.8, 0.2, and 0.2 μg/mL for K. pneumoniae ATCC 13884, E. coli ATCC 25922, S. aureus ATCC 6538, and S. pyogenes ATCC 19615, respectively. Afterwards, MBEC (minimum biofilm eradication concentration) and MBIC (minimum biofilm inhibitory concentration) were investigated to detect Ɣ-PGA NPs efficiency against the biofilms. MBEC and MBIC increased with increasing Ɣ-PGA NPs concentration or time of exposure. Interestingly, MBIC values were at lower concentrations of Ɣ-PGA NPs than those of MBEC. Moreover, MBEC values showed that K. pneumoniae was more resistant to Ɣ-PGA NPs than E. coli, S. aureus, and S. pyogenes, and the same pattern was observed in the reference strains. The most effective results for MBEC were after 48 h, which were 1.6, 0.8, 0.4, and 0.2 µg/mL for K. pneumoniae, E. coli, S. aureus, and S. pyogenes, respectively. Moreover, MBIC results were the most impactful after 24 h but some were the same after 48 h. MBIC values after 48 h were 0.2, 0.2, 0.2, and 0.1 μg/mL for K. pneumoniae, E. coli, S. aureus, and S. pyogenes, respectively. The most effective results for MBEC were after 24 h, which were 1.6, 0.8, 0.4, and 0.4 µg/mL for K. pneumoniae ATCC 13884, E. coli ATCC 25922, S. aureus ATCC 6538, and S. pyogenes ATCC 19615, respectively. Also, MBIC results were the most impactful after an exposure time of 12 h. MBIC values after exposure time of 12 h were 0.4, 0.4, 0.2, and 0.2 μg/mL for K. pneumoniae ATCC 13884, E. coli ATCC 25922, S. aureus ATCC 6538, and S. pyogenes ATCC 19615, respectively. Besides that, results were confirmed using confocal laser scanning microscopy (CLSM), which showed a decrease in the number of living cells to 80% and 60% for MBEC and MBIC, respectively, for all the clinical bacterial strains. Moreover, living bacterial cells decreased to 70% at MBEC while decreasing up to 50% at MBIC with all bacterial refence strains. These data justify the CFU quantification. After that, ImageJ software was used to count the attached cells after incubating with the NPs, which proved the variation in live cell count between the manual counting and image analysis methods. Also, a scanning electron microscope (SEM) was used to detect the biofilm architecture after incubation with the Ɣ-PGA NP. In in vivo wound healing experiments, treated wounds of mice showed faster healing (p < 0.00001) than both the untreated mice and those that were only wounded, as the bacterial count was eradicated. Briefly, the infected mice were treated faster (p < 0.0001) when infected with S. pyogenes > S. aureus > E. coli > K. pneumoniae. The same pattern was observed for mice infected with the reference strains. Wound lengths after 2 h showed slightly healing (p < 0.001) for the clinical strains, while treatment became more obvious after 72 h > 48 h > 24 h (p < 0.0001) as wounds began to heal after 24 h up to 72 h. For reference strains, wound lengths after 2 h started to heal up to 72 h.

Unveiling the stealthy tactics: mycoplasma's immune evasion strategies

Mycoplasmas, the smallest known self-replicating organisms, possess a simple structure, lack a cell wall, and have limited metabolic pathways. They are responsible for causing acute or chronic infections in humans and animals, with a significant number of species exhibiting pathogenicity. Although the innate and adaptive immune responses can effectively combat this pathogen, mycoplasmas are capable of persisting in the host, indicating that the immune system fails to eliminate them completely. Recent studies have shed light on the intricate and sophisticated defense mechanisms developed by mycoplasmas during their long-term co-evolution with the host. These evasion strategies encompass various tactics, including invasion, biofilm formation, and modulation of immune responses, such as inhibition of immune cell activity, suppression of immune cell function, and resistance against immune molecules. Additionally, antigen variation and molecular mimicry are also crucial immune evasion strategies. This review comprehensively summarizes the evasion mechanisms employed by mycoplasmas, providing valuable insights into the pathogenesis of mycoplasma infections.

Drug sensitivity and genome-wide analysis of two strains of Mycoplasma gallisepticum with different biofilm intensity

Mycoplasma gallisepticum (MG) is one of the major causative agents of chronic respiratory diseases in poultry. The biofilms of MG are highly correlated to its chronic infection. However data on genes involved in biofilm formation ability are still scarse. MG strains with distinct biofilm intensity were screened by crystal violet staining morphotyped and characterized for the drug sensitivity. Two MG strains NX-01 and NX-02 showed contrasted ability to biofilm formation. The biofilm formation ability of NX-01 strain was significantly higher than that of NX-02 strain (p < 0.01). The drug sensitivity test showed that the stronger the ability of MG stain to form biofilms, the weaker its sensitivity to 17 antibiotic drugs. Moreover, putative key genes related to biofilm formation were screened by genome-wide analysis. A total of 13 genes and proteins related to biofilm formation, including ManB, oppA, oppD, PDH, eno, RelA, msbA, deoA, gapA, rpoS, Adhesin P1 precursor, S-adenosine methionine synthetase, and methionyl tRNA synthetase were identified. There were five major discrepancies between the two isolated MG strains and the five NCBI-published MG strains. These findings provide potential targets for inhibiting the formation of biofilm of MG, and lay a foundation for treating chronic infection.

Biofilm formation and correlations with drug resistance in Mycoplasma synoviae

Infectious synovitis in chickens caused by Mycoplasma synoviae infections are characterized by exudative synovial joint membranes and tenosynovitis. We isolated M. synoviae from chickens on farms in Guangdong, China and identifed 29 K-type and 3 A-type strains using vlhA genotyping and all displayed decreased susceptibilities to enrofloxacin, doxycycline, tiamulin and tylosin compared with the type strain WVU1853 (ATCC 25204). M. synoviae biofilms were present after staining as block or continuous dot shape morphologies and these appeared as tower-like and mushroom-like structures in scanning electron micrographs. The optimal temperature for biofilm formation was 33 °C and these biofilms enhanced the resistance of M. synoviae to all 4 antibiotics we tested and minimum biofilm inhibitory concentration for enrofloxacin and biofilm biomass were significantly negatively correlated (r < 0, 0.3 ≤|r|<0.5, P < 0.05). This work is the first study of the biofilm formation ability of M. synoviae and provides the foundation for further investigations.

Fabrication, bacteriostasis and osteointegration properties researches of the additively-manufactured porous tantalum scaffolds loading vancomycin

Infected bone defects (IBDs) remains a challenging problem for orthopedists. Clinically, routine management for IBDs has two stages: debridement and systematic antibiotics administration to control infection, and secondary grafting to repair bone defects. Whereas the efficacy is not satisfactory, because the overuse of antibiotics may lead to systemic toxicity, and the emergence of drug-resistant bacteria, as well as the secondary surgery would cause additional trauma and economic burden to the patients. Therefore, it is imperative to develop a novel scaffold for one-stage repair of IBDs. In this study, vancomycin (Van) was encapsulated into poly(lactic co-glycolic acid) (PLGA) microspheres through the double emulsion method, which were then loaded into the additively-manufactured porous tantalum (AM-Ta) through gelatin methacryloyl (GelMA) hydrogel to produce the composite Ta/GelMA hydrogel (Gel)/PLGA/vancomycin(Van) scaffolds for repairing IBDs. Physiochemical characterization of the newly-developed scaffold indicated that the releasing duration of Van was over 2 weeks. Biological experiments indicated good biocompatibility of the composite scaffold, as well as bacteriostasis and osteointegration properties, which showed great potential for clinical application. The construction of this novel scaffold would provide new sight into the development of orthopaedic implants, shedding a novel light on the treatment of IBDs.

Genotyping and biofilm formation of Mycoplasma hyopneumoniae and their association with virulence

Mycoplasma hyopneumoniae, the causative agent of swine respiratory disease, demonstrates differences in virulence. However, factors associated with this variation remain unknown. We herein evaluated the association between differences in virulence and genotypes as well as phenotype (i.e., biofilm formation ability). Strains 168 L, RM48, XLW-2, and J show low virulence and strains 232, 7448, 7422, 168, NJ, and LH show high virulence, as determined through animal challenge experiments, complemented with in vitro tracheal mucosa infection tests. These 10 strains with known virulence were then subjected to classification via multilocus sequence typing (MLST) with three housekeeping genes, P146-based genotyping, and multilocus variable-number tandem-repeat analysis (MLVA) of 13 loci. MLST and P146-based genotyping identified 168, 168 L, NJ, and RM48 as the same type and clustered them in a single branch. MLVA assigned a different sequence type to each strain. Simpson’s index of diversity indicates a higher discriminatory ability for MLVA. However, no statistically significant correlation was found between genotypes and virulence. Furthermore, we investigated the correlation between virulence and biofilm formation ability. The strains showing high virulence demonstrate strong biofilm formation ability, while attenuated strains show low biofilm formation ability. Pearson correlation analysis revealed a significant positive correlation between biofilm formation ability and virulence. To conclude, there was no association between virulence and our genotyping data, but virulence was found to be significantly associated with the biofilm formation ability of M. hyopneumoniae.

Antimicrobial susceptibility profiles of Mycoplasma hyorhinis strains isolated from five European countries between 2019 and 2021

Mycoplasma hyorhinis is an emerging swine pathogen bacterium causing polyserositis and polyarthritis in weaners and finishers. The pathogen is distributed world-wide, generating significant economic losses. No commercially available vaccine is available in Europe. Therefore, besides improving the housing conditions for prevention, antimicrobial therapy of the diseased animals is the only option to control the infection. Our aim was to determine the minimal inhibitory concentrations (MIC) of ten antimicrobials potentially used against M. hyorhinis infection. The antibiotic susceptibility of 76 M. hyorhinis isolates from Belgium, Germany, Hungary, Italy and Poland collected between 2019 and 2021 was determined by broth micro-dilution method and mismatch amplification mutation assay (MAMA). Low concentrations of tiamulin (MIC₉₀ 0.312 μg/ml), doxycycline (MIC₉₀ 0.078 μg/ml), oxytetracycline (MIC₉₀ 0.25 μg/ml), florfenicol (MIC₉₀ 2 μg/ml) and moderate concentrations of enrofloxacin (MIC₉₀ 1.25 μg/ml) inhibited the growth of the isolates. For the tested macrolides and lincomycin, a bimodal MIC pattern was observed (MIC₉₀ >64 μg/ml for lincomycin, tulathromycin, tylosin and tilmicosin and 5 μg/ml for tylvalosin). The results of the MAMA assay were in line with the conventional method with three exceptions. Based on our statistical analyses, significant differences in MIC values of tiamulin and doxycycline were observed between certain countries. Our results show various levels of antimicrobial susceptibility among M. hyorhinis isolates to the tested antibiotics. The data underline the importance of susceptibility monitoring on pan-European level and provides essential information for proper antibiotic choice in therapy.

Continuous local antibiotic perfusion: A treatment strategy that allows implant retention in fracture-related infections

PURPOSE

Fracture-related infections are difficult to treat because of the formation of biofilms around implants. Systemic antibiotics are notoriously ineffective against biofilms due to their insufficient penetration of tissues with poor vascularity. The goal of treating fracture-related infections is to achieve bone union while retaining the implant. Our proposal of continuous local antibiotic perfusion is a sustained local delivery system of sufficient antibiotics to bone and soft tissue infection sites, including to bone marrow via needles as intra-medullary antibiotics perfusion and to soft-tissue via double-lumen subcutaneous tubes as intra-soft tissue perfusion.

METHODS

In this study, we examined the outcomes of 40 patients treated for fracture-related infections using continuous local antibiotic perfusion between 2015 and 2021 at Steel Memorial Hirohata Hospital, Himeji, Japan.

RESULT

The antibiotic used for continuous local antibiotic perfusion was gentamicin in all cases. Implant removal was required in five patients. Two patients required toe amputation and knee arthrodesis, while the remaining 38 patients achieved fracture union. Only one case of transient acute renal injury as a systemic side effect was observed, but it soon resolved. The blood concentration of gentamicin could be adjusted to less than the trough level.

CONCLUSIONS

Continuous local antibiotic perfusion is a novel local drug delivery system that has the potential of delivering sufficient concentrations of antibiotics with few systemic side effects; it is a useful option for the treatment of fracture-related infections.

The effects of magainin 2-derived and rationally designed antimicrobial peptides on Mycoplasma pneumoniae

Combating the spread of antimicrobial resistance (AMR) among bacteria requires a new class of antimicrobials, which desirably have a narrow spectrum because of their low propensity for the spread of AMR. Antimicrobial peptides (AMPs), which target the bacterial cell membrane, are promising seeds for novel antimicrobials because the cell membrane is essential for all cells. Previously, we reported the antimicrobial and haemolytic effects of a natural AMP, magainin 2 (Mag2), isolated from the skin of Xenopus laevis (the African clawed frog), four types of synthesised Mag2 derivatives, and three types of rationally designed AMPs on gram-positive and gram-negative bacteria. To identify novel antimicrobial seeds, we evaluated the effect of AMPs on Mycoplasma pneumoniae, which also exhibits AMR. We also evaluated the antimicrobial effects of an AMP, NK2A, which has been reported to have antimicrobial effects on Mycoplasma bovis, in addition to Mag2 and previously synthesised seven AMPs, on four strains of M. pneumoniae using colorimetric, biofilm, and killing assays. We found that three synthesised AMPs, namely 17base-Ac6c, 17base-Hybrid, and Block, had anti-M. pneumoniae (anti-Mp) effect at 8–30 μM, whereas others, including NK2A, did not have any such effect. For the further analysis, the membrane disruption activities of AMPs were measured by propidium iodide (PI) uptake assays, which suggested the direct interaction of AMPs to the cell membrane basically following the colorimetric, biofilm, and killing assay results. PI uptake assay, however, also showed the NK2A strong interaction to cell membrane, indicating unknown anti-Mp determinant factors related to the peptide sequences. Finally, we conclude that anti-Mp effect was not simply determined by the membrane disruption activities of AMPs, but also that the sequence of AMPs were important for killing of M. pneumoniae. These findings would be helpful for the development of AMPs for M. pneumoniae.

Treatment of Chronic Osteomyelitis of the Femur by Intramedullary Antibiotic Perfusion (iMAP): A Case Report

INTRODUCTION

Chronic osteomyelitis is difficult to cure definitively, because local areas are often covered with sequestrum and scar tissues with a poor blood flow; these may render systemic antibiotic administration ineffective. We present a case of chronic osteomyelitis that was successfully treated with continuous local antibiotic perfusion (CLAP) through an intramedullary antibiotic perfusion (iMAP) pin.

CASE PRESENTATION

A 65-year-old man who suffered an episode of the right femoral osteomyelitis at the age of 15 years experienced a relapse at the age of 63 years. Systemic administration of antibiotics could not control the infection; thus, a surgery was performed. A bone marrow needle (i.e., an iMAP pin; diameter: 3 mm) was percutaneously inserted, from the front, distally and proximally to the cystic lesion in the distal femur. After washing through the iMAP pins, the pins were left indwelling. A closed drain tube was placed on the bone surface, which was close to the fistula of the bone marrow lesion. CLAP therapy was then initiated. Gentamicin was continuously infused through the iMAP pin at a rate of 2 mL/h and drained using the tube. Accordingly, 2.4 mg/mL, 1.2 mg/mL, and 1.2 mg/mL of gentamicin were administered for 4 days using two iMAP pins, for 5-8 days using two iMAP pins, and for 9-15 days using one iMAP pin, respectively, with a syringe pump. The iMAP pins and the drain tube were removed 15 days after the initiation of the CLAP therapy. The C-reactive protein level normalized 25 days postoperatively. The patient recovered full range of motion of the knee joint and recreational sports activity without recurrence of osteomyelitis for 5 years after the therapy.

CONCLUSIONS

CLAP therapy allows local administration of a sufficient concentration of antibiotics and device removal after treatment is simple. This may be a novel treatment for chronic osteomyelitis.

Intra-medullary antibiotics perfusion (iMAP) for the control of fracture-related infection early after osteosynthesis

PURPOSE

In our hospital, cases of bone and soft tissue infections have been treated with continuous local antibiotics perfusion that allows for continuous circulation of antibiotics throughout the infected lesion. We termed this treatment "intramedullary antibiotics perfusion (iMAP)" for bone infection such as fracture-related infection (FRI) and "intrasoft tissue antibiotics perfusion" for soft tissue infection. Many cases are treated with both modalities. To introduce iMAP, this study focused on the patients with FRI treated with iMAP and reviewed their treatment outcomes.

METHODS

We included 10 patients with FRI treated with iMAP between 2004 and 2017. The iMAP needles were inserted near the infected lesion, and an aminoglycoside antimicrobial was continuously administered. Patient characteristics, pathogenic bacteria, administered antibiotics, duration of administration, concentrations of antibiotics in blood and leachate fluid, fracture union rate, implant retention rate, and complications were studied.

RESULTS

The mean age of patients was 59.9 years, and the mean follow-up period was 2.5 years. Affected bones were the tibia (n = 8), humerus (n = 1), and fibula (n = 1). Deep infections developed on average 29.9 days after osteosynthesis. Pathogenic bacteria were methicillin-susceptible Staphylococcus aureus (n = 6), methicillin-resistant S. aureus (n = 2), and unknown (n = 2). Average iMAP duration was 17.1 days. In all patients, infection was eradicated while preserving the implants, and fracture union was achieved without complications.

CONCLUSION

iMAP is a novel local drug delivery system allowing high concentrations of antibiotics to be administered without complications and is useful in the treatment of FRI.

Integrating the Human and Animal Sides of Mycoplasmas Resistance to Antimicrobials

Mycoplasma infections are frequent in humans, as well as in a broad range of animals. However, antimicrobial treatment options are limited, partly due to the lack of a cell wall in these peculiar bacteria. Both veterinary and human medicines are facing increasing resistance prevalence for the most commonly used drugs, despite different usage practices. To date, very few reviews have integrated knowledge on resistance to antimicrobials in humans and animals, the latest dating back to 2014. To fill this gap, we examined, in parallel, antimicrobial usage, resistance mechanisms and either phenotype or genotype-based methods for antimicrobial susceptibility testing, as well as epidemiology of resistance of the most clinically relevant human and animal mycoplasma species. This review unveiled common features and differences that need to be taken into consideration in a "One Health" perspective. Lastly, two examples of critical cases of multiple drug resistance are highlighted, namely, the human M. genitalium and the animal M. bovis species, both of which can lead to the threat of untreatable infections.

Effect of antibiotic treatment on Mycoplasma hyopneumoniae detection and infectious potential

Mycoplasma hyopneumoniae (M. hyopneumoniae) causes significant economic losses in the swine industry. Antibiotics with activity against Mycoplasma spp. are employed for disease mitigation and pathogen elimination. However, veterinarians are often challenged with the detection of M. hyopneumoniae by PCR after antibiotic treatment, thus raising the question whether the bacterium is still infectious. The objective of this study was to evaluate the effect of tulathromycin treatment on M. hyopneumoniae detection and infectious potential during the acute and chronic phases of infection. For each infection phase, one age-matched naïve gilt was placed in contact with one M. hyopneumoniae infected gilt that was either treated with tulathromycin, treated and vaccinated, or non-treated, for 14 days. Four replicates per treatment group were performed for each infection phase. A numerical reduction in relative bacterial load was observed in acutely treated gilts compared to non-treated gilts. The rate at which naïve gilts became infected with M. hyopneumoniae was numerically reduced when co-housed with treated, acutely infected gilts compared to those housed with non-treated, infected gilts. During the chronic infection phase, M. hyopneumoniae was detected by PCR in more than 50 % of treated infected gilts and persisted for up to three months post-treatment. Transmission was not detected in all treatment groups however, the possibility that the pathogen was infectious could not be completely ruled out. Further research focused on assessing M. hyopneumoniae detection and viability post-treatment is necessary to guide control and elimination efforts.

Pathogenicity & virulence of Mycoplasma hyopneumoniae

Mycoplasma hyopneumoniae: is the etiological agent of porcine enzootic pneumonia (EP), a disease that impacts the swine industry worldwide. Pathogen-induced damage, as well as the elicited host-response, contribute to disease. Here, we provide an overview of EP epidemiology, control and prevention, and a more in-depth review of M. hyopneumoniae pathogenicity determinants, highlighting some molecular mechanisms of pathogen-host interactions relevant for pathogenesis. Based on recent functional, immunological, and comparative “omics” results, we discuss the roles of many known or putative M. hyopneumoniae virulence factors, along with host molecules involved in EP. Moreover, the known molecular bases of pathogenicity mechanisms, including M. hyopneumoniae adhesion to host respiratory epithelium, protein secretion, cell damage, host microbicidal response and its modulation, and maintenance of M. hyopneumoniae homeostasis during infection are described. Recent findings regarding M. hyopneumoniae pathogenicity determinants also contribute to the development of novel diagnostic tests, vaccines, and treatments for EP.

Infection strategies of mycoplasmas: Unraveling the panoply of virulence factors

Mycoplasmas, the smallest bacteria lacking a cell wall, can cause various diseases in both humans and animals. Mycoplasmas harbor a variety of virulence factors that enable them to overcome numerous barriers of entry into the host; using accessory proteins, mycoplasma adhesins can bind to the receptors or extracellular matrix of the host cell. Although the host immune system can eradicate the invading mycoplasma in most cases, a few sagacious mycoplasmas employ a series of invasion and immune escape strategies to ensure their continued survival within their hosts. For instance, capsular polysaccharides are crucial for anti-phagocytosis and immunomodulation. Invasive enzymes degrade reactive oxygen species, neutrophil extracellular traps, and immunoglobulins. Biofilm formation is important for establishing a persistent infection. During proliferation, successfully surviving mycoplasmas generate numerous metabolites, including hydrogen peroxide, ammonia and hydrogen sulfide; or secrete various exotoxins, such as community-acquired respiratory distress syndrome toxin, and hemolysins; and express various pathogenic enzymes, all of which have potent toxic effects on host cells. Furthermore, some inherent components of mycoplasmas, such as lipids, membrane lipoproteins, and even mycoplasma-generated superantigens, can exert a significant pathogenic impact on the host cells or the immune system. In this review, we describe the proposed virulence factors in the toolkit of notorious mycoplasmas to better understand the pathogenic features of these bacteria, along with their pathogenic mechanisms.

Antimicrobial susceptibility monitoring of Mycoplasma hyopneumoniae isolated from seven European countries during 2015-2016

Mycoplasma hyopneumoniae is the causative agent of porcine enzootic pneumonia, a chronic respiratory disease, causing significant economic losses. Results from the 2015-2016 MycoPath pan-European antimicrobial susceptibility monitoring survey of M. hyopneumoniae are presented. In total, 147 M. hyopneumoniae porcine isolates from Belgium, France, Germany, Great Britain, Hungary, Italy, and Spain were tested. One isolate per farm was retained from pigs that had not been recently treated with antimicrobial agents. The minimal inhibitory concentration (MIC) of 13 antimicrobial agents was determined in a central laboratory using a broth microdilution method, with Friis Medium, incubated at 35 ± 1 °C for 5-12 days. M. hyopneumoniae NCTC 10110 was used as Quality Control. MIC₅₀/MIC₉₀ (mg/L) values were: enrofloxacin 0.06/1; marbofloxacin 0.06/2; spiramycin 0.06/0.25; tulathromycin ≤0.001/0.004; gamithromycin 0.06/0.5; tylosin 0.016/0.06; tilmicosin 0.06/0.5; florfenicol 0.5/1; doxycycline 0.25/1; oxytetracycline 0.25/2; lincomycin 0.06/0.25; tiamulin 0.016/0.06 and valnemulin ≤0.001/0.004. Compared with the data from 2010 to 2012 MycoPath study (50 isolates), MIC_50/90 results were similar and the majority were within ± two dilution steps, except for the MIC₅₀ of oxytetracycline which is more than two dilution steps higher in the present study. Between-country comparisons show some differences in the MIC values for the fluoroquinolones, tulathromycin and tylosin, but the limited sample size per country precludes performing meaningful country comparisons for several countries. Standardized laboratory methods and interpretive criteria for MIC testing of veterinary mycoplasmas are clearly needed; there are currently no clinical breakpoints available to facilitate data interpretation and correlation of MICs with in vivo efficacy.

Antimicrobial drug resistance mechanisms among Mollicutes

Representatives of the Mollicutes class are the smallest, wall-less bacteria capable of independent reproduction. They are widespread in nature, most are commensals, and some are pathogens of humans, animals and plants. They are also the main contaminants of cell cultures and vaccine preparations. Despite limited biosynthetic capabilities, they are highly adaptable and capable of surviving under various stress and extreme conditions, including antimicrobial selective pressure. This review describes current understanding of antibiotic resistance (ABR) mechanisms in Mollicutes. Protective mechanisms in these bacteria include point mutations, which may include non-target genes, and unique gene exchange mechanisms, contributing to transfer of ABR genes. Better understanding of the mechanisms of emergence and dissemination of ABR in Mollicutes is crucial to control these hypermutable bacteria and prevent the occurrence of highly ABR strains.

Persistence in Livestock Mycoplasmas—a Key Role in Infection and Pathogenesis

Purpose of Review

Mycoplasma, economically important pathogens in livestock, often establishes immunologically complex persistent infections that drive their pathogenesis and complicate prophylaxis and therapy of the caused diseases. In this review, we summarize some of the recent findings concerning cellular and molecular persistence mechanisms related to the pathogenesis of mycoplasma infections in livestock.

Recent Findings

Data from recent studies prove several mechanisms including intracellular lifestyle, immune dysregulation, and autoimmunity as well as microcolony and biofilm formation and apoptosis of different host cell types as important persistence mechanisms in several clinically significant Mycoplasma species, i.e., M. bovis, M. gallisepticum, M. hyopneumoniae, and M. suis.

Summary

Evasion of the immune system and the establishment of persistent infections are key features in the pathogenesis of livestock mycoplasmas. In-depth knowledge of the underlying mechanisms will provide the basis for the development of therapy and prophylaxis strategies against mycoplasma infections.

Pharmacodynamics of Ceftiofur Selected by Genomic and Proteomic Approaches of Streptococcus parauberis Isolated from the Flounder, Paralichthys olivaceus

We employed an integrative strategy to present subtractive and comparative metabolic and genomic-based findings of therapeutic targets against Streptococcus parauberis. For the first time, we not only identified potential targets based on genomic and proteomic database analyses but also recommend a new antimicrobial drug for the treatment of olive flounder (Paralichthys olivaceus) infected with S. parauberis. To do that, 102 total annotated metabolic pathways of this bacterial strain were extracted from computational comparative metabolic and genomic databases. Six druggable proteins were identified from these metabolic pathways from the DrugBank database with their respective genes as mtnN, penA, pbp2, murB, murA, coaA, and fni out of 112 essential nonhomologous proteins. Among these hits, 26 transmembrane proteins and 77 cytoplasmic proteins were extracted as potential vaccines and drug targets, respectively. From the FDA DrugBank, ceftiofur was selected to prevent antibiotic resistance as it inhibited our selected identified target. Florfenicol is used for treatment of S. parauberis infection in flounder and was chosen as a comparator drug. All tested strains of fish isolates with S. parauberis were susceptible to ceftiofur and florfenicol with minimum inhibitory concentrations (MIC) of 0.0039-1 μg/mL and 0.5-8 μg/mL, IC50 of 0.001-0.5 μg/mL and 0.7-2.7 μg/mL, and minimum biofilm eradication concentrations (MBEC) of 2-256 μg/mL and 4-64 μg/mL, respectively. Similar susceptibility profiles for ceftiofur and florfenicol were found, with ceftiofur observed as an effective and potent antimicrobial drug against both planktonic and biofilm-forming strains of the fish pathogen Streptococcus parauberis, and it can be applied in the aquaculture industry. Thus, our predictive approach not only showed novel therapeutic agents but also indicated that marketed drugs should also be tested for efficacy against newly identified targets of this important fish pathogen.

Extracellular DNA release from the genome-reduced pathogen Mycoplasma hyopneumoniae is essential for biofilm formation on abiotic surfaces

Mycoplasma hyopneumoniae is an economically devastating, globally disseminated pathogen that can maintain a chronic infectious state within its host, swine. Here, we depict the events underpinning M. hyopneumoniae biofilm formation on an abiotic surface and demonstrate for the first time, biofilms forming on porcine epithelial cell monolayers and in the lungs of pigs, experimentally infected with M. hyopneumoniae. Nuclease treatment prevents biofilms forming on glass but not on porcine epithelial cells indicating that extracellular DNA (eDNA), which localises at the base of biofilms, is critical in the formation of these structures on abiotic surfaces. Subpopulations of M. hyopneumoniae cells, denoted by their ability to take up the dye TOTO-1 and release eDNA, were identified. A visually distinct sub-population of pleomorphic cells, that we refer to here as large cell variants (LCVs), rapidly transition from phase dark to translucent "ghost" cells. The translucent cells accumulate the membrane-impermeable dye TOTO-1, forming readily discernible membrane breaches immediately prior to lysis and the possible release of eDNA and other intracellular content (public goods) into the extracellular environment. Our novel observations expand knowledge of the lifestyles adopted by this wall-less, genome-reduced pathogen and provide further insights to its survival within farm environments and swine.