Efficacy of gallium maltolate against Lawsonia intracellularis infection in a rabbit model

Prevalence and associated risk factors for Lawsonia intracellularis infection in farmed rabbits: A serological and molecular cross-sectional study in South Korea

Lawsonia intracellularis is the etiological agent of proliferative enteropathy, which is globally considered an important enteric disease in pigs and horses. Experimental studies suggest that the organism spreads by subclinical infection of many animals, including rabbits. Despite the importance of rabbits in the epidemiology of L. intracellularis, the extent of exposure to L. intracellularis in the rabbit population is poorly defined and remains unclear. The objective of this cross-sectional study was to investigate the seroprevalence and shedding of L. intracellularis in farmed rabbits. Furthermore, we aimed to identify risk factors associated with seropositivity. Sera from the rabbits were used to measure L. intracellularis-specific antibodies by immunoperoxidase monolayer assay, and rectal swabs were used to detect L. intracellularis DNA using a real-time PCR assay. Antibodies against L. intracellularis were detected in 12.3% of farms (20/163) and 6.3% of rabbits (49/774). Lawsonia intracellularis DNA in rectal swabs was detected in 3.8% of farms (6/156) and 1.2% of rabbits (8/667). The risk factor analysis showed that the presence of pigs or horses on the farm or the neighboring farm was associated with an increase in the risk of seropositivity (p < 0.05). We observed significantly increased odds of positivity for L. intracellularis in rabbits with a history of digestive trouble (diarrhea) on the farm during the 3 months before the samples were obtained (p < 0.05). Collectively, these findings demonstrated that L. intracellularis infection was evident among farmed rabbits and that rabbits might serve as an important reservoir for L. intracellularis epidemiology.

Topical treatment with gallium maltolate reduces Treponema pallidum subsp. pertenue burden in primary experimental lesions in a rabbit model of yaws

Background

Gallium is a semi-metallic element known since the 1930s to have antimicrobial activity. This activity stems primarily from gallium's ability to mimic trivalent iron and disrupt specific Fe(III)-dependent pathways, particularly DNA synthesis (due to inhibition of ribonucleotide reductase). Because of its novel mechanism of action, gallium is currently being investigated as a new antibacterial agent, particularly in light of the increasing resistance of many pathogenic bacteria to existing antibiotics. Gallium maltolate (GaM) is being developed as an orally and topically administrable form of gallium. Yaws is a neglected tropical disease affecting mainly the skin and skeletal system of children in underprivileged settings. It is currently the object of a WHO-promoted eradication campaign using mass administration of the macrolide azithromycin, an antibiotic to which the yaws agent Treponema pallidum subsp. pertenue has slowly begun to develop genetic resistance.

Methods

Because yaws transmission is mainly due to direct skin contact with an infectious skin lesion, we evaluated the treponemicidal activity of GaM applied topically to skin lesions in a rabbit model of yaws. Treatment efficacy was evaluated by measuring lesion diameter, treponemal burden in lesion aspirates as determined by dark field microscopy and amplification of treponemal RNA, serology, and immunohistochemistry of biopsied tissue samples.

Results

Our results show that topical GaM was effective in reducing treponemal burden in yaws experimental lesions, particularly when applied at the first sign of lesion appearance but, as expected, did not prevent pathogen dissemination.

Conclusion

Early administration of GaM to yaws lesions could reduce the infectivity of the lesions and thus yaws transmission, potentially contributing to current and future yaws control campaigns.

Yaws is a neglected tropical disease affecting children in underprivileged countries, transmitted through direct skin contact with an active lesion. This infection, although rarely fatal, can lead to disfigurement and serious disability. The World Health Organization is currently conducting a yaws eradication effort that employs mass administration of azithromycin, an antibiotic against which the yaws pathogen has slowly begun to develop genetic resistance. Because this phenomenon has the potential to undermine the eradication effort, we investigated the antimicrobial activity of gallium maltolate, which has a novel mechanism of action, against the yaws pathogen. Our initial results show that topical application of gallium maltolate has significant treponemicidal activity, and suggest that this compound might find an application in the effort to eradicate yaws. Future studies will evaluate whether oral administration of gallium maltolate is as effective as the antibiotics currently approved for yaws treatment to clear systemic infection.

Indium/Gallium Maltolate Effects on Human Breast Carcinoma Cells: In Vitro Investigation on Cytotoxicity and Synergism with Mitoxantrone

In this study, we aimed to investigate in vitro whether the synthetized indium maltolate (InMal) and gallium maltolate (GaMal) could exert either a toxic effect toward breast cancer cell line MDA-MB-231 or an agonistic activity with mitoxantrone (MTX) in comparison to fibroblast cell line NIH-3T3. Both GaMal and InMal reduced viability of MDA-MB-231, and at a lesser extent of NIH3-T3, in a dose- and time-dependent mode, the outcome was more effective in comparison to MTX sole exposure. Both GaMal and InMal toxicity was reverted by iron citrate addition on NIH3-T3, not on MDA-MB-231, showing indirectly that gallium and indium's mechanisms of action may include iron targeting. The agonistic activity against MDA-MB-231 survival was shown pretreating with 100 μM InMal for 24 h followed by medium exchange with MTX at 10 ng mL^-1 or vice-versa but not with co-incubation of both compounds. In particular, InMal pretreating resulted more protective to MTX subsequent exposure.