In vitro and in vivo efficacy of combinations of colistin and different endolysins against clinical strains of multi-drug resistant pathogens

Abstract

The emergence of multidrug resistant (MDR) pathogenic bacteria is jeopardizing the value of antimicrobials, which had previously changed the course of medical science. In this study, we identified endolysins ElyA1 and ElyA2 (GH108-PG3 family), present in the genome of bacteriophages Ab1051Φ and Ab1052Φ, respectively. The muralytic activity of these endolysins against MDR clinical isolates (Acinetobacter baumannii, Pseudomonas aeruginosa and Klebsiella pneumoniae) was tested using the turbidity reduction assay. Minimal inhibitory concentrations (MICs) of endolysin, colistin and a combination of endolysin and colistin were determined, and the antimicrobial activity of each treatment was confirmed by time kill curves. Endolysin ElyA1 displayed activity against all 25 strains of A. baumannii and P. aeruginosa tested and against 13 out of 17 strains of K. pneumoniae. Endolysin ElyA2 did not display any such activity. The combined antimicrobial activity of colistin and ElyA1 yielded a reduction in the colistin MIC for all strains studied, except K. pneumoniae. These results were confirmed in vivo in G. mellonella survival assays and in murine skin and lung infection models. In conclusion, combining colistin (1/4 MIC) with the new endolysin ElyA1 (350 µg) enhanced the bactericidal activity of colistin in both in vitro and in vivo studies. This will potentially enable reduction of the dose of colistin used in clinical practice.

(p)ppGpp and Its Role in Bacterial Persistence: New Challenges

“…Even if no effect of the Rel inhibitor relacin was observed in E. coli, the authors suggested that this could be due to the inability of relacin to penetrate Gram-negative cells and reach its target. However, agents such as polymyxins can destabilize the outer membrane in Gramnegative organisms, facilitating the entrance of therapeutic molecules, e.g., relacin, or endolysins (106). The absence of known (p)ppGpp synthetases in mammalian cells and the specificity of these inhibitors for the Rel protein make this protein a good candidate as an antibacterial agent.…”

Exploiting Lactoferricin (17–30) as a Potential Antimicrobial and Antibiofilm Candidate Against Multi-Drug-Resistant Enteroaggregative Escherichia coli

“…These concerns in lab animal welfare warrants the possibility of utilizing invertebrate models in expediting the efficacy of antimicrobial agents for preliminary in vivo screening to reduce the candidate molecules for its further evaluation in ethical mammalian models. Having shared the innate immune response to the microbes (Wojda, 2017;Cutuli et al, 2019;Blasco et al, 2020), insects could be selected as suitable alternative models for extrapolating in vitro laboratory findings for probing the potential of Lfcin (17-30) against MDR-EAEC strains. The innate immune system of G. mellonella comprises a progressive cellular as well as humoral response compared to other existing invertebrate models.…”

“…The histopathology of the larval model was found closely interrelated with the MDR-EAEC burden, with estimation of various immune markers (melanization, hemocyte density), and with the in vitro time-kill kinetic assays. Additionally, it was concluded that those factors permitting the larval survival could be well pertinent to similar infections in humans ( Sheehan and Kavanagh, 2018 ; Blasco et al, 2020 ).…”

“…Therefore, as an alternative in vivo model, Galleria mellonella larvae have recently been explored to evaluate the therapeutic potential of novel candidates including AMPs against various bacterial pathogens, including MDR-EAEC ( McCloskey et al, 2019 ; Vergis et al, 2019 ). Moreover, the short life span of larvae and their ability to simulate humans while exploring pathogens of public health significance ( Wojda, 2017 ; Cutuli et al, 2019 ; Blasco et al, 2020 ) extends their importance as an excellent in vivo model to screen novel therapeutics including AMPs. However, studies addressing in vivo antibacterial efficacy of Lfcin (17–30) against MDR-EAEC have never been explored in the G. mellonella larvae model.…”

Viral Related Tools against SARS-CoV-2

“…Since the discovery of bacteriophages in 1915 [ 25 ], they have been used as an alternative treatment for critical bacterial infections, on some occasions even life-threatening [ 26 , 27 ]. In the last decade, i.e., in the post-antibiotic era, the therapy based on lytic phages (phage therapy) or phage derived proteins (enzybiotics) such as, for instance, phage-encoded endolysins [ 28 ], has gained popularity, being one of the few options currently available for infections caused by multi-drug resistant (MDR) bacteria [ 26 , 29 ]. Phages have demonstrated their innocuousness for humans, although some concerns still need to be investigated such as the purity of the preparation [ 26 ].…”