Plasmid Mediated mcr-1.1 Colistin-Resistance in Clinical Extraintestinal Escherichia coli Strains Isolated in Poland

Objectives: The growing incidence of multidrug-resistant (MDR) bacteria is an inexorable and fatal challenge in modern medicine. Colistin is a cationic polypeptide considered a “last-resort” antimicrobial for treating infections caused by MDR Gram-negative bacterial pathogens. Plasmid-borne mcr colistin resistance emerged recently, and could potentially lead to essentially untreatable infections, particularly in hospital and veterinary (livestock farming) settings. In this study, we sought to establish the molecular basis of colistin-resistance in six extraintestinal Escherichia coli strains.

Methods: Molecular investigation of colistin-resistance was performed in six extraintestinal E. coli strains isolated from patients hospitalized in Medical University Hospital, Bialystok, Poland. Complete structures of bacterial chromosomes and plasmids were recovered with use of both short- and long-read sequencing technologies and Unicycler hybrid assembly. Moreover, an electrotransformation assay was performed in order to confirm IncX4 plasmid influence on colistin-resistance phenotype in clinical E. coli strains.

Results: Here we report on the emergence of six mcr-1.1-producing extraintestinal E. coli isolates with a number of virulence factors. Mobile pEtN transferase-encoding gene, mcr-1.1, has been proved to be encoded within a type IV secretion system (T4SS)-containing 33.3 kbp IncX4 plasmid pMUB-MCR, next to the PAP2-like membrane-associated lipid phosphatase gene.

Conclusion: IncX4 mcr-containing plasmids are reported as increasingly disseminated among E. coli isolates, making it an “epidemic” plasmid, responsible for (i) dissemination of colistin-resistance determinants between different E. coli clones, and (ii) circulation between environmental, industrial, and clinical settings. Great effort needs to be taken to avoid further dissemination of plasmid-mediated colistin resistance among clinically relevant Gram-negative bacterial pathogens.

[The effect of selected antibacterial antibiotics on production of interferon gamma (IFN-G) by mouse T lymphocytes stimulated by Listeria monocytogenes]

The aim of the study was to determine the influence of certain antibiotics on the production of IFN-gamma by mouse lymphocytes T after four days incubation with Listeria monocytogenes. The level of mouse IFN-gamma was determined by ELISA method (Inter Test-gamma Mouse IFN-gamma Kit, Genzyme). The strongest immunosuppression effect was demonstrated using rifampicin (39 ng/ml IFN-gamma) (Control: 123 +/- 29 ng/ml IFN-gamma, p < 0.05). Lower immunosuppression effects were observed also with cephradine (54 ng/ml IFN-gamma), amikacin (56 ng/ml IFN-gamma) and ticarcillin (83 ng/ml). The obtained results show that all tested cephalosporins (cephamandole, cefotaxime, cephradine) and aminogllycosides (gentamicin, streptomycin, amicacin) inhibit production of IFN-gamma by mouse lymphocytes T. The influence of penicillin G and ampicillin, as well as, erythromycin and lincomycin on the production IFN-gamma was not observed. Our results suggest that rifampicin, ticarcillin, cephalosporins and aminoglycosides act as inhibitors of production IFN-gamma.

[The influence of antibiotics on phagocytic and bacteriocidal activity of rabbit peritoneal macrophages stimulated by filtrates of cultured t-lymphocytes]

The aim of the study was to determine the influence of twelve antibacterial antibiotics (various concentrations) on the activation of rabbit peritoneal macrophages. Macrophages were stimulated by filtrates of culture of lymphocytes T obtained from OVA immunized rabbits. Phagocytic activity and intracellular killing against Listeria monocytogenes were tested by fluorescence method. Penicillin G (0.4-50 mg/l), erythromycin and lincomycin (2.5-40 mg/l) used at all concentrations, were not exerting significant effects on activation of peritoneal macrophages. Cephalosporins, aminoglycosides, and rifampicin at low concentrations (0.4-5.0 mg/l) had no influence on phagocytosis and intracellular killing, also. Cephalosporins at concentration 10 mg/l (cephradine and cefamandole) and 50 mg/l (cefotaxime) inhibited intracellular killing and phagocytic activity. The same results were observed with ampicillin and ticarcillin (50 mg/l). The highest suppression effect was demonstrated using rifampicin at concentration 10 mg/l or more. Gentamicin, streptomycin and amicacin at concentrations 40 mg/l or more significantly inhibited macrophage activation in response to filtrates lymphocytes of culture. These inhibitions were more marked with gentamicin (10 mg/l) than amicacin (20 mg/l) or streptomycin (40 mg/l). All antibiotics did not stimulated the activity of peritoneal macrophages. The suppression activity of peritoneal macrophages by some antibiotics probably acts at the level of specific immune system by interfering with cytokine production.