The Effect of Bacteriophage Preparations on Intracellular Killing of Bacteria by Phagocytes

Abstract

Intracellular killing of bacteria is one of the fundamental mechanisms against invading pathogens. Impaired intracellular killing of bacteria by phagocytes may be the reason of chronic infections and may be caused by antibiotics or substances that can be produced by some bacteria. Therefore, it was of great practical importance to examine whether phage preparations may influence the process of phagocyte intracellular killing of bacteria. It may be important especially in the case of patients qualified for experimental phage therapy (approximately half of the patients with chronic bacterial infections have their immunity impaired). Our analysis included 51 patients with chronic Gram-negative and Gram-positive bacterial infections treated with phage preparations at the Phage Therapy Unit in Wroclaw. The aim of the study was to investigate the effect of experimental phage therapy on intracellular killing of bacteria by patients' peripheral blood monocytes and polymorphonuclear neutrophils. We observed that phage therapy does not reduce patients' phagocytes' ability to kill bacteria, and it does not affect the activity of phagocytes in patients with initially reduced ability to kill bacteria intracellularly. Our results suggest that experimental phage therapy has no significant adverse effects on the bactericidal properties of phagocytes, which confirms the safety of the therapy.

Figure 1

Analysis of the influence of phage therapy on the ability of phagocytes (PMNs and PBMCs) isolated from peripheral blood of patients to kill bacteria intracellularly.  ^∗Effectiveness evaluation of EPT according to Międzybrodzki et al. (2012) [14].

Figure 2

Mean intracellular killing of E. coli B (±SD) by monocytes (in the mononuclear cell suspension) isolated from patients with urinary tract infections before (n = 18), during (n = 17), and after phage therapy (n = 13).  ^∗Statistically significant increase of IKB observed after EPT compared to the value at the beginning of EPT (Mann-Whitney U test).

Figure 3

Mean intracellular killing of E. coli B (±SD) by PBMCs isolated from patients with good response to phage therapy before (n = 19), during (n = 17), and after phage therapy (n = 13).  ^∗Statistically significant increase of IKB observed during EPT compared to the value at the beginning of EPT (Mann-Whitney U test).  ^∗∗Statistically significant increase of IKB observed after EPT compared to the value at the beginning of phage treatment.

Figure 4

Mean level of inflammatory markers (±SD). (a) CRP. (b) Sedimentation rate in patients' peripheral blood before (n = 39), during (n = 28), and after (n = 15) EPT.

Figure 5

Leukocytosis in patients with infections caused by P. aeruginosa treated with EPT before (n = 10), during (n = 8), and after the treatment (n = 4). The differences were tested using Wilcoxon's test.  ^∗Statistically significant difference between the number of leukocytes in the peripheral blood of patients after EPT and the number of leukocytes before the treatment, Wilcoxon's test.