The use of phages is an attractive option to battle antibiotic resistant bacteria in certain bacterial infections, but the role of phage ecology in bacterial infections is obscure. Here we surveyed the phage ecology in septicemia, the most severe type of
The use of phages is an attractive option to battle antibiotic resistant bacteria in certain bacterial infections, but the role of phage ecology in bacterial infections is obscure. Here we surveyed the phage ecology in septicemia, the most severe type of bacterial infection. We observed that the majority of the bacterial isolates from septicemia patients spontaneously secreted phages active against other isolates of the same bacterial strain, but not to the strain causing the disease. Such phages were also detected in the initial blood cultures, indicating that phages are circulating in the blood at the onset of sepsis. The fact that most of the septicemic bacterial isolates carry functional prophages suggests an active role of phages in bacterial infections. Apparently, prophages present in sepsis-causing bacterial clones play a role in clonal selection during bacterial invasion.
Citation: Gaidelytė A, Vaara M, Bamford DH (2007) Bacteria, Phages and Septicemia. PLoS ONE 2(11): e1145. https://doi.org/10.1371/journal.pone.0001145
Academic Editor: Floyd Romesberg, The Scripps Research Institute, United States of America
Received: July 16, 2007; Accepted: October 16, 2007; Published: November 7, 2007
Copyright: © 2007 Gaidelytė et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: This work was supported by the Academy of Finland Finnish Centre of Excellence Programme 2006-2011 (grants 1210253, 1213992, 1213467 to DHB).
Competing interests: The authors have declared that no competing interests exist.
Septicemia is a serious medical condition where bacteria present in the blood circulatory system provoke an amplified and dysregulated immune response in the individual. The most common infection sites leading to bacterial entry into the circulatory system are bacterial infections in the lungs, urinary tract, abdominal cavity, and primary infections of the bloodstream. Rapid antibiotic intervention is currently the only way to treat septicemia (as well as other bacterial infections). However, many bacterial pathogens have become resistant to antibiotic regimens, resulting in an urgent health problem worldwide,. One potentially useful method for the treatment of antibiotic resistant bacterial infections employs bacterial viruses called bacteriophages (also known as phages) capable of killing bacteria –. They were widely used to treat bacterial infections since their discovery in the beginning of the twentieth century, but their use was neglected in western countries after the discovery of antibiotics,. The modern application of phages in parts of the world that require documented and scientifically controlled clinical experiments is limited to the protection of ready-to-eat meat and poultry products. Phage derived enzymes lytic to Gram-positive bacteria are the most promising candidates to enter the markets for therapeutic use,.
In contrast to virulent phages, which kill bacteria immediately, temperate phages integrate their genomes into bacterial chromosomes to establish a prophage state. Prophages and other genetic elements such as transposons, plasmids, and pathogenicity islands encode virulence factors. Temperate phages disseminate virulence genes and thus contribute to the evolution and emergence of new pathogenic bacteria. Only the most virulent bacterial clones are capable of tissue invasion possibly leading to septicemia, as the bacteria have to overcome anatomical and host immune system barriers to enter the circulatory system. Although there is considerable information regarding prophages,  and phage-encoded virulence factors in bacterial pathogens, few studies have investigated microbial ecology in clinical bacterial infections. Here we surveyed the phage ecology in septicemia, the most severe type of bacterial infection. We observed that the majority of septicemia-causing bacteria could be induced to produce phages active against other isolates of the same bacterial strain. Such phages were also detected in the initial blood cultures, indicating that phages are circulating in the blood at the onset of sepsis. Further characterization of the phage isolates revealed that the virus detected in the blood culture was the same as induced from the bacterium isolated from that particular blood culture sample.
The Majority of Septicemia-Causing Bacteria Can Be Induced to Produce Phages
In this report we investigated Escherichia coli (Ec), Pseudomonas aeruginosa (Pa), Staphylococcus aureus (Sa) and Klebsiella pneumoniae (Kp) isolates from septicemia patients. Two sets of bacterial isolates and blood culture samples were obtained (Set I 150 and Set II 30 bacterial isolates, Ta