Analyses of the Distribution Patterns of Burkholderia pseudomallei and Associated Phages in Soil Samples in Thailand Suggest That Phage Presence Reduces the Frequency of Bacterial Isolation.
BACKGROUND
Burkholderia pseudomallei is a soil saprophytic bacterium that causes melioidosis. The infection occurs through cutaneous inoculation, inhalation or ingestion. Bacteriophages (phages) in the same ecosystem may significantly impact the biology of this bacterium in the environment, and in their culturability in the laboratory.


RESULTS
The soil samples were analysed for the presence of bacteria using culture methods, and for phages using plaque assays on B. pseudomallei strain 1106a lawns. Of the 86 soil samples collected from northeastern Thailand, B. pseudomallei was cultured from 23 (26.7%) samples; no phage capable of infecting B. pseudomallei was detected in these samples. In contrast, phages capable of infecting B. pseudomallei, but no bacteria, were present in 10 (11.6%) samples. B. pseudomallei and their phages were co-isolated from only 3 (3.5%) of soil samples. Since phage capable of infecting B. pseudomallei could not have appeared in the samples without the prior presence of bacteria, or exposure to bacteria nearby, our data suggest that all phage-positive/bacteria-negative samples have had B. pseudomallei in or in a close proximity to them. Taken together, these findings indicate that the presence of phages may influence the success of B. pseudomallei isolation. Transmission electron microscopy revealed that the isolated phages are podoviruses. The temperate phages residing in soil-isolated strains of B. pseudomallei that were resistant to the dominant soil borne phages could be induced by mitomycin C. These induced-temperate phages were closely related, but not identical, to the more dominant soil-isolated phage type.


CONCLUSIONS
The presence of podoviruses capable of infecting B. pseudomallei may affect the success of the pathogen isolation from the soil. The currently used culture-based methods of B. pseudomallei isolation appear to under-estimate the bacterial abundance. The detection of phage capable of infecting B. pseudomallei from environmental samples could be a useful preliminary test to indicate the likely presence of B. pseudomallei in environmental samples.
Department of Immunology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand.
Patoo
P
Withatanung
Department of Microbiology and Immunology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.|Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
Narisara
N
Chantratita
Department of Immunology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand.
Veerachat
V
Muangsombut
Department of Microbiology and Immunology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
Natnaree
N
Saiprom
Department of Clinical Immunology, Faculty of Associated Medical Sciences, Khon Kaen University, Khon Kaen, Thailand.
Ganjana
G
Lertmemongkolchai
Institute of Food, Nutrition and Health, ETH Zurich, Zurich, Switzerland.
Jochen
J
Klumpp
Department of Infection, Immunity and Inflammation, University of Leicester, Leicester, United Kingdom.
Martha R J
MR
Clokie
Department of Infection, Immunity and Inflammation, University of Leicester, Leicester, United Kingdom.
Edouard E
EE
Galyov
Department of Immunology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand.
Sunee
http://orcid.org/0000-0003-4732-0733
S
Korbsrisate
Chest. 1995 Nov;108(5):1420-4
7587451
J Infect Dis. 1989 May;159(5):890-9
2708842
Am J Trop Med Hyg. 2014 Jun;90(6):1043-6
24710616
PLoS Negl Trop Dis. 2013;7(3):e2105
23556010
J Clin Microbiol. 2006 Jul;44(7):2553-7
16825379
Virol J. 2011 Jul 26;8:366
21791081
Microbiol Immunol. 1996;40(6):451-3
8839431
BMC Microbiol. 2010 Jul 28;10:202
20667135
Bacteriophage. 2011 Jan;1(1):31-45
21687533
Front Microbiol. 2014 Nov 14;5:599
25452746
Proc Natl Acad Sci U S A. 2004 Sep 28;101(39):14240-5
15377794
Folia Microbiol (Praha). 2003;48(2):253-6
12800512
Appl Environ Microbiol. 2012 Feb;78(3):876-7
22101048
Emerg Infect Dis. 2002 Feb;8(2):225-30
11897082
Clin Microbiol Rev. 2005 Apr;18(2):383-416
15831829
Infect Immun. 1997 Oct;65(10):4319-21
9317042
Virulence. 2013 Jul 1;4(5):354-65
23611873
Nat Rev Microbiol. 2015 Oct;13(10):641-50
26373372
Nat Rev Microbiol. 2006 Apr;4(4):272-82
16541135
J Appl Microbiol. 2013 Jun;114(6):1616-24
23490045
Nat Microbiol. 2016 Jan 11;1:15008
27571754
Curr Opin Microbiol. 2007 Aug;10(4):410-7
17719265
J Med Microbiol. 1990 Oct;33(2):121-6
2231678