Interaction between Mycobacterium avium subsp. paratuberculosis and environmental protozoa.
BACKGROUND
Interactions between Mycobacterium avium subsp. paratuberculosis (Map) and free-living protozoa in water are likely to occur in nature. The potential impact of ingestion of Map by two naturally occurring Acanthamoeba spp. on this pathogen's survival and chlorine resistance was investigated.


RESULTS
Between 4.6 and 9.1% of spiked populations of three Map strains (NCTC 8578, B2 and ATCC 19698), which had been added at a multiplicity of infection of 10:1, were ingested by Acanthamoeba castellanii CCAP 1501/1B and A. polyphaga CCAP 1501/3B during co-culture for 3 h at 25 degrees C. Map cells were observed to be present within the vacuoles of the amoebae by acid-fast staining. During extended co-culture of Map NCTC 8578 at 25 degrees C for 24 d with both A. castellanii and A. polyphaga Map numbers did not change significantly during the first 7 days of incubation, however a 1-1.5 log10 increase in Map numbers was observed between days 7 and 24 within both Acanthamoeba spp. Ingested Map cells were shown to be more resistant to chlorine inactivation than free Map. Exposure to 2 mug/ml chlorine for 30 min resulted in a log10 reduction of 0.94 in ingested Map but a log10 reduction of 1.73 in free Map (p < 0.001).


CONCLUSIONS
This study demonstrated that ingestion of Map by and survival and multiplication of Map within Acanthamoeba spp. is possible, and that Map cells ingested by amoebae are more resistant to inactivation by chlorine than free Map cells. These findings have implications with respect to the efficacy of chlorination applied to Map infected surface waters.
Whan
Lynne
L
Department of Food Science, Queen's University Belfast, Newforge Lane, Belfast BT9 5PX, Northern Ireland, UK. lynnewhan@hotmail.com
Grant
Irene R
IR
Rowe
Michael T
MT
D000048:Acanthamoeba / Q000254:growth & development / Q000382:microbiology*; D048248:Acanthamoeba castellanii / Q000254:growth & development / Q000382:microbiology*; D000818:Animals; D002713:Chlorine / Q000494:pharmacology*; D018920:Coculture Techniques; D024881:Drug Resistance, Bacterial; D008854:Microscopy, Electron; D016927:Mycobacterium avium subsp. paratuberculosis / Q000187:drug effects* / Q000254:growth & development*; D014867:Water / Q000469:parasitology; D014871:Water Microbiology
D014867:Water; D002713:Chlorine