Comparative evaluation of four decontamination protocols for the isolation of Mycobacterium avium subsp. paratuberculosis from milk.
OBJECTIVE
Four chemical decontamination protocols for milk were compared with respect to mean percentage recovery of spiked Mycobacterium avium subsp. paratuberculosis, minimum detection limit and ease of application.


RESULTS
Raw milk spiked with 106 cfu M.a. paratuberculosis was decontaminated prior to culture by: (1) treatment with 0.75% (w/v) hexadecylpyridinium chloride (HPC) for 5 h; (2) and (3) Cornell methods employing brain heart infusion broth containing 0.75% (w/v) and 0.9% (w/v) HPC, respectively; and (4) a C18-carboxypropylbetaine (CB-18)


METHODS
The 0.75% HPC method yielded the highest mean percentage recovery of M.a. paratuberculosis (28.7%) and was capable of detecting the lowest number of cells (30 cfu/40 ml).


CONCLUSIONS
Treatment of milk with 0.75% HPC for 5 h was shown to be superior to the other methods for decontaminating milk prior to culture for M.a. paratuberculosis.


CONCLUSIONS
Certain chemical decontamination protocols are too harsh for application to milk. The "best" decontamination protocol only recovered a fraction of the M.a. paratuberculosis cells present in a milk sample.
Dundee
L
L
Department of Food Science (Food Microbiology), Queen's University of Belfast, Newforge Lane, Belfast BT9 5PX, Northern Ireland, UK.
Grant
I R
IR
Ball
H J
HJ
Rowe
M T
MT
D000818:Animals; D001622:Betaine / Q000031:analogs & derivatives; D002594:Cetylpyridinium; D003470:Culture Media; D008892:Milk / Q000382:microbiology*; D016927:Mycobacterium avium subsp. paratuberculosis / Q000254:growth & development / Q000302:isolation & purification*
C114390:C(18)-carboxypropylbetaine; D003470:Culture Media; D001622:Betaine; D002594:Cetylpyridinium