Role of subtyping in detecting Salmonella cross contamination in the laboratory

BMC Microbiology

Table 1 Case 3 – Molecular Analysis of S. Typhimurium PT Untypable, ASSuT isolates in NSRL databases.

Isolate no	Year	Lab	Source	PFGE		MLVA
				XbaI	BlnI
03–0407	2003	D	Human	B	A	05-02-07-14-02
05–0802	2005	E	Human	A	A	04-03-10-02-02
05–0900	2005	E	Dairy product	B	A	04-04-11-00-02
05–0902	2005	E	Swine	B	A	04-04-11-00-02
07–0146	2007	E	Dairy product	A	B	04-03-11-02-02
07–0237	2007	E	Swine	A	B	04-03-11-02-02
07–0200	2007	L	Pork	C	C	05-02-07-00-02
07–0201	2007	L	Unknown	B	A	04-03-07-02-02
07–0204	2007	L	Unknown	A	A	04-04-16-21-02
07–0028	2007	L	Pork	A	A	04-03-10-02-02
07–0060	2007	L	Pork	A	A	04-03-10-02-02
07–0174	2007	L	Swine	A	A	04-03-11-02-02

Investigation of a suspected contamination incident involving 07–0146, a S. Typhimurium, PT Untypable, resistance profile ASSuT, isolated from a dairy product involved molecular analysis of all isolates sharing this isolates phenotype (n = 12). PFGE with XbaI digestion showed the isolates to be closely related, e.g. patterns A and B were 92.8% similar while C was 89% similar to A. All isolates were indistinguishable with BlnI digestion apart from 07–0146 and 07–0237 (86% similarity) and 07–0200. MLVA provided further evidence that the Salmonella isolated from the dairy product was in fact contamination from swine isolate 07–0237.
The 2005 Lab E dairy isolate (05–0900) differed from 07–0146 but was indistinguishable from a swine isolate (05–0902) from Lab E which was isolated at the same time.

ISSN: 1471-2180