The characterization of Listeria spp. isolated from food products and the food-processing environment.
OBJECTIVE
To enhance the information pertaining to the epidemiology of a collection of 378 Listeria spp. isolates obtained from several food-processing plants in Ireland over a 3-year period (2004-2007).


RESULTS
The collection was characterized by pulsed-field gel electrophoresis (PFGE). The most prevalent pulse-type was PFGE profile I (n=14·5%) that consisted mainly of environmental Listeria spp. samples. Serotyping of 145 Listeria monocytogenes isolates was performed. The most common serovar was 1/2a and comprised 57·4% (n=77) of the L. monocytogenes collection. The other serovars were as follows: 4b (14·1%, n=19), 1/2b (9·7%, n=13), 4c (4·4%, n=6) and 1/2c (6·7%, n=9), respectively. Eleven isolates were identified as non-Listeria spp., the remaining ten L. monocytogenes isolates were nontypeable. The antimicrobial susceptibility testing revealed the antibiotic that isolates displayed the most resistance to was gentamicin (5%) followed by sulfamethoxazole-trimethoprim (2%), tetracycline and ciprofloxacin (1·5%).


CONCLUSIONS
The subtyping has indicated the diversity of the Listeria spp. The presence of serotype 1/2a, 1/2b and 4b in both raw and cooked ready-to-eat food products is a public health concern, as these serotypes are frequently associated with foodborne outbreaks and sporadic cases of human listeriosis. In addition, the emergence of antimicrobial-resistant L. monocytogenes isolates could have serious therapeutic consequences.


CONCLUSIONS
The molecular subtyping and the further characterization of these isolates may be valuable particularly in the context of a suspected common source outbreak in the future.
O'Connor
L
L
Department of Chemical and Life Science, Waterford Institute of Technology, Waterford, Ireland. loconnor@wit.ie
O'Leary
M
M
Leonard
N
N
Godinho
M
M
O'Reilly
C
C
Coffey
L
L
Egan
J
J
O'Mahony
R
R
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D015373:Bacterial Typing Techniques; D004269:DNA, Bacterial / Q000235:genetics; D005506:Food Contamination / Q000032:analysis*; D005511:Food Handling; D005516:Food Microbiology; D005638:Fruit / Q000382:microbiology; D008087:Listeria / Q000145:classification / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification*; D008460:Meat / Q000382:microbiology; D008969:Molecular Sequence Data; D010802:Phylogeny; D014675:Vegetables / Q000382:microbiology
D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial