Typing of Listeria monocytogenes strains isolated in Italy by inlA gene characterization and evaluation of a new cost-effective approach to antisera selection for serotyping.
OBJECTIVE
In this study, 105 Listeria monocytogenes strains isolated from humans, foods and environmental samples were characterized using several typing methods. Moreover, serotyping procedure was evaluated, and a cost-effective methodological approach based on preliminary PCRs screening was proposed.


RESULTS
The isolates were analysed by conventional serotyping, multiplex-PCRs for serogroup and lineage identification and PCR-RFLP of inlA gene to identify potentially noninvasive L. monocytogenes. Among the strains, only the serotypes 1/2a, 1/2c, 1/2b, 4b and 3a were identified. The isolates were classified into serogroups I (58.10%), II (22.85%), III (12.38%) and IV (6.67%). Among clinical strains, lineage I was more represented (68.75%) than lineage II; whereas, lineage II was more associated with food (90.24%) and environmental (85.72%) isolates. Most of food (89.02%) and environmental (85.71%) isolates were classified into truncated InlA profiles, whereas the 93.75% of clinical strains were associated with a complete form of the protein.


CONCLUSIONS
Molecular techniques were sensitive and specific for classifying strains into serogroup and lineage and in agreement with the serotyping. Moreover, a preliminary PCRs-based screening was proposed to select only the necessary antisera by a flow chart; this methodological approach allows cost saving up to 42%. Our results further suggest the role of InlA protein in human listeriosis, particularly in immunocompetent individuals, and a correlation between truncated protein and serotype.


CONCLUSIONS
This study further validates molecular methods for L. monocytogenes analysis and proposed a new cost-effective approach for serotyping. It could help to improve a national surveillance network for L. monocytogenes infections in Italy.
Tamburro
M
M
Department of Health Sciences, Faculty of Medicine and Surgery, University of Molise, Campobasso, Italy.
Ripabelli
G
G
Fanelli
I
I
Grasso
G M
GM
Grasso
G Maria
GM
Sammarco
M L
ML
Sammarco
M Lucia
ML
D001426:Bacterial Proteins / Q000235:genetics*; D004783:Environmental Microbiology; D005516:Food Microbiology; D006801:Humans; D007106:Immune Sera / Q000378:metabolism; D007558:Italy; D008089:Listeria monocytogenes / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification; D008088:Listeriosis / Q000382:microbiology; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D012703:Serotyping / Q000191:economics* / Q000379:methods*
D001426:Bacterial Proteins; D007106:Immune Sera; C069761:internalin protein, Bacteria