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Proceedings of the 10th International Colloquium on Paratuberculosis

Proceedings of the 10th International Colloquium on Paratuberculosis

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#86<br />

Typing <str<strong>on</strong>g>of</str<strong>on</strong>g> Mycobacterium avium subsp. paratuberculosis (MAP) strains<br />

isolated from different Italian regi<strong>on</strong>s by four Variable-Number Tandem Repeat<br />

(VNTR) methods al<strong>on</strong>e or in associati<strong>on</strong><br />

Ricchi M, Taddei R, Barbieri I, Belletti GL, Pacciarini ML and Arrig<strong>on</strong>i N<br />

Istituto Zoopr<str<strong>on</strong>g>of</str<strong>on</strong>g>ilattico Sperimentale della Lombardia e dell’Emilia Romagna (IZSLER), Italy<br />

ABSTRACT<br />

The c<strong>on</strong>trol <str<strong>on</strong>g>of</str<strong>on</strong>g> <strong>Paratuberculosis</strong> requires <str<strong>on</strong>g>the</str<strong>on</strong>g> knowledge <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> causative agent,<br />

Mycobacterium avium subsp. paratuberculosis (MAP), both in terms <str<strong>on</strong>g>of</str<strong>on</strong>g> epidemiology and<br />

biodiversity within different strains. One <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> most widely used method for MAP typing is<br />

IS900 sequence restricti<strong>on</strong> fragment length polymorphism. However it is applicable <strong>on</strong>ly <strong>on</strong><br />

cultivable strains, is technically demanding and has limited discriminatory power. More<br />

recently, tandem-repeat PCR based methods overcame <str<strong>on</strong>g>the</str<strong>on</strong>g>se problems and, at present, are<br />

c<strong>on</strong>sidered <str<strong>on</strong>g>the</str<strong>on</strong>g> emerging techniques for MAP typing. The aim <str<strong>on</strong>g>of</str<strong>on</strong>g> this study was to evaluate<br />

<str<strong>on</strong>g>the</str<strong>on</strong>g> discriminatory power <str<strong>on</strong>g>of</str<strong>on</strong>g> four PCR typing methods. We selected ten different strains from<br />

various Italian regi<strong>on</strong>s. We used MIRU (3 loci), VNTR-MIRU (7 loci), MLSSR (11 loci) and<br />

MLVA (5 loci) analysis to differentiate <str<strong>on</strong>g>the</str<strong>on</strong>g> bacterial DNA. Both MIRU and VNTR-MIRU gave 2<br />

clusters (DI 0.556), while MLVA and MLSSR gave respectively 5 (DI 0.667) and 9 (DI 0.978)<br />

clusters. The combinati<strong>on</strong>s gave different results: MIRU+MLVA and VNTR-MIRU+MLVA<br />

gave 5 clusters (DI 0.806), MLSSR+MIRU or MLSSR+VNTR-MIRU did not increase <str<strong>on</strong>g>the</str<strong>on</strong>g><br />

discriminatory results <str<strong>on</strong>g>of</str<strong>on</strong>g> MLSSR al<strong>on</strong>e (9 clusters); MLSSR+MLVA gave 10 clusters<br />

(maximum <str<strong>on</strong>g>the</str<strong>on</strong>g>oretic DI value i.e. 1.00). Although a limited number <str<strong>on</strong>g>of</str<strong>on</strong>g> strains was used in this<br />

study, our data suggest that applying a single analysis, MLSSR provides <str<strong>on</strong>g>the</str<strong>on</strong>g> highest DI.<br />

Moreover, MLSSR coupled with MLVA showed <str<strong>on</strong>g>the</str<strong>on</strong>g> best discriminatory power. Finally, <str<strong>on</strong>g>the</str<strong>on</strong>g><br />

combinati<strong>on</strong> between MIRU or VNTR-MIRU and MLVA enhanced <str<strong>on</strong>g>the</str<strong>on</strong>g> indexes as compared<br />

to single analysis.<br />

INTRODUCTION<br />

The c<strong>on</strong>trol <str<strong>on</strong>g>of</str<strong>on</strong>g> <strong>Paratuberculosis</strong> requires <str<strong>on</strong>g>the</str<strong>on</strong>g> knowledge <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> causative agent,<br />

Mycobacterium avium subsp. paratuberculosis (MAP), both in terms <str<strong>on</strong>g>of</str<strong>on</strong>g> epidemiology and<br />

biodiversity within different strains.<br />

Many methods have been proposed to type MAP: multiplex PCR for IS900 integrati<strong>on</strong><br />

loci (MPIL) 1 , IS900 sequence restricti<strong>on</strong> fragment length polymorphism (RFLP) 2 , amplified<br />

fragment length polymorphism (AFLP) 3 and Pulsed Field Gel Electrophoresis (PFGE) 4 . The<br />

most popular is IS900 RFLP, however it is applicable <strong>on</strong>ly <strong>on</strong> cultivable strains, is technically<br />

demanding and has limited discriminatory power.<br />

More recently, tandem-repeat PCR based methods (TR-PCR) overcame many <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g>se<br />

problems and, at present, are c<strong>on</strong>sidered <str<strong>on</strong>g>the</str<strong>on</strong>g> emerging techniques for MAP typing.<br />

The aim <str<strong>on</strong>g>of</str<strong>on</strong>g> this study was to evaluate <str<strong>on</strong>g>the</str<strong>on</strong>g> discriminatory power <str<strong>on</strong>g>of</str<strong>on</strong>g> four PCR typing<br />

methods al<strong>on</strong>e or in associati<strong>on</strong>. We evaluated: mycobacterial interspersed repetitive units<br />

(MIRU) 5 , variable number tandem repeat - mycobacterial interspersed repetitive units<br />

(VNTR-MIRU) 6 , multilocus variable-number tandem-repeat (MLVA) 7 and multilocus short<br />

sequence repeat (MLSSR) 8 techniques.<br />

METHODS<br />

We selected ten different strains from various Italian regi<strong>on</strong>s. Seven samples derived from<br />

faeces, two from milk and <strong>on</strong>e from ileum. Eight strains derived from cattle and two from<br />

goats. When <str<strong>on</strong>g>the</str<strong>on</strong>g> strain grown in culture was available, <str<strong>on</strong>g>the</str<strong>on</strong>g> DNA was extracted suspending<br />

<strong>on</strong>e col<strong>on</strong>y in 100 μl <str<strong>on</strong>g>of</str<strong>on</strong>g> distilled sterile water and boiling for 20 min. For <str<strong>on</strong>g>the</str<strong>on</strong>g> strains 9 and 10,<br />

since <str<strong>on</strong>g>the</str<strong>on</strong>g> culture was not possible, we extracted MAP DNA respectively from faeces and<br />

ileum tissue with DNA QIAmp Tissue Kit (Qiagen, Milan, Italy). In order to differentiate <str<strong>on</strong>g>the</str<strong>on</strong>g><br />

bacterial DNA, we used <str<strong>on</strong>g>the</str<strong>on</strong>g> following Tandem Repeat-PCR methods:<br />

60

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