Biofilm formation by Mycobacterium avium isolates originating from humans, swine and birds.
BACKGROUND
Mycobacterium avium includes the subspecies avium, silvaticum, paratuberculosis and hominissuis, and M. avium subspecies has been isolated from various environments all over the world including from biofilms in water distribution systems. The aim of this study was to examine isolates of M. avium subsp. avium and M. avium subsp. hominissuis of different origin for biofilm formation and to look for correlations between biofilm formation and RFLP-types, and to standardise the method to test for biofilm formation. In order to determine the best screening method, a panel of 14 isolates of M. avium subsp. avium and M. avium subsp. hominissuis, were tested for their ability to form biofilm in microtiter plates under different conditions. Subsequently, 83 additional isolates from humans, swine and birds were tested for biofilm formation. The isolates were tested for the presence of selected genes involved in the synthesis of glycopeptidolipids (GPLs) in the cell wall of M. avium, which is believed to be important for biofilm formation. Colony morphology and hsp65 sequvar were also determined.


RESULTS
Nine isolates from swine produced biofilm. There was a significant higher frequency of porcine isolates forming biofilm compared to human isolates. All isolates were previously characterised by IS1311- and IS1245-RFLP typing. The ability to form biofilm did not correlate with the RFLP-type, hsp65 sequevar, colony morphology or the presence of gene sequences related to GPL synthesis.


CONCLUSIONS
The observed differences in biofilm forming abilities between porcine and human isolates raises questions regarding the importance of biofilm formation for infectious potential. The optimised method worked well for screening of multiple isolates.
Johansen
Tone Bjordal
TB
Department of Animal Health, National Veterinary Institute, Oslo, Norway. tone.bjordal-johansen@vetinst.no
Agdestein
Angelika
A
Olsen
Ingrid
I
Nilsen
Sigrun Fredsvold
SF
Holstad
Gudmund
G
Djønne
Berit
B
D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics; D015373:Bacterial Typing Techniques; D018441:Biofilms; D001717:Birds / Q000382:microbiology; D018834:Chaperonin 60; D018833:Chaperonins / Q000235:genetics; D006001:Glycoconjugates / Q000235:genetics*; D006801:Humans; D009162:Mycobacterium avium / Q000145:classification / Q000235:genetics* / Q000254:growth & development* / Q000302:isolation & purification; D012150:Polymorphism, Restriction Fragment Length; D013552:Swine / Q000382:microbiology
D001426:Bacterial Proteins; D018834:Chaperonin 60; D006001:Glycoconjugates; C074119:heat-shock protein 65, Mycobacterium; D018833:Chaperonins