58
Colorni 2004 ). Str. iniae serotype II, which differed in arginine hydrolase activity,
was described as the cause of disease in rainbow trout initially within Israel and then
the USA (Bachrach et al. 2001 ; Barnes et al. 2003a ; Lahav et al. 2004 ). The pathogen is now recognised in Saudi Arabia in tilapia culture (Al-Harbi 2011 ). Two phenotypes were recognised serologically among cultures from Japan (mostly from
fl ounder), with differences refl ecting the presence or absence of polysaccharide capsule (Kanai et al. 2006 ). Genetic variability as a result of PFGE has been recorded
among Australian isolates (Nawawi et al. 2008 ). Korean isolates recovered during
2000–2005 from diseased olive fl ounder were examined by REP-PCR and RAPDs
enabling division into two genotypes refl ective of pathogenicity of which genotype
1 was more highly virulent than genotype 2 (Kim et al. 2014 ).
By serology using streptococcal specifi c antisera, the original isolates equated
with Str. shiloi were untypeable. Moreover, these isolates were considered to belong
to a separate and distinct DNA homology group, with DNA relatedness between
members of 89–100 % (Eldar et al. 1994 ). Some phenotypic differences were noted
between fi sh and human isolates, however molecular techniques did not discriminate the two sets of cultures (Dodson et al. 1999 ).
Diagnosis
Serology iFAT incorporating monoclonal antibodies has successfully recognised
Str. iniae in tissues (Klesius et al. 2006 ).
Molecular Methods A multiplex PCR has been developed, and successfully recognised from cultures and fi sh tissues a range of fi sh pathogenic lactococcistreptococci, i.e. Lactococcus garvieae, Str. diffi cilis, Str. iniae and Str. parauberis
with a sensitivity for the purifi ed DNA of 30 pg, 12.5 pg, 25 pg and 50 pg, respectively (Mata et al. 2004 ). Specifi cally for Str. iniae, a PCR amplifying a 377-bp
DNA fragment detected only 10 CFU (Zhou et al. 2011 ). Yet other studies, advocated LAMP for Str. iniae with a stated detection limit of 100 fg of purifi ed genomic
DNA, which corresponds to ~4.63 × 10
1 genomic copies/reaction, and is ~10 times
more sensitive that conventional PCR (Han et al. 2011b ). Cai et al. ( 2011 ; 2012)
reported a sensitivity of only 12.4 cells/reaction, and commented on the high degree
of specifi city. An accelerated and specifi c colorimetric LAMP with the pre-addition
of calcein was developed for the detection of Str. agalactiae and Str. iniae in tilapia,
with positivity refl ecting a clearly observable colour change from orange to green.
The LAMP was reported as 10 times more sensitivity than nested PCRs (Suebsing
et al 2013 ).
Pathogenicity
Environmental factors, notably water temperature, have profound effect on the progression of infection caused by Str. iniae. Thus, water temperatures of 25–28 °C led
to the highest mortalities in barramundi; pH and salinity could not be linked with
2 Gram-Positive Bacteria (Anaerobes and ‘Lactic Acid’ Bacteria)
Colorni 2004 ). Str. iniae serotype II, which differed in arginine hydrolase activity,
was described as the cause of disease in rainbow trout initially within Israel and then
the USA (Bachrach et al. 2001 ; Barnes et al. 2003a ; Lahav et al. 2004 ). The pathogen is now recognised in Saudi Arabia in tilapia culture (Al-Harbi 2011 ). Two phenotypes were recognised serologically among cultures from Japan (mostly from
fl ounder), with differences refl ecting the presence or absence of polysaccharide capsule (Kanai et al. 2006 ). Genetic variability as a result of PFGE has been recorded
among Australian isolates (Nawawi et al. 2008 ). Korean isolates recovered during
2000–2005 from diseased olive fl ounder were examined by REP-PCR and RAPDs
enabling division into two genotypes refl ective of pathogenicity of which genotype
1 was more highly virulent than genotype 2 (Kim et al. 2014 ).
By serology using streptococcal specifi c antisera, the original isolates equated
with Str. shiloi were untypeable. Moreover, these isolates were considered to belong
to a separate and distinct DNA homology group, with DNA relatedness between
members of 89–100 % (Eldar et al. 1994 ). Some phenotypic differences were noted
between fi sh and human isolates, however molecular techniques did not discriminate the two sets of cultures (Dodson et al. 1999 ).
Diagnosis
Serology iFAT incorporating monoclonal antibodies has successfully recognised
Str. iniae in tissues (Klesius et al. 2006 ).
Molecular Methods A multiplex PCR has been developed, and successfully recognised from cultures and fi sh tissues a range of fi sh pathogenic lactococcistreptococci, i.e. Lactococcus garvieae, Str. diffi cilis, Str. iniae and Str. parauberis
with a sensitivity for the purifi ed DNA of 30 pg, 12.5 pg, 25 pg and 50 pg, respectively (Mata et al. 2004 ). Specifi cally for Str. iniae, a PCR amplifying a 377-bp
DNA fragment detected only 10 CFU (Zhou et al. 2011 ). Yet other studies, advocated LAMP for Str. iniae with a stated detection limit of 100 fg of purifi ed genomic
DNA, which corresponds to ~4.63 × 10
1 genomic copies/reaction, and is ~10 times
more sensitive that conventional PCR (Han et al. 2011b ). Cai et al. ( 2011 ; 2012)
reported a sensitivity of only 12.4 cells/reaction, and commented on the high degree
of specifi city. An accelerated and specifi c colorimetric LAMP with the pre-addition
of calcein was developed for the detection of Str. agalactiae and Str. iniae in tilapia,
with positivity refl ecting a clearly observable colour change from orange to green.
The LAMP was reported as 10 times more sensitivity than nested PCRs (Suebsing
et al 2013 ).
Pathogenicity
Environmental factors, notably water temperature, have profound effect on the progression of infection caused by Str. iniae. Thus, water temperatures of 25–28 °C led
to the highest mortalities in barramundi; pH and salinity could not be linked with
2 Gram-Positive Bacteria (Anaerobes and ‘Lactic Acid’ Bacteria)