Characterization of Small-Colony Variants of Enterococcus faecalis Isolated from Chickens with Amyloid Arthropathy

Abstract

In this study we report the isolation and characterization of normal-sized and small-colony variants of Enterococcus faecalis from outbreaks of amyloid arthropathy in chickens. Postmortem examinations of 59 chickens revealed orange deposits in the knee joints, typical for amyloid arthropathy. Bacterial cultures from 102 joints and 43 spleens exhibited pure (n ‫؍‬ 88) and mixed (n ‫؍‬ 11) cultures of normal (n ‫؍‬ 60) and pinpoint (n ‫؍‬ 28) colonies of E. faecalis. Pulsed-field gel electrophoresis of 62 isolates demonstrated seven different band patterns with at most two band size variations, and multilocus sequence typing demonstrated two different sequence types, sharing six out of seven alleles, suggesting a close evolutionary relationship between isolates obtained from four outbreaks. In addition, all isolates were clonally related to an amyloid arthropathy reference strain from The Netherlands, previously shown to be globally dispersed. Initial investigation of the isolated small-colony variant phenotype revealed no difference in whole-cell protein profiling between normal and pinpoint colonies. However, the pinpoint colony isolates appeared to be more virulent in an in vivo challenge model in chickens than their normal-sized-colony counterparts. In addition, pinpoint morphology and associated slow growth were expressed without reversion after in vitro and in vivo passage, suggesting a genuine altered phenotype, and in some instances normal colonies converted to pinpoint morphology postinfection. In conclusion, small-colony variants of E. faecalis are described for the first time from veterinary clinical sources and in relation to amyloid arthropathy in chickens.

Isolation and Characterization of Small-Colony Variants of Ornithobacterium rhinotracheale

“…This is in accordance with a previous study on E. faecalis SCVs that reported identical 16S rRNA sequences for SCVs and their wild-type isolates (7). This finding indicates that other phylogenetic methods should be used to discriminate between the O. rhinotracheale SCVs and their WT isolates.…”

“…(7,13). However, their uncommon morphological and physiological properties cause them to be frequently undetected or misidentified by standard clinical microbiology procedures (1).…”

Characterization of Clinical Enterococcus faecalis Small-Colony Variants

“…While SCVs of staphylococci, especially those of S. aureus, are intensively studied for their morphological, ultrastructural, metabolic, and growth characteristics (3,4,(15)(16)(17)22), little is known about the SCVs of Enterococcus species. Their occurrence in a patient with endocarditis (13) and in chickens with amyloid arthropathy (20) has only been briefly mentioned, without further characterization.In chickens, Enterococcus faecalis SCVs appeared to be more virulent in an in vivo infection model than the normal phenotype, but the underlying mechanisms were not investigated (20).In this report, we present a clinical case of persistent aortic valve endocarditis caused by E. faecalis SCVs. Furthermore, we characterize the Enterococcus SCVs in comparison to the normal phenotype with respect to microscopic and ultrastructural morphology, growth behavior, metabolite production, and antimicrobial susceptibility.…”

“…In chickens, Enterococcus faecalis SCVs appeared to be more virulent in an in vivo infection model than the normal phenotype, but the underlying mechanisms were not investigated (20).…”

“…While SCVs of staphylococci, especially those of S. aureus, are intensively studied for their morphological, ultrastructural, metabolic, and growth characteristics (3,4,(15)(16)(17)22), little is known about the SCVs of Enterococcus species. Their occurrence in a patient with endocarditis (13) and in chickens with amyloid arthropathy (20) has only been briefly mentioned, without further characterization.…”