ENTEROCCI BACTERIA
Type D Streptococcus: The Enterococci include E. faecalis, a cause of urinary tract infections,
and E. faecium, a bacterium resistant to many common antibiotics. Diseases such as septicemia,
endocarrditis, and appendicitis have also been attributed to group D Strep.
bladder, pathogen,
urinary tract, pathogen
wounds, pathogen
Recent findings: (2007) Frequent horizontal gene transfer and recombination, resulting in high-
level genome plasticity, facilitating rapid responsiveness of enterococci to changing environmental
conditions may have contributed to the worldwide emergence. For Enterococcus faecium this has
resulted in the development of a distinct genetic subspecies, clonal complex 17, responsible for
the majority of glycopeptide-resistant enterococci-related hospital burden. Preliminary data also
suggest that such high-risk enterococcal clonal complexes may exist within Enterococcus faecalis.
The last 2 years have not only disclosed novel determinants implicated in enterococcal
pathogenesis, but also showed that enterococci are able to sense their environment and regulate
virulence gene expression accordingly. Linkage of glycopeptide resistance in enterococci to
plasmid maintenance systems holds a doomed perspective for controlling antibiotic resistance
emergence.
Enterococcal pathogenicity was initially addressed at the end of the 19th century by
MacCallum and Hastings (46), who isolated an organism from a case of acute endocarditis, and
designated it Micrococcus zymogenes based on its fermentative properties. The organism was
shown to be resistant to dessication, heating to 60°C, and several antiseptics, including carbolic
acid and chloroform (46). It was also found to be lethal when injected intraperitoneally in white
mice, and capable of producing endocarditis in a canine model (46). A century later, enterococci
are prominent among nosocomial pathogens, ranking second only to E. coli in total nosocomial
infections, accounting for more than 12% of all cases (56).
Enterococci, 1998, leading causes of nosocomial bacteremia, surgical wound infection, and
urinary tract infection, are becoming resistant to many and sometimes all standard therapies.
The past few years have witnessed increasing interest in enterococci. Until recently, these
ordinary bowel commensals languished as misclassified streptococci, commonly perceived "with
the exception of endocarditis and rare cases of meningitis … [as] not … a major cause of serious
infection"
Commentary
The enterococcus (previously Streptococcus faecalis), causes many of the same problems as
other members of the intestinal flora. These include opportunistic urinary tract infections and
wound infections. In contrast to the Enterobacteriaceae, enterococcal infection is often associated
with bacteremia which can lead to endocarditis or colonization of previously damaged heart
valves. Little is known about its pathogenesis. The D in an older name, group D strep, refers to
the Lancefield classification which is based on the antigenicity of a carbohydrate which is soluble
in dilute acid and called the C carbohydrate. Lancefield identified 13 types of C carbohydrate,
designated A through O, that could be serologically differentiated. The organisms that most
commonly infect humans are found in groups A, B, D, and G. Streptococci that do not contain the
C carbohydrate substance are called viridans streptococci or non-typable streptococci.