++
Historically classified as group D streptococci, enterococci
are now classified as a separate genus with at least 35 different
species.
++
Only two species, Enterococcus faecalis and Enterococcus
faecium, account for all but a rare case of human disease. E
faecalis is responsible for about 80% to 90% of
human cases, but several studies show a rising proportion of cases
due to E faecium. Enterococci are facultatively
anaerobic oxidase- and catalase-positive gram-positive cocci that
normally inhabit the bowel Approximately half of newborn infants
have acquired colonization with enterococci by 1 week of age. These
very hardy organisms grow at temperatures of 10°C to 60°C (50°F–140˚F)
and remain viable for weeks on environmental surfaces such as bed rails,
sinks, faucets, and doorknobs. Human-to-human spread is common in
hospital settings.
++
Enterococci are generally not highly invasive pathogens and are
typically classified as opportunists. They lack not only the major
exotoxins and endotoxins associated with virulent streptococci and
staphylococci, but also the enzymes that enable rapid tissue spread. Infections
are most often associated with prolonged hospitalization particularly
in intensive care or hematology/oncology units; use of broad-spectrum
antibiotics; indwelling lines; immunocompromised state; or loss
of integrity of the gastrointestinal tract, urinary tract, or skin.1
++
Clinical Manifestations
++
The three most common types of infection associated with enterococci
are urinary tract infection (UTI), polymicrobial abdominal infections,
and bacteremia or sepsis. Although infrequent, cases of focal organ
infection, such as endocarditis, meningitis, and wound infections,
may be severe. UTI caused by enterococci almost never occurs in
otherwise healthy children. They are most often associated with indwelling
urinary catheters and account for approximately 15% of
nosocomial UTIs in children. Anatomic urinary tract anomalies, particularly
vesicoureteral reflux, are more common in community-acquired enterococcal UTIs
than those associated with gram-negative Enterobacteriaceae.2
++
Enterococci may be involved in intra-abdominal polymicrobial
infections following intestinal perforation such as ruptured appendix
or necrotizing enterocolitis. Although there has been controversy regarding
the pathogenic role of enterococci in such infections, most authorities
recommend adding an antibiotic to cover for enterococci in such
infections.3 Enterococcal bacteremia or sepsis
in children may not be identified with a specific focus, but common
risk factors are use of broad-spectrum antibiotics or intravascular catheters
in association with underlying conditions such as surgery, immunosuppression, transplants,
or major organ dysfunction.4 Bacteremia without
a focal infection may result in a self-limited illness or a severe
and life-threatening illness, particularly in newborns or children
with underlying disease. Bacteremia is often polymicrobial with
other enteric microorganisms. Mortality occurs in up to 25% of
cases, but is hard to separate from the underlying health problems.
++
In newborns, infection may present as early onset sepsis in the
first several days of life, similar to early onset group B streptococcal sepsis.
However, most neonatal enterococcal infections are nosocomial and
occur after the second week of life, typically in ...