1. What is the causative agent, how does it enter the body and
how does it spread a) within the body and b) from person to
(UPEC) is the major cause of urinary tract infec-
tions (UTIs) in anatomically normal, unobstructed urinary tracts.
is a motile nonsporing gram-negative bacillus approximately
m wide and 2–3
m long (Figure 2). It has a typical gram-negative
cell wall with an outer hydrophobic membrane containing
(LPS). It has peritrichous flagella and possesses
, which are
important in adhesion (Figure 3). Eighty percent of all urinary tract infec-
tions are caused by
in the community and about 60% in hospital.
The LPS is composed of lipid A, an inner core of polysaccharide linked
to the lipid A by ketodeoxyoctonate (KDO) and an outer variable polysac-
charide (Figure 4). The general arrangement of LPS is similar in most
A 50-year-old worker at a school cafeteria went to her
primary care physician complaining of tiredness, shaking
chills, a pain in her loin, and a burning sensation on
passing urine, which she was doing more frequently than
On examination, her doctor noted that she seemed a
bit pale and that she had some suprapubic tenderness. He
tested her urine with a dipstick and found she had a
positive result for nitrite,
cells, and protein.
The doctor took a blood and urine sample for
confirmation and sent them to the local hospital
laboratory. A diagnosis of
was made and
she was started on antibiotics. The following day the
laboratory results were available. The full blood count
and a pure culture of
was grown from the urine (Figure 1).
cultured from the urine.
This shows the growth of
lactose-fermenting (yellow colonies)
on a medium containing
lactose and a pH indicator. In routine practice urine is cultured on
cystine lactose electrolyte-deficient (CLED) medium. Cystine is a growth
factor for some organisms; lactose is incorporated to differentiate
utilization of lactose from nonutilization (e.g.
); and the
electrolyte deficiency inhibits the swarming of
, which may
obscure bacterial colonies.
This is a Gram
showing the red
© Lydyard, Peter; Cole, Michael; Holton, John; Irving, Will; Porakishvili, Nino; Venkatesan, Pradhib; Ward, Kate, Jan 01, 201
Garland Science, Hoboken, ISBN: 9780203856871