Urinary tract infection
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Only the lower part of the urethra is usually colonized by bacteria;
the flushing action of urinary flow prevents ascending
infection. The shorter female urethra makes urinary infection
Epidemiology and Pathogenesis
Dehydration, obstruction, the disturbance of smooth urinary flow
or the presence of a foreign body such as a stone or urinary catheter
predisposes to urinary infection. Trauma during sexual intercourse
may precipitate infection in women. Infection in children,
especially in boys, is often associated with congenital abnormalities,
such as ureteric reflux or urethral valves.
- Lower urinary tract infections: urinary frequency, dysuria and
suprapubic discomfort; fever may be absent.
- Pyelonephritis: fever, loin pain, renal angle tenderness and signs
- Infection in children, elderly people and antenatal patients: may
be clinically silent.
- Recurrent infections can result in scarring and renal failure.
Treatment and Prevention
- 'Dip-stick' test for leukocyte esterase and nitrite can identify
patients with infection and the need for treatment without culture.
- Culture using a midstream urine (MSU) specimen to reduce the
risk of contamination.
- >105 colony-forming units/mL of a single organism indicate
infection, whereas <105 organisms/mL or a mixed growth suggests
- Chronically catheterized patients usually have 'significant'
numbers of organisms and multiple pathogens and may not have
- All isolates are potentially significant from a suprapubic aspirate
from an infant with suspected infection.
- Susceptibility tests should be performed on all significant
- Empirical therapy is based on the known susceptibilities of
- Most community-acquired infections respond to oral antibiotics
(e.g. cefalexin, amoxicillin, trimethoprim or nitrofurantoin).
- If septicaemia is present, ciprofloxacin or cefotaxime should be
- Recurrent urinary infection may require nocturnal prophylaxis
(e.g. low-dose trimethoprim, nitrofurantoin or naladixic acid),
together with advice on ensuring an adequate urine flow is
- Children with recurrent infection should be investigated for anatomical
- Significant bacteriuria in pregnant women should be treated,
even if asymptomatic.
- Anatomical obstructions to urine flow should be removed if
Genital infection presents in many ways (see Table). It may be
followed by pelvic inflammatory disease, infertility, prostatitis,
arthritis or bacteraemia. Other sites may be involved, for example
the throat and rectum in gonococcal infection.
||Genitourinary infection syndromes and causative organisms.
Chlamydia trachomatis types L1–4
Haemophilus ducreyi (see Small Gram-negative coccobacilli: Haemophilus, Brucella, Francisella, Yersinia and Bartonella
Treponema pallidum (see Spiral bacteria
Mixed anaerobic infection
Mobiluncus spp. and others in
Urethral and cervical swabs should be taken for both bacterial and
viral diagnosis. N. gonorrhoeae
and herpes simplex are
optimally detected by nucleic acid amplification tests (NAATs; see
Chlamydia, Mycoplasma and Rickettsia
and Herpesviruses II
). Samples positive for N. gonorrhoeae can be
cultured for susceptibility testing. Syphilis is diagnosed with
enzyme immunoassay (EIA) together with traditional treponemal
tests (see Spiral bacteria
). Direct microscopy may show evidence of
Patients must be treated before a laboratory diagnosis, so Treatment
is guided by a 'syndromic approach' where therapy is based
on the agents that are likely to treat at least 95% of organisms in
a community. For example, patients with uncomplicated urethritis
can be treated with a single dose of a suitable cephalosporin or
fluoroquinolone followed by a 1-week course of either doxycycline
or single-dose azithromycin. Syphilis is treated with penicillin (see
- Risk avoidance (e.g. monogamous relationships).
- Risk reduction (e.g. barrier contraceptive methods).
- Tracing of sexual contacts to treat asymptomatic disease.
- Antigen variability in N. gonorrhoeae means that there is no
effective vaccine for gonorrhoea.
- Causes an itchy vaginal infection with an offensive discharge.
- Treatment of sexual contacts may be necessary to prevent recurrent
- Caused by disruption to the normal vaginal flora.
- Results in an offensive discharge with a characteristic fishy smell
- Diagnosis is based on clinical findings and near-patient tests (e.g.
'clue cells', which are epithelial cells heavily coated with bacteria,
and a positive amine test) and defined syndrome scoring schemes.
- Clindamycin preparations, oral metronidazole, and oral and
intravaginal tablets of lactobacillus are effective treatments.
Infection of the epididymis may arise (i) from a urinary tract infection,
(ii) as part of a genital infection or (iii) as a primary systemic
infection, such as brucellosis or tuberculosis. Patients present with
a painful, acutely inflamed epididymis and testis, which must be
differentiated from testicular torsion. Diagnosis is made clinically
and confirmed by the result of urinary or blood cultures and tests
for sexually transmitted infections.