MMIC PBL - Case 3

Specimen 3:
Preliminary Information:
Patient: Maisy Hong (67 years)
Sample: Urine
Symptoms: Fever, chills, bladder distension; on indwelling catheter
Bladder distension: Inability to urinate. May be due to obstruction.
Indwelling catheter: prevent catheter from being pulled out of the bladder
Diagnosis: Urinary Track Infection

- Women are more prone to UTI as the urethra is much shorter and closer to the anus than in males. Also, they lack the bacteriostatic properties of prostatic secretions.
- Use of urinary catheters (foreign body) in elderly may result in an increased risk of urinary tract infection.

Possible causative agents:

1. Bacteria: Causes up to 85% of all UTI cases.
(a) Escherichia coli: Most common causative agent of UTI, typically from bowels (colon).

(b) Enterococcus Species: Originate from colon.
E. faecalis

(c) Klebsiella Species: Opportunistic pathogens that causes nosocomial infections
K. pneumoniae

(d) Enterobacter Species: Opportunistic pathogen; Present in large intestine but also present in soil and water.
E. aerogenes
E. cloacae
E. taylorae

(e) Proteus Species: Have urease activity that raises urinary pH. Causes stone formation.
P. mirabilis

(f) Pseudomonas Species: Causes UTI primarily in patients with lowered host defences
P. aeruginosa

2. Fungi: Account for 40% of nosocomial UTI cases.

(a) Candida Species: may cause UTI in diabetic patients
C. albicans - causes vaginitis and chronic mucocutaneous candidiasis


As patient has a catheter, it is likely associated with contributing to UTI.
In this case, most incidences are caused by bacterial infection/colonization of the catheter, hence bacteria are suspected to be the cause.
Fungal stain may be used to rule out fungal infection in this case.

To narrow down type of bacteria, a gram stain should be done, to determine gram stain as well as morphology or bacteria:
Gram Stain:
Negative (pink): Escherichia coli (rod), Proteus Species (rod), Enterobacter Species (bacilli), Klebsiella Species (bacilli), Pseudomonas Species (bacilli).
Positive (purple): Enterococcus Species (cocci)

Gram negative strains are the most common causes; hence further biochemical test, urine cultures and antibiotic susceptibility must be employed to narrow down causative agent.

Most probable agents: according to incidence seen in UTI patients
Escherichia coli – 53-72%
Klebsiella pneumoniae – 6-12%
Proteus mirabilis – 4-6%
Enterococcus faecalis – 2-12%

References:
calder.med.miami.edu > pointis > indwelling.html
wrongdiagnosis.com > medical > bladder_distension.htm
kcom.edu > faculty > chamberlain > Website > lectures > lecture > uti.htm

Cheers,
Debra (TGo2)