21 Urinary Tract infections Flashcards
Bacterial infection acquired by ascending route from urethra to bladder, then kidney. Can then invade bloodstream
What organisms commonly cause UTIs?
- Gram negatives (most common) E. Coli - most common by far Proteus Klebsiella Enterobacter Serratia Pseudomonas aeroginosa Mycoplasma genitalium
- Gram postives (less common)
Enterococcus
Coagulase negative staph - epidermidis/ saprophyticus
Staph aureus
Candida
Occasionally some bugs can spread from blood to urinary tract e.g TB, Staph aureus, salmonella typhi
Why are gram negatives more common in hospitalised patients?
Which organism causes urinary calculi
Antibiotic use drives resistance, favours growth of gram negatives. Catheters increase risk
Proteus produces urease, which acts on urea to produce ammonia, making environment more alkaline
Viral causes of UTI are rare
Which organisms can cause UTI
Polyomaviruses - JC/ BK virus. Very similar, both share 75% of DNA
Enter via respiratory tract, spread through body and infect epithelial cells in kidney utubules and ureter. Establish latency - 35% healthy individuals have this.
During pregnancy or immunocompromised (renal transplant) - can reactivate causing haemorrhagic cystitis
Which fungi/parasites can cause UTIs
Candida
Histoplasma capsulatum
Protozoan -
Tichomonas vaginalis - usually vaginitis
Schistosomiasis - eggs penetrate bladder wall, cause granulomatous reaction which can lead to bladder cancer
What host factors increase risk of UTI
pH, chemical content, and flushing mechanism help prevent infection. Antibodies are produced, but not in high levels. So no long lasting immunity
Incomplete bladder emptying - neurogenic/ enlarged prostate/ reflux
Diabetes
Catheterisation (form biofilms)
Certain virulence factors an help developing an infection e.g proteus with urease
What virulence factors increase risk infection for E. coli
Most urinary pathogens originate from faecal flora, but only certain species of E.Coli are specialised as colonising urinary tract.
Uropathogenic E. coli cause 90% of all UTI (has certain O/H/K serotypes. This is different strain to those serotypes which infect GI tract
- P fimbriae adhesion molecule helps adhere to to urethral/ bladder epithelium
- Capsular acid polysacharide (K) antigens inhibit phagocytosis, produces biofilm
- Haemolysin produced by E. Coli causes membrane damage in kidney tubules
Symptoms of UTI
Prostatitis can have similar symptoms, may include perineal pain, and low back pain
Dysuria
Urgency
Frequency
Cloudy urine due to pus/ blood
Symptoms of pyelonephritis
Haematuria could be infection, or could be sign of infective endocarditis due to immune complex deposition
Fever
Flank pain
Urinary symptoms
Recurrent pyelonephritis can cause hypertension due to renal damage
Laboratory diagnosis - can do traditional culture, but can also do rapid tests to count cell number and resistance test
Lab specimens often contaminated by periurethral bacteria.
How many organisms needed in MSU to be significant
Over 10power5/ ml
Usually only one organism grown
If multiple organisms grown, at rate <10power5/ml, then most likely contaminated
These parameters do not apply when taking catheter/ nephrostomy sample, as samples unlikely to be contaminated by peri-urethral flower
Can also take 3 early morning urine samples for TB.
Can take urine samples for S. haematobium
Causes of haematuria - as it may not indicate UTI
Clotting disorder/ thrombocytopenia IE Renal trauma Renal calculi Urinary cancers Menstruation
Treatment duration
Treatment for UTI
3 days women
7 days men
7 days pyelonephritis
28 days prostatits
- Trimethoprim - antinucleic acid synthesis
- Nitrofurantoin - urinary antiseptic. Not active in alkaline pH, therefore not useful in proteus infections
- Pivmecillinam - cell wall inhibitor
- Cefalexin - cell wall inhibitor
- Co-trimoxazle - combination trimethoprim and sulphamethoxazole (also nucleic acid synthesis inhibitor)
- Cipro/ levo/ ofloxacin - fluoroquinolone - very broad spectrum, not active against enterococci
- Fosfomycin - inhibit cell wall synthesis
Children/ pregnant women with asymptomatic bacteruria should be treated.
Treatment UTI pregnancy
Treatment pyelonephritis
Treatment prostatitis
Pregnancy -
- Nitrofurantoin (avoid at term due to haemolysis)
- Trimethoprim (2nd/3rd trimester only)
- Cephalexin
- Amoxicillin
Pyelonephritis -
- Co-amoxiclav
- Gentamicin
- Ciprofloxacin
Prostatitis treat for 4 weeks-
- Ciprofloxacin
- trimethoprim
Pathogenic E. coli strains can be categorised based on elements that can elicit an immune response in animals. What is role of each antigen?
O antigen
K antigen
H antigen
O antigen: part of lipopolysaccharide layer (somatic). Up to 181 variants
K antigen: capsule. Up to 60 variants
H antigen: flagellin. Up to 56 variants
E. Coli named according to O/H antigen serotypes e.g E. Coli O157/H7
E. Coli strains can classified into sub-categories based on serological characteristics and virulence properties.
- commensal
- Pathogenic - intestinal
- Pathogenic - extra-intestinal
What are forms of pathogenic -intestinal E. coli?
Enteropathogenic EPEC
Enterhohaemorrhagic EHEC
Enteroinvasive EIEC
Enterotoxigenic ETEC
Enteroaggregative EAEC
Diffusely adherent E. coli DAEC
E. Coli strains can classified into:
- commensal
- Pathogenic - intestinal
- Pathogenic - extra-intestinal
What are forms of pathogenic - extra-intestinal E. coli?
Meningitis associated E. coli MNEC
Sepsis associated E. coli SEPEC
Uropathogenic E. coli UPEC
