Microbiology Flashcards
The lower end of the urethra is colonised by:
Coliforms and Enterococci from large bowel
Definition of UTI
Microorganisms in urinary tract causing infection
Define pyelonephritis
Inflammation of kidneys due to infection
Complicated UTI
UTI complicated by sepsis, structural abnormality or stones = longer course of antibx
Bacteriuria
Presence of bacteria in urine, but no infection
Cystitis
Inflammation of bladder (not always due to LUTI)
Causal organisms
Coliforms: E. coli, Klebsiella, Enterobacter, Proteus Enterococcus (GI Strep) Staph saphrophyticus Staph aureus Pseudomonas aeruginosa
Proteus
Coliform associated with renal stones
Foul smelling urine
Produces ammonia = increased pH
Staph saphrophyticus
Women child bearing age
Pseudomonas aeruginosa
Associated with catheters
Tx: Ciprofloxacin
Symptoms and signs of UTI
Dysuria, frequency, nocturia, haematuria
Fever, rigors, loin pain (UUTI)
MSSU
Mid stream specimen urine
Wash perineum, middle stream
Clean catch urine
Nurse catches MSSU, kids and elderly
Bag urine
Mini bag over urethra in babies, often contaminated
Only negative results useful
CSU
Catheter specimen urine - often colonised, only send if symptoms
Suprapubic aspiration
Babies if positive bag urine
Boricon container
Red top
Boric acid stops bacteria multiplying
24 hours
Sterile universal container
White top
2 hours
Leukocyte esterase
Indicates presence of WBCs or pus
Nitrites
Indicates presence of bacteria - Coliforms (NOT Enterococcus)
Which bacteria does not give positive nitrites?
Enterococcus
What to look for on microscopy?
Polymorphs - pus cells (multi-lobed nucleus)
Bacteria
RBCs
Less than 104
Not significant
104
May be contamination
Early UTI
= repeat
> 105
Significant
Mixed growth >105
Probably not significant
ESBL
Extended Spectrum Beta Lactamase
Makes bacteria resistant to Cephalosporins and almost all Penicillins
Useful antibiotics for ESBL strains
Nitrofurantoin
Pevmecillinam
Fosfomycin
Merepenem
CPE
Carbapenemase Producing Enterobacteriae
Coliforms (gram neg bacilli) resistant to merepenem (last choice antibx)
India travel
Length of antibx course in uncomplicated UTI in women and men
Women: 3 days
Men: 7 days
1st line for UTI
Amoxicillin
Trimethoprim
Nitrofurantoin
Gentamicin
2nd line for UTI
Pevmecillinam
Temocillin
Co-amoxiclav
Ciprofloxacin
Trimethoprim inhibits:
Folic acid synthesis = avoid 1st trimester
Trimethoprim can also be given as:
Co-trimoxazole BUT risk of SJS
Nitrofurantoin is only useful in:
Uncomplicated LUTI
When should you avoid nitrofurantoin?
Third trimester
Breast feeding
Kids
Gentamicin risks
Renal and VIII toxicity
Gentamicin can only be given for:
3 days
Risk of using Co-amoxiclav
C.diff
Risks of Ciprofloxacin
C. diff Damages cartilage (not used in kids/pregnancy)
Female LUTI Tx
Trimethoprim or Nitrofurantoin 3 days
Uncatheterised male UTI Tx
Trimethoprim or Nitrofurantoin 7 days
Complicated UTI or pyelonephritis Community Tx
Co-amoxiclav or Co-trimoxazole (14 days)
Complicated UTI or pyelonephritis Hospital Tx
Amoxicillin and Gentamicin (3 days) - cotrimoxazole and gen in pen allergic
Bacteriuria in pregnancy
TREAT - many progress to pyelonephritis = IUGR
Abacterial cystitis/urethral syndrome
Symptoms but no growth on culture
Early phase UTI
Urethral trauma (honeymoon cystitis)
Chlamydia/Gonorrhoea cystitis
Treatment of abacterial cystitis
Alkalinise urine - lemon bicarbonate of soda
Empty bladder before/after sex
Cotton/loose pants
When do you give antibiotics in catheterised patient?
> 105 and supporting evidence (fever, symptoms)
Dose of gentamicin
7mg/kg Online calculator (height, weight, creatinine)
How to treat C.diff
Oral Metronidazole (10 days) No improvement = Oral Vancomycin (10 days)