Microbiology
Infections
Question 23 of 77
A 21 year old female presents to ED complaining of a 2 day history of dysuria and urinary frequency. Urine dipstick shows leucocytes ++, nitrites +, blood +. Which of the following is the most appropriate first line antibiotic:
Answer:
Uncomplicated lower urinary tract infection should be treated first line with either trimethoprim 200 mg bd or nitrofurantoin 50 mg qds/100 mg bd, for 7 days in men and 3 days in women. More severe, complicated or resistant infections may require longer courses or specific antibiotic therapy based on laboratory results.Urinary Tract Infection
Microbiology / Infections
Last Updated: 18th September 2024
Urinary-tract infection is more common in women than in men; when it occurs in men there is frequently an underlying abnormality of the renal tract. Recurrent episodes of infection are an indication for radiological investigation especially in children in whom untreated pyelonephritis may lead to permanent kidney damage.
Infective Agents
- Escherichia coli (most common)
- Staphylococcus saprophyticus (especially in sexually active young women)
- Proteus mirabilis
- Klebsiella pneumoniae
- Pseudomonas aeruginosa (particularly in long term catheters)
- Staphylococcus epidermidis
- Enterococcus faecalis
Risk Factors
- Poor hygiene
- Sexual activity in females
- Outflow obstruction e.g. BPH or prostate cancer, vaginal prolapse in elderly women, renal calculi, urethral strictures, bladder tumours
- Neurogenic bladder
- Immunocompromised e.g. chemotherapy, diabetes mellitus
- Pregnancy
- Urethral catheters
- Dehydration
Clinical Disease
- Lower UTI
- urinary frequency or urgency
- dysuria
- suprapubic discomfort
- Acute pyelonephritis
- fever, rigors
- loin pain
- renal angle tenderness
- signs of septicaemia
- Acute prostatitis
- fever, rigors
- Urinary voiding symptoms or acute urinary retention
- Perineal or suprapubic pain (penile pain, low back pain, pain on ejaculation, and pain during bowel movements can also occur)
- Tender prostate on examination
Diagnosis
- Dipstick test for leucocyte esterase, nitrites and blood
- If both dipstick tests are negative, a UTI is unlikely.
- If the leucocyte esterase test alone is positive, a UTI is moderately likely.
- If the nitrite test is positive, with or without a positive leucocyte esterase test, a UTI is highly likely.
- Midstream urine (MSU) for culture, microscopy and sensitivities (M, C & S) before starting antibacterial therapy:
- in men;
- in pregnant women;
- in children under 3 years of age;
- in patients with suspected upper urinary-tract infection;
- complicated infection, or recurrent infection;
- if resistant organisms are suspected;
- if urine dipstick testing gives a single positive result for leucocyte esterase or nitrite;
- if clinical symptoms are not consistent with results of dipstick testing.
- Further investigation in men or children
Treatment
Treatment should not be delayed while waiting for results. The antibacterial chosen should reflect current local bacterial sensitivity to antibacterials.
- Empirical treatment for uncomplicated lower UTI
- Non-pregnant women
- 1: Nitrofurantoin, or trimethoprim (if low risk of resistance)
- 2: Nitrofurantoin (if not used first line), fosfomycin, pivmecillinam hydrochloride, or amoxicillin (high rate of resistance, so only use if culture susceptible)
- Suggested duration 3 days
- Men
- 1: Nitrofurantoin, or trimethoprim
- 2: Consider pyelonephritis or prostatitis
- Suggested duration 7 days
- Non-pregnant women
- Empirical treatment for acute pyelonephritis
- 1: Oral cefalexin, or ciprofloxacin (if sensitivity known: co-amoxiclav, or trimethoprim)
- 1: Intravenous first line (if severely unwell or unable to take oral treatment) amikacin, ceftriaxone, cefuroxime, ciprofloxacin, or gentamicin (co-amoxiclav may be used if given in combination or sensitivity known)
- Suggested duration 10 - 14 days
- Empirical treatment for acute prostatitis
- 1: Oral ciprofloxacin, or ofloxacin, or trimethoprim if unable to take fluoroquinolones
- 2: Oral levofloxacin, or co-trimoxazole
- 1: Intravenous first line (if severely unwell or unable to take oral treatment) amikacin, ceftriaxone, cefuroxime, ciprofloxacin, gentamicin, or levofloxacin
- Suggested duration 14 days
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
