Common Infections


  • Definition of Infection: Infection is defined as the presence of microorganisms causing damage to body tissues, often accompanied by acute inflammation.

    • Acute Inflammation Symptoms: Common symptoms include pain, swelling, redness, heat, and loss of function.

    • Example: Staphylococcus aureus is a bacterium that is part of the normal flora of the skin and does not cause harm unless the skin is cut, which can lead to an infection.

Causative Pathogens of Common Infections

  • Categorized into:

    • Gram-positive (G+) Pathogens

    • Gram-negative (G-) Pathogens

    • Anaerobic Pathogens

Antimicrobial Stewardship Program

  • Program aimed at optimizing the use of antimicrobials to combat infection and resistance.

Urinary Tract Infections (UTIs)

Types

  • Uncomplicated UTI: Occurs in a structurally and functionally normal urinary tract, typically affecting non-pregnant women.

  • Complicated UTI: Infects an abnormal urinary tract or occurs post urological surgery.

    • UTIs in pregnancy and children are always classified as complicated.

  • Catheter-associated UTIs: Have the same symptoms as uncomplicated and complicated UTIs but are caused by different pathogens.

  • Recurrent UTI: Defined as two separate culture-proven episodes within six months or more than three episodes in a year.

Anatomy of the Urinary System

  • Components: Right ureter, left ureter, kidneys, bladder, urethra.

Site of Infection

  • - Lower UTI: Urethra and bladder.

    • Upper UTI: Ureter and kidneys, leading to conditions like Pyelonephritis, which can cause acute kidney injury (AKI).

Causative Pathogens in UTIs

  1. Gram-negative (G-):

    • E. coli

    • Proteus spp.

    • Klebsiella spp.

    • Pseudomonas aeruginosa

  2. Gram-positive (G+):

    • Enterococcus spp.

    • Staph saprophyticus

  3. Fungal: Candida albicans, rarely causes UTIs, typically in hospitalized individuals with risk factors.

Factors Enhancing Infection Risk

  • Adherence Mechanisms: Type 1 pili in Escherichia coli enhance binding to vaginal fluid, especially when the fluid's pH is altered post-menopause.

Risk Factors for UTIs

  • Blockages in the ureter or kidneys, diabetic conditions, and the presence of catheters increase susceptibility.

Signs & Symptoms of UTI

  • Common indicators include:

    • Cloudy urine

    • Pain, typically proportional to location

    • Urinary urgency or increased frequency

    • Hematuria (blood in urine)

    • Polyuria (frequent urination)

    • Malaise, fever, and potential confusion in older populations.

    • Foul-smelling urine and pelvic pain in women, especially around the pubic bone.

Pyelonephritis

  • Characterized by:

    • Inflammation and potential scarring of kidney cortex

    • Symptoms include a temperature greater than 37.9°C, chills, kidney pain, nausea, and vomiting.

Diagnosis of UTI

  • Diagnostic methods include:

    • Clinical history and physical examination.

    • Exclusion of other potential causes (e.g., sexually transmitted infections).

    • Urine dipstick tests, microscopy, and cultures.

    • Specimens should ideally be collected first thing in the morning.

Urine Dipstick Tests

  • Purpose: Rapid testing for various substances in urine including:

    • Leucocyte esterase (indicating WBC)

    • Nitrites (produced by gram-negative bacteria)

    • Presence of glucose, protein, ketones, hemoglobin, bilirubin, urobilinogen, and specific gravity.

  • Interpreting Results:

    • Normal pH ranges from 4.5 to 8.0; deviations may imply infection or renal issues.

    • Positive results for glucose, protein, blood, bilirubin, nitrites, etc., indicate specific health conditions ranging from diabetes to infections.

UTI Treatment Guidelines

For Non-Pregnant Women

  • Recommended antibiotics for uncomplicated UTIs include:

    1. First choice: Nitrofurantoin (if eGFR ≥ 45 ml/min).

    2. Second choice: Trimethoprim (consider low risk of resistance).

  • For emergency or severe cases, immediate antibiotics may be warranted.

For Complicated UTIs (In Children, Pregnant Women, or Men)

  • Reviews of antibiotic treatment should follow proper guidelines, adjusting for patient symptoms and previous cultures.

  • Assess risk factors like age and underlying health conditions before prescribing.

Treatment of Recurrent UTIs

  • Nitrofurantoin is typically first line for recurrent infections. Pivmecillinam or other options may be given if intolerance occurs.

Skin and Soft Tissue Infections (SSTIs)

Cellulitis

  • Affects the lower dermis and subcutaneous fat, characterized by redness and swelling, sometimes accompanied by systemic symptoms.

Distinction Between Cellulitis and Erysipelas

  • Cellulitis: Blurring of involved area.

  • Erysipelas: Clear demarcation of infection in the upper dermis.

Causative Pathogens in SSTIs

  • Gram-positive bacteria are most common, including Staphylococcus aureus and beta-haemolytic streptococcus. Exceptions exist for severe cases involving organisms like Pseudomonas aeruginosa.

Treatment of Cellulitis and Erysipelas

  • First-Line Antibiotic: Flucloxacillin, alternative options include clarithromycin or doxycycline (especially for those allergic to penicillin).

  • Severe infections: Require intravenous treatment with potentially higher dosing.

Community Acquired Pneumonia (CAP)

Diagnostic Definitions

  • Symptoms include cough, respiratory distress, and systemic signs of an infection (fever, vasculitis).

  • Diagnosed corroborated by chest X-Ray showing shadowing.

Treatment Protocols

CURB-65 Scoring System

  • Used to determine treatment settings for pneumonia based on various clinical indicators (confusion, urea levels, respiration rate, blood pressure, and age).

  • Treatment Guidelines: Vary from oral antibiotics for low scores to intensive admission for high scores.

Antibiotic Choices for CAP

  1. First Degree: Doxycycline or Benzylpenicillin for inpatient management.

  2. Second Options: Levofloxacin based on patient conditions and reaction history.

Summary of Treatment Considerations

  • Proper assessment of the antibiotic need, choice, dosage, route, and duration is essential

  • Monitoring symptoms and reassessing treatment effectiveness every 48 hours can provide critical clinical guidance.