Model Answer
0 min readIntroduction
Acute pyelonephritis is an inflammation of the kidney, typically resulting from a bacterial urinary tract infection (UTI) that ascends from the lower urinary tract. It is a relatively common clinical condition, often presenting with fever, flank pain, and urinary symptoms. Understanding the causative organisms is vital for appropriate antibiotic selection and effective treatment. While various microorganisms can cause pyelonephritis, certain bacteria are significantly more prevalent than others.
Common Organisms Causing Acute Pyelonephritis
The following organisms are commonly implicated in acute pyelonephritis, listed in approximate order of frequency:
1. Gram-Negative Bacteria
- Escherichia coli (E. coli): This is the most frequent cause, accounting for approximately 70-85% of community-acquired acute pyelonephritis cases. Specific virulence factors like P-fimbriae contribute to its ability to adhere to uroepithelial cells.
- Klebsiella pneumoniae: Represents 5-10% of cases. Often associated with more severe infections, particularly in patients with underlying structural abnormalities or immunocompromised states.
- Proteus mirabilis: Accounts for around 5-10% of cases. Frequently linked to urinary stones (struvite stones) due to its urease production, which increases urine pH.
- Enterobacter species: Less common, but can cause infections, especially in hospital-acquired settings.
- Pseudomonas aeruginosa: More frequently seen in hospital-acquired pyelonephritis, particularly in patients with indwelling urinary catheters or those who are immunocompromised.
2. Gram-Positive Bacteria
- Enterococcus faecalis: Represents approximately 5-10% of cases. Often associated with recurrent UTIs, previous antibiotic use, and structural abnormalities.
- Staphylococcus saprophyticus: More common in sexually active young women.
- Staphylococcus aureus: Rare, but can occur, especially in the context of bacteremia or intravenous drug use.
3. Less Common Organisms
- Serratia marcescens: Typically associated with nosocomial infections.
- Citrobacter species: Can cause infections, particularly in individuals with underlying urinary tract abnormalities.
4. Polymicrobial Infections
In some cases, particularly in complicated pyelonephritis or in patients with underlying conditions, infections may be caused by multiple organisms simultaneously.
Risk Factors influencing causative organisms: Factors like age, sex, underlying medical conditions (diabetes, immunosuppression), urinary tract obstruction, and recent antibiotic use can influence the specific organisms involved.
Conclusion
In conclusion, <em>Escherichia coli</em> remains the predominant causative agent of acute pyelonephritis, but a range of other Gram-negative and Gram-positive bacteria can also be responsible. Accurate identification of the causative organism through urine culture and sensitivity testing is crucial for guiding appropriate antibiotic therapy and preventing complications. The increasing prevalence of antibiotic resistance necessitates careful antimicrobial stewardship to ensure effective treatment of this common infection.
Answer Length
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