Proteus vulgaris / Proteus penneri
Gram-negative bacilli
Identification & Growth
Identification
- Urease-positive, H2S-positive, phenylalanine deaminase-positive
- Indole-positive (differs from P. mirabilis, which is indole-negative)
Growth Conditions
- Blood agar with swarming; MacConkey agar lactose-negative, 35–37 °C, 24 h
Clinical Significance
- Complicated UTI, wound infection and struvite stones
Intrinsic Resistance
- Chromosomal beta-lactamase: ampicillin, amoxicillin-clavulanate and cefuroxime should not be reported
- Resistant to colistin, tigecycline, nitrofurantoin and tetracyclines (EUCAST Expected Resistant Phenotypes v1.2)
Bench Alerts
- Swarming can obscure another colony on the plate — subculture to isolate
- Never report colistin as an option
Clinical Notes
Clinical presentations
- Urinary tract infections, often complicated, associated with stone formation due to urease production.
- Bacteremia and wound infections can occur in hospitalized patients, especially with long-term urinary catheters.
- Healthcare-associated intra-abdominal infections and pneumonia are less common but described.
Specimens and collection
- Urine culture with colony counts is essential, considering swarming that may hinder reading on nonselective agar.
- Blood cultures should be drawn before starting empiric antibiotics in patients with suspected urosepsis.
- Surgically removed urinary calculi can be cultured to identify embedded urease-producing bacteria.
Epidemiology and at-risk populations
- Associated with complicated urinary infections in patients with structural urinary tract abnormalities or catheters.
- More common in healthcare-associated infections than Proteus mirabilis, which predominates in the community.
- Patients with recurrent struvite stones should be investigated for persistent infection by urease-producing organisms.
Resistance and therapeutic implications
- Shows intrinsic resistance to nitrofurantoin and to colistin/polymyxins, limiting oral therapeutic options for UTI.
- Extended-spectrum beta-lactamase production is reported with increasing frequency, requiring individualized susceptibility testing.
- Catheter removal or exchange and stone treatment are essential for eradication, as the organism persists within biofilm.
Bench and reporting notes
- Swarming phenomenon on blood agar can obscure mixed colonies, requiring subculture on MacConkey agar for isolation.
- Strongly positive urease test within hours aids presumptive screening for Proteus/Providencia/Morganella.
- Differentiation from P. mirabilis is based on positive indole production in P. vulgaris/penneri versus indole-negative P. mirabilis.
Sources
Educational decision-support content. It does not replace laboratory validation, current guidelines or review by the responsible professional.
FAQ: Frequently Asked Questions
How to identify Proteus vulgaris / Proteus penneri in the lab?
Proteus vulgaris / Proteus penneri is identified through urease-positive, h2s-positive, phenylalanine deaminase-positive, indole-positive (differs from p. mirabilis, which is indole-negative).
What are the intrinsic resistances of Proteus vulgaris / Proteus penneri?
This organism is naturally resistant to chromosomal beta-lactamase: ampicillin, amoxicillin-clavulanate and cefuroxime should not be reported, resistant to colistin, tigecycline, nitrofurantoin and tetracyclines (eucast expected resistant phenotypes v1.2). These drugs should not be reported as susceptible.
Where is Proteus vulgaris / Proteus penneri commonly found?
It is typically associated with complicated uti, wound infection and struvite stones.
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