{ "schema_version": "1.0", "level": "genus", "genus": "Citrobacter", "overview": { "short": "Citrobacter species are Gram-negative, facultatively anaerobic rods within the Enterobacterales, commonly found in the intestinal tract and environment.", "clinical_context": "Associated with opportunistic infections including urinary tract, bloodstream, neonatal meningitis, and intra-abdominal infections." }, "expected_fields": { "Gram Stain": "Negative", "Shape": "Rods", "Motility": "Variable", "Capsule": "Variable", "Spore Formation": "Negative", "Haemolysis": "Negative", "Haemolysis Type": "None", "Media Grown On": [ "MacConkey Agar", "Blood Agar" ], "Colony Morphology": [ "Smooth", "Grey", "Moist" ], "Oxygen Requirement": "Facultative Anaerobe", "Growth Temperature": "10//45", "Catalase": "Positive", "Oxidase": "Negative", "Indole": "Variable", "Urease": "Variable", "Citrate": "Positive", "Methyl Red": "Positive", "VP": "Negative", "H2S": "Variable", "DNase": "Negative", "ONPG": "Positive", "Coagulase": "Negative", "Gelatin Hydrolysis": "Variable", "Esculin Hydrolysis": "Variable", "Nitrate Reduction": "Positive", "NaCl Tolerant (>=6%)": "Negative", "Lipase Test": "Negative", "Lysine Decarboxylase": "Variable", "Ornithine Decarboxylase": "Variable", "Ornitihine Decarboxylase": "Variable", "Arginine dihydrolase": "Negative", "Glucose Fermentation": "Positive", "Lactose Fermentation": "Variable", "Sucrose Fermentation": "Variable", "Maltose Fermentation": "Positive", "Mannitol Fermentation": "Variable", "Sorbitol Fermentation": "Variable", "Xylose Fermentation": "Positive", "Rhamnose Fermentation": "Variable", "Arabinose Fermentation": "Positive", "Raffinose Fermentation": "Variable", "Trehalose Fermentation": "Positive", "Inositol Fermentation": "Negative", "Gas Production": "Variable", "TSI Pattern": "A/A", "Colony Pattern": "Unknown", "Pigment": "None", "Motility Type": "Peritrichous" }, "field_notes": { "Lactose Fermentation": "Often delayed or variable on MacConkey Agar.", "H2S": "Some species produce H2S, which may cause confusion with Salmonella.", "Indole": "Indole reactions vary by species and are useful at the species level." }, "key_differentiators": [ { "field": "Methyl Red", "expected": "Positive", "distinguishes_from": ["Enterobacter", "Klebsiella"], "notes": "MR positivity helps separate Citrobacter from VP-positive Enterobacterales." }, { "field": "H2S", "expected": "Variable", "distinguishes_from": ["Escherichia"], "notes": "Possible H2S production differentiates Citrobacter from E. coli." }, { "field": "Lactose Fermentation", "expected": "Variable", "distinguishes_from": ["Escherichia"], "notes": "Delayed or absent lactose fermentation helps exclude E. coli." } ], "common_confusions": [ { "genus": "Salmonella", "reason": "Shared H2S production and Enterobacterales profile." }, { "genus": "Enterobacter", "reason": "Overlapping sugar fermentation and citrate positivity." } ], "when_to_question_identification": [ "Strong VP positivity suggests Enterobacter or Klebsiella.", "Consistent lactose fermentation suggests Escherichia.", "Absence of nitrate reduction argues against Citrobacter." ], "recommended_next_tests": [ { "test": "Indole test", "reason": "Critical for species-level differentiation." }, { "test": "H2S production assessment", "reason": "Helps separate Citrobacter from related genera." }, { "test": "API 20E", "reason": "Standard biochemical panel for Enterobacterales identification." }, { "test": "MALDI-TOF MS", "reason": "Provides rapid and reliable species-level identification." } ], "supported_species": [ "braakii", "freundii", "koseri" ] }