{ "schema_version": "1.0", "level": "genus", "genus": "Cronobacter", "overview": { "short": "Cronobacter species are Gram-negative, facultatively anaerobic Enterobacterales that are opportunistic pathogens, best known for association with powdered infant formula contamination and invasive neonatal infections.", "clinical_context": "Can cause neonatal meningitis, sepsis, and necrotizing enterocolitis; also opportunistic infections in immunocompromised adults." }, "expected_fields": { "Gram Stain": "Negative", "Shape": "Rods", "Motility": "Positive", "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": "6//45", "Catalase": "Positive", "Oxidase": "Negative", "Indole": "Negative", "Urease": "Variable", "Citrate": "Positive", "Methyl Red": "Variable", "VP": "Positive", "H2S": "Negative", "DNase": "Negative", "ONPG": "Positive", "Coagulase": "Negative", "Gelatin Hydrolysis": "Variable", "Esculin Hydrolysis": "Variable", "Nitrate Reduction": "Positive", "NaCl Tolerant (>=6%)": "Negative", "Lipase Test": "Negative", "Lysine Decarboxylase": "Positive", "Ornithine Decarboxylase": "Variable", "Ornitihine Decarboxylase": "Variable", "Arginine dihydrolase": "Negative", "Glucose Fermentation": "Positive", "Lactose Fermentation": "Variable", "Sucrose Fermentation": "Positive", "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 variable or delayed; some strains appear weakly lactose-positive on MacConkey Agar.", "Motility": "Typically motile with peritrichous flagella, but some isolates may appear weakly motile depending on conditions.", "Growth Temperature": "Many isolates grow at lower temperatures than typical Enterobacterales; growth at ~6–10°C is reported for some strains and may support food-associated persistence." }, "key_differentiators": [ { "field": "ONPG", "expected": "Positive", "distinguishes_from": [ "Salmonella", "Shigella" ], "notes": "ONPG positivity supports a lactose-delayed/β-galactosidase-positive Enterobacterales rather than classic ONPG-negative genera." }, { "field": "Oxidase", "expected": "Negative", "distinguishes_from": [ "Aeromonas", "Vibrio" ], "notes": "Oxidase negativity supports Enterobacterales and helps exclude oxidase-positive Gram-negative rods." }, { "field": "Citrate", "expected": "Positive", "distinguishes_from": [ "Escherichia" ], "notes": "Citrate positivity supports Cronobacter/Enterobacter-like profiles rather than typical E. coli." } ], "common_confusions": [ { "genus": "Enterobacter", "reason": "Strong overlap in citrate/VP positivity and broad sugar fermentation patterns within Enterobacterales." }, { "genus": "Klebsiella", "reason": "Some isolates can appear lactose-positive and mucoid, overlapping with Klebsiella phenotypes." }, { "genus": "Citrobacter", "reason": "Citrate positivity and variable sugar reactions can overlap; species-level resolution often requires panels or MALDI-TOF." } ], "when_to_question_identification": [ "Oxidase positivity argues against Cronobacter (suggests Aeromonas/Vibrio/Pseudomonas-type organisms).", "H2S production argues against Cronobacter and suggests Salmonella/Citrobacter freundii complex possibilities.", "Non-motile isolate with strong capsule and consistent lactose positivity may suggest Klebsiella." ], "recommended_next_tests": [ { "test": "API 20E", "reason": "Useful Enterobacterales biochemical panel to support genus/species identification.", "api_kit": "API 20E" }, { "test": "MALDI-TOF MS", "reason": "Rapid and reliable identification within Enterobacterales when biochemical overlap is high.", "api_kit": "Not applicable" }, { "test": "Chromogenic Cronobacter medium (if available)", "reason": "Selective/differential support for Cronobacter from food/infant formula contexts.", "api_kit": "Not applicable" } ], "supported_species": [ "sakazakii", "malonaticus", "turicensis" ] }