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"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"
]
} |