Makindo Medical Notes

📖 About

• Member of the Enterobacteriaceae family: Gram-negative, non-lactose fermenting rods.
• Notable species: Serratia marcescens.
• Historically known for producing a distinctive red pigment (prodigiosin), sometimes seen in colonies.

🔬 Characteristics

• Gram-negative rods.
• Facultative anaerobes.
• Glucose fermenting.
• Oxidase-negative, catalase-positive.
• Reduce nitrates → nitrites.
• Non-lactose fermenters → pale colonies on MacConkey agar.
• Motile via peritrichous flagella.
• Often demonstrate intrinsic resistance to multiple antibiotics (Ampicillin, first-gen cephalosporins).

⚠️ Pathogenicity

• 💧 Urinary Tract Infections (UTIs): Often linked to indwelling catheters (CAUTIs); symptoms: dysuria, frequency, fever.
• 🫁 Respiratory Tract Infections: Ventilator-associated pneumonia (VAP); cough, fever, hypoxia.
• 🩸 Bacteraemia / Sepsis: Secondary to UTIs, VAP, or IV lines; features: fever, rigors, hypotension, confusion.
• 🩹 Wound & Burn Infections: Redness, swelling, pain, purulent discharge; problematic in surgical/ICU settings.
• ❤️ Endocarditis: Rare but serious; associated with IV drug use or prosthetic valves → fever, murmur, heart failure signs.
• 🧠 Meningitis: Rare; usually neonates or immunocompromised; fever, neck stiffness, altered mental status.

🎯 Risk Factors

• 🏥 Hospitalisation: Particularly in ICUs and surgical wards.
• 🛡️ Immunocompromise: HIV, neutropenia, chemotherapy, transplant patients.
• 🧴 Indwelling devices: Catheters, central venous lines, ventilators.
• 🔧 Recent surgery: Especially with prosthetic implants or long operative times.

🖥️ Imaging

• 🫁 Respiratory infection: CXR or CT chest.
• ❤️ Endocarditis: Echocardiography (TEE preferred).
• 🧾 Abscess / deep infection: Ultrasound or CT scan.

💊 Management (key points)

• Always guided by culture & sensitivity (multidrug resistance is common).
• Empiric options: carbapenems, aminoglycosides, or cefepime (depends on local resistance patterns).
• Device-associated infections → removal/replacement of catheter or line is essential.
• Supportive care: IV fluids, oxygen, source control.

⚠️ Exam pearl: Serratia marcescens is a classic cause of hospital-acquired UTIs, pneumonias, and device-related sepsis, notable for red pigment and multidrug resistance.