Gram positive

Diagnosis of Listeriosis

• Culture samples are used to diagnose Listeriosis, depending on symptoms:
  • Stool culture for gastroenteritis
  • Blood culture for bacteremia
  • Cerebrospinal fluid (CSF) culture for meningitis
  • Amniotic fluid culture for trans-placental infection
• Imaging studies like ultrasound or CT scan can identify liver abscesses

Treatment of Listeriosis

• Gastrointestinal Listeriosis: Supportive care (hydration, rest) is used
• Disseminated Listeriosis: Intravenous ampicillin combined with gentamicin is used
• Alternatives: Meropenem is used for those with contraindications to ampicillin (e.g., pregnant individuals, those allergic to ampicillin)

Clostridium Bacteria

• General characteristics:
  • Gram-positive, may appear Gram-negative in older cultures
  • Straight or curved rods, may appear singly, in pairs, or in chains
  • Spore former, with endospores
  • Motile, with peritrichous flagella (except C. ramosum and C. innocuum)
  • Non-encapsulated (except C. perfringens)
  • Obligate anaerobes, strict anaerobes
  • Catalase-negative
• Virulence factors:
  • Exotoxins, varied among species
  • C. perfringens has type A, B, C, D, E toxins

Clostridium difficile

• Growth and laboratory identification:
  • Gram-positive, appearing purple and rod-shaped under the microscope
• Colonization and infection:
  • Fecal-oral route, typically acquired through ingestion of bacteria from fecal matter
  • Asymptomatic carriers, about 5% of the population
  • Disturbance of gut flora, allowing C. difficile overgrowth
• Pathogenic mechanism:
  • Toxin production, main pathogenic mechanism
  • Toxin A (TCDA), a potent enterotoxin
  • Toxin B (TCDB), a cytotoxin
• Symptoms and complications:
  • Diarrhea, abdominal pain, and high fever
  • Severe complications, such as toxic megacolon, intestinal rupture, septic shock, and death if untreated

Foodborne Illness

• Common cause, often called the "cafeteria germ"
• Contamination, spores can contaminate food left out for a while
• Toxin production, produces Clostridium perfringens enterotoxin (CPE) within 24 hours of colonization
• Heat sensitivity, CPE is heat-labile and can be inactivated by cooking at 72°C or above
• Symptoms, abdominal cramping, watery diarrhea, and vomiting
• Symptoms typically improve within a day without the need for antibiotics, hydration is the primary treatment

Wound Infections

• Introduction to wounds, can infect wounds made by dirty, sharp objects in contact with soil
• Myonecrosis, causes clostridial myonecrosis (gas gangrene) via Clostridium perfringens alpha-toxin (CPAT)
• Symptoms, extreme pain, swelling, thin watery pus, blood-filled bullae, and crepitus (crackling sound of gas in tissue)
• Pathogenesis and symptoms of myonecrosis:
  • Cell death, causes necrosis (uncontrolled cell death)
  • Progression, rapidly progresses to fever, tachycardia, hypotension, shock, and potentially death within hours if untreated

This quiz covers the diagnosis and treatment of Listeriosis, including culture samples and imaging studies, as well as treatment options for gastrointestinal and disseminated Listeriosis.