Anaerobic Bacterial Infections

What are some facultative anaerobes

Salmonella spp; vibrio spp; aeromonas spp

What are facultative anaerobes commonly associated with

Foodborne disease

What is clostridium spp.

Found in soil or animal/human intestinal tract; motile and peritrichous flagella; anaerobes are aerotolerant; form endospores

What do spores do

Survival mechanism

What samples are used for clostridium botulinum diag

Food, stool or intestinal content

What disease is caused by clostridium botulinum

Botulism

What does C botulinum look like

Gram positive; pleomorphic rod, oval; sub terminal spore and motile

What samples are used for C. tetani diag

Soil and animal feces

What disease is caused by C. tetani

Stiffness in muscle

What does C tetani look like

Gram positive; long thin rods; terminal spores, motile

What samples are used for clostridium perfringens diag

Wound swabs, necrotic tissue, muscle fragment, pus, stool and food

What disease is caused by clostridium perfringens

Food poisoning, tissue necrosis, gas gangrene

What does C. perfringens look like

Gram positive; pleomorphic rods, subterminal spores and NON-motile

What samples are used for C. difficile

Stool

What disease is caused by C. difficile

Diarrhea

What does C. difficile look like

Gram positive; long thin rods, large oval; sub-terminal spores and motile

What does the botulinum toxin do

Blocks nerve function and can cause paralysis

What are the toxins found in C. botulinum

A-G; A and B found in many foods, E in fish, D in animal products

What is cause of infant botulism

Honey; spores enter infant and germinate in GI tract and get absorbed in the bloodstream

Botulism clinical findings

Symptoms after 18-24 hours; visual disturbance, inability to swallow and speech difficulty

What are the toxins in C. tetani

Tetanolysin and tetanospasmin

What is the the function of tetanospasmin

Degrade synaptobrevin and prevents muscle relaxation

Pathogenesis of C tetani

Not invasive; strictly localized

Clinical finding of C tetani

4-5 days to many week incubation; tonic contraction of voluntary muscle; lockjaw

What toxins in C. perfringens

Invasive; enterotoxin that causes hypersecretion in jejunum and ileum, loss of fluid and electrolytes in diarrhea

Pathogenesis of C. perfringens

Spores reach tissue and germinate and produce gas; secretion of necrotizing toxin and hyaluronidase spread infection; tissue necrosis

Clinical findings of C. perfringens

1-3 days spread in contaminated wounds; food poisoning if LARGE amounts are consumed; onset of diarrhea WITHOUT vomiting or fever in 7-30 hours lasting 1-2 days

What is C. difficile

Spread by spores; broad spectrum reduce normal flora can cause C. difficile infection

What does pseudomembranous colitis

Diagnosed by detection of c. difficile in stool; plaque or microabcess in bowel; watery/bloody diarrhea

What is antibiotic associated diarrhea

Antibiotics too frequently cause mild diarrhea

What is bacteroides fragilis

Gram negative anaerobes; pleomorphic as either rods or coccobacilli; opportunistic; ferment carbs

Virulence of bacteroides fragilis

Fimbriae and LPS adhere to host tissue; superoxide dismutase and catalase + capsule + conjugative transposons protect against immune response; hyaluronidase + enterotoxin + neuraminidase destroy hose tissue

Pathogenesis of bacteroides fragilis

Capsule causing abscess; cause disease mostly when it escapes small intestine; associated with pelvic inflammatory disease and ovarian abscesses

what is the clinical disease of bacteroides fragilis

Gastroenteritis for children, skin and soft tissue infection, gas gangrene, bacteremia

What is salmonella spp

gram negative facultative anaerobes; most don’t ferment lactose or sucrose, ferment glucose and produce H2S; resistant to some chemicals that inhibit other enteric bacteria; pathogenic when ingested; fecal oral route

What classifies salmonella spp

O antigen and H antigen combination

Typhoidal salmonella is characterized by what

Typhoid fever and paratyphoid fever

Non-Typhoidal salmonella is characterized by what

Gastroenteritis

Antigenic structure of salmonella spp

O (cell wall) antigens; Vi antigens in 3 serovars; H antigen

What are the 3 main types of disease caused by salmonella spp

Enteric fever by S. typhi; bacteremia by S. choleraesuis; food poisoning by s. typhimurium and enteritidis

What is enterocolitis

Most common salmonella manifestation; caused by eating uncooked/raw meat, EGGS; infection in SMALL intestine lining

Signs of enterocolitis

8-48 hour after ingesting there is nausea, headache, vomiting with few leukocytes in stool; salmonellosis will recover WITHOUT specific treatment; negative blood culture but positive stool

Bacteremia in salmonella characteristic

S. choleraesuis; common for immunocompromised hosts; high fever; postive blood culture

What causes enteric fevers

S. typhi, S paratyphi A, B, C

Enteric fever clinical finding

10-14 day incubation, fever, malaise, headache constipation, bradycardia and myalgia; enlarged spleen and liver

How is salmonella spread by salmonella carriers

S. typhi in stool that passes bacterium through food/water contamination

What test is used to detect O and H antigen

Widal test

What is used to identify cultures with known sera

Serological technique (Agglutination, Widal)

What is the treatment of invasive salmonella infection

Ampicillin, trimethoprim-sulfamethoxazole or third gen cephalosporin

What is vibrio spp

Gram negative rods, curves or comma shape; non-spore forming highly motile-single polar flagella; oxidase positive

What is antigenic structure of vibrio spp

H antigen and O antigen

what is V cholerae

Comma shaped, curved rod; grows well in TCBS sugar; rapidly killed by acid; oxidase positive

What is the enterotoxin in V cholerae

Heat labile; ganglioside GM1 is mucosal receptor for subunit B that allows subunit A into cell; subunit A increases cAMP and water and electrolytes are hypersecreted

Pathogenesis and pathology of V. cholerae

Cause acute diarrhea and dehydration; treat with oral rehydration therapy; NOT invasive; medication that decreases stomach acidity INCREASES infection risk

What are the clinical manifestation of v cholerae

50% are asymptomatic, 75% are from El Tor biotype; 12 hour-3 day incubation with nausea and vomiting with diarrhea and abdominal cramps; rice water like stool

What is aeromonas spp

gram negative, oxidase positive, facultative anaerobic, rod shaped; motile colony similar to enteric gram negative rod; beta hemolysis

Virulence factors of aeromonas spp

A. hydrophilia has ACT that causes tissue damage; more severe disease is common for alt and AST gene; form biofilm

What is the clinical infection of aeromonas spp

Gastroenteritis and wound infection (with/without bacteremia)

Gastroenteritis in aeromonas

12-72 hours after contraction symptoms show; diarrhea, vomiting and sometimes severe abdominal pain

Diarrhea in aeromonas

Watery, acute to chronic, has many presentation, aeromonas associated diarrhea occurs in summer

Cellulitis and wound infection in aeromonas

Cause mild to severe infection, pattern can be uncomplicated to necrotizing fascitis

Septicemia in aeromonas

GI symptoms (abdominal pain, nausea, vomiting, diarrhea), in older patients with severe hepatic disease