Week 12 Diseases & Pathogenesis

Food Poisoning Signs and Symptoms

Non-bloody diarrhea, vomiting, cramps, malaise; rapid onset, usually mild 

Food Poisoning Causative Organism

Staph. Aureus, Bacillus Cereus

Food Poisoning Pathogenesis

Ingestion of pre-formed bacterial toxins in food; symptoms due to toxins (intoxication) not bacterial growth in gut 

Food Poisoning Epidemiology

Toxins are heat and acid stable; high risk foods are those left in 20-60 C

Food Poisoning Treatment & Prevention

Usually self-limiting (<24 hrs): OTC medications for symptom relief, proper food handling and storage to prevent

Cholera Signs and Symptoms

Profuse watery diarrhea (rice-water stool), dehydration

Cholera Causitive Organism

Vibrio Cholerae (cholera toxin is key virulence factor)

Cholera Pathogenesis

Cholera toxin causes massive fluid secretion in intestines, leading to dehydration 

Cholera Epidemiology

Fecal-oral spread, pandeics documented worldwide

Cholera Treatment & Prevention

Supportive care, tetracycline in some cased, short-lived vaccine available,maintain hygiene and clean water 

Shigellosis (Bacterial Dysentery) Signs and Symptoms

Bloody diarrhea with mucus/pus, cramps, fever; some develop HUS

Causative Organism of Shigellosis

Shigella species (virulence: adhesions, invasins, shiga toxin)

Shigellosis Pathogenesis

Bacteria invade intestinal lining, producing Shiga Toxin, can lead to kidney failure, arthritis, death in severe cases 

Shigellosis Epidemiology

Fecal-oral route, contaminated food/water, fomites, can cause epidemics

Shigellosis Treatment & Prevention

Stool culture or PCR for diagnosis; supportive care; severe cases need broad-spectrum (azithromycin or ciprofloxacin) 

Salmonellosis Signs and Symptoms

Nausea, vomiting, cramps, diarrhea, rarely fatal

Typhoid Fever Signs and Symptoms

High fever, aches, nausea, lethargy, rash; 10% untreated fatality, complications can involve liver, gallbladder, blood, lymph 

Salmonellosis Causative Organism

Salmonella enterica serotypes: Enteritids/Typhimurium

Typhoid Fever Causative Organism

Salmonella enterica serotypes: Typhi/Paratyphi

Typhoid & Salmonellosis Pathogenesis

Bacteria tolerate stomach acid, toxins disrupt cellular activity

Typhoid Epidemiology

Contaminated food/water

Salmonellosis Epidemiology 

Undercooked poultry, reptiles, eggs rarely contaminated 

Salmonellosis Treatment & Prevention 

Self-limiting, oral-rehydration therapy, antibiotics such as ampicillin, fluoroquinolones are recommended in serious cases 

Typhoid Fever Treatment & prevention

Antibiotics (azithromycin, ceftriaxone), diagnosis via stool culture, hygiene is preventive

Traveler’s Diarrhea Signs and Symptoms

Watery Diarrhea, cramps malaise, low fever (ETEC); EIEC resembles shigellosis 

Causative Organisms of Traveler’s Diarrhea

Escherichia coli Enterotoxigenic (ETEC) or Enteroinvasive E.Coli (EIEC); virulence, adhesins, fimbriae, toxins

Traveler’s Diarrheaa Pathogenesis

Enterotoxins or invasion disrupt intestinal cells

Traveler’s Diarrhea Epidemiology

Fecal-oral, contaminated food and water

Traveler’s diarrhea treatment & prevention

Fluid/electrolyte replacement, antidiarrheals may prolong symptoms, antibiotics rarely needed for mild cases 

Enterohemorrhagic E. Coli (EHEC) Signs and Symptoms

Bloody diarrhea with severe cramps, usually no fever; risk of HUS and hemorrhagic colitis 

EHEC Causative Organism

E.Coli O167:H7

EHEC Pathogenesis

Shiga-like toxin damages intestinal lining; can lead to kidney failure

EHEC Epidemiology

found in cattle; transmitted via undercooked beef, contaminated produce

EHEC Treatment and Prevention

Supportive care, antibiotics can worsen HUS, hygiene and proper cooking of meat 

Campylobacter Diarrhea S&S

Gastroenteritis symptoms (diarrhea, cramps, fever), occasionally bacteremia, pancreatitis, hepatitis, associated with Gullain-Bare syndrome 

Campylobacter Diarrhea CO

Campylobacter Jejuni (adhesins, cytotoxins, endotoxins)

Campylobacter Diarrhea PG

Bacteria cause intestinal lesions and inflammation

Campylobacter Diarrhea ED

Contaminated poultry, fecal-oral

Campylobacter Diarrhea T&B

Usually self-limiting, proper hygiene after handling raw poultry, supportive care if needed

Botulism S&S

Foodborne: blurred visions, drooping eyelinds, difficulty swallowing, cramps, nausea, vomiting, constipation, possible diarrhea, progressive flaccid paralysis

Infant: failure to thrive, slower onset

Wound: slower onset than foodbourne

Botulism CO

Clostridium botulinum (produces one of seven neurotoxins)

Botulism PG

Toxin blocks acetylcholine release at neuromuscular junction → flaccid paralysis

Botulism ED

Rare, infant botulism most common; toxin heat-sensitive, strict anaerobe, honey can be source for infants 

Botulism T&P

Wash intestinal tract, administer botulism immune globulin, antibiotics if needed, prevent by destroying endospores in food and avoiding giving honey to infants 

C.Difficile S&S

Necorsis and ulceration of colon, pseudomembranous colitis in severe cases; perforation → septicemia, shock, death 

C. Diff CO

Clostridium Difficile

C.Diff PG

antibiotics disrupt normal gut flora → C. difficile overgrowth; toxins damage intestinal lining → inflammation 

C. Diff ED

Endospores spread easily, mostly nosocomial, any antibiotic can trigger, broad-spectrum most common

C. Diff T&P

Diagnose via toxin in stool, symptoms, history, treat with antimicrobials, fecal transplant to restore normal flora, avoid unnecessary antibiotics 

Tetanus S&S

localized or sytemic muscle spasms starting at wound or jaw, progressive tetanic paralysis, opisthotonos, inability to swallow or breathe

Tetanus CO

Clostridium Tetani (produces tetanus neurotoxin)

Tetanus PG

TeNT blocks GABA release → unregulated motor neuron activity → spastic paralysis 

Tetanus ED

Common soil bacterium; infects contaminated wounds; neonatal tetanus from umbilical corn in unsanitary conditions 

Tetanus T&P

Antibiotics, tetanus antitoxin, ventilation, vaccination, recovery prolonged due to permanent toxin, good wound care, boosters every 10 years 

Gas Gangrene (Clostridial Myonecrosiss) S&S

Rapidly spreading muscle necrosis; foul-smelling wound with gas bubbles; bluish-purple wound, brown necrotic tissue; edema; septic shock and organ failure 

Gas Gangrene CO

Clostridium Perfringens or other clostridia (produces a & b toxin)

Gas Gangrene PG

A-toxin destroys RBC membranes, blocks vessels, create anaerobic environment cuases edema

B-toxin damages vasculature, constricts dirty, deep wounds, can also cause foodborne illness depending on strain 

Gas Gangrene ED

common soil bacterium, infects dirty, deep wounds, can also cause foodborne illness depending on strain 

Gas Gangrene T&P

Diagnose by symptoms and culture, treat with antibiotics, surgical debridement, drainage, hyperbaric oxygen may help, severe cases require amputation 

Bacterial Meningitis S&S

Sudden high fever, severe headache, stiff neck, confusion, vomiting, photophobia, encephalitis may cause behavioral changes, coma, death; rapid onset 

Bacterial Meningitis CO

Neisseria meningitidis – rapid, deadly, petechial rash on palms

Streptococcus pneumoniae – most common

Haemophilus influenzae type b

Listeria monocytogenes – foodborne, at-risk populations

Streptococcus agalactiae – newborns only

Bacterial Meningitis PG

S. agalactiae acquired during birth

Listeria via contaminated food

Others via respiratory droplets

Bacterial Meningitis ED

S. pneumoniae colonizes throat of ~75% of humans

Not spread by casual contact

N. meningitidis can cause epidemics

Bacterial Meningitis T&P

Diagnosis via CSF culture: IV antibiotics; vaccines for S. pneumoniae, H. influenza type b, N. meningitidis, avoid high-risk foods 

Viral Meningitis S&S

fevere, severe headache, stiff neck, photophobia, nausea, vomiting, may include sore throat, chest pain, swollen parotid gland, skin rash 

Viral Meningitis CO

Small non-enveloped RNA viruses, mainly enteroviruses, mumps may also be possible 

Viral Meningitis PG

Infection of throat/intestine → viremia → meningeal infection; may also cause rash/chest pain 

Viral Meningitis ED

Environmentally stable; survives chlorinated water; transmitted fecal-oral or respiratory droplets 

Viral Meningitis T&P

supportive care;; handwashing; avoid crowded swimming pools; mumps vaccine available 

Rabies (Viral Encephalitis) S&S

Early: fever, fatigue, headache, muscle aches, sore throat, nausea, tingling/twitching at entry site (1–2 months post-exposure)

Late: encephalitis, agitation, confusion, hallucinations, seizures, hypersensitivity to light/touch, increased salivation, difficulty swallowing (hydrophobia), coma; ~50% die within 4 days of onset.

Rabies CO

Rabies virus (rhabdoviridae)

Rabies PG

Virus enters via saliva/bite → multiplies in muscle → travels via nerves in the CNS → replicates extensively; Negri bodies form in brain

Rabies ED

widespread in wild animals - 5,000 cases in animals/year in US, 0-4 human cases/year; long incubation period; bats main source of human cases

Rabies T&P

Immediate wound cleaning (soap/antiseptic); post-exposure prophylaxis:4-dose vaccine series at wound site and IM; no effective treatment once symptoms appear, only six survivors known 

Strep Throat S&S 

Sore throat, difficulty swallowing, red throat with pus patches and tiny hemorrhages, scarlet fever, fine red rash, strawberry tongue 

Strep Throat CO

Streptoccocus Pyogens (Group A strep, B Hemolytic)

Strepthroat PG

Virulence factors vary by strain; bacteria adhere to throat epithelium; immune response can lead to post-streptococcal complications

Strep Throat ED

Spread by direct/indirect contacts and droplets; common in children 

Strep Throat T&P

Diagnoses by rapid antigen test or cutlure; B-lactams effective, usually resolves within a week; treatment prevents transmission and complications 

Common Cold S&S

Incubation 1-4 days, runny nose, sneezing, tissue swelling, mild fever, sometimes sore throat 

Common Cold CO

rhinovurses, other viruses; non-enveloped, ssRNA picornaviruses

Common Cold PG

Virus infects respiratory epithelium → cillary motion stops → cell death → cytokine release → inflammation, nasal secretions, can spread to ears, sinuses, lower respiratory tract 

Common Cold ED

humans are only source, spread by droplets or contaminated surfaces, most contagious days 1-3, no line to cold weather; stress increases risk

COMMON COLD T&P

No proven treatment; symptomatic relief with analgesics/antihistamines; prevent via handwashing, avoid touching face, avoid contact with infected individuals 

Respiratory Syncytial Virus S&S

Runny nose, coughing, wheezing, difficulty breathing, possible fever croup in infants, dusky color indicates hypoxia 

RSV CO

Syncytial Virus (ssRNA paramyxovirus)

RSV PG

Infects respiratory epithelium → cell death → bronchioles plugged with sloughed cells/mucus → obstruction → wheezing; secondary infections common 

RSV ED

Late to fall spring; mild in healthy adults, severe in infants/elderly

RSV T&P

No effective antivirals; supportive care; prevent nosocomial spread via isolation; passive immunity via immune globulin or palivizumab; vaccine available for pregnant women and adults 60+.

Influenza (Flu) S&S

Fever, chills, body aches, headache, cold-like symptoms; can progress to pneumonia; severe strains can cause cytokine storm

Flu CO

Influenza Virus A (severe), B (moderate), and C (mild, rare)

Flu PG

Virus infects respiratory epithelium; antigenic shift/drift cause seasonal epidemics; immune response contributes to symptoms 

Flu ED

Seasonal spread via droplets, indirect contact, aerosols, global pandemics possible with antigenic shift 

Flu T&P

Diagnosed by symptoms or rapid antigen test; yearly vaccine, antivirals like oseltamivir shorten disease if given early 

Hantavirus Pulmonary Syndrome (HPS) S&S

2-4 week incubation; flu-like symptoms (shortness of breath, nausea, vomiting, diarrhea; progresses to acute respiratory distress, cardiac failure, shock 

HPS CO

Hantaviruses

HPS PG

Virus inhaled from dried rodent feces/urine; infects pulmonary epithelium→ vascular leakage, respiratory distress 

HPS ED

North America; deer mouse, cotton rat, white-footed mouse reservoirs, 36% case-fatality case 

HPS T&P

Supportive care (ventilation, oxygen); avoid contact with rodent droppings 

SARS Viruses (SARS-CoV-1, SARS-CoV-2, MERS-CoV) S&S

fever, chills, dry cough, shortness of breath, fatigue, aches, loss of taste/smell, nausea, vomiting, can cause acute respiratory distress, cytokine storm, multi-organ failure