Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
31 Cards in this Set
- Front
- Back
|
Enterics
|
Found as part of normal intestinal flora BUT can also
cause disease • 4 Major Groups: Enterobacteriaceae (Salmonellae, Shigellae, E. coli ), Vibrionaceae (Vibrio, Campylobacter) Pseudomonadaceae (Pseudomonas), Bacterioidaceae • Organisms are divided into groups based on biochemical and antigenic properties |
|
|
Biochemical
Classifications of enterics |
Ability to ferment lactose
• EMB Media: • Lactose fermentors are dark purple/black • Inhibits Gram positive bacteria • MacConkey Media: • Lactose fermentors are pink-purple • Inhibits Gram positive bacteria ?? What type of media are these ?? SELECTIVE/DIFFERENTIAL |
|
|
Biochemical
Classifications (production of what chemicals) |
H2S production
• Hydrolysis of urea • Liquefy gelatin • Decarboxylation of amino acids |
|
|
Classification Using Surface
Antigens |
Variable O-antigen: outermost layer of LPS
• Changes between enterics • K-antigen: covers the O-antigen • H-antigen: flagellar sub-unit • Only in motile bacteria |
|
|
Diseases Caused by Enterics
|
Cause diarrhoea with various complications and other
infections |
|
|
1) Diarrhea-with/without systemic invasion
|
• Bacteria bind intestinal cells but do not enter
• EXOTOXIN release causes diarrhoea; ENTEROTOXIN causes fluid/electrolyte loss • Watery diarrhoea, NO FEVER • ETEC and Vibrio cholera |
|
|
2) Diarrhea with intestinal cell invasion
|
• Bacterial virulence factors allow binding and invasion of cells
• Toxin release destroys cells > bloody stools • Fever response • EIEC, Shigella, Salmonella enteriditis, VTEC |
|
|
3) Diarrhea with invasion of lymph nodes and bloodstream
|
• Abdominal pain with diarrhoea containing white and red cells
• Fever, headache, increased white cell counts • Salmonella Typhi, Yersinia enterocolitica, Campylobacter jejeuni |
|
|
Other Enteric Infections
|
• Urinary tract infects, pneumonia, bacteremia and sepsis
• Nosocomial infections by: E. coli, Klebsiella pneumoniae, Proteus mirabilis, Enterobacter, Serratia, Pseudomonas aeruginosa • Pseudomonas aeruginosa: opportunistic pathogen, often infects burn patients and can disseminate through body into CNS |
|
|
Salmonellae
|
• Member of Enterobacteriaceae family
• Unable to ferment lactose • All have animal reservoirs EXCEPT S. enterica serovar Typhi> Humans |
|
|
Two species of salmonellae
|
S. enterica and S. bongori
Enterocolitis (tummy problems): – S. enterica serovar Enteritidis – S. enterica serovar Typhimurium • Enteric fever: – S. enterica serovar Typhi – S. enterica serovar Paratyphi • Types of infections in humans: enterocolitis, enteric fever, opportunistic infections, septicemia and osteomyelitis |
|
|
Enterocolitis pathogenesis depends on:
|
• Pathogenesis depends on:
• Dose of ingested organism (min 10^5) • Immune status of host • Virulence of strain • Incubation time: 6-48h; multiplication in small intestine |
|
|
Enterocolitis symptoms
|
• Symptoms
• Nausea, vomiting, profuse diarrhoea, abdominal pain • Fever, chills, headache, myalgia • 2-3 years recovery • Septicaemia Rare • Use stool culture for lab diagnosis |
|
|
Enterocolitis transmission
|
• Ingestion of contaminated food
• Poultry, eggs, meat and milk • Person to person spread • Most cases occur at home • Under-reported and undiagnosed • Antibiotics NOT RECOMMENDED WHY? |
|
|
Enteric Fever
|
S. enterica serovar Typhi = typhoid fever
• S. enterica serotypes Paratyphi A, Schottmuelleri, Hirschfeldii= paratyphoid fever (milder) |
|
|
enteric fever facts
|
• Enteric fever: generalized infection; bacterial
multiplication in lymphoid tissue • Necrosis of intestinal lymphoid tissue ulceration, haemorrhage, perforation • Untreated: 10% mortality • Convalescent carriers: excrete bacteria for 3 months • Chronic carriers (1-2%): excrete bacteria for at least 6 months, sometimes life long |
|
|
Enteric Fever diagnosis
|
Diagnosis: Isolation of bacteria from blood (1st week)
Stool and urine (2nd-3rd week) • Infective dose is 10^6 organisms • Sources are contaminated drinking water, shellfish, milk and milk products • Clean handling of food, water treatment and safe sewage disposal are essential • Vaccine available, but only effective against small bacterial load |
|
|
Escherichia coli
|
Enterobacteriaceae group
Most numerous aerobic bacteria of normal gut flora • Lactose fermenting • Pathogenic to other parts of the body • responsible for 85% of bacteriuria |
|
|
e. coli = Gastroenteritis
|
Enterotoxigenic E. coli
• Infant diarrhoea (developing countries) • Traveller’s diarrhoea • Enterotoxins • Enteroinvasive E. coli • Symptoms similar to shigellosis Enteropathogenic E. coli • older name for some serotypes causing infant diarrhoea • E. coli 0157:H7 • Haemorrhagic colitis • Hamburger disease • Proper handling of food, safe preparation and proper cooking practices are essential to prevent illness • E. coli is also implicated in neonatal meningitis and nosocomial urinary and wound infections |
|
|
Shigellae (remember shigellae card number two is at the end)
|
•Enterobacteriaceae
Cause acute diarrhoea with mucus, pus and blood • Generally non-lactose fermentors • Dose of 10^5infects 25% of people, 10^9 infects 95% |
|
|
Vibrio cholerae•
|
• Vibrionaceae
Causes cholera: acute gastrointestinal illness • Profuse watery diarrhoea, cramps and vomiting • Enterotoxin binds cells in small intestine • Cells secrete chlorides, decrease in Na+ absorption • Water accumulates in gut =watery diarrhoea • Can lead to severe dehydration and death if untreated • Endemic in South East Asia and parts of Africa • Lack of clean drinking water! • Mainly water-borne • Massive (10-15 litres per day) loss |
|
|
Campylobacter
|
Vibrionaceae
C. jejuni and C. coli • Major cause of human enteritis • Normal flora in birds and domestic animals • Some strains invasive, others toxigenic • Symptoms: fever, abdominal pain, bloody diarrhoea • Maybe one cause of traveller’s diarrhoea |
|
|
Pseudomonas
|
Pseudomonadaceae
Opportunistic pathogen • Found in many moist habitats and water • Source of infection can be humidifiers etc. • Treatment is difficult because all Pseudomonas sp. are resistant to many antibiotics!!!! |
|
|
Pseudomonas aeruginosa
|
• Respiratory pathogen in cystic fibrosis
patients • Infections in lesions of burn patients |
|
|
Pseudomonas cepacia
|
Common contaminant of saline solutions and
water • Able to multiply in low nutrient environment • Respiratory pathogen of cysitic fibrosis patients |
|
|
Haemophilus influenzae
|
Part of normal nasopharyngeal flora in many adults and
children • Causes invasive infections of young children • Meningitis, pneumonia, joint infections • Development of vaccine, now used routinely, decreased the number of cases in Canada • Can cause increased bronchial inflammation in patients already having chronic bronchitis |
|
|
Enterobacter spp.
|
Can cause nosocomial infections
• Wound infections, pneumonia, bacteremia • E. sakazakii linked to infant illness from powdered infant formula |
|
|
Helicobacter pylori
|
• Microaerophillic, spiral bacilli
• Most common cause of stomach ulcers • In the past, cause was thought to be stress and diet • 1982-Dr.Robin Warren and Dr. Barry Marshall discovered link between H. pylori and ulcers • Medical community slow to accept their theory (1994- National Institute of Health Conference concludes strong association between ulcers and H. pylori) • Urease: protection form low pH • Triple therapy treatment: antibiotics and H+ pump inhibitors |
|
|
Bordetella pertussis
|
• Whooping cough *VIOLENT COUGH*
• 4 Virulence Factors • Pertussis toxin (A-B) • Extra cytoplasmic adenylate cyclase (weakens host defense) • Filamentous hemagglutinin (bronchial attachment and exotoxoin release) • Tracheal cytotoxin (destroys ciliated cells poor clearance of mucous and bacteria) • Prevention: vaccination with heat-killed organism |
|
|
Legionella pneumophila
|
• Causes Legionnaires disease
• Opportunistic pathogen • May cause severe pneumonia • Grows in water and is found in shower heads, water tanks, air cooling/heating tanks • Exposure is by aerosol and there is NO person-to-person transmission |
|
|
two types of shigellae and their symptoms
|
• Shigella sonnei Europe and North America
• S. dysenteriae: • Tropics • SEVERE illness: watery diarrhoea, cramps, fever • Infection from SMALL numbers of organism • Most commonly seen in children; poor sanitation and crowding • Prevention by safe handling of food, treatment of water, safe disposal of sewage • NO VACCINE |
