Gram Negative Bacterial Infections Flashcards
Clinically Important Gram Negative Cocci
- Neisseria meningitidis (meningococcus)
- Neisseria gonorrhea
- Moraxella catarrhalis
*primary human pathogens
whatever this means
Neisseria species
Classification of Neisseria
Gram Negative diplococci
“kissing kidney beans”
Outer membrane characteristics of all Neisseria
Lipooligosaccharide (LOS) and *not LPS
–>Lipid A endotoxin is connected to a SHORTER chain than LPS’s O antigen
Leading cause of meningitis in 2-18 year olds
N. meningitidis (meningococcus)
Define meningococcemia
sepsis + meningitis
Route o infection of N. meningitidis
Respiratory
who is at greatest risk for N meningitidis
military personnel and dorm residents are susceptible to outbreaks
*vaccines are available but do not cover all serotypes
Key virulence factor for N meningitidis
- polysaccharide capsule
2. Endotoxin (lipid A of LOS)
Mode of infection for N. gonorrhea (gonococcus)
Sexually-transmitted
*second to only chlamydia for reported bacterial infections
Prominent diseases associated with N. gonorrhea
- purulent urethritis
- pelvic inflammatory disease
- disseminated infection
- frequently occurs in conjunction with chlamydia
* clinical note,during pelvic exams you often swab for “GC/Chlamydia”= Gonococcus/Chlamydia
Virulence factors of N. gonorrhea
- pili (attachment, antiphagocytic, and antigenic variation caa lead to over 100 serotypes)
- Iga Protease
Gram Negative rods related to the GI/GU tract
- Escherichia coli
- Salmonella
- Shigella
- Campylobacter jejjuni
- Vibrio cholera
- Helicobacter pylori
- Bacteroides
8.Pseudomonas aeruginosa - Klebseilla pneumoniae
10.
Gram negative rod prevalence in colon and feces
bacteroides (obligate anaerobes) are most prevalent and second is E. coli
Unique metabolic features of Gram Negative rods
- Facultative anaerobes that can ferment glucose
2. some can ferment lactose
Normal Flora of the colon
E. coli
Prominent diseases caused by E. coli
- UTI
- Neonatal meningitis
- Sepsis
- diarrheal disease
Virulence factor of E. coli leading to UTI’s
P-type pilus allows for adherence to upper urinary tract
Virulence factor of E. coli leading to neonatal meningitis
K1 capsule, LPS
Virulence factor of E. coli leading to Sepsis (aka disseminated intravascular coagulation)
Capsule formation, LPS (lipid A endotoxin)
Unique characteristics of E. coli induced diarrheal disease
- Normal flora E. coli CANNOT CAUSE ENTERIC DISEASE
2. acquired PAI’s (pathogenicity islands) determine the type of diarrhea
Type of diarrhea
- Traveler’s diarrhea (ETEC=enterotoxogenic E. coli)
2. Enterohemorrhagic diarrhea (EHEC O157: H7)
ETEC characters
- contracted thru poor sanitation
2. Presents as watery diarrhea as the result of two exotoxins ( an AB toxin)–> acts similar to cholera
EHEC characters
- contracted thru consumption of uncooked ground beef
- Shiga Toxin encoded on lysogenic phage (an AB toxin that inhibits protein synthesis–> produces inflammatory (bloody) diarrhea
other key virulence factors of EHEC
- type III secretion system encoded on a PAI
2. Hemolytic Uremic Syndrome (usually in the very young) where SHIGA toxin causes anemia and renal failure
What Type of pathogen is Salmonella
Frank Pathogen (its presents constitutes having the disease)
Prominent diseases associated with salmonella
- enterocolitis (salmonellosis)
* caused by Salmonella enteriditis or Salmonella typhimurium
top cause of food poisoning
salmonella from contaminated food, especially poultry and eggs
Key virulence factor of salmonella
- type III secretion system
2. ability to kill macrophages
Typhoid (enteric) fever causing pathogen
S. Typhi
*associated with wars and abject poverty
transmission of S. typhi
human to human only
Virulence factors of S. Typhi
- Vi antigen–> inhibits phagocytosis by neutrophils and baulity to replicate in macrophages
Means by which S. typhi infect host
- begins in GI tract
- quickly disseminates due to survival in macrophages
- Eventually reaches RES
- death can occur by hemorrhage at ruptured peyers patches
Shigella causes
Bloody diarrhea (dysentery)
Reservoir for Shigella transmission
humans only, very low dose needed for infection
*fecal-oral route most common in small children
two forms of Shigella
- S. sonnei (most common form in US)
2. S. dysenteria (worldwide)–> more severe symptoms
Virulence factor for shigella
Phage encoded SHIGA toxin
define microerophile
a microorganism that requires oxygen to survive, but requires environments containing lower levels of oxygen than are present in the atmosphere
H. Pylori and Campylobacter
Most common bacterial GI infection in developed countries
Campylobacter jejuni
ex of a microaerophile
C. jejuni
*s shaped curved rods
Source of C. jejuni
undercooked poultry, beef and unpasteurized milk
Symptoms of C. jejuni
watery diarrhea that progresses to inflammatory (bloody) diarrhea
What shape are Vibrio species?
curved rods
Vibrio cholera causes _______ which results from_____?
- Cholera
2. shit-tastic water and shit-tastic food (literally)
Geographical distribution of Cholera
tropical strains–> posses O1 and O139 strains (most virulent)
Virulence factor of Cholera
- Cholera toxin (A-B exotoxin) derived from lysogenic phage
2. AB toxin ADP ribosylates G proteins–> leading to release of electrolyts and water from enterocytes
V. parahemolyticus causes_____ from______?
watery diarrhea
from
consumption of poopy shellfish
Shape of H. Pylori
curved rods
Disease caused by H. pylori
GI ulcer
Key virulence factor for H. pylori
- urease which turns urea into ammonia and CO2
- -> reduces stomach acidity of the stomach making it more neutral) - TWO TOXINS ARE INTRODUCED TO THE CELL VIA TYPE III SECRETION SYSTEM
chronic ulceration by H. Pylori can lead to?
MALT B-cell tumors
Key characteristics of Bacteroides
- obligate anaerobes
2. predominant species of colon
When bacteroides escape GI tract due to sx. trauma they cause
intra-abdominal abscesses
*many H. pylori infections are mixed with another microbes that requires O2
Key Virulence Factors for H. Pylori
- polysaccharide capsule
2. enzymes that destroy tissue (collagenase and lipase)
Characters of Pseudomonas aeruginosa
- obliate anaerobe
- found mostly in soil and water
- carried by 10% of population in colon but causes extra-GI disease
Prominent disease of P. aeruginosa
- opportunistic pathogen that is multi-drug resistant
1. skin infection of burn pt.’s
2. pulmonary infection of CF pt.’s
3. nosocomial pneumonia associated with ventialtorse
4. sepsis
Key virulence factors of P. aeruginosa
- LPS endotoxin
- Numerous degradative enzymes (elastace and proteases)
- Exotoxin A: Ab toxin similar to diphtheria toxin–>tissue necrosis
- pyocyanin–> blue enzyme that damages lung tisseue
- Type III secretion system
Where would you pick up Klibseilla pneumoniae
GI tract, Soil, water
Opportunistic infections cauased by K. pneumoniae
- nosocomial pneumonia
- aspiration penumonia
- bloody sputum called “currant jelly”
Key virulence factor of K. pneumoniae
thick polysaccharide capsule–> “goopy colonies” on agar plates
KPC
Carbapenem resistant K penumoniae–> resistant to almost all antibiotics
Major resistance factor more prevalent in Gram negative species than gram positive
Plasmid mediated antibiotic resistance
90% of acute diarrheas are caused by
viruses
persistent diarrhea is caused often by
parasites
Gram Negative rods related to the Respiratory tract
- Haemophilus influenzae
- Bordatella pertussis
- Legionella pneumophila
H. influenzae characteristics
- coccobacillus ???
- human reservoir
- most infection occur in the very young
Prominent diseases caused by H. influenzae
- meningitis–> now less common due to capsular vaccine
- Otitis media and sinusitis
- ->second only to S. penumoniae - almost exclusively the cause of epiglottitis in children
- pneumonia in the elderly
Key virulence factor of H. influenzae
Type b capsule
Feature of Bordatella pertussis
encapsulated coccobacillus
human reservoir
B. pertussis causes
whooping cough (tracheo-bronchitis with severe cough)
Key virulence factor of B. pertussis
- pertussis toxin–> AB toxin (acts similar to cholera toxin= Ribosylation of G proteins)
- cytotoxin-> fragment of cell wall that kills cilia in lungs
Why is pertussis rare disease in US
- acellular vaccine that contains altered pertussis toxin
* part ot DTap, TdaP
Characteristics of Legionella pneumophila
- water-born pathogen
2. community and hospital acquired atypical pneumonia
Virulence factor for L. pneumophila
LPS