Gram Negative Bacteria Flashcards
Describe neisseria
Diplococci, gram negative
What are the virulence factors for neisseria meningitidis
- Capsule
- Endotoxin (LPS)
- IgA1 protease
- Extract iron from human cells
- Pili
High risk groups for neisseria meningitidis
- Infants aged 6 months to 2 years
- Army recruits
- College freshmen
Illness that causes petechial rash
Neisseria meningitidis
What are the 3 microorganisms that cause meningitis in babies under 3 months?
Listeria monocytogenes, e coli, group B strep
What are the organisms that cause meningitis in people older than 3 months
Neisseria meningitidis, haemophilus influenzae
What agar is used to grow Neisseria meningitis
Thayer Martin VCN- chocolate agar
Treatment for neisseria meningitis patient? Close contacts?
Penicillin G or ceftriaxone
Close contacts- rifampin or ciprofloxacin
Who should have the meningitis vaccine?
Certain high risk groups and during epidemics, serogroup B ages 10-25
Slow growing gram negative pathogens that cause endocarditis
HACEK group
Haemophilus influenzae
Actinobacillus species
Cardiobacterium species
Eikenella species
Kingella species
Describe moraxella catarrhalis
Gram negative diplococcis, Part of normal resp flora, causes otitis media in children, can cause respiratory infections and pneumo, exacerbates COPD, resistant to penicillin
What enterics ferment lactose
E. Coli, most enterobactericeae
What enterics do not ferment lactose
Salmonella, shigella, pseudomonas aeruginosa
Is e coli found outside of the intestine normally?
No
Describe Eosine methylene blue agar
Inhibits gram positive and lactose fermenters turn black, e coli turns metallic green
Describe macconkey agar
Inhibits gram positive bacteria and lactose fermenters turn pink/ purple
Antigens used to classify enterics
O antigen- outer layer LPS in membrane
K antigen- capsule (covers O antigen)
H antigen- flagella for mobile bacteria
Enterics that don’t invade cell but release exotoxins that causes watery diarrhea
Enterotoxogenic e coli and vibrio cholera
Enteroinvasive organisms
EHEC, shigella, salmonella enteritidis
What enterics can invade the lymph nodes and bloodstream?
Salmonella typhi, yersinia enterocolitica, campylobacter jejuni
What are examples of hospital acquired gram negative how can they be acquired?
E Coli
klebsiella pneumoniae
Proteus mirabilos
Enterobacte
serratia
pseudomonas aeruginosa
Invade Foley catheters, aspirate vomit, etc.
What are the main groups of enterics?
Enterobactericeae
Vibrionaceae
Bacteroidaceae
Psuedomonadacea
Example of bacteria that can ferment lactose
Escherichia coli
Examples of bacteria that cannot ferment lactose
Salmonella, shigella, pseudomonas aeruginosa
What are the biochemical classification methods for gram negative bacilli
Ability to ferment lactose and production of H2S
What agars are used to help classify enterics?
- EMB agar (Eosine methylene blue) - inhibit gram + growth and lactose fermenters become deep purple / black and e coli gets green sheen.
- Mackonkey agar - inhibit gram + a s lactose fermenters become pink purple color
Is E coli usually endogenous or exogenous?
Endogenous in the colon
3 surface antigens of enterics
1) o antigen
2) k antigen
3) H antigen
Describe the o atnigen
Part of enterics bacteria- outer most component of LPS, differs between the dif gram - bacteria
Describe K antigen
Capsule antigen (covers O antigen)
Describe H antigen
Makes up subunits of bacterial flagella. Only motile bacteria have this antigen.
Example of bacteria without h antigen
Shigella
Example of bacteria with h antigen
Salmonella- changes and protects from our antibodies
Describe non invasive enteric diarrhea
Bacteria bind to intestinal epithelial cells, but do not enter cell. Release exotoxins that cause watery diarrhea without systemic symptoms.
Examples of organisms that cause noninvasive enteric diarrhea
ETEC
Vibrio cholera
Describe pathogenesis of invasive enteric diarrhea
Bacteria with virulence factors that allow for binding and invasion of cell. Toxins released that kill cell. Leukocytes in stool and systemic symptoms + diarrhea.
Examples of enteroinvasive organisms
EIEC
Shigella
Salmonella enteritidis
Examples of enteric organisms that cause bacteriema
Salmonella typhi
Yersinia enterocolitica
Campylobacter jejuni
Two example situations when enterics normally part of our gut flora cause disease (hospital acquired gram negatives)
1) Foley catheter
2) patient aspirates vomit colonized with enterics
Examples hospital acquired gram negative organisms
E Coli
Klebsiella pneumoniae
Proteus mirabilis
Enterobacter
Serratia
Pseudomonas aeruginosa
What bacteria are in the family enterobactericeae?
E coli
Proteus mirabilis
Klebsiella pneumoniae
Enterobacter
Serratia
Shigella
Salmonella
Yersinia enterocolitica
What bacteria are in the family vibrionaceae?
Vibrio cholera
Vibrio parahaemolyticus
Campylobacter jejuni
Helicobacter pylori
What bacteria are in the family bacteroidaceae?
Bacteroides fragilis
Bacteroides melaninogenicus
Fusobacterium
How can normal gut flora e
Coli cause disease?
Obtain virulence factors through plasmid exchange, transduction, etc.
Virulence factors E coli can obtain
1) mucousal adherence and invasion factors
2) exotoxin production (heat liable and stable toxins, or shiga like toxin)
3) endotoxin : lipid A
4) iron binding ability
What diseases can E coli cause when virulence factors are present
1) diarrhea
2) UTI
3) neonatal meningitis
4) gram-negative sepsis
What diseases does enterotoxogenic E coli cause?
Traveler’s diarrhea
What virulence factors does ETEC have?
Colonization factor (pili to bind)
Exotoxins- heat liable toxin (LT) and heat stable toxin (ST) - causes water loss and stool to look like rice water (like cholera)
What virulence factors does Enterohemorrhagic E coli have?
-Colonization factor (pili to bind to cells)
-Shiga-like toxin (aka verotoxin) - causes intestinal epithelial cell death. Causes bloody diarrhea
Name for disease caused by EHEC
Hemorrhagic colitis
Disease and symptoms cause by E Coli O157:H7
Hemolytic uremic syndrome (HUS)
-anemia
-thrombocytopenia (decrease in platelets)
-renal failure
Describe the pathogenesis of enteroinvasive E coli
- virulence factors shared on plasmid with shigella
- invades epithelial cells and releases shiga- like toxin
-inflammatory response with fever and bloody diarrhea
Bladder infection
Cystitis
Kidney infection
Pylenophritis
Most common organism for utis
E coli
Symptoms of uti
Dysuria (burn)
Frequency
Feeling fullness of bladder
Number of colonies needed to dx uti
100,000
Most common organism for gram - sepsis for hospitalized patients
E coli, sepsis due to lipid A toxin
Enteric common cause of neonatal meningitis
E coli
Most common disease causing Proteus species
Proteus mirabilis
Describe Proteus mirabilis
1) motile
2) splits urea
Cross reactivity for proteus
Rickettsia
Infections that Proteus spp cause
UTI
HAI
Dx for proteus UTI
Alkaline pH since it splits urea
Describe klebsiella pneumonia
-encapsulated (k antigen), non motile
Second most common cause of gram negative sepsis
Klebsiella (first e coli)
Organism commonly associated with UTIs in hospitalized patients with Foley catheters
Klebsiella pneumoniae
Risk factors for klebsiella pneumoniae pneumonia
Hospitalization
Alcoholics
Describe clinical outcomes of klebsiella pneumoniae pneumonia
Bloody sputum (red currant jelly), destroys lung tissue, produces cavities, high mortality rate
Characteristic trait of pneumonia causes by klebsiella pneumoniae
Sputum that looks like red currant jelly
Describe enterobacter
Part of normal intestinal flora, highly motile
Concern for enterobacter
Antibiotic resistance due to ampC (beta lactamase). Resistant to ampicillin and early generation cephalosporin, increasingly later generation cephalosporin.
If unsure use carbepenem
What color are serratia colonies in culture?
Bright red
What diseases can serratia cause?
UTI
Wound infections
Pneumonia
What are the 4 species of shigella?
Shigella dysenteriae
Shigella flexneri
Shigella boydii
Shigella sonnei
Describe basics of shigella
Non-motile
Does not ferment lactose
Does not produce H2S
Hosts for shigella
Humans
Population at risk for dysentery
Pre school age
Nursing homes
Is shigella part of the normal intestinal flora?
No
How is shigella transmitted?
Water, hands
Pathogenesis of shigella
Invades intestinal epithelial cells, releases shiga toxin which kills cells, inflammatory response, systemic infection and colon ulcers
Diarrhea presentation from shigella
Bright red flecks of blood and pus
Describe basics of salmonella
Motile
Non lactose fermenter
Distinguishing virulence factor salmonella
Vi antigen- polysaccharide capsule- protects from antibodies
Two main groups of salmonella
Typhoidal - typhi and paratypho
Non-typhoidal- salmonella enteritidis…
How does salmonella differ from other enterics in terms of reservoirs?
Lives in GI tract of animals, transmitted through animal feces
What type of salmonella only can be found in humans?
Salmonella typhi
Is salmonella part of the normal intestinal flora?
No, salmonella like shigella is always pathogenic
What are the 4 disease states of salmonella?
Typhoid fever
Carrier state
Sepsis
Gastroenteritis
Salmonella typhi can only survive intracellularly, so it is a …
Facultative intracellular parasite
Pathogenesis of typhoid fever
Salmonella typhi invades intestinal cells, then invades regional lymph nodes and seeds in organ systems. Evades phagocytosis
Incubation period salmonella typhi
1-3 weeks
Characteristic symptoms Salmonella typhi
Fever
Rose spots on belly
Pain in lower right quadrant
Enlarged spleen
Empiric therapy when salmonella typhi suspected
Ciprofloxacin or ceftriaxone
When people become salmonella typhi carriers, where does the salmonella live?
Gallbladder
What species of salmonella can cause systemic infection and does not involve GI tract
Salmonella choleraesuis
Populations more susceptible to salmonella infections
Sickle cell anemia and no speen
Reason: neutrophils in the spleen opsonize and phagositize encapsulated bacteria
What population is prone to salmonella osteomyelitis?
Sickle cell anemia
Clinical symptoms of diarrheal, non-typhoidal salmonella
Abdominal pain
Watery diarrhea (typically no blood)
Fever in half
What causes diarrhea from non-typhoidal salmonella?
Cholera-like toxin and/ or ileal inflammation
Basic description yersinia enterocolitica
Motile
Gram negative ros
Major source of yersinia enterocolitica infections
Animals - fecal oral food contamination
Clinical symptoms yersinia enterocolitica
Fever
Diarrhea
Abdominal pain in right lower abdomen
Mucousal ulceration
Pathogenesis of yersinia enterocolitica
1) invasion of intestinal epithelial cells, lymph nodes, and bloodstream (like salmonella)
2) secrete enterotoxin
General concern about survival of yersinia in food
Can live and reproduce in cold temps (concern for refrigeration)
Basic description vibrio cholera
Gram negative rod
Stains red
Single flagella
Does vibrion cholera invade epithelial cells?
No, releases cholera toxin (choleragen)
Population at greatest risk for vibrio cholera
Children in endemic areas
Us adult travelers
Clinical manifestations cholera
Watery diarrhea, loss of 1 liter of fluid per day
Pathogenicity of choleragen
Causes production of cAMP, throws off NaCl balance
Microscopic exam of vibrio reveals…
No leukocytes but fast darting rods
Leading cause of diarrhea in Japan from sushi
Vibrio parahaemolyticus
Basic description campylobacter jejuni
Gram negative rod
Single polar flagellum
One of the most common causes of diarrhea in the world
What are the reservoirs for campylobacter?
Wild and domestic animals
Poultry
Mode of transmission vibrio cholera
Fecal contaminated water
Common modes of transmission for campylobacter
Fecal contaminated water, unpasteurized milk
Population at highest risk campylobacter
Children
Clinical illness campylobacter jejuni
- prodrome of fever and headache
- abdominal cramps
- bloody, loose diarrhea
Pathogenesis of campylobacter jejuni
Similar to salmonella typhi and yersinia enterocolitica - invades gi epithelial cells and spreads systemically.
Secrete LT toxin (similar to e coli) - destroys colon mucosal cells
Most common cause of duodenal ulcers and chronic gastritis
Helicobacter pylori
Treatment for helicobacter pylori
Bismuth salts (pepto-bismol) inhibit helicobacter pylori growth + antibiotics
Describe basics of the family bacteriodaceae
- obligate anaerobes
- gram negative rods
- make up 99 percent of intestinal flora (mouth and vagina also have bacteroides)
Species of not bacteroidaceae
Bacteroides fragilis
Bacteroides melaninogenicus
Fusobacterium
basic description bacteroides fragilis
- does not contain lipid A endotoxin like most gram negatives
- capsule
Bacteroides fragilis are a normal part of intestinal flora, but can cause infection when…
There are tears, laceration, penetration. Of the intetine
This bacteria forms abcssses in the peritoneal cavity
Bacteroides fragilis
Bacteria associated with abdominal surgery
Bacteroides fragilis
What are the prophylaxis recommendations to prevent bacteroides fragilis after abdominal surgery?
Antibiotics for anaerobes
- metronidazole (flagyl)
- piperacillin/tazobactsm
- meropenem
Action if abscess forms in abdominal cavity?
Surgically drain
Disease caused by bacteroides melaninogenicus
Necrotizing anaerobic pneumonias from aspiration if sputum from the mouth
Periodontal disease
What bacteroides melaninogenicus looks like in culture
Black pigmented colonies
Where does bacteroides melaninogenicus normally live?
Mouth vagina, intestines
Diseases caused by fusobacterium
Periodontal disease
Aspiration pneumonia
Abdominal and pelvic abscesses
Otitis media
Strep that are often isolated from abdominal abscesses with other gram negative bacteria
Strep viridans group
(Strep anginosus and strep milleri)
Common general types of HAIs a s what they are associated with
- pneumonia (endotracheal intubation and mechanical ventilation)
- UTI (Foley catheters)
- wound infections (recent surgery and implanted devices)
- bloodstream infections ( IV and central lines)
Most common group of gram negative bacteria that cause HAIs
Enterobacteriaceae (E coli, klebsiella, enterobacter)
Types of gram negative bacteria with increases in MDR
Pseudomonads-
(Pseudomonas aeruginosa
Stentrophomonas maltophilia
Burkholderia cepacia)
Acinetobacter