Microbiology: Gram Negative Bacteria Flashcards
Types of E-coli
1) enteroinvasive E. coli (EIEC)
- invades intestinal mucosa and causes necrosis I and inflammation (can be bloody of watery diarrhea)
2) enterohemorrhagic E. coli (shiga-like toxin form) (STEC)
- most common serotype and is O157:H7
- produces shiga-like toxins which destroy GI tract tissues
- can cause hemolytic uremic syndrome (infection of kidneys after GI infection which causes apoptosis of glomerular and endothelial cells. also produces schistocyte red blood cells).
- symptoms: low grade-fever, bloody diarrhea, confusion, jaundice, ab pain
3) enterotoxigenic E. Coli (ETEC)
- uses heat liabile and heat stable enterotoxin s in the GI system (causes intestinal inflammation and watery diarrhea (NO BLOOD))
4) Enteropathogenic E. Coli (EPEC)
- similar to #1, but only seems to target yrs <2
- causes destruction of cell cytoskeleton which causes flattened cells that cant absorb water properly (watery diarrhea, NO BLOOD)
5) Uropathogenic E. Coli (UPEC)
- causes 90% of community UTIs and 50% hospital acquired UTIs
- cystitis is almost always shown
- ONLY ONE to not cause diarrhea
Treatment:
- doxycycline/cotrimoxazole (severe only)
- supportive care
- plasmapheresis/ corticosteroids (only in STEC with HUS present)
What are some diagnostic special agars and the respective pathogen they help diagnosis?
Eosin methylene blue: E. Coli
Cystine- telluride: diphtheria
Triple sugar iron agar: Salmonella species, yersinia enterocolitica
MacConkey agar: E. Coli, enterobacters, klebsiella (any (+) lactose fermenters)
Buffered Charcoal yeast extract (BYCE) agar: legionella, tularemia
Cefsulodin-irgasan- novobiocin (CIN) agar: yersinia enterocolitica
Thayer-Martin agar: Neisseria species
Chocolate agar: Haemophilus influenza and ducreyi, tularemia
Hemolytic uremic syndrome (HUS)
Caused by STEC E.coli O157:H7.
Causes the following the triad of symptoms:
- anemia
- thrombocytopenia
- acute kidney damage (proteinuria/hemouria/uremia)
What subtypes of E. Coli can cause bloody diarrhea?
EIEC
STEC
Salmonella typhi (typhoid fever)
Gram (-) bacilli
- is transmitted only by humans*
Characteristics:
- (-)oxidase*
- (-) lactose fermentation
- facultative intracellular
- facultative anaerobes
- (+) glucose fermentation
- (+) suffer producer (H2S)*
- (+) triple sugar iron agar (black precipitate)*
- motile
Virulence:
- capsule (polysaccharide capsule that prevent phagocytosis)
- VI capsular antigen (protect from leukocytes in Peyer patches, when invading M cells in distal ileum)
- *type 3 secretion system (a needle like protein that allows the pathogen to exocytosis effector proteins into the cytoplasm to prevent lysosome fusion)
- very dangerous in patients with asplenia or sickle cell disease and can hematogenous spread*
- requires large doses of bacterium since they are acid-liable*
Complications:
1) typhoid/enteric fever
- rose/salmon colored macula on the chest/abdomen
- abdominal pain
- diarrhea
- hepatosplenomegaly
- weakness
- headaches
- AMS
2) bacteremia/sepsis
Treatment:
- symptomatic management
- fluroquinolone and ceftriaxone*
- vaccine is possible (oral live or IM attenuated with the Vi capsule)*
- gall bladder surgery (carriers only)*
Salmonella (NOT s. Typhi)
Gram (-) bacilli
Characteristics:
- encapsulated
- motile
- facultative intracellular
- facultative anaerobes
- (-) oxidase*
- (-) lactose fermentation*
- (+) sulfate fermentation*
- (+) triple sugar iron agar* (turns black)
Complications:
- ulcerative colitis
- bacteremia/sepsis
- zoonotic infection very common type of food poisoning, especially among eggs and poultry and infected animals such as reptiles and dogs*
- requires a large amount of bacterium to infect due to acid-liable*
Treatment:
- symptomatic treatment
- antibiotics are only given if bacteremia/sepsis and/or patient is immunocompromised
Where specifically in the body does all salmonella and shigella species infect humans?
The M cells located in the distal ileum Peyers patches
Pseudomonas aeruginosa
- VERY challenging bacteria to fight and is common among immunocompromised individuals*
- commonly found in humid/wet areas (similar to legionella)*
Gram (-) rod
Characteristics:
- obligate aerobic
- motile
- non spore forming
- (+) catalase*
- (+) citrate*
- (+) oxidase*
- (-) lactose fermentation
- HAS A GRAPE LIKE ODOR
Virulence:
- *multi-drug efflux pumps: allows for safe exocytosis of numerous antibiotic drugs
- B-lactamase: inhibits beta lactam drugs
- biofilms and exopolysaccharide capsule
- *type 3 secretion system (uses a needle like protein to secrete other virulence factors out in cytoplasmic environment and into endothelial tissues)
- *Phospholipase C: (degrades host cellular membranes)
- *exotoxins A: (inactivates EF-2 and prevents intracellular protein synthesis)
- endotoxins: causes inflammation and produces fevers
- *pyoverdine and pyocyanin pigments (iron chelator that enables increased iron digestion for growth and generates ROS respectively)
- these are what causes the grape like odor*
Complications:
- *“Hot tub colliculitis” (infection of hair follicles that produces a widespread rash)
- *ecthyma gangrenosium (blister like lesions that quickly turn to necrotic lesions)
- pneumonia (common in CF patients)
- sepsis/bacteremia
- *osteomyelitis (usually only if you have diabetes)
- *otitis externa
- nosocomial secondary infections (UTIs via catheter is the most common)
- *tricuspid value specific endocarditis
Treatment: “CAMPFIRE”
- Carbipenames
- Aminoglycosides
- monobactams
- polymyxins
- fluroquinolones
- ceftriaxone/cefepime (third gen cephalosporins)
- pipicillin/ticarcillin (extended spectrum penicllins)
- note folliculitis only requires symptomatic treatment*
Enterobacters (cloacae and aerogenes)
Is an opportunistic infection and is only a problem in immunocompromised individuals or patients that OVERUSE ANTIBOTICS
Gram (-) bacilli
Characteristics:
- Motile
- facultative anaerobic
- non- spore forming
- (-) oxidase
- (+) urease
- (+) lactose fermentation
Virulence:
- fimbriae ( allow for easier attachment)
- hemolysin ( destroys RBCs if it enters blood system)
Complications: (pretty much only affects immunocompromised)
- tracheobronchitis
- pneumonia
- pleural empyema
- UTIs
- bacteremia/sepsis
- endocarditis (tricuspid value)
- cellulitis/fasciitis
- myositis
- peritonitis
Treatment:
- carbapenems
- fluroquinolones
- Aminoglycosides
- polymyxins
Klebsiella pneumoniae
Gram (-) bacilli
common lobar pneumonia producer in alcoholics and diabetics and 3rd most common cause of UTIs
Characteristics:
- non motile
- facultative anaerobic
- non- spore forming
- (+) urease*
- DARK RED JELLY SPUTUM*
- PINK COLONIES*
- (+) lactose fermenter*
- (+) capsule
Virulence:
- VERY HIGH LPS*: disables compliment activation
- sideophores*: iron chelating compounds to aid in growth
- B-lactamase
Complications:
- lobar pneumonia* (common in alcoholics and diabetics)
- lung abscesses
- UTIs* (cystitis, prostatits, pyelonephritis)
- meningitis
- bacteremia
- spontaneous bacterial peritonitis* ( only in cirrhosis or ascites patients)
Treatment:
- third gen cephalosporins (ceftriaxone)
- Aminoglycosides
- fluroquinolones
- carbapenems* (only for extended spectrum B-lactamase klebsiella)
- colistin/fosfomycin* (only for carbapenamase resident klebsiella)
Legionella pneumophillia
- VERY COMMON IN WARM HUMID AREAS SUCH AS: AC units, hot tubs, smoke stacks, irrigation systems*
- most common route of transmission is inhalation of infected water droplets*
Gram (-) bacilli
Characteristics:
- *requires silver staining to best visualize
- (+) charcoal yeast agar (grows silver “cut-glass” colonies)
- obligate aerobe
- (+) oxidase
- (+) catalase
- facultative intracellular
- non spore forming
Virulence:
- *factor B system: (allows legionella to invade phagosomes and inhibit phagolysosome fusion)
Complications:
- legionnaires disease: ( high fever >40C, headache, and severe pneumonia)
- Pontiac fever: (high fever > 40C, but NO PNEUMONIA. Flu-like symptoms)
Treatment: (only required for legionnaires disease. Symptomatic treatment ONLY for Pontiac fever)
- macrolides
- fluroquinolones
Yersinia enterocolitica
gram (-) cocobacilli
common blood diarrheal disease that is most commonly transmitted via dog feces or contaminated animal products
Characteristics:
- facultative anaerobe
- non spore former
- facultative intracellular
- (-) lactase*
- (-) lactose fermentation*
- (-) oxidase*
- (-) hydrogen sulfate producer (CANT grow on Triple sugar iron agar)*
- motile at 25C*
- non-motile at 37C*
Virulence:
- adhesions (YadA): attaches to gut epithelial cells specifically
- type 3 secretion system* (T3SS): proteins that block pro inflammatory cytokines (TNF-a/IL-8) and macrophages, preventing immune response*
- siderophores: chelating agents for iron that promote growth
- enterotoxin YST*: promotes diarrheal disease states
Complications:
- terminal ileitis
- enterocolitis
- psudeoappendicitis
- sepsis/bacteremia (only immunocompromised)
- reactive arthritis* (if having the HLA-B27 antigens on host leukocytes)
- erythema Nodosa* (if having the HLA-B27 antigens on host leukocytes)
- high amounts of bloody diarrhea
Treatment:
- ceftriaxone
- TMP-SMX
- Aminoglycosides
- fluroquinolones
- tetracyclines
Serratus marcescens
Gram (-) bacilli
common water and soil and hospital-acquired infections
Characteristics:
- facultative anaerobic
- motile
- (+) urease
- (+) catalase
- (+) DNase, Lipase and gelatinase*
- (+) lactose fermentation (macconkey)*
- (+) PRODIGIOSIN (makes the bacteria look RED)
Complications: (very high in immunocompromised people)
Pneumonia
UTIs
Infective endocarditis (tricuspid)
- sepsis/bacteremia
- meningitis
- cellulitis/fasciitis (only in burns or deep surgical wounds)
Treatment: (B-lactams (+))
- Aminoglycosides
- piperactillin-tazobactam
- fluroquinolones (only if the above doesn’t fix it)
Neisseria Gonorrhoeae
Gram (-) dipolococci
Characteristics:
- obligative aerobe
- non-motile
- non sporeforming
- (+) catalase
- (+) oxidase
- (-) maltose fermentation*
- (+) Thayer Martin agar growth
- (-) capsule*
- most commonly spread via sexually or perinatal*
Virulence
- IgA proteases: destroys IgA in mucosal tissues
- pilli: helps swap genetic information between bacterium
- antigenic protein variation*: phase variation occurs with self-antigens at each infection (cant build a vaccine against it)
- lipooligosaccharides* (LOS): cell wall antigens that trigger widespread sepsis in blood stream
- Sialylation*: wraps LOS cell wall w/ sialic acid which mimics host cells and helps evade immune system
Complications:
- sepsis/ bacteremia (gonococcemia)
Septic/gonococcal arthritis*: more common sexually active teenagers
- gonorrhea*
(males = urethritis/prostatitis/ epididymitis)
(females = urethritis/vaginitis/cervicitis) - neonatal conjunctivitis*: 2-5 days after birth from infected mother
- fitz-Hugh-Curtis syndrome*: inflammation of the peritoneum as a complication of pelvic inflammatory disease (PID)
(causes violin string adhesions which attach liver to peritoneum) - diagnosed with NAT (nucleic acid amplification testing)*
Treatment:
- ceftriaxone*
- azithromycin/doxycycline in conjunction (if coinfection with chlamydia)*
- use condoms to lower infection rates
- erythromycin (for neonatal conjunctivitis ONLY)
Neisseria meningococcal (meningitidis)
Gram (-) dipplococci
Characteristics:
- obligate aerobes
- non spore forming
- non-motile
- (+) capsule*
- (+) catalase
- (+) oxidase
- (+) maltose fermentation* (turns yellow)
- (+) Thayer Martin agar growth
- most commonly transfers via oral and respiratory droplets*
Virulence:
- Pilli w/ OPA/OPC proteins*: help bind to host cells
- NO CAPSULE*
- NO ANTIGENIC VARIATION*
- IgA proteases: destroys mucosal IgA
- lipooligosacchardies (LOS): cell wall antigens that trigger widespread sepsis/bacteremia and widening of endothelial cells.
- Factor H binding protein*: disables alternative complement pathway
Complications: (is more dangerous In immunosupression patients)
- DIC* : due to widespread endothelial vessel cell damage via LOS and factor H binding protien (severe bleeding through out the body due to clots being formed to repair blood vessels)
- water-house frechreich syndrome*: pooling of blood in adrenal gland, causing ischemia/necrosis of adrenal gland.
- meningitis*: only known bacteria to cause outbreaks of meningitis
(LOS causes widening of the endothelial cells in the BBB, allowing pathogen to go into CSF and grow) - meningiococcemia (sepsis with meningococcal, marked by petechiae rash usually in trunk and lower extremities)
Treatment:
- ceftriaxone*
- penicillin G ( only once antibiogram determines its okay)
- rifampin (as a prophylaxis for people who were in contact with someone who had it)
- vaccine* (especially babies/children/teens/immunocompromised adults)
