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BDI > Enterobacterales > Flashcards

Enterobacterales Flashcards

1
Q

Enterobacterales is

A

The largest collection of medically important gram - rods (ex. E. coli, Klebsiella pneumoniae, Klebsiella oxytocin, Proteus mirabilis, Salmonella serovar Typhi, Salmonella nonthyphoidal Serotypes, Shigella flexneri)

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2
Q

Enterobacterales are found

A

Soil, water, vegetation, normal intestinal flora

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3
Q

Main Enterobacterales caused infections

A

Bacteremias
UTIs
intestinal infections

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4
Q

Enterobacterales that are always pathogenic

A

E. coli
Klebsiella pneumoniae
Proteus mirabilis

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5
Q

Enterobacterales pathogenesis

A

Spread from animal reservoir (Yersinia, nontyphoidal Salmonella)
From human carrier (Shigella)
endogenously (E Coli)
Acquire virulence (E Coli)

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6
Q

Enterobacterales structure

A

Non spore forming
Gram - rods
Flagella for motility (except Klebsiella, Shigella, and Yersinia)
Pili for attachment
Common Enterobacterial antigen (polysaccharide core)
Facultative anaerobe that grow on both selective and non selective media

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7
Q

Enterobacterales metabolism

A

Simple nutritional requirements
Ferment glucose
Reduce nitrate to nitrite
catalase +
Oxidase -

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8
Q

LPS

A

Major cell wall antigen consisting of 3 components
O polysaccharide (classification of strain)
Polysaccharide core (classification as enterobacterales order)
Lipid A- responsible for endotoxin activity, important virulence factor

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9
Q

Epidemiological classification is based on 3 major antigens

A

O polysaccharide (part of LPS)
H antigen (part of flagella)
K antigen (part of capsule)

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10
Q

Enterobacterales that ferment lactose on MacConkeys agar

A

E. coli
Klebsiella
Enterobacter
Serratia
Citrobacter

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11
Q

Enterobacterales virulence factors

A

Endotoxin- Lipid A component, causes fever and shock (hypotension)
Capsule (repels hydrophobic phagocytic cell surface
Antigenic phase variation (can turn expression of O, H, and K antigens on or off to protect from antibody-mediated cell death)
Type III secretion system (Salmonella, Shigella, EPEC)-effector systems for delivering virulence factors into targeted eukaryotic cells
Antimicrobial resistance- transferable plasmids

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12
Q

Escherichia Coli

A

Commensal residen of GI trace
Most common Gram - rod associated with sepsis
Most common cause of community acquired UTI
Causes bacterial gastroenteritis

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13
Q

Commensal infections caused by E. coli

A

Bacteremia
Peritonitis

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14
Q

Specialized E. coli infections

A

UTI (uropathogenic E. coli- UPEC)
Meningitis (neonatal meningitis-associated E. coli- NMEC)
Gastroenteritis (Enterotoxigenic-ETEC, Enteropathogenic-EPEC, Enteroaggregative-EAEC, Shiga toxin producing/enterohemorrhagic EHEC, Enteroinvasive- EIEC)

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15
Q

Normally sterile sites

A

Blood
CSF
Pleural fluid
peritoneal fluid
Pericardial fluid
Bone
Synovial fluid
Internal body sites (lymph node, brain, heart, liver)

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16
Q

UTI

A

Ascending infection
Colonization in bladder mediated by pili and adhesions
Neutrophil infiltration
Biofilm formation
Epithelial damage by bacterial toxin
Ascension into kindness
Colonization of kidneys
Bacteremia
Hemolysis HlyA lyses erythrocytes leading to cytokine release and inflammation

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17
Q

Neonatal meningitis due to E. coli (NMEC) pathogenesis

A

K1 capsular antigen helps evade host

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18
Q

E. coli caused gastroenteritis

A

Transmitted by contaminated food
5 major patho types cause diarrhea
Enterotoxigenic (ETEC) acute watery diarrhea (pili, ST/LT enterotoxins)
Enteropathogenic (EPEC) infantile watery diarrhea (pili, effacement of intestinal microvilli)
Shiga toxin producing (STEC) and Enterohemorrhagic (EHEC) bloody diarrhea due to HUS, foodborne outbreaks (Stx1, Stx2)
Enteroinvasive (EIEC) foodborne outbreaks, invade and destroy colonic epithelium

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19
Q

ETEC

A

Acute, self limited watery diarrhea
Travelers and infantile diarrhea in resource limited countries
Ingestion of contaminated food or water

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20
Q

ETEC Pathogenesis

A

Colonization factors (CFA/I, CFA/II) used to attach to small bowel epithelium
Produces two enterotoxins (Heat stable-ST and Heat labile-LT) interacts with cyclase receptors leading to increased cAMP and hypersecretion into gut

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21
Q

ETEC treatment

A

supportive care
Antimicrobial for those with sever diarrhea, prolonged symptoms, or immunocompromised hosts)

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22
Q

EPEC

A

Severe diarrhea in children <2 in resource limited settings
Rapid onset watery diarrhea
From contaminated food or water

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23
Q

EPEC pathogenesis

A

Virulence genes called locus of enterocyte effacement (LEE)
Forms attaching and effacing (A/E) lesions

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24
Q

EAEC

A

Acute and chronic watery diarrhea in both resource limited and rich areas
Spread by contaminated food and water

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25
Q

EAEC pathogenesis

A

autoagglutination in “stacked-brick” arrangement in epithelium of small intestine leading to epithelial barrier dysfunction

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26
Q

STEC

A

EHEC is a subset
Large herbivores are reservoir (passed through feces)
Associated with undercooked meat, petting zoo, contaminated produce, raw milk
Low infectious (<100 viable) dose to cause disease
Causes watery then bloody diarrhea
Complication: hemolytic uremic syndrome (toxin mediated, acute kidney failure, thrombocytopenia, microangiopathic hemolytic anemia)

27
Q

STEC pathogenesis

A

biofilm formation
Survival at low pH
Attachment using locus of enterocyte effacement (LEE)
Type III secretion system
Intimidating receptor inoculated into host by T3SS
Intimidating on bacterial cell promotes attachment leading to the attaching and effacing histopathology
Shiga toxin 1 (Stx1) and Shiga toxin 2 (Stx2- more potent and more often causes disease)

28
Q

_ is the critical first step in the pathogenesis of most bacterial infections

A

Adherence to the host mucosa

29
Q

STEC treatment

A

No antimicrobials just support
Antimicrobials increase toxin release which increases risk of HUS

30
Q

EIEC

A

Watery diarrhea
Foodborne outbreaks
Pathogenesis similar to Shigella
Plasmid mediated invasion
E Terence into phagocytes
Epithelial cell destruction leading to colonic ulceration

31
Q

E. coli infection diagnosis

A

Bacterial culture
PCR recommended (molecular PCR testing)
Due to high sensitivity and ability to differentiate between pathogenic and non pathogenic
Limitations: does distinguish between viable and non viable organism/nucleic acid

32
Q

Klebsiella species are

A

Aerobic lactose fermenters

33
Q

Proteus are

A

Aerobic lactose non-fermenters

34
Q

Lower urinary tract infections include

A

Urethritis
Cystitis
Prostatitis

35
Q

Upper urinary tract infections include

A

Pyelonephritis
Perinephrinc abscess

36
Q

Two mechanisms of UTI pathogenesis

A

Ascending (most common)
Hematogenous (unusual)

37
Q

Ascending UTI

A

Colonization of periurethral area
Urethral colonization migration to the bladder
Bladder entry
Infection with possible ascension

38
Q

Hematogenous UTI

A

S aureus
Mycobacterium tuberculosis

39
Q

Risk factors for uncomplicated UTI

A

Females
Older age
Younger age

40
Q

Risk factors for complicated UTI

A

Indwelling catheters
Immunosuppression
Urinary tract abnormalities
Antibiotic exposure

41
Q

Top bacteria that cause UTIs

A

UPEC (uropathogenic E. coli)
K pneumoniae
P mirabilis

42
Q

Klebsiella pneumoniae

A

lactose fermenting
Non-motile
Gram - rod
Causes Nosocomial pneumonia, UTI, bacteremia, wound infection, pyogenic liver abscess)

43
Q

Klebsiella pneumoniae pathogenesis/virulence factors

A

Capsular serotypes
Hypermucoviscosity phenotype
LPS
Sideophores (allow bacteria to enhance iron uptake)
Pili
Antimicrobial resistance

44
Q

Klebsiella pneumoniae Capsular serotypes

A

K1 and K2 most virulent
Polysaccharide matrix coats the cell
Thick mucoid colonies on blood agar (sting test)
Hyoermucoviscosity causes more invasive disease
Dark red currant jelly sputum

45
Q

Klebsiella pneumoniae resistance genes

A

encoded on plasmids
CTX-M
KPC
NDM-1
SHV
TEM
OXA-48
resistance to most extended spectrum beta lactamases

46
Q

Proteus mirabilis causes

A

UTI

47
Q

Proteus mirabilis virulence factors

A

Urease production
Flagella
Swarm cell differentiation
Bacterial adhesion using 4 types of flagella
Hemolysis and IgA protease
Iron aquisition using siderophores

48
Q

Proteus mirabilis urease production

A

Hydrolyzes urea into ammonia and carbon dioxide
Ammonia used as a nitrogen source for bacteria
Increase in pH in the bladder leading to precipitation of phosphate carbonate and magnesium which forms Struvite stones 

49
Q

Proteus mirabilis swarm cell differentiation

A

Differentiate into elongated highly flagellated cells
Move over solid surfaces inform concentric rings on growth media

50
Q

Lactose fermenting bacteria are _ on _ agar

A

Pink
MacConkeys

51
Q

Salmonella

A

Bacilli
Aerobic
Lactose non-fermenter
Oxidase -

52
Q

Salmonella infection requires

A

A large infectious dose

53
Q

Typhoid fever

A

Caused by Salmonella typhi and paratyphi (human serotypes)
Transmitted though human feces
Carrier state within gallbladder colonization

54
Q

Nontyphoidal salmonella

A

transmitted though animal feces
Poultry, eggs, dairy products, and food prepared on contaminated surfaces

55
Q

Salmonella pathogenesis

A

Attached to an in bed M cells in Pyers patches
Replicate an Endo psychotic vacuoles
Transported across the cytoplasm and released into blood or lymphatic circulation (disseminate hematogenously) 

56
Q

S. typhi has the _ antigen

A

VI

57
Q

Typhoid fever

A

5-21 day incubation
Abdominal pain, fever, chills, bradycardia
Rose spots
abnormal bowel movements ranging from constipation to bloody diarrhea

58
Q

Non-typhoidal salmonella

A

Incubation period 8-72 hours
Diarrhea, nausea, vomiting, fever, abdominal cramping
Bacteremia: endovascular infections, HIV
Osteomyelitis: sickle cell disease

59
Q

Shigella

A

Non-motile
Non-encapsulated
Gram -
Rod
47 serotypes grouped into 4 groups (S. Dysenteriae, S. Flexneri, S. Boydii, S. Sonnei)

60
Q

Shigella pathogenesis

A

Attached to/transport across the epithelial layer
Engulfed into macrophages where shigella induces apoptosis
Multiply in cytoplasm
Tissue destruction, impaired absorption of water and nutrients, blood and mucus in stool

61
Q

Shigella toxins

A

Shiga toxin (Stx) produced by S. Dysenteriae is only major toxin

62
Q

Shigella epidemiology

A

Humans and large primates are the only natural reservoir
Outbreaks in daycare centers and men who have sex with men
High communicable with low infectious dose (100 viable cells)
Withstand low pH (acid-stable)
Watery diarrhea to severe dysentery

63
Q

Diagnosis of Enterobacterales infections

A

Molecular detection is sample
Cultures
Stool culture on Hektoen enteric agar (Shigella-green, Salmonella-black)

64
Q

Other enterobacterales are rare in immunocompetent individuals

A

BDI (18 decks)

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