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Enterobacterales Flashcards

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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
EAEC pathogenesis
autoagglutination in “stacked-brick” arrangement in epithelium of small intestine leading to epithelial barrier dysfunction
26
STEC
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
STEC pathogenesis
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
_ is the critical first step in the pathogenesis of most bacterial infections
Adherence to the host mucosa
29
STEC treatment
No antimicrobials just support Antimicrobials increase toxin release which increases risk of HUS
30
EIEC
Watery diarrhea Foodborne outbreaks Pathogenesis similar to Shigella Plasmid mediated invasion E Terence into phagocytes Epithelial cell destruction leading to colonic ulceration
31
E. coli infection diagnosis
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
Klebsiella species are
Aerobic lactose fermenters
33
Proteus are
Aerobic lactose non-fermenters
34
Lower urinary tract infections include
Urethritis Cystitis Prostatitis
35
Upper urinary tract infections include
Pyelonephritis Perinephrinc abscess
36
Two mechanisms of UTI pathogenesis
Ascending (most common) Hematogenous (unusual)
37
Ascending UTI
Colonization of periurethral area Urethral colonization migration to the bladder Bladder entry Infection with possible ascension
38
Hematogenous UTI
S aureus Mycobacterium tuberculosis
39
Risk factors for uncomplicated UTI
Females Older age Younger age
40
Risk factors for complicated UTI
Indwelling catheters Immunosuppression Urinary tract abnormalities Antibiotic exposure
41
Top bacteria that cause UTIs
UPEC (uropathogenic E. coli) K pneumoniae P mirabilis
42
Klebsiella pneumoniae
lactose fermenting Non-motile Gram - rod Causes Nosocomial pneumonia, UTI, bacteremia, wound infection, pyogenic liver abscess)
43
Klebsiella pneumoniae pathogenesis/virulence factors
Capsular serotypes Hypermucoviscosity phenotype LPS Sideophores (allow bacteria to enhance iron uptake) Pili Antimicrobial resistance
44
Klebsiella pneumoniae Capsular serotypes
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
Klebsiella pneumoniae resistance genes
encoded on plasmids CTX-M KPC NDM-1 SHV TEM OXA-48 resistance to most extended spectrum beta lactamases
46
Proteus mirabilis causes
UTI
47
Proteus mirabilis virulence factors
Urease production Flagella Swarm cell differentiation Bacterial adhesion using 4 types of flagella Hemolysis and IgA protease Iron aquisition using siderophores
48
Proteus mirabilis urease production
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
Proteus mirabilis swarm cell differentiation
Differentiate into elongated highly flagellated cells Move over solid surfaces inform concentric rings on growth media
50
Lactose fermenting bacteria are _ on _ agar
Pink MacConkeys
51
Salmonella
Bacilli Aerobic Lactose non-fermenter Oxidase -
52
Salmonella infection requires
A large infectious dose
53
Typhoid fever
Caused by Salmonella typhi and paratyphi (human serotypes) Transmitted though human feces Carrier state within gallbladder colonization
54
Nontyphoidal salmonella
transmitted though animal feces Poultry, eggs, dairy products, and food prepared on contaminated surfaces
55
Salmonella pathogenesis
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
S. typhi has the _ antigen
VI
57
Typhoid fever
5-21 day incubation Abdominal pain, fever, chills, bradycardia Rose spots abnormal bowel movements ranging from constipation to bloody diarrhea
58
Non-typhoidal salmonella
Incubation period 8-72 hours Diarrhea, nausea, vomiting, fever, abdominal cramping Bacteremia: endovascular infections, HIV Osteomyelitis: sickle cell disease
59
Shigella
Non-motile Non-encapsulated Gram - Rod 47 serotypes grouped into 4 groups (S. Dysenteriae, S. Flexneri, S. Boydii, S. Sonnei)
60
Shigella pathogenesis
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
Shigella toxins
Shiga toxin (Stx) produced by S. Dysenteriae is only major toxin
62
Shigella epidemiology
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
Diagnosis of Enterobacterales infections
Molecular detection is sample Cultures Stool culture on Hektoen enteric agar (Shigella-green, Salmonella-black)
64
Other enterobacterales are rare in immunocompetent individuals

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