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Thera VII > 05 Gram-Negative Rods > Flashcards

05 Gram-Negative Rods Flashcards

1
Q

What are the large family of GNRs primarily in the colon?

A

Enterobacteriaceae

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2
Q

What are the general characteristics of Enterobacteriaceae?

A

All facultative anaerobes. Ferment glucose, oxidase-negative

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3
Q

What are the common Enterobacteriaceae?

A

E. coli, Klebsiella, Proteus, Enterobacter, Serratia, Shigella, Salmonella, Yersinia, Vibrio. Pseudomonas aeruginosa

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4
Q

Which Enterobacteriaceae produce exotoxins –> diarrhea?

A

E. coli, Vibrio

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5
Q

What are the common causes of E. coli?

A

Most common cause of UTIs, gram-neg bacteremia. Traveler’s diarrhea

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6
Q

What is the most abundant facultative anaerobe in the colon and feces?

A

E. coli

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7
Q

What is E.coli’s lactose test?

A

Positive

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8
Q

What are the Virulence factors for E. coli?

A

Pili (intestinal mucosa, urinary tract epithelium). Capsule (interferes with phagocytosis). Endotoxin. Exotoxins (enterotoxins)

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9
Q

What are the clinical findings for E. coli?

A

Intestinal tract infections (Traveler’s diarrhea, “dysentery”, fever, abdominal cramping, bloody diarrhea, c/b HUS). Systemic infections

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10
Q

What are the systemic infections caused by E.coli?

A

UTIs, bacteremia, intra-abdominal infections, neonatal meningitis

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11
Q

What are the characteristics of Klebsiella, Enterobacter, and Serratia?

A

Opportunists. Large intestine; soil and water. Respiratory tract in 10% of normal hosts (Klebsiella)

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12
Q

What can Klebsiella, Enterobacter, and Serratia cause?

A

Pneumonia, UTIs, bacteremia

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13
Q

Which ones are lactose-fermenting and lactose-NON-fermenting (Klebsiella, Enterobacter, and Serratia)?

A

Klebsiella (+), Enterobacter (+), Serratia (-)

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14
Q

What are the characteristics of Proteus, Providencia, and Morganella?

A

Produce urease –> cleaves urea to form NH3 and CO2 –> alkaline pH in urine, stone formation. Colon; soil, water. Highly motile, lactose (-)

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15
Q

What are some common causes of Proteus, Providencia, and Morganella?

A

Community and hospital acquired UTI. Stone formation in bladder

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16
Q

What are the common characteristics of Pseudomonas aeruginosa?

A

Opportunist. Tap water, withstand disinfectants. Colon in 10% of normal hosts, respiratory tract of hospitalized patients

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17
Q

What can Pseudomonas aeruginosa cause?

A

Pneumonia, UTIs, wound infections, bacteremia

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18
Q

What are the testing results for Pseudomonas aeruginosa?

A

“Nonfermenter”, lactose (-), oxidase-positive, blue-green pigments “pyocyanin, pyoverdin”

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19
Q

What is the virulence arsenal of P. aeruginosa?

A

Flagellum. Alginate/biofilm. Pilus. Non-pilus adhesins. LPS. T3SS. Quorum sensing system. Type 1, II secretion system. Crap load of “-ases”

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20
Q

What Quorum Sensing-Controlled Virulence?

A

“Cell-density” sensing via small signaling molecules. Coordinated expression of virulence genes by an entire bacterial population once a certain density is reached allowing P. aeruginosa to secrete extracellular factors only when they can be produced at high enough levels to overcome host defenses

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21
Q

Which GNR are found in the Respiratory Tract?

A

Hemophilus influenzae. Legionella pneumophila. Bordetella pertussis

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22
Q

What are the general characteristics of H. influenzae?

A

Small coccobacillary GNR with polysaccharide capsule (Type B (invasive disease)). Unencapsulated strains - noninvasive disease. Portal of entry is the respiratory tract. Most infections - age 6 months - 6 years

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23
Q

What are the effects of H. influenzae?

A

Pneumonia in adults. Otitis media, sinusitis, sepsis

24
Q

What is the Hib vaccine?

A

Capsular polysaccharide of H. influenzae type b conjugated to carrier protein (i.e. diphtheria toxoid) –> reduce incidence of meningitis by 90% in immunized children, given b/w age 2 and 15 months

25
Q

What are the characteristics of Legionella pneumophila?

A

Environmental water sources - air conditioners, water-cooling towers. Nosocomial outbreaks - organisms in water, taps, sinks, showers

26
Q

What does Legionella pneumophila usually cause?

A

“Atypical pneumonia” - elderly, immunocompromised patients

27
Q

How is Legionella pneumophila diagnosed?

A

Urinary antigen for serogroup 1; culture

28
Q

How is Bordetella pertussis diagnosed?

A

Detects by culture or direct fluorescent antibody stain on nasopharyngeal swab

29
Q

Which GNRs affect the enteric tract?

A

Salmonella. Shigella. Vibrio. Campylobaccter. Helicobacter

30
Q

What are the general characteristics of Salmonella?

A

Notifiable disease; need to determine source. Transmitted by ingestion of food and water contaminated by human and animal wastes; poultry and eggs, dogs and reptiles. Lactose (-) GNR

31
Q

What are the 3 types of infections caused by Salmonella?

A

Enterocolitis, Enteric fever (typhoid fever), septicemia

32
Q

What are the different cultures done for Salmonella?

A

Stool culture (enterocolitis), blood culture (enteric fevers, septicemia)

33
Q

What is Enterocolitis?

A

Invasion of the epithelial and subepithelial tissue of the small and large intestine –> inflammation, diarrhea

34
Q

What is the incubation period for Enterocolitis?

A

6-48 hours –> n/v, abdominal pain, diarrhea (self-limited)

35
Q

What is the most common cause of Enterocolitis?

A

S. typhimurium. Infectious dose: at least 100,000 organisms

36
Q

What is Typhoid Fever?

A

Infection begins in small intestine –> organisms enter and multiply in the mononuclear phagocytes of Peyer’s patches, then spread to phagocytes of the liver, gallbladder, and spleen –> bacteremia

37
Q

What is the onset of illness like for Typhoid Fever?

A

Slow, with fever and constipation –> high fever, tender abdomen, enlarged spleen. 3% of patients become chronic carrier –> excrete bacteria in feces for long periods

38
Q

What is a common cause of Typhoid Fever?

A

S. typhi

39
Q

What is Bacteremia?

A

Accounts for 5-10% of infections. Patients with underlying chronic disease (sickle cell anemia, cancer, AIDS). Child with enterocolitis. Indolent course: fever and focal symptoms of affected organs (bone, lungs, meninges)

40
Q

What are the characteristics of Shigella sonnei, S. flexneri?

A

3rd most common cause of bacterial gastroenteritis; age < 5 yo. Causes Enterocolitis. Lactose (-); S. sonnei. Fecal-oral transmission from person to person

41
Q

What is the infectious dose of S. sonnei, S. flexneri?

A

Less than 100 organisms. Infects only humans and non-human primates

42
Q

What is Enterocolitis (dysentery) like for S. sonnei, S. flexneri?

A

Incubation period 1-4 days, begins with fever and abdominal cramps, followed by diarrhea (watery then blood and mucus), resolves in 2-3 days. Locally invasive, destroying cells of the intestinal mucosa. Rarely penetrates beyond the lamina propria –> phagocytosis

43
Q

What is Campylobacter?

A

Comma or S-shaped GNR. Fecal-oral transmission; improperly cooked poultry or cross-contamination by raw poultry

44
Q

What are the 2 most frequently recovered bacterial gastroenteritis in USA?

A

Campylobacter jejuni (along w/ Salmonella). Most frequent cause of bacterial gastroenteritis (food poisoning) in college students in US; Males warm-weather months, peak in July. Infants (< 1 yo), adolescents, young adults (15-29)

45
Q

What is Campylobacter Enterocolitis?

A

Watery, foul-smelling diarrhea followed by blood stools, fever, severe abdominal pain. Locally invasive, bacteremia rare in immunocompetent patients (rarely in neonates of HIV+). Resistance in fluoroquinolones increasing. Most commonly caused by C. jejuni

46
Q

For Diarrhea, what are the different differential diagnosis?

A

Stool specimens, either looking for presence of PMNs (invasive organisms) or absence of PMNs (toxin mediated)

47
Q

For Diarrhea with the presence of PMNs, what are some common bacterial causes?

A

Shigella (local). Campylobacter (local). Salmonella (can disseminate, survives w/in phagocytes)

48
Q

For Diarrhea with the absence of PMNs (toxin-mediated), what are some common bacterial causes?

A

Vibrio. E. coli. Clostridium perfringens

49
Q

Which GNRs are Lactose-Negative?

A

SPASM: Salmonella, Shigella, Serratia. Pseudomonas, Proteus, Providencia. Acinetobacter. Stenotrophomonas maltophilia. Morganella

50
Q

Which GNRs are Lactose-Positive?

A

CEEK: Citrobacter. E.coli. Enterobacter. Klebsiella

51
Q

What are the Anaerobic GNRs?

A

Bacteroides. Fusobacterium nucleatum. Prevotella melaninogenica

52
Q

What are the characteristics of Bacteroides?

A

Peritonitis, abscesses, bacteremia. B. fragilis group is predominant in colon. Non-spore forming anaerobic GNR

53
Q

How do Bacteroides (i.e. B. fragilis) work with E. coli in the colon?

A

Mixed facultative (i.e. E. coli) and anaerobic flora (bacteroides) –> E. coli utilize the O2 thereby reducing it to a level that allows the anaerobic Bacteroides strains to grow

54
Q

What are some infections caused by Bacteroides?

A

Intrabdominal infections

55
Q

What are the characteristics of Fusobacterium nucleatum?

A

Anaerobic GNR. Mouth, colon, female genital tract. Pulmonary, intra-abdominal and pelvic abscesses

56
Q

What are the characteristics of Prevotella melaninogenica?

A

Anaerobic GNR. Mouth flora. Oral, pharyngeal, pulmonary abscesses

Thera VII (37 decks)

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