Gram negative rods Flashcards
1
Q
Most Gram negative rods resistent to
A
- Penicillin
- Vancomycin
2
Q
Gram negative rods ABx
A
- Ceftriaxone
- Fluoroquinolones
3
Q
Klebsiella feautes
A
- intestinal flora
- non-motile/capsular
- impaired host defenses (alcoholis, sick people)
- treatment based on susceptibility testing
4
Q
Klebsiella illnesses
A
Lovar pneumonia
Lung abscesses
liver abscesses
UTI (3-4%)
5
Q
Klebsiella pneumonia
A
- Lobar
- occurs in alcoholics or diabetics (aspiration)
- results in red “currant jelly” sputum
6
Q
Klebsiella lung abscesses
A
- usually caused by mouth anaerobes
- Peptostreptococcus, Fusobacterium, Prevotella, Bacteroides
7
Q
Klebsiella liver abscess
A
usually in patients with underlying disease or cholangitis
8
Q
Features of E. coli
A
- gram neg rods with fimbriae (pili)
- attach to surfaces (may be specialized for particular surfaces)
- K capsule
- K1 capsular antigen present in 75% meningitis cases (babies)
- inhibits phagocytosis and complement
9
Q
E. coli illnesses
A
- Watery diarrhea
- Bloody diarrhea (dysentary)
- UTI/pyelonephritis
- E coli bacteremia, sepsis (rare), usually from UTI
- Meningitis in newborns
10
Q
E. coli diarrheal illnesses
A
- Enteroinvasive E. coli (EIEC)
- Enterotoxigenic E coli (ETEC)
- Enteropathogenic E coli (EPEC)
- EnteroHemorrhagic E coli (EHEC)
11
Q
Enteroinvasive E. coli (EIEC)
A
- Clinically similar to shigella (no toxins in this but Shigella does make a toxin of course)
- Invades intestinal mucosa
- Necrosis
- Inflammation
- Bloody diarrhea
12
Q
Enterotoxigenic E coli (ETEC)
A
- Two toxins: Labile and Stable
- watery (traveler’s diarrhea) from contaminated food/water
- No imflammation
- No invasion
13
Q
Enteropathogenic E coli (EPEC)
A
- No toxin
- No inflammation
- Blunt villi prevent absorption
- Diarrhea usually in children (p=pediatrics)
14
Q
EnteroHemorrhagic E coli (EHEC)
A
- Does not ferment sorbitol (sorbitol-McConkey agar)
- Classic serotype: E. coli 0157:H7
- Does not invade host cells (toxin causes disease)
- Produces Shiga-like toxin -> bloody diarrhea
- bacteriophage encoded (lysogenic) toxin
- Usually from undercooked beef
- Toxin effects
- Endothelium swells -> vessel lumens narrow
- Deposition of fibrin/platelets in microvasculature
- Hemolysis, inflammation
- Feared complication is if the toxin gets into the bloodstream causing Hemolytic Uremic Syndrome (HUS)
15
Q
HUS
A
- Hemolytic Uremic Syndrome
- complication of 10% of EHEC cases
- common in children
- Triad
- Hemolytic anemia
- Thrombocytopenia
- Acute renal failure (uremia)
- HUS + fever; mental status changes = TTP (Thrombotic Thrombocytopenic purpura)
- usually occurs 5-7 days post diarrhea
16
Q
Gram negative sepsis
A
- Fever
- Tachycardia
- Hypotension
- Life-threatening
- Driven by endotoxin (LPS; Lipid A)
- Common scenario
- Elderly patient
- UTI (catheter, BPH)
- Gram negative sepsis (+blood cultures)
17
Q
Infectious causes of bloody diarrhea
7 listed
A
- Campylobacter
- Salmonella enterica
- Shigella
- Yersinia entercolitica
- EiEC
- Entamoeba histolytica
- EHEC
18
Q
Infectious causes of watery diarrhea
8 listed
A
- ETEC
- Cholera
- C. diff
- C. perfringens
- Giardia
- Crypto
- Rotavirus
- Norovirus
19
Q
Fecal leukocytes and RBC iindicate?
A
usually indicate invasive infection
Bloody diarrhea
20
Q
Mucous and epithelial cells in stool only seen in
A
toxin-mediated disease
Watery diarrhea
21
Q
Parasitic diarrhea can be Dxd by?
A
Stool ova and parasites from protozoal infections
22
Q
Causes of diarrhea that invade the mucosa
5 listed
A
- Campylobacter
- Salmonella enterica
- Shigella
- Yersinia entercolitica
- EIEC
23
Q
Enterobacter features
A
- Rare cause of nosocomial UTIs
- Resistant to many antibiotics
- ESBL
- Resistance to most beta-lactams; penicillins, cephalosporins and aztreonam
- Often treated with Carbapenems
- Imipenem
- Meropenem
24
Q
Enterobacter treatment
A
Resistant to a lot of Abx because they have ESBLs
- Carbapenems
- Imipenem
- Meropenem
25
Q
Nosocomial means?
A
disease originating from a hospital
26
Q
Citrobacter & Serratia
A
- Slow Lactose Fermenters
- Gram negative rods
- Not dominant pathogen for any condition
- often resistant to many Abx
27
Q
Citrobacter features
A
- Can be found in normal gut flora
- Gram negative sepsis (with other GN bugs)
28
Q
Features of Serratia
A
- GN rod
- produce diistinctive red colonies (red pigment)
- Catalase positive
- Hospital outbreaks of UTIs; contaminated water, soap, IV solutions
- Sometimes osteomyelitis in IV drug users (also Pseudomonas)
29
Q
Slow Lactose Fermenters
A
Citrobacter & Serratia
30
Q
Types of Salmonella
A
- Salmonella typhi
- Salmonella Enterica
- Salmonella Enteritidis
31
Q
Salmonella illnesses
A
- Salmonella typhi -> typhoid fever
- Non-typhoid strains cause gastroenteritis (enterica, enteritidis)
- NVcramps, bloody diarrhea
- ingestion of contaminated meat, eggs, poultry
- osteomyelitis in sickle cell patients
32
Q
Features of Salmonella
A
- Flagellated, mobil, encapsulated gram negative rod
- disseminate through blood
- osteomelitis in sickle cell pts
- Live in GI tract of mammals, birds and reptiles
- produce hydrogen sulfide
- triple sugar iron (TSI) test -> media turns black
- differentiates from shigella
- Invades GI mucosa
- The cellular response is largely monocytes
33
Q
Typhoid fever
A
- caused by Salmonella typhi
- Travelers to Asia, Africa, South America
- Classic features
- Rose spots
- Faint salmon-colored macules
- Trunk and abdomen
- Pulse-termperature dissociation
- High fever -> slow pulse
- Rose spots
- Can remain in the gall bladder (carrier state)
- endemic countries 1-4% people may be carriers
- May be risk factor for carcinoma
34
Q
Diagnosis of Salmonella
A
- Culture (stool, blood (typhoid))
35
Q
Treatment of Salmonella Gastroenteritis
A
Gastroenteritis
- Fluids/electrolytes
- Abx not really helpful (only in severely ill)
- has lots of resistance
- Anti-peristalsis contraindicated because prolong illness
36
Q
Treatment of Typhoid Fever
A
- Ceftriaxone
- Fluoroquinolones
- Typhoid vaccine is available
- inactive variant given orally
- used for high risk travelers
37
Q
Shigella features
A
- non-motile (no flagella)
- not normal GI flora
- Commin in children
- Dx: stool culture
- Invades mucosal cells (M cels in Peyer’s Patches)
- Macropinocytosis
- Induces apoptosis
- Spreads from cell-to-cell
- does not spread hematogenously (salmonella does)
- Releases Shiga toxin
- but non-toxin strains still cause disease
- Cellular invasion more important mechanisms of disease
- Very few bacteria are required to cause disease (few as 10)
- Cellular response is largely PMNs (neutrophils)
38
Q
Shigella treatment
A
- Fluids/electrolytes
- Abx improve symptoms, reduce shedding in stool
- can limit spread
- Ceftriaxone or Ciprofloxacin
39
Q
How to tell Salmonella vs Shigella
A
- Salmonella
- Produces H2S so black color on triple sugar iron TSI
- Mostly Monocyte response
- Hematogenous spread
- No antibiotics
- Motile (flagella)
- Shigella
- No H2S
- Mostly Neutrophil response
- Cell-to-cell spread (Macropinocytosis)
- Yes Abx (Ceftriaxone or Ciprofloxacin)
- Nonmotile
- Shiga toxin
- Low infectious dose
40
Q
Proteus features
A
- Rare cause of UTIs
- “Swarm phenotype”
- long flagella
- facilitates urinary ascent
- Bulls-eye on agar plates
- Produces urease
- converts urea to ammonia
- Associated with Struvite Kidney Stones
41
Q
Pseudomonas aeruginosa features
A
- highly-feared bacteria
- serious hospital acquired infections (i.e. VAP “Ventilator Acquired Pneumonia)
- Resistant to many Abx
- Obligate aerobe
- gram negative rod
- Loves the water (commonly found in environmental water sources
- Produces blue-green pigment (pyocyanin)
- smooth, fluorescent green colonies on culture media
- sweet grape-like odor
42
Q
Pseudomonas aeruginosa illnesses
A
- Pneumonia (Nosocomial) (Cystic fibrosis)
- UTIs
- Surgical wound infections
- Bacteremia/sepsis
- Osteomyelitis (IV drug users)
- Ottitis externa (swimmers ear)
- Burn infections
- Hot tub folliculitis
43
Q
Pseudomonas toxins
A
- Endotoxin (LPS)
- can cause fever, shock
- Endotoxin A
- Inactivates elongation factor EF-2
- EF-2 is necessary for protein synthesis
44
Q
Pseudomonas Pneumonia
A
- classic pneumonia in CF pts
45
Q
Pseudomonas
A
46
Q
Hot tub folliculitis
A
tender itchy papules after using hot tub or spa
47
Q
Otitis externa
A
- Swimmer’s ear
- painful ear with discharge
48
Q
Pseudomonas Osteomyelitis
A
- IV drug users
49
Q
Ecthyma gangrenosum
A
- Caused by Pseudomonas bacteremia
- Black, necrotic ulcers on skin with bacteremia
- invasion/destruction of blood vessels by bacteria
- Classic case is neutropenic cancer patient with fever, chills (bacteremia) who develops black lesions on chest and back
50
Q
Burkholderia cepacia
A
- Gram negative rod similar to Pseudomonas
- Oxidase positive
- Catalase positive
- Rare cause of infections in
- Cystic fibrosis
- Chronic Granulomatous Disease
51
Q
H pylori illnesses
A
- gastritis & ulcers
- common in paitents with ulcers (majority of duodenal ulcers)
- many with gastric ulcers
- MALT lymphoma
- mucosal associated lymphatic tissue lymphoma
- B-cell cancer; usually in the stomach
- Highly associated with H. pylori
52
Q
H pylori features
A
- Causes gastritis and ulcers (abdominal pain)
- Urease positive
- hydrolyzes urea to compounds that damage epithelium
- produces ammonium (alkaline) (protects from acidic environment in stomach
- Protects bacteria from stomach acid
- Urea breath test
- patients swallow urea with isotopes (carbon-14 or Carbon-13)
- detection of isotope labled carbon dioxide in exhaled breath is evidence indicating urea was split (urease is present)
53
Q
H pylori diagnosis
A
- Biopsy
- Urea breath test
- Stool antigen
54
Q
H pylori treatment
A
- Triple therapy for 7-10 days
- Proton pump inhbitor (omeprazole)
- Clarithromycin
- Amoxicillin or Metronidazole
- Test to determine eradication (failure in 20% of attempts)
- breath test, stool antigen or biopsy
55
Q
Legionella features
A
- Does not gram stain well
- silver stains used
- special culture requirements
- Buffered charcoal Yeast Extract (BCYE) with Iron and Cysteine added for growth
- Supplemented with antibiotics and silver dyes
- Antimicrobials prevent overgrowth by competing organisms
- dyes give distinctive color to Legionella
56
Q
Legionella illneses
A
- Nosocomial pneumonia in Nursing homes
*
57
Q
Legionella pneumonia symptoms
A
- initially mild pneumonia symptoms
- fever; mild, slightly productive cough
- can progress to severe pneumonia
- GI symptoms
- NVwD, abdominal pain
- Hyponatremia (Na<130 mEq/L) common
- can occur in any pneumonia but more common with Legionella Pneumonia
58
Q
Classic case of Legionella infection
A
- Mild cough
- Watery diarrhea
- Confusion (low Na)
- Negative bacteria on gram stain (poorly visualized)
59
Q
Treatment of Legionella
A
- Fluoroquinolone
- or
- Macrolide
60
Q
Pontiac fever
A
Mild form of Legionella infection
- fever
- malaise
- chills
- fatigue
- headache
- no respiratory complaints
- Chest radiograph usually normal
61
Q
Bacteroides fragilis
A
- Gneg rod anaerobic
- normal GI flora
- cause infection after breach of mucosal barrier
62
Q
Bacteroides fragilis infections
A
- rare to cause infections by itself
- Usually part of polymicrobial infections from the GI tract
- peritonitis (following perforation)
- Intraabdominal abscess
- Lung abscess (aspiration)
- E. coli/GNR and B fragilis often components together
63
Q
Bacteroides fragilis treatment
A
- Covered by Metronidazole
- Common GI therapy: Cipro/Flagyl
- Quinolone for E. coli
- Metronidazole for B. fragilis
