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Microbiology > Gram +/- > Flashcards

Gram +/- Flashcards

1
Q

Group A Streptococcus

A

Strep pyogenes
Beta hemolytic
Pain out of proportion to exam (may look just erythematous & warm (cellulitis) – with pain however, gives hint to GAS and need to debride)
- can advance quickly
Pharyngitis (strep throat); impetigo (child - honey crusted on face); erysipelas; scarlet fever; necrotizing fasciitis
- Universally susceptible to PCN

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2
Q

Clostridium perfringens

A

Gram positive rod (* Large Boxcar shape)
Spores are commonly found in the soil
Wounds get infected.
Toxin mediated (Alpha toxin)
- Severe cellulitis, gangrene (necrosis), septic shock, crepitus from gas gangrene
- Hemolysis is common
Can also cause diarrhea (3rd highest cause)
- spores survive cooking and toxin is produced causing diarrhea
— Also sensitive to PCN

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3
Q

Clostridium difficile

A

Gram positive rod
Spores
Most common nosocomial cause of diarrhea
Most common cause of antibiotic associated diarrhea (typically clindamycin and ampicillin)
- Can range from mild to severe
- Inflammatory or watery or sometimes bloody
Can get colitis (inflammatory)
Can be toxic megacolon
-fecal-oral route
—Can get from hospital workers, hospital environment, opportunistic infection (colonized) or roommates
toxin mediated

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4
Q

Clostridium tetani

A

Tetanus
Gram positive rods
Found in soil – usually acquired through wounds or cuts (nail)
- produces AB toxin that causes muscle spasticity and spastic paralysis
- Tdap provides immune protection against the toxin.
High mortality rate

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5
Q

Clostridium botulinum

A

Botulism
Gram positive rods
Spores survive cooking and grow to form AB toxin (raw honey, spores from carpet)
-commonly seen in infants causing flaccid paralysis or floppy baby syndrome
- hypotonia, poor feeding, flaccid paralysis

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6
Q

UTIs - Most common cause? Would you obtain a urine culture for a clinic patient? What about a hospital patient? Patient with indwelling catheter?

A

E.coli - 90% of cases (gram negative rod) especially community acquired (fecal-urethral); next would be
Staphylococcus saprophyticus (sex-> vag to urethra)
- No, unless UTI was persistent or recurring
- Hospital patient = Yes, would obtain urine culture especially if suspected as nosocomial
- Common hospital causes are enterococcus and Pseudomonas aeruginosa
- if indwelling catheter or immunocompromised, obtain culture and treat immediately.

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7
Q

E.coli is a part of the normal flora of the colon. Why does this not cause disease?

A

Depends on the pathogenicity acquired islands (PAIs) and virulence that can be obtained from nearby non-pathogenic bacteria in order to cause disease.

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8
Q

EHEC vs ETEC

A

Enterohemorrhagic E.coli is O157:H7 gram negative rod that causes BLOODY diarrhea (hemorrhagic colitis) and can lead to HUS and renal failure.

  • Usually obtained via undercooked meat especially ground beef and contaminated vegetables
  • Toxin mediated = inhibits protein synthesis
  • Do not treat with antibiotics because it will precipitate the toxin and cause or worsen HUS

Enterotoxigenic E.coli is obtained from contaminated food or water

  • Secretory toxin mediated
  • Watery diarrhea from mild to severe
  • “Travelor’s Diarrhea”
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9
Q

What is HUS, hemolytic uremic syndrome?

A

Hemolytic uremic syndrome is when an infection from the GI secretes toxins that get into the bloodstream and cause hemolysis of blood, anemia, and renal failure.

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10
Q

E.coli - what is it, in general? what can it cause?

A

Gram negative rod; common normal flora of colon

  • # 1 cause of UTIs (usually uncomplicated)
    • Uses P-fimbriae to adhese and colonize to urethra and bladder
  • Can cause neonatal meningitis during birth of colonized mothers (vaginas) - requires capsule
  • Can cause sepsis and DIC - can acquire from own flora causing bacteremia and consequently sepsis and DIC
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11
Q

Neonatal meningitis can be caused by?

A

E. Coli due to colonized vagina that the infant contracted during birth (capsule required)

GBS - strep agalactiae

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12
Q

Gram positive cocci that causes UTI? How is this organism acquired?

How do you prevent this?

A

Staphylococcus saprophyticus (coagulase negative)

  • obtained usually via sexual activity
  • Colonized in vagina and colon of women that gets inadvertently transferred to urethra causing UTI
  • 2nd most common cause of UTIs behind E.coli
  • Pee after sex.
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13
Q

young boy comes in with fever, chills, headache and N/V. Sent home. Comes back with same symptoms but worse – suffered seizure, is confused and HA worse. petechial rash is noted. What is this?

What should have be drawn on initial visit?

A

Neisseria meningitidis - gram negative diplococci

MENINGITIS

  • ## BC and LP
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14
Q

Neisseria meningitidis

A

Gram negative diplococci - kissing kidney beans

  • also called meningococcus
  • Almost always nasopharyngeally colonized (prerequisite for disease)
  • Causes severe meningitis in children to teenagers and those >65yo
  • HA, NV, Fever, chills, bacteremia, petechial rash over entire body,
  • Sudden and can be fatal quickly
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15
Q

What is the major disease associated with Neisseria meningitidis?

What presentation (lab and physical) is characteristic of this disease?

A

meningitis
Life-threatening

meningitis with accompanying meningococcemia
or
meningococcemia without meningitis

petechial rash

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16
Q

What causes petechiae?

A

small blood clots in small blood vessels due to hypercoag state from inflammation and due to toxin mediated mechanisms

accumulation of petechia can coalesce and form purple lesions

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17
Q

Gram positive cocci in pairs and chains are typically what, in general?

A

streptococci

e.g. agalactiae, viridans, pneumoniae, pyogenes, enterococci, gallolyticus

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18
Q

Gram positive cocci in clusters are typically what?

A

staphylococci

e.g. aureus, epidermidis, saprophyticus

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19
Q

Staphylococcus aureus
Describe.
What are some symptoms and consequences?

A

Gram positive cocci in clusters, coagulase positive
Commonly colonized on skin and mucosa
- Boils, abscesses, folliculitis, wound infections, impetigo
- Disseminated infections (boils or wounds to blood): bacteremia, endocarditis, osteomyelitis, PNA (HAP is common)
- Food poisoning, TSS, scalded skin syndrome

  • Virulence factors: LOTS! Surface proteins, enzymes and toxins
  • —Protein A, coagulase, TSST, Panton Valentine Leukocidin Exfoliative toxin
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20
Q

If a patient is diagnosed with bacteremia that is confirmed as staph aureus, what do you always want to check for?

A

endocarditis

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21
Q

Staphylococcus epidermidis
Describe it.
Where is usually found?
What kind of problems can it cause?

A

Gram positive cocci in clusters, coagulase negative

  • normal flora of skin
  • can penetrate wounds or central lines
  • Creates biofilms on foreign objects especially central line infections, prosthetics, artificial valves, and orthopedic devices
  • Has surface adhesins that help it adhere to foreign objects
  • Describe biofilm
  • —Extracellular polysaccharide matrix or slime is produced which encases the bacteria. Biofilm functions as barrier to antibiotic penetration and may interfere with host defenses.
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22
Q

What is a biofilm and why is it harmful?

What organism is notorious for producing biofilm (among the many)?

A

Extracellular polysaccharide matrix or slime is produced which encases the bacteria. Biofilm functions as barrier to antibiotic penetration and may interfere with host defenses.

staphylococcus epidermidis

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23
Q

Vibrio cholerae

A

Cholera

  • curved rods, gram negative rods
  • caused by fecal contamination of water due to poor sanitation, malnutrition and natural disasters (Haiti)
  • Toxin mediated = secretory
  • Causes massive diarrhea that looks like rice due to the mucus in the stool
  • leads to dehydration and death
  • Treat with oral hydration salts
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24
Q

Vibrio parahaemolyticus

A

Gram negative curved rods
- caused by eating raw or undercooked shellfish or seafood, especially oysters
- Causes watery diarrhea
Can also cause wound infections

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25
Q

Vibrio vulnificus

A

Gram negative curved rods

  • Caused by raw shelfish
  • Diarrhea
  • SEVERE soft tissue infections
  • Can lead to sepsis and death ESPECIALLY IN THOSE WITH UNDERLYING LIVER DISEASE.
26
Q

What organism is very dangerous for those with liver disease?

A

Vibrio vulnificus

27
Q

What 2 organisms can you get from eating raw shellfish or seafood (oysters)?

A

vibrio haemolyticus

vibrio vulnificus

28
Q

What are the group D streptococcus organisms? Hemolysis?

A 
Enterococcus
Streptococcus gallolyticus (bovis)

gamma-nonhemolytic

29
Q

Streptococcus gallolyticus

A

Group D strep
Gram positive cocci in chains or pairs

If bacteremic and has endocarditis, check for colon cancer, strong association

If have patient with endocarditis that blood cultures show strep gallolyticus, check for colon cancer (ALWAYS).

30
Q

What organism has a strong correlation (if bacteremic) of colon cancer and endocarditis?

A

streptococcus gallolyticus

31
Q

Enterococcus

A

Group D strep
Gram positive cocci in pairs and chains
non-hemolytic

  • Normal flora of colon

causes hospital acquired UTIs
endocarditis
Blood stream infections (CL related)

32
Q

Viridans group strep

A

Gram positive cocci in chains, pairs
alpha hemolytic

  • can be normal flora of oropharynx and colon
  • can enter bloodstream after dental work
  • BRAIN abscesses, liver abscesses, abdominal abscesses, endocarditis
33
Q

Streptococcus agalactiae

A

Group B strep
Gram positive cocci in pairs, chains
beta-hemolytic

Adults: can invade and cause septic arthritis, cellulitis, osteomyelitis; Diabetes and breast cancer are predisposing factors

Neonatal: Source of meningitis; Some women are colonized with GBS in genital tract (tested at 36 weeks and if positive, receive PCN before delivery). Can cause neonatal meningitis, sepsis and PNA

34
Q

Streptococcus pneumoniae

A

Gram positive lancet shaped diplococci
alpha hemolytic

  • Affects young and old and immunocompromised
  • Lobar PNA
  • Bacteremia
  • Meningitis (MOST common cause)
  • Otitis media (MOST common cause)
  • VIRULENCE factor: CAPSULE
    Vaccine available for major serotypes
35
Q

Epiglottitis is associated with what organisms mostly?

A

Haemophilus influenzae

36
Q

Haemophilus influenzae

A

Gram negative coccobacillus

  • Meningitis (capsule!!!)
  • formerly a big problem before vaccine
  • Otitis media (2nd most common cause)
  • sinusitis
  • Epiglottitis - acute inflammation in supraglottic region of oropharynx -> can lead to airway compromise and death
  • PNA (elderly)
  • COPD exacerbations

CXR/neck would show thumb sign

37
Q

SOB, stridor, no history of vaccines, CXR thumb sign —?

A

Haemophilus influenzae

epiglottitis

38
Q

thumb sign on CXR/neck would indicate?

A

Haemophilus influenzae

39
Q

currant jelly sputum with patient with PNA?

A

Klebsiella pneumoniae

40
Q

Klebsiella pneumoniae

A

Gram negative rod
OPPORTUNISTIC INFECTION
- Found in water, soil, GI tract

  • Common cause of HA-PNA
  • Common cause of PNA in alcoholics and malnourished
  • Produces currant jelly sputum (bloody, thick and mucoid)
  • Resistance to Abx is common
41
Q

What organism do alcoholics tend to acquire (or malnourished)?
Why?

A

Klebsiella pneumoniae
Alcohol depresses normal immune defenses, depresses mucociliary movement
-Dampens PMN and macrophage recruitment to fight infection
-risk for aspiration PNA due to drunkeness/decreased or altered LOC
-Poor nutrition, immunosuppression from chronic liver disease and smoking decrease defenses

42
Q

What is a common area of the lung where aspiration PNA is seen on x-ray?

A

Superior portion of Right Lower Lobe

Lingula of left lung

43
Q

What organism is common HAP especially VAP?

A

Pseudomonas aeruginosa

44
Q

Pseudomonas aeruginosa

A

Gram negative bacillus
OPPORTUNISTIC
Obligate aerobe
Found in water and soil and some colons

Causes PNA especially in the hospital setting r/t VAP and Cystic fibrosis (biofilm)

  • Sepsis
  • Skin infections in burn patients
  • UTI - hospital acquired
  • **Affects mainly sick patients

MDR*

Has fruity odor

45
Q

coughing fits that may cause vomiting

A

Bordetella pertussis

46
Q

Bordetella pertussis

A

Gram negative coccobacillus
Encapsulated

  • Whooping cough
  • Progressively worsening cough
  • Coughing can be so forceful it can lead to post-tussive vomiting.

Dtap vaccine prevents

47
Q

Salmonella enteritidis

A

Gram negative bacillus

  • causes enterocolitis
  • Caused by eating contaminated food - especially poultry and eggs
  • Can be caused by contact with pets: reptiles, turtles, lizards, etc
  • VERY common cause of food poisoning
48
Q

Salmonella enterica serotype Typhimurium

A

Gram negative bacillus

  • Contaminated food/water
  • human to human transmission
  • poor sanitation/impoverished areas
  • causes Typhoid fever
  • Does not cause gastroenteritis
  • What is typhoid fever?
  • –fever, chills, abdominal pain, “rose spots”; septic shock can develop; GI perforation as well.
49
Q

What is typhoid fever? What causes it?

A

fever, chills, abdominal pain, “rose spots”; septic shock can develop; GI perforation as well.

associated with Salmonella enterica serotype Typhimurium

50
Q

Causes of bloody diarrhea?

A

EHEC

Shigella

51
Q

Shigella

A

Gram negative bacillus

  • Causes bloody diarrhea = dysentery
  • fecal-oral route
    • poor hand hygiene in DAYCARES
  • Toxin mediated (like EHEC but less severe)
  • S. sonnei most common species in the U.S.
  • S. dysenteriae more common worldwide – causes more severe disease; Can cause Hemolytic uremic syndrome but not as common as EHEC
52
Q

Campylobacter

A

Thin, spiral shaped Gram negative rods

  • causes watery diarrhea from undercooked chicken or raw milk
  • watery diarrhea progresses to bloody
  • MOST COMMON cause of enteric bacterial infection in developed countries
53
Q

Bacteroides

A

gram negative rod (most common: Bacteroides fragilis)

PREDOMINANT organism in human colon
- Found in most of women’s vaginas too

  • Obligate anaerobe
  • Causes intra-abdominal abscesses when there is a break in the mucosal surface (trauma, surgery, adhesions)
54
Q

Helicobactor pylori

A

Gram negative CURVED rods

Causes ulcers and eventually cancer

55
Q

Legionella pneumophila

A

Gram negative rod - respiratory

  • Water-borne pathogen
  • Transmission occurs through contaminated fountains, whirlpool baths, air conditioners, etc.
  • Causes an atypical pneumonia – Fever, HA, Myalgia
  • Symptoms are different than with a “typical” pneumonia; CXR can also look different. – can have PNA symptoms too
56
Q

Gram negative rods that cause respiratory disease?

A

Haemophilus influenzae
Bordetella pertussis
Legionella pneumophila

Pseudomonas aeruginosa
Klebsiella pneumoniae
(opportunistic)

57
Q

Neisseria gonorrheae

A

Gram negative cocci

  • Called Gonococcus
  • Sexually transmitted infection second only to Chlamydia in incidence
  • Causes purulent urethritis or cervicitis. - Can also cause pharyngitis and proctitis
  • PID is a complication
  • Infection can also disseminate and cause gonococcemia – manifestations include purulent arthritis, tenosynovitis, dermatitis
58
Q

Moraxella catarrhalis

A

Gram negative Diplococcus

  • Part of normal throat flora
- Causes Sinusitis
Otitis media (3rd leading cause)
Bronchitis
Pneumonia – increasingly recognized as a cause in the elderly
Common cause of acute COPD exacerbations
59
Q

bacillus anthracis

A

Gram positive rod
anthrax
AB toxin

  • Inhalation of spores –> fatal if untreated
  • cutaneous –> spores enter subcutaneous (common)
      • from infected animals or animal products

Red lesion with eschar in center. Edema. Some lymphadenopathy.

60
Q

bacillus cereus

A

gram positive rod

causes food poisoning (reheating rice.. spores leftover)
- toxin mediated
- diarrheal syndrome
or
- emetic syndrome

self-limiting

61
Q

Corynebacterium diptheriae

A

gram positive rod
causes diptheria

  • Pleomorphic, club-shaped, arranged in palisades, beaded appearance.
  • Toxin mediated: AB toxin
  • Causes an acute pharyngitis with formation of an
    overlying gray membrane (pseudomembrane) which
    can cause mechanical obstruction
  • Vaccine is protective (DTaP, TDaP)
62
Q

Listeria monocytogenes

A

Gram positive rods

Causes meningitis, bacteremia at extremes of age
and in immunosuppressed population
Also a rare cause of febrile gastroenteritis
Infection in pregnancy can be devastating –
nonspecific flu-like symptoms. Can result in fetal
demise/miscarriage/infection at birth (no lunchmeat,
hot dogs, soft cheeses in pregnancy!)

Microbiology (3 decks)

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