Microbiology: Intro & Gram (+)'s Flashcards Preview

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Flashcards in Microbiology: Intro & Gram (+)'s Deck (91):
1

Gram (+) Cocci

Staph
Strep

2

Gram (+) Catalase (+) Cocci

Staph

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Function of endospores

Mechanism of resistance

4

Important endospores (2)

Bacillus
Clostridium

5

MacConkeys

Differential medium
Grows Enteric Bacterias

6

Charcoal Yeast extract Agar (CYE agar)

Selective medium
Grows Legionella

7

Chocolate Agar

Grows Neisseria from normal sterile sites and Haemophilus

8

Thayer-Martin

Selective medium
Chocolate Agar +Antibiotics
Grows Neisseria from sites with normal flora

9

Obligate aerobes

Pseudomonas
Mycobacterium

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Obligate anaerobes

ABC
Actinomyces
Bacteroides
Clostridium

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Gram (+) bacilli

Listeria
Bacillus
Corynebacterium
Clostridium

12

Gram (+) branching filaments

Actinomyces
Nocardia

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Gram (+) Catalase (-) Cocci

Streptococcus

14

Staph family

S. aureus
S. epidermidis
S. saprophitycus

15

Beta hemolytic bacteria characteristics

Complete lysis of RBC
Clear area surrounding colony on blood agar
Color yellow

16

Beta hemolytic bacterias

S. aureus
S. pyogenes
S. agalactiae
Listeria monocytogenes
E. coli

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Subacute Endocarditis with this pathogen makes you concern of Colon Ca? (Specially after GI procedures)

Strep bovis
Bovis in the blood = Ca in the colon

18

Disease presentations of S. aureus

Gastroenteritis
Infective endocarditis
Abscesses
TSS
Impetigo (bullous)
Osteomyelitis

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Gastroenteritis by S. aureus

2-6 hours onset of ingesting toxin
Pathogenicity factor: Enterotoxin A-E (heat stable)
Contaminated foods: Custard pastries, potato salad and canned foods
Characterized by non bloody diarrhea and emesis

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Infective endocarditis by S. aureus

Acute onset
Usually in iv drug users

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TSS

Causal agent: S. aureus
Pathogenicity factor: TSST-1
Clinical Manifestations include: Desquamating rash (particularly in palms and soles), fever, hypotension, multi organ failure
Elevated ALT, AST & bilirubin

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Pneumonia by S. aureus

Productive pneumonia with rapid onset
NOSOCOMIAL
Usual in: IV drug users, CF px's and CGD px's
Salmon colores sputum

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#1 causal agent for osteomyelitis

S. aureus

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Virulence factor: Adherence mechanisms

Pili/fimbriae (gram neg cells)
Teichoic acids (gram pos cells)
Adhesins (pertussis toxin & hemagglutinin)
IgA proteases (binds to Fc receptor)

25

Virulence factor: Partial adherence mechanism

Biofilms (S. epidermidis & S. mutans)

26

Virulence factor: Capsules (agents)

Please SHINE my Skis
Pseudomonas
S. pneumoniae
H. Influenzae type B
Neisseria
E.coli
Salmonella
Klebsiella
S. agalactiae (B)

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ENdotoxins

LPS
Gram neg bacteria
Toxic portion: Lipid A

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LPS mechanism

Activates macrophages
Release cytokines
Fever, tissue damage
Shock
Coagulation (DIC)

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EXotoxins

Are protein toxins generally quite toxic
Component protein toxins: A-B
B component: binds to specific cell receptors to facilitate internalization of A (B = binds)
A component: Active toxic component (often an enzyme)

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Major exotoxins

Inhibitors of protein synthesis
Neurotoxins
Super-antigens
cAMP inducers
Cytolysins

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Inhibitors of protein synthesis exotoxin

C. diphtheriae - Diphteria toxin (interfere with elongation)
P. aeruginosa - Exotoxin A (interfere with elongation)
S. dysenteriae - Shiga toxin (interfere with ribosomal 60S)
Enterohemorrhagic E. coli - Shiga like toxin (interfere with ribosomal 60S)

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Neurotoxins

C. tetani (Gycine and GABA)
C. botulinum (Ach)

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Cytolysins

Lyse cells from outside by damaging membrane.
C. perfringes alpha toxin
S. aureus

34

Treatment for S. aureus

Naf for Staph or Oxacillin
Vanco for MRSA

35

Impetigo in Staph vs Strep

Staph is catalase (+)
Strep is catalase (-)

36

Strep family

S. pyogenes (group A)
S. agalactiae (group B)
S. pneumoniae
S. viridian's
Entrecoccus faecalis / Enterococcus faecium

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Distinguishing features of S. pyogenes

Beta hemolytic
Bacitracin sensitive

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Pathogenesis (virulence)

M-protein: antiphago
M12 strains associated with acute glomerulonephritis
Streptolysin O & S for rheumatic fever

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Diseases caused by S. pyogenes

Pharyngitis
Scarlet fever
Pyoderma/Impetigo
Rheumatic fever
Acute glomerulonephritis (M12 serotype)

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Characteristics of Scarlet Fever

Caused by S. pyogenes
Sandpaper rash (palms and soles are spared)
Strawberry tongue

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Characteristics of impetigo caused by S. pyogenes

Honey-crusted lessions

42

Treatment and Prevention

Beta lactam
Macrolides (penicillin allergy)

Prophylactic treatment should be considered in patients for at least 5 years post acute rheumatic fever.

43

Causal agent of lobar pneumonia in Alcoholics

Strep pneumo (#1)
Klebsiella

44

Ziehl-Neelsen Acid Fast Stain

Acid fast: Red or hot pink
Mycobacterium
Nocardia (partially acid fast)

Non-acid fast: blue

45

Reservoir for S. agalactiae

Vagina (15-20%)
GI tract

46

Distinguishing feats of S. agalactiae

Gram (+) cocci
Catalase (-)
Beta hemolytic
Bacitracin resistant
CAMP test (+)

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#1 causal agent of neonatal septicemia and meningitis

S. agalactiae

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Treatment of diseases cause by S. agalactiae

Ampicillin + Aminoglycoside or Cephalo (3rd gen)

49

Distinguishing feats of S. pneumoniae

Gram (+) DIPLOcocci
Catalase (-)
Alpha-hemolytic
Lysed by bile
Optochin sensitive

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Predisposing factors for S. pneumoniae

COPD
CHF
Alcoholism (#1)
Asplenia

51

Major virulence factor for S. pneumoniae

Polysaccharide capsule

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Diseases caused by S. pneumoniae

Pneumonia
Meningitis
Otitis media
Sinusitis

53

Principal and second causal agent of lobar pneumonia

S. pneumoniae (#1)
Klebsiella (#2)

54

Principal causal agent of community acquired pneumo

S. pneumoniae (specially in 6th decade of life)

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Principal causal agent of childhood and adult meningitis

S. pneumoniae

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Principal causal agent of meningitis in vaccinated child

Principal causal agent

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Principal causal agent of meningitis in unvaccinated child

Haemophilus

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Principal causal agent of meningitis between ages 18-22

Neisseria

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Principal causal agent of meningitis in immunocompromised px (no AIDS)

Listeria

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Principal causal agent of meningitis in AIDS px

Cryptococcus

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Principal causal agent of otitis media or sinusitis in neonates

S. agalactiae

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Clinical manifestations of pneumonia cause by S. pneumoniae

Blood tinged
"Rusty" sputum
Lobar consolidation

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Findings in CSF of S. pneumoniae meningitis

High WBC (neutrophils)
Low glucose
High proteins

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Treatment for bacterial pneumonia caused by S. pneumo

Macrolides

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Treatment for adult meningitis caused by S. pneumo

Ceftriaxone or Cefotaxime
Vancomycin if there is resistance in community

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Treatment for otitis media or sinusitis in children by S. pneumo

Amoxicillin
Erythromicin if allergic

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Vaccine for S. pneumo in pediatric

Conjugated vaccine (PCV) (T dependant)
13 serotypes

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Vaccine for S. pneumo in adults

Polysaccharide vaccine (PPV) (Capsule)
23 serotypes
Recommended for all adults >65 y/o or risk individuals

69

Causal agents of meningitis in neonates

#1 - S. agalactiae
#2 - E. coli
#3 - Listeria mono

70

Genus feats of Mycobacterium

Acid Fast rods with waxy cell wall (parmesan cheese like)
OBLIGATE AEROBE
Sensitive to UV

71

TSST-1 mechanism

Superantigen that binds to MHC II and TCR, resulting in a polyclonal T-cell activation

72

General feats of S. epidermidis

Gram (+) cocci in clusters
Catalase +
Coagulase (-)
Urease (+)
Novobiocin sensitive
Produces biofilms

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Normal flora bacteria that usually contaminates blood cultures

S. epidermidis

74

Most common disease caused by S. epidermidis

Endocarditis in IV users
Catheter and prosthetic device infections by producing adherent biofilms

75

Second most common cause of uncomplicated UTI in young women

S. saprophyticus

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Most common cause of UTI's

E. coli

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Causal agent of sepsis in patients with sickle cell disease or splenectomy

S. pneumoniae

78

2 step screen diseases (dx and confirmatory) (3)

Tb
Siphilys
HIV

79

Lowenstein-Jensen medium grows

M. tuberculosis (slow growing)

80

Principal virulence factor of Tb

Facultative intracellular organism

81

Primary and secondary tb

Primary:
Organisms replicate in naive macrophages
Formation of Gohn focus (alveolar in mid/lower lobes)
Formation of Gohn complex (Gohn focus+hilar lymph nodes)
>90% heals by fibrosis calcification

Secondary:
Reactivation because of inmunocompromise leads to replication
Fibrocaseous cavitary lesion (upper lobes)
May produce miliary tb (disseminated)

82

Diagnosis of Tb

2 step microscopy of sputum:
1. Auramine-rhodamine stain (fluorescent apple green)
2. Acid fast stain

PPD or Mantoux

83

PPD skin test interpretation

Measure zone of induration after 48-72 hrs
Positive if:
>5 mm in HIV pos (reduced ability to mount skin test) and recent exposure to Tb
>10 mm in high risk population
>15 mm in low risk population (vaccinated)

84

Treatment of Tb

RIPE for first 2 mo:
Rifampin + Isoniazid + Pyrazinamide + Ethambutol
Next 4 mo:
Rifampin + Isoniazid

Ethambutol or Streptomycin added if resistance

85

Tb prophylaxis

Isoniazid for 9 mo (infection without symptoms)
BCG vaccine (live attenuated)

86

Nontb organism that affects AIDS patients with <50 T cell count

MAK COMPLEX
M. avian intracellulare
M. kansasii

87

Fish tank granuloma

M. marinum

88

Causes subacute endocarditis in damage heart valves

S. sanguinis (Viridian's group)
Also causes dental cavities

89

Major criteria for rheumatic fever

J<3NES
Joints - Polyartrithis
<3 - Carditis
Nodules (subcutaneous)
Erythema marginatum
Sydenham chorea

90

Diseases caused by Enterococcus

After GI procedures:
Subacute endocarditis (elderly males)
Urinary/biliary tract infections (elderly males)`

91

VRE?

Vancomycin-resistant enterococci
Enterococcus are very resistan bacterias which are an important cause of nosocomial infections