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CLM > Microbiology I > Flashcards

Microbiology I Flashcards

1
Q

Bacteria

A

Unicellular organisms

Reproduce by binary fission

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2
Q

Four basic morphological types of bacteria

A

Cocci (spherical-shaped cells)
Bacilli (rod-shaped cells)
Spirilla (spiral-shaped cells)
Vibrios (comma-shaped cells)

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3
Q

Obligate anaerobes

A

Require oxygen

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4
Q

Facultative anaerobes

A

Grow in both aerobic and anaerobic environments

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5
Q

Obligate anaerobes

A

Cannot grow in the presence of oxygen

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6
Q

Capnophilic

A

Require 5%-10% CO2 for optimal growth

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7
Q

Microaerophilic

A

Grow optimally in a reduced level of oxygen

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8
Q

Cell membrane of bacteria

A

Osmotic barrier

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9
Q

Cell wall of bacteria

A

Gm pos- thick rigid peptidoglycan layer
Gm neg- Also has an outer lipopolysaccharide (LPS) layer
-Endotoxin (important virulence factor)

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10
Q

Polysaccharide capsule of bacteria

A

Covers many bacteria and serves to prevent or inhibit phagocytosis (S. pneumoniae)

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11
Q

Endotoxin side effects

A 
Shock
Sepsis
Fever
DIC
Leukopenia
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12
Q

Gram stain process

A

Crystal violet, iodine, decolorizer, safranin O

  • Gm pos cells stain purple
  • Gm neg cells stain red
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13
Q

Acid-fast stain

A

Used to detect organisms that do not stain well with other conventional stains due to their high lipid content (Mycobacterium spp)

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14
Q

Nl flora in skin

A

Micrococcus

Staphylococcus spp

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15
Q

Nl flora in mouth

A

Streptococcus spp

Anaerobes

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16
Q

Nl flora in nasopharynx

A

Staph and strep

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17
Q

Nl flora in GI

A

Mostly anaerobes

Enterobacteriaceae

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18
Q

Nl flora in GU

A

Vagina is colonized with Lactobacillus

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19
Q

General guidelines for taking microbial specimens

A

Specimen should be from the infection site and not contaminated by the surrounding area
Whenever possible, the specimen should be collected before antimicrobials are administered
Aseptic technique is required

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20
Q

Throat collection

A

Tongue depressed, swab between the tonsillar pillars and behind the uvula (cheek, tongue, and teeth should not be touched)

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21
Q

Nasopharynx collection

A

Flexible wire nasopharyngeal swab inserted into posterior nasopharynx

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22
Q

Sputum collection

A

1st gargle with water, early morning deep cough specimen preferred

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23
Q

Blood collection

A

2-3 cultures obtained after skin disinfected with 70% alcohol, followed by iodine
-Iodine must dry and area cannot be palpated again

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24
Q

Urine collection

A

Midstream clean-catch is preferred

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25
Q

Stool collection

A

Never taken from toilet nor contaminated with urine

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26
Q

Kirby-Bauer disk diffusion test

A

Measure diameter of growth inhibition around filter paper disk containing abx
Zone of inhibition

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27
Q

Minimum inhibitory concentration (MIC)

A

Lowest concentration of antibiotic that inhibits visible growth, as detected by lack of turbidity

  • Antibiotic is added to broth in serial twofold dilutions
  • Standard inoculum of bacterium is added to each
  • The MIC is the concentration of the first well that shows no growth or turbidity
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28
Q

Susceptible results

A

The organism should respond to the usual doses of the drug

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29
Q

Moderately susceptible

A

The isolate may be inhibited by concentrations of a drug that are achieved when the maximum parenteral doses are given

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30
Q

Intermediate susceptibility

A

The results are equivocal or indeterminate

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31
Q

Resistant- susceptibility

A

The bacterium is not inhibited by achievable concentrations of the drug

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32
Q

Staphylococcus

A

Catalase-positive, nonmotile, facultative anaerobes in grape-like clusters
Nl inhabitants of the skin and mucous membranes
-Commonly cause human infections

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33
Q

Coagulase test for staphylococcus

A

Pos- Staphylococcus aureus

Neg- S. epidermidis, S. saprophyticus

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34
Q

S. aureus and skin infections

A

Boils
Carbuncles
Furuncles
Folliculitis

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35
Q

S. aureus and food poisoning

A

Enterotoxins A and D

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36
Q

S. aureus and scalded skin syndrome (Ritter’s disease)

A

Extensive exfoliative dermatitis due to toxin

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37
Q

S. aureus and toxic shock syndrome (TSS)

A 
High fever
Rash
Hypotension
Shock
Desquamation of the hands and feet
Possible death
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38
Q

S. aureus and osteomyelitis

A

Often secondary to bacteremia

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39
Q

Antibiotic susceptibility to staphylococcus

A

Penicillin resistance is high

B-lactamase: an enzyme that inactivates the B-lactam abx

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40
Q

B-lactamase pcns (Methicillin, Oxacillin)

A

Methicillin-resistant S. aureus (MRSA)
-Nosocomial and community-associated infections
-Tx with bactrim (skin) or vancomycin
Methicillin-resistant S. epidermidis (MRSE)

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41
Q

Steptococcus/enterococcus

A

Catalase-negative, facultative anaerobes
Hemolysis patterns on sheep blood agar are helpful in identification
Gm-pos cocci, arranged in pairs or chains

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42
Q

S. pneumoniae

A

Important human pathogen causing sinusitis, otitis media, pneumonia
-Meningitis, bacteremia
-Vaccination
The key virulence factor is an antiphagocytic capsule

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43
Q

Lab findings in S. pneumoniae

A

Gram pos cocci in pairs

44
Q

S. pyogenes

A

AKA group A streptococcus or B-hemolytic group A streptococcus (GABHS)
Streptolysin O- causes hemolysis of RBC
-Antistreptolysin O titer (ASO titer)

45
Q

Infections of S. pyogenes

A

Pharyngitis- “Strep throat” or scarlet fever
Skin infections
-Impetigo, necrotizing fasciitis, pyoderma
-Rheumatic fever and glomerulonephritis

46
Q

Group D streptococci

A

Strep bovis and Strep equinus
May be nl intestinal flora
May also be etiologic agents of bacterial endocarditis and other infections

47
Q

Viridans Streptococci

A

Alpha hemolytic streptococci that do not meet full criteria for S. pneumoniae
Part of nl flora of the oropharynx
May cause subacute bacterial endocarditis

48
Q

Enterococcus

A

Genus found in the intestinal tract

  • E. faecalis, E. facium, E. avium, E. durans
  • Share many similarities as the Group D streptococci
  • May cause UTIs
  • Vancomycin-resistant Enterococcus (VRE)
  • E. faecium> E. faecalis
49
Q

Listeria monocytogenes

A

Aerobic Gm pos bacilli
Widespread in the environment
Various infections in neonates and immunosuppressed persons including meningitis

50
Q

Corynebacterium diphtheriae

A

Aerobic Gm pos bacilli
Causes diphtheria- inflammation of the throat with a pseudomembrane. Toxin damages major organs. Tx: antitoxin, erythromycin

51
Q

Neisseria

A

Gm neg cocci seen in pairs (intracellular diplococci)

52
Q

Neisseria gonorrhoeae

A

Venereal disease with burning and d/c from the urethra. May lead to female PID or spread to skin and/or joints
Ophthalmia neonatorum- newborn conjunctival infection
Grows on chocolate agar (but NOT on blood agar) and in selective media like Thayer-Martin media

53
Q

Neisseria meningitidis

A

Meningococcal meningitis transmitted by respiratory droplets usually between prolonged close contacts
Onset is abrupt, with HA, stiff neck, fever +/- rash
Specimens
-CSF, blood, and joint fluid
-Nasopharyngeal swabs can be cultured to detect carriers

54
Q

Morexella catarrhalis

A

Nl upper respiratory tract flora

Sinusitis, otitis media, community acquired pneumonia

55
Q

Haemophilus

A

Gm-neg nonmotile bacilli and coccobacilli

56
Q

Haemophilus influenzae

A

Can cause sinusitis, otitis media, epiglottitis, pneumonia, meningitis
Vaccination

57
Q

Haemophilus ducreyi

A

Causes chancroid, a sexually transmitted disease with a painful ulcer

58
Q

Bordetella

A

Very small gram-neg bacilli

59
Q

Bordetella pertussis

A

Causes whooping cough via droplets
Catarrhal stage (cold)- paroxysmal stage (cough)- convalescence stage (healing +/- complications)
Nasopharyngeal swab specimen
Tx: macrolide antibiotic

60
Q

Enterobacteriaceae

A

Largest and most medically important family of Gm neg bacilli

  • Escherichia
  • Klebsiella
  • Salmonella
  • Shigella
  • Yersinia
  • Proteus
61
Q

Escherichia

A 
Nl intestinal flora
Opportunistic organism
Mcc of UTI
Sx
-Urgency
-Frequency
-Dysuria
-Hematuria
-Pyuria
62
Q

Klebsiella

A

Gm-neg rod-shaped bacteria

  • Facultative anaerobes
  • Found routinely as nl flora in nose, mouth, GI tract
  • Pathogen
  • -Pneumonia- K. pneumoniae
  • -UTI, meningitis, diarrhea
63
Q

Enterobacter

A

Gm-neg, rod-shaped bacteria

  • Pathogenic and opportunistic infections
  • -Respiratory and urinary tract
  • Tx
  • -Cefepime, aminoglycosides, quinolones
64
Q

Salmonella

A 
Gm-neg rod-shaped bacteria
Pathogenic when acquired by oral route
-Usually a self-limiting disease
--Diarrhea
-Typhoid fever, paratyphoid fever, food poisoning
--+/- toxin
--Hypovolemic and/or septic shock
--Oliguria and azotemia
-Tx: Ciprofloxacin (inc. resistance), Azithromycin
65
Q

Shigella

A

Natural habitat limited to the intestine of humans and other primates where they produce bacillary dysentery
-Slender gm neg rods
-Facultative anaerobes (ferment glucose)
Infections are almost always limited to the GI tract

66
Q

Sx and resolution of shigella

A

Sudden abd pain, fever, watery diarrhea due to exotoxin
Each BM is accompanied by straining and rectal spasms
More than half resolve in 2-5 days but most shed dysentery bacilli for a short period while few remain chronic carriers
Tx: Cipro, Ampicillin, Bactrim, supportive

67
Q

Serratia

A

Opportunistic pathogen in hospitalized pt
Pneumonia, bacteremia, endocarditis esp in narcotic addicts and hospitalized pts
S. marcescens is often resistant to aminoglycosides and pcn
Tx: 3rd gen cephalosporin

68
Q

Yersinia

A 
Gm neg, rod-shaped bacteria
Yersinia pestis causes the plague
-Rodents are reservoirs
--Flea bites spread to lymphatics
-May be associated with Crohn's disease
-Implicated as one of the causes of worldwide reactive arthritis
-Tx: streptomycin and tetracycline
69
Q

Proteus

A

Produce infections in humans when bacteria leave the intestinal tract
UTI, bacteremia, pneumonia
Produce urease resulting in alkaline urine
Organism is rapidly motile
Tx: Cephalosporin, aminoglycosides

70
Q

Campylobacter

A

Campylobacter jejuni
Ingestion of contaminated food/water (raw chicker)
Causes diarrhea +/- blood

71
Q

Helicobacter

A

H. pylori
Gastritis, nausea, abd pain
Increased risk of ulcers and stomach cancer

72
Q

Vibrionaceae

A

Vibrio cholerae
Life-threatening diarrhea loss of 20 L/day
Rice water stools

73
Q

Pseudomonas

A

Gm-neg rod-shaped bacteria

-Ubiquitous organism that thrives in harsh conditions

74
Q

Pseudomonas aeruginosa

A 
Ermerging opportunistic infection
Cystic fibrosis
Hot tub folliculitis
Otitis externa
ICU pneumonia, sepsis
Tx: beta-lactam and aminoglycoside antibiotic
75
Q

Legionella

A

Gm-neg rod-shaped bacteria

Sx: pneumonia, hyponatremia

76
Q

Labs for legionella

A 
Silver stain
Charcoal yeast extract agar
UV light
Immunological assays
PCR
77
Q

Tx for legionella

A

Quinolones

Macrolides

78
Q

Gardnerella

A

Gram-variable bacteria
Causes bacterial vaginosis
-Gardnerella vaginalis
Sx: vaginal d/c, fish-like odor

79
Q

Labs for gardnerella

A

Chocolate agar
Wet-mount slide
Clue cells (bacteria adhering to the surface of squamous epithelial cells)

80
Q

Tx for gardnerella

A

Metronidazole or clindamycin

81
Q

Mycoplasma

A

Bacteria that lack a cell wall around their cell membrane

  • Unaffected by many common abx like pcn
  • Atypical pneumonia
  • -Mycoplasma pneumoniae
  • Infertility, vaginal infections
  • Tx: macrolide or doxycycline
82
Q

Chlamydia

A

Bacteria that replicate inside host cells and are termed intracellular
Located in an inclusion body or vacuole

83
Q

Pathogen of chlamydia

A

Chlamydia trachomatis
STI
Genital and eye disease (trachoma)
Reactive arthritis

84
Q

Lab of chlamydia

A

Culture
Nucleic acid amplification tests
PCR

85
Q

Tx of chlamydia

A

Azithromycin

Doxycycline

86
Q

Spirochetes

A

Helical shaped gram-neg bacteria with spiral coils

87
Q

Treponema pallidum

A 
Spirochete
Syphilis
Primary- painless chancre
Secondary- rash on palms and soles, arthritis
Tertiary- cardiac/neuro
88
Q

Labs for Treponema pallidum

A

RPR
VDRL
FTA-ABS

89
Q

Tx for Treponema pallidum

A

PCN

90
Q

Borrelia burgdorferi

A 
Lyme disease
Spirochete
Transmitted by Ixodes tick
Stage 1- localized rash
Stage 2- heart, bones, nervous system
Stage 3- chronic arthritis
91
Q

Labs for Borrelia burgdorferi

A

Serology (ELISA)

92
Q

Tx for Borrelia burgdorferi

A

Doxycycline x 10-14 days

93
Q

Mycobacterium leprae

A

Leprosy- granulomas of nerves, skin, etc.

94
Q

Mycobacterium tuberculosis

A

Mostly lung infection- cough, blood-tinged sputum, fever, night sweats, weight loss
Spread by air droplets

95
Q

Lab for mycobacteria

A

Acid-fast bacilli

PCR

96
Q

Tx for mycobacteria

A

Isoniazid x 9 mos for latent infection

97
Q

Gram-neg bacilli- anaerobes

A

Bacteroides fragilis

90% of anaerobic peritoneal infections

98
Q

Gram-pos spore-forming bacilli- anaerobes

A 
Clostridium- produce endospores
Clostridium botulinum- botulism (toxin)
Clostridium tetani- tetanus (lockjaw)
Clostridium difficile- diarrhea
Clostridium perfringens- gas gangrene
99
Q

Clostridium difficile

A

Gm-pos spore forming bacilli

Antibiotic-associated diarrhea and pseudomembranous enterocolitis

100
Q

Lab for Clostridium difficile

A

Culture
Serology for toxin (ELISA)
Stool antigen
PCR

101
Q

Tx for Clostridium difficile

A

Metronidazole
Oral vancomycin
Stool transplantation

102
Q

Gm-pos nonspore-forming bacilli

A

Actinomyces israelii
Propionibacterium
Lactobacillis

103
Q

Actinomyces israelii

A

Periodontal disease

104
Q

Propionibacterium

A

P. acnes is the most common isolate (skin)

105
Q

Lactobacillis

A

Nl flora in the mouth, intestinal tract, and vagina

Long chains of Gm pos rods

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