Microbiology I Flashcards
1
Q
Bacteria
A
Unicellular organisms
Reproduce by binary fission
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)
3
Q
Obligate anaerobes
A
Require oxygen
4
Q
Facultative anaerobes
A
Grow in both aerobic and anaerobic environments
5
Q
Obligate anaerobes
A
Cannot grow in the presence of oxygen
6
Q
Capnophilic
A
Require 5%-10% CO2 for optimal growth
7
Q
Microaerophilic
A
Grow optimally in a reduced level of oxygen
8
Q
Cell membrane of bacteria
A
Osmotic barrier
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)
10
Q
Polysaccharide capsule of bacteria
A
Covers many bacteria and serves to prevent or inhibit phagocytosis (S. pneumoniae)
11
Q
Endotoxin side effects
A
Shock Sepsis Fever DIC Leukopenia
12
Q
Gram stain process
A
Crystal violet, iodine, decolorizer, safranin O
- Gm pos cells stain purple
- Gm neg cells stain red
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)
14
Q
Nl flora in skin
A
Micrococcus
Staphylococcus spp
15
Q
Nl flora in mouth
A
Streptococcus spp
Anaerobes
16
Q
Nl flora in nasopharynx
A
Staph and strep
17
Q
Nl flora in GI
A
Mostly anaerobes
Enterobacteriaceae
18
Q
Nl flora in GU
A
Vagina is colonized with Lactobacillus
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
20
Q
Throat collection
A
Tongue depressed, swab between the tonsillar pillars and behind the uvula (cheek, tongue, and teeth should not be touched)
21
Q
Nasopharynx collection
A
Flexible wire nasopharyngeal swab inserted into posterior nasopharynx
22
Q
Sputum collection
A
1st gargle with water, early morning deep cough specimen preferred
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
24
Q
Urine collection
A
Midstream clean-catch is preferred
25
Stool collection
Never taken from toilet nor contaminated with urine
26
Kirby-Bauer disk diffusion test
Measure diameter of growth inhibition around filter paper disk containing abx
Zone of inhibition
27
Minimum inhibitory concentration (MIC)
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
28
Susceptible results
The organism should respond to the usual doses of the drug
29
Moderately susceptible
The isolate may be inhibited by concentrations of a drug that are achieved when the maximum parenteral doses are given
30
Intermediate susceptibility
The results are equivocal or indeterminate
31
Resistant- susceptibility
The bacterium is not inhibited by achievable concentrations of the drug
32
Staphylococcus
Catalase-positive, nonmotile, facultative anaerobes in grape-like clusters
Nl inhabitants of the skin and mucous membranes
-Commonly cause human infections
33
Coagulase test for staphylococcus
Pos- Staphylococcus aureus
| Neg- S. epidermidis, S. saprophyticus
34
S. aureus and skin infections
Boils
Carbuncles
Furuncles
Folliculitis
35
S. aureus and food poisoning
Enterotoxins A and D
36
S. aureus and scalded skin syndrome (Ritter's disease)
Extensive exfoliative dermatitis due to toxin
37
S. aureus and toxic shock syndrome (TSS)
```
High fever
Rash
Hypotension
Shock
Desquamation of the hands and feet
Possible death
```
38
S. aureus and osteomyelitis
Often secondary to bacteremia
39
Antibiotic susceptibility to staphylococcus
Penicillin resistance is high
| B-lactamase: an enzyme that inactivates the B-lactam abx
40
B-lactamase pcns (Methicillin, Oxacillin)
Methicillin-resistant S. aureus (MRSA)
-Nosocomial and community-associated infections
-Tx with bactrim (skin) or vancomycin
Methicillin-resistant S. epidermidis (MRSE)
41
Steptococcus/enterococcus
Catalase-negative, facultative anaerobes
Hemolysis patterns on sheep blood agar are helpful in identification
Gm-pos cocci, arranged in pairs or chains
42
S. pneumoniae
Important human pathogen causing sinusitis, otitis media, pneumonia
-Meningitis, bacteremia
-Vaccination
The key virulence factor is an antiphagocytic capsule
43
Lab findings in S. pneumoniae
Gram pos cocci in pairs
44
S. pyogenes
AKA group A streptococcus or B-hemolytic group A streptococcus (GABHS)
Streptolysin O- causes hemolysis of RBC
-Antistreptolysin O titer (ASO titer)
45
Infections of S. pyogenes
Pharyngitis- "Strep throat" or scarlet fever
Skin infections
-Impetigo, necrotizing fasciitis, pyoderma
-Rheumatic fever and glomerulonephritis
46
Group D streptococci
Strep bovis and Strep equinus
May be nl intestinal flora
May also be etiologic agents of bacterial endocarditis and other infections
47
Viridans Streptococci
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
Enterococcus
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
Listeria monocytogenes
Aerobic Gm pos bacilli
Widespread in the environment
Various infections in neonates and immunosuppressed persons including meningitis
50
Corynebacterium diphtheriae
Aerobic Gm pos bacilli
Causes diphtheria- inflammation of the throat with a pseudomembrane. Toxin damages major organs. Tx: antitoxin, erythromycin
51
Neisseria
Gm neg cocci seen in pairs (intracellular diplococci)
52
Neisseria gonorrhoeae
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
Neisseria meningitidis
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
Morexella catarrhalis
Nl upper respiratory tract flora
| Sinusitis, otitis media, community acquired pneumonia
55
Haemophilus
Gm-neg nonmotile bacilli and coccobacilli
56
Haemophilus influenzae
Can cause sinusitis, otitis media, epiglottitis, pneumonia, meningitis
Vaccination
57
Haemophilus ducreyi
Causes chancroid, a sexually transmitted disease with a painful ulcer
58
Bordetella
Very small gram-neg bacilli
59
Bordetella pertussis
Causes whooping cough via droplets
Catarrhal stage (cold)- paroxysmal stage (cough)- convalescence stage (healing +/- complications)
Nasopharyngeal swab specimen
Tx: macrolide antibiotic
60
Enterobacteriaceae
Largest and most medically important family of Gm neg bacilli
- Escherichia
- Klebsiella
- Salmonella
- Shigella
- Yersinia
- Proteus
61
Escherichia
```
Nl intestinal flora
Opportunistic organism
Mcc of UTI
Sx
-Urgency
-Frequency
-Dysuria
-Hematuria
-Pyuria
```
62
Klebsiella
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
Enterobacter
Gm-neg, rod-shaped bacteria
- Pathogenic and opportunistic infections
- -Respiratory and urinary tract
- Tx
- -Cefepime, aminoglycosides, quinolones
64
Salmonella
```
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
Shigella
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
Sx and resolution of shigella
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
Serratia
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
Yersinia
```
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
Proteus
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
Campylobacter
Campylobacter jejuni
Ingestion of contaminated food/water (raw chicker)
Causes diarrhea +/- blood
71
Helicobacter
H. pylori
Gastritis, nausea, abd pain
Increased risk of ulcers and stomach cancer
72
Vibrionaceae
Vibrio cholerae
Life-threatening diarrhea loss of 20 L/day
Rice water stools
73
Pseudomonas
Gm-neg rod-shaped bacteria
| -Ubiquitous organism that thrives in harsh conditions
74
Pseudomonas aeruginosa
```
Ermerging opportunistic infection
Cystic fibrosis
Hot tub folliculitis
Otitis externa
ICU pneumonia, sepsis
Tx: beta-lactam and aminoglycoside antibiotic
```
75
Legionella
Gm-neg rod-shaped bacteria
| Sx: pneumonia, hyponatremia
76
Labs for legionella
```
Silver stain
Charcoal yeast extract agar
UV light
Immunological assays
PCR
```
77
Tx for legionella
Quinolones
| Macrolides
78
Gardnerella
Gram-variable bacteria
Causes bacterial vaginosis
-Gardnerella vaginalis
Sx: vaginal d/c, fish-like odor
79
Labs for gardnerella
Chocolate agar
Wet-mount slide
Clue cells (bacteria adhering to the surface of squamous epithelial cells)
80
Tx for gardnerella
Metronidazole or clindamycin
81
Mycoplasma
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
Chlamydia
Bacteria that replicate inside host cells and are termed intracellular
Located in an inclusion body or vacuole
83
Pathogen of chlamydia
Chlamydia trachomatis
STI
Genital and eye disease (trachoma)
Reactive arthritis
84
Lab of chlamydia
Culture
Nucleic acid amplification tests
PCR
85
Tx of chlamydia
Azithromycin
| Doxycycline
86
Spirochetes
Helical shaped gram-neg bacteria with spiral coils
87
Treponema pallidum
```
Spirochete
Syphilis
Primary- painless chancre
Secondary- rash on palms and soles, arthritis
Tertiary- cardiac/neuro
```
88
Labs for Treponema pallidum
RPR
VDRL
FTA-ABS
89
Tx for Treponema pallidum
PCN
90
Borrelia burgdorferi
```
Lyme disease
Spirochete
Transmitted by Ixodes tick
Stage 1- localized rash
Stage 2- heart, bones, nervous system
Stage 3- chronic arthritis
```
91
Labs for Borrelia burgdorferi
Serology (ELISA)
92
Tx for Borrelia burgdorferi
Doxycycline x 10-14 days
93
Mycobacterium leprae
Leprosy- granulomas of nerves, skin, etc.
94
Mycobacterium tuberculosis
Mostly lung infection- cough, blood-tinged sputum, fever, night sweats, weight loss
Spread by air droplets
95
Lab for mycobacteria
Acid-fast bacilli
| PCR
96
Tx for mycobacteria
Isoniazid x 9 mos for latent infection
97
Gram-neg bacilli- anaerobes
Bacteroides fragilis
| 90% of anaerobic peritoneal infections
98
Gram-pos spore-forming bacilli- anaerobes
```
Clostridium- produce endospores
Clostridium botulinum- botulism (toxin)
Clostridium tetani- tetanus (lockjaw)
Clostridium difficile- diarrhea
Clostridium perfringens- gas gangrene
```
99
Clostridium difficile
Gm-pos spore forming bacilli
| Antibiotic-associated diarrhea and pseudomembranous enterocolitis
100
Lab for Clostridium difficile
Culture
Serology for toxin (ELISA)
Stool antigen
PCR
101
Tx for Clostridium difficile
Metronidazole
Oral vancomycin
Stool transplantation
102
Gm-pos nonspore-forming bacilli
Actinomyces israelii
Propionibacterium
Lactobacillis
103
Actinomyces israelii
Periodontal disease
104
Propionibacterium
P. acnes is the most common isolate (skin)
105
Lactobacillis
Nl flora in the mouth, intestinal tract, and vagina
| Long chains of Gm pos rods
