Exam 3 Flashcards
1
Q
Grams Stain
A
Bacteria only
Cell wall either takes up stain (gram positive) or doesnt (gram negative)
Guides initial antibiotic choice
2
Q
Gram stain positive
A
purple/ blue stain
3
Q
Gram stain negative
A
pink/red
4
Q
Gram stain sample
A
Can be performed on any body fluid or tissue biopsy.
Most common- sputum (want mucus not spit), blood, wound, urine, tissue, sterile body fluids.
5
Q
Information obtained from gram stain
A
Cell wall form: Gram positive, gram negative
Shape- cocci, bacilli, diplococci, clusters, pairs, chains
Quantity of bacteria
Other cells in sample- WBCs, RBCs, eosinophils, inclusion bodies, casts
6
Q
Gram stain: Bad samples will be full of
A
Epithelial cells
7
Q
Gram stain: Bad CSF cultures will contain
A
Multiple RBCs
8
Q
Acid-fast stain
A
For bacteria resistant to traditional gram staining
Largely used for the detection of mycobacterium and Nocardia
Cell wall: composed of a thin layer of peptidoglycan and large amount of mycolic acid
9
Q
Non-selective media
A
Contains no inhibitory substance and supports the growth of most bacterial species
10
Q
Selective media
A
Contains inhibitory substances or antimicrobials which allow growth of some organisms and suppress growth of others
11
Q
Differential media
A
Contains substances which allow detection of organism characteristics
12
Q
Broth media
A
Very small numbers of organisms or hard to grow pathogens can be propagated
HIgh risk of growing contaminants
13
Q
MIC90
A
The lowest concentration of tested antibiotic that inhibits visible growth in 90% of the tested isolates
Same as MIC, except MIC 90 refers to the study of many isolates
Guides empiric therapy although a better guide is to use the institutions antibiogram. Definitive therapy based on patient-specific MIC values
14
Q
Rationale for Abx combinations
A
Empiric therapy- broaden spectrum Synergy- enterococcal endocarditis prevent resistance Mixed aerobic-anaerobic infections Lower dose of toxic drug (only theory)
15
Q
Why the increase in antimicrobial resistance?
A
Increased consumption of antibiotics (humans and animals)
Overuse
16
Q
Intrinsic resistance
A
Bacteria naturally resistant to an antibiotic due to physical characteristics
17
Q
Acquired resistance
A
Developed through mutation or transfer of genetic material
18
Q
Cephalosporinases (AmpC)
A
If AmpC is present, 1st line treatment is cefepime (4th gen cephalosporin) or a carbapenem
19
Q
Mutation of AmpD protein
A
Leads to binding to AmpR and constant high-level expression of AmpC. Leading to clinical resistance to most beta lactams except carbapenems and cefepime
20
Q
ESBLs
A
Hydrolyze penicillins and cephalosporins but not carbapenems
1st line treatment- carbapenems
21
Q
Carbapenemases
A
Classes:
A, C, and D contain a serine residue in the active region
B requires a zinc for enzymatic activity
Risk factors: invasive medical devices, open wounds, long courses of abx, ICU, diabetes, surgery
22
Q
What is ESBL resistant to?
A
Inhibition by clavulante
Hydrolyzes 1st-3rd gen cephalospotins
Cefepime
23
Q
What is ESBL susceptible to?
A
Cephamycins (cefoxitin/cefotetan)
Carbapenems
24
Q
What is AmpC resistant to?
A
hydrolyzes 1st-3rd gen cephalosporins
Cephamycins
25
What is AmpC susceptible to?
Inhibited by clavulanate
Cefepime
Carbapenem
26
What is CRE resistant to?
Everything
27
___ out of every 3 antibiotic prescriptions are unnecessary
1
28
Antimicrobial stewardship programs
ASPs improve abx use and the need is recognized nationally
29
Antimicrobial Stewardship initiatives
Preauthorization and prospective audit with feedback
Antibiotic time-outs
Antibiograms
others
30
Antimicrobial Stewardship Program Goals
Improve patient care and health care outcomes
31
Antimicrobial stewardship patient care rounds/ chart reviews
Involvement in rounds is dependent on hospital
| Antibiotic time-outs at 48-72 hours
32
Advantages of combination therapy
```
Empiric therapy to broaden spectrum
Polymicrobial "mixed" infections
Synergy
Prevent emergence of resistance
Reduce dosage of toxic drug
```
33
Disadvantages of combination therapy
Antagonism
Induction of beta lactamase (resistance)
Increased cost
34
Cystitis
Infection of the bladder (lower UTI)
35
Pyelonephritis
Infection involving the kidneys (upper UTI)
36
Prostatitis
Infection of the prostate gland
| Can be acute or chronic
37
Uncomplicated UTI
Requires an otherwise healthy, premenopausal female with no structural or functional abnormalities of the urinary tract
38
Complicated UTI
```
Does not meet criteria for uncomplicated UTI
Often involves:
Indwelling urethral catheters
Urinary obstruction or stones
Prostatic involvement
Neurologic deficits
Recurrence and MDRO
```
39
Presentation of UTI
Urinary symptoms (not always present)
Urinalysis- leukocyte esterase, nitrites, bacteria, WBCs
Urine culture- bacteria >100,000CFU/mL, lower counts are considered if pt is symptomatic
Altered mental status
Systemic signs of infection (uncommon with cystitis)
40
Etiology of UTI
Most often related to GI flora
E. coli causes most
Complicated UTIs are more likely to be caused by resistant organisms
41
Asymptomatic Bacteriuria
Positive urine culture w/o infections or urinary symptoms
Screening and treatment indicated ONLY for pregnant women and patients with planned urologic procedures with anticipated bleeding
42
Uncomplicated cystitis first-line treatment
Typically treated with short courses of antibiotics
Nitrofurantoin (macrobid) 100mg BID for 5-7 days
Bactrim DS 800/160mg for 3 days
Fosfomycin (Monurol) 3g for 1 dose
43
Nitrofurantoin
Macrobid
Contraindicated in CrCL < 60mL/min
Macrodantin= QID
Macrobid= BID
44
Sulfamethoxazole/ Trimethoprim
Bactrim DS
Need to assess for sulfa allergy
Decrease dose to 1/2 if CrCl 15-30mL/min
Contraindicated if CrCl <15mL/min
45
Does fosfomycin have renal or hepatic adjustments?
No
46
Uncomplicated cystitis alternative treatments
Fluoroquinolones
Levofloxacin 250mg QD for 3 days
Ciprofloxacin 250mg BID for 3 days
Beta lactams
47
Uncomplicated pyelonephritis management
Urine culture should ALWAYS be performed if pyelonephritis is suspected.
Initial dose of parenteral abx is preferred.
Ceftriaxone 1g or 5-7mg/kg tobramycin/gentamycin
48
Uncomplicated pyelonephritis management for non-hospitalized patients
```
Oral fluoroquinolone for 7 days
-Ciprofloxacin 500mg BID
-Levofloxacin 750mg QD
Oral bactrim
Oral beta lactams
```
49
Uncomplicated pyelonephritis management for hospitalized patients
Definitive therapy guided by susceptibility tests
Fluoroquinolone
Aminoglycoside +/- penicillin/ cephalosporin
Carbapenem
50
Acute bacterial prostatitis management
```
Typically involves sudden fever, tenderness, and urinary symptoms
2-4 week duration oral therapy
Bactrim BID
Ciprofloxacin 500mg BID
Levofloxacin 500mg QD
```
Severely ill patients need IV cipro or bactrim
51
chronic bacterial prostatitis management
4-6 weeks of systemic abx recommended
Fluoroquinolones preferred
Surgery may be required
52
UTI in pregnant women
Avoid fluoroquinolones, caution with nitrofurantoin, avoid bactrim after 32 weeks gestation
53
UTIs in patients with indwelling catheters
Remove short-term catheters if possible
| Initiate therapy if symptoms occur, prophylaxis not recommended
54
UTIs in patients with more than 3 episodes/ year
Self-administered short course therapy
| Low dose continuous therapy should be avoided
55
Avoid nitrofurantoin for what?
Pyelonephritis and prostatitis
56
Syphilis etiology
Treponema pallidum spirochete
57
Syphilis presentation by stage
Primary- single lesion (chancre) that heals spontaneously
Secondary- Multiple mucocutaneous eruptions, rash, flu-like symptoms
Latent- no symptoms
Tertiary- progression to other organ symptoms. Occurs 10-30 years after infection
58
How is syphilis diagnosed?
Organism visualization on microscopy or serology for antibodies
Serologic tests unreliable if HIV coinfection present
59
Primary, secondary, or latent syphilis <1 year treatment
Benzathine penicillin G 2.4 million units IM once
Alternatives-
Doxycycline 100mg PO BID for 14 days
Ceftriaxone 1g IM/IV daily for 8-10 days
60
Latent syphilis > 1 year (or unknown duration) and tertiary treatment
Benzathine penicillin G 2.4 million units IM weekly for 3 weeks
Alternative-
Doxycycline 100mg BID for 28 days
61
Neurosyphilis treatment
Normal penicillin G 18-24 million units/day IV for 10-14 days
62
Jarisch-Herxheimer reaction
Fever and flu like symptoms are common in the first 24 hours of syphilis treatment
63
Chlamydia etiology
Most common bacterial ID in the US
| Caused by C. trachomatis
64
Untreated chlamydia infections can result in
pelvic inflammatory disease
65
Chlamydia presentation
Often asymptomatic
Symptom onset= 7-21 says
Most common S/S- urethral discharge, dysuria
66
When do you retest with chlamydia?
3 months
67
Chlamydia first line treatment
Azithromycin (Zithromax) 1g PO once (counsel about GI upset)
| Doxycycline 100mg BID x 7 days
68
Chlamydia treatment for neonates and infants
Erythromycin base 12.5mg/kg QID for 14 days
69
How long must you not have sex after chlamydia?
7 days
70
Trichomoniasis etiology
Trichomonas vaginalis- protozoan
71
Trichomoniasis presentation
Frequently associated with STI coinfection
Can be asymptomatic
Dysuria, urethritis, vaginal or urethral discharge
72
Untreated trichomoniasis infections lead to
pelvic inflammatory disease
73
Bacterial vaginosis etiology
Disruption of normal vaginal flora
| - replacement of lactobacillus with various anaerobes
74
Clinical diagnosis of BV
```
Requires 3 of the following 4 criteris:
Presence of thin, white vaginal discharge
"Clue cells" on microscopy
Vaginal pH > 4.5
Fishy odor of vaginal discharge
```
75
BV and trichomoniasis are both what?
Frequent coinfections with HIV and other STIs
76
When do you treat BV?
If symptomatic
77
Trichomoniasis 1st line treatment
Metronidazole (Flagyl) 2g PO once (same in pregnancy)
| 7 day treatment recommeded in pts with HIV
78
BV treatment
Metronidazole 500mg BID for 7 days or 0.75% gel- 5g applicators for 5 days
Clindamycin 2% cream for 7 days
79
Gonorrhea etiology
Neisseria gonorrhoeae (gram negative cocci)
80
Gonorrhea presentation
May be asymptomatic
| Symptom onset within 2-8 days in males and 10 days in females
81
Gonorrhea coinfection
Gonorrhea is often coninfected with asymptomatic chlamydia
82
Gonorrhea diagnosis
Gram stain
83
Gonorrhea treatment
Oral cephalosporins are no longer first line
Ceftriazone 250mg IM once PLUS doxycyline 100mg BID for 7 days
Azithromycin also added to cover chlamydia coninfection
84
PID treatment
Broad IV abx switching to oral to complete 14 days
| Ceftriaxone 250mg IM x1 PLUS Doxycycline 100mg BID +/- Metronidazole 500mg BID for 14 days
85
Genital herpes etiology
Herpes simplex virus 2
86
Genital herpes presentation
Most initial infections are symptomatic, but many people are typically asymptomatic after
87
Genital herpes treatment
```
No cure
Antiviral treatment (7-10 days primary episode)
Acyclovir 400mg TID
Valacyclovir 1g BID
Famciclovir 250mg TID
```
88
Genital herpes chronic suppressive therapy
Acyclovir 400mg BID
Famciclovir 250mg BID
Valacyclovir 500mg BID
89
Does suppressive therapy reduce HSV or HIV transmission?:
NO
90
Human Papilloma Virus (HPV)
```
Most common viral STI
HPV-6 and 11- genital warts
HPV-16 and 18- cervical cancer
Less than 1% of infected patients develop visible warts
3 vaccines recommended aged 11-12
```
91
GI AE
Tetracyclines, macrolides, clindamycin, metronidazole
92
Impetigo
Superficial skin infection of the exposed skin (usually face)
More common during hot, humid weather)
High communicable
93
Impetigo etiology
Gram positive organisms
S. pyogenes (Group A strep)
S. aureus (MSSA)
94
Impetigo presentation
Vesicles develop pustules which rupture and dry into brown or golden-yellow crusts
Pruritis common, systemic symptoms rare
95
Impetigo treatment
Topical or systemic therapy can be used
S. aureus should be covered until streptococci confirmed
Recommended:
Dicloxacillin 250mg QID for 7 days
Cephalexin (Keflex) 250mg QID for 7 daus
Mupirocin (Bactroban) ointment BID x 5 days
96
If MRSA is suspected with impetigo, what tx?
Bactrim Ds
| Doxycycline
97
Erysipelas
St. Anthonys Fire
Superficial skin infection with cutaneous lymphatic involvement
Risk factors: lymphatic obstruction or efema
98
Erysipelas etiology
S. pyogenes (Group A strep)
99
Esypelas presentation
Very red, acute onset, erythema, kwarmth, edema, pain, margins
Diagnosis made on characteristic clinical picture.
100
Erysipelas in children
Requires hospitalization
| Penicillin DOC
101
Erysipelas Tx
Pen G 600,000-1.2 million units IM Q 12 H
Pen VK 250-500mg QID
Clindamycin 300-600mg PO Q 6-7 H
102
Erysipelas severe infections
Pen G
103
Cellulitis
Infection of the epidermis and dermis, may reach superficial fascia
w or w/o abscess
104
Cellulitis etiology
Most common S. pyogenes and S. auerues
105
Cellulitis presentation
Non-elevated erythematous and edamatous skin lesion
| Systemic symptoms can occur
106
Cellulitis risk factors
IV drug use
Uncontrolled DM
Recent surgery
107
Cellulitis tx
Oral therapy of 5 days
Pen VK or amoxicillin
initial coverage of S. aureus- cephalexin
MRSA coverage if trauma or purulence- Bactrim
I&D is primary therapy for abscess
Vanc used if severely ill
108
Diabetic Foot Infections (DFIs)
At baseline, diabetic pts have increased neuropathy, vascular insufficiency, and impaired wound healing
Infection can arise from ulceration, minor trauma, poor nail care
Osteomyelitis occurs in 30-40%
Severe infections are polymicrobial
109
DFI treatment
**Augmentin BID 1-2 weeks
Cephalexin 250-500mg PO Q6H
Doxycycline 100-200mg BID
IV regimen if severe
110
Osteomyelitis
Can progress from skin/soft tissue infection
Diagnosed by MRI
MSSA most common
111
Osteomyelitis tx
```
Nafcillin/ oxacillin 2g IV Q4H or Cefazolin 2g IV Q8H for 4-6 weeks
Surgical interventions (debridement and/or amputation often required)
```
112
Bite wounds
Cat bites more often to cause infection
Etiology- Pasteurella
Humans- Eikenella
Sharks- Vibrio
113
Bite wounds Tx
Augmentin PO BID 7-14 days
| 3-5 day prophylactic course
