Infectious Disease II - Bacterial Infections Flashcards

Question

What are risk factors for MRSA and pseudomonas in CAP patients? How does that change the treatment?

Answer 1

Prior respiratory isolation of MRSA or Positive MRSA nasal swab -> add MRSA activity (vancomycin or linezolid) Prior respiratory isolation of Pseudomonas -> use b-lactam with pseudomonas activity (cefepime, mero, zosyn, ceftazidime, imipenem/cilastatin) Recent hospitalization in last 90 days AND IV antibiotic exposure -> use a regimen with abx active against MRSA and Pseudomonas

Answer 2

HAP - 48 hours in hospital VAP - 48 hours ventilated Pathogens: - MRSA, MSSA, Pseudomonas aeruginosa, other gram negatives (ex. E. coli, acinetobacter, enterobacter) Duration of treatment: 7 days

Answer 3

Need at least 1 antibiotic that is active against both psuedomonas AND MSSA (cefepime, piperacillin/tazobactam, meropenem, or levofloxacin) - If risk factors for MRSA -> add vancomycin or linezolid - If risk factors for MDR gram-negs and MRSA -> add a 2nd antipseudomonal antibiotic (ex. fluoroquinolone or aminoglycoside) AND vanc or linezolid **Pseudomonas agents:** *b-lactams* - piperacillin/tazobactam - cefepime, ceftazidime - meropenem, imipenem/cilastatin - aztreonam - ceftolaozane/tazobactam, ceftazidime/acibactam (reserve for MDR) *fluoroquinolones* - cipro - levo aminoglycosides - gentamicin - tobramycin - amikacin)

Answer 4

MRSA only: - IV abx in past 90 days - MRSA prevalence > 20% or unknown - Prior MRSA infection or positive MRSA nasal swab MDRs: - IV abx in past 90 days - Gram-neg resistance >10% - Hospitalization ≥ 5 days prior to VAP onset

Answer 5

Perferred: interferon gamma release assay (IGRA) Tuberculin skin test (TST) - ≥ 5mm: positive if close contacts of active TB, HIV, or immunosuppressed - ≥ 10mm: positive if high-risk setting employees or residents, IV drug use - ≥15mm: positive if no risk factors Diagnosis: positive TST or IGRA - rule out active disease through negative chest ray and no symptoms

Answer 6

**isoniazid (INH) + rifapentine weekly for 12 weeks** - directly observed therapy - NOT for pregnant patients **isoniazid (INH) + rifampin daily for 2 months** **rifampin daily for 4 months** **isoniazid daily for 6 or 9 months** - may be preferred in HIV positive patients taking ART due to less drug interactions compared to the others. Do regimen for 9 months in this case *shorter regimens (3-4 months) preferred due to less hepatotoxicity and better adherence

Answer 7

Symptoms (cough >2-3 weeks, hemoptysis, fever, night sweats, unintentional weight loss) Diagnostic tests - positive TST or IGRA - CXR - Sputum culture with acid fast bacilli (AFB) - M. tuberculosis identified on sputum culture

Answer 8

Initial phase with RIPE for 2 months - Rifampin - Isoniazid - Pyrazinamide - Ethambutol Continuation phase with RI for ≥4 months (if no evidence of resistance and repeat sputum cultures are neg) - Rifampin - Isoniazid

Answer 9

Contraindications: - with protease inhibitors Side effects: - increased LFTs, hemolytic anemia (detected with positive Coombs test), flu-like syndrome - orange-red discoloration of body secretions **significant drug interactions** - potent CYP450 INDUCER and pgp - rifabutin has fewer drug interactions and can replace rifampin in some cases - notable interactions: protease inhibitors, warfarin and DOACs, oral contraceptives

Answer 10

Boxed warning: - severe (and fatal) hepatitis Contraindications: - active liver disease - previous severe adverse reaction to INH Warnings: - peripheral neuropathy **pyridoxine (vitamin B6) supplementation is recommended** Side effects: - increased LFTs - drug-induced lupus erythematosus (DILE) - hemolytic anemia (identified with positive Coombs test) Notes: - Pyridoxine (vitamin B6) 25-50mg PO daily should be used to reduce the risk of peripheral neuropathy!!

Answer 11

Contraindications: - acute gout, severe hepatic damage Side effects - increased LFTs, hyperuricemia/gout

Answer 12

Contraindications: - optic neuritis Side effects - increased LFTs, optic neuritis (dose-related), confusion, hallucinations Requires visual exam at baseline and monthly

Answer 13

Staphylococci Streptococci Enterococci Diagnosis: using Modified Duke Criteria - echocardiogram - positive blood cultures - symptoms

Answer 14

treatment duration likely 4-6 weeks viridans strep - penicillin or CRO (+/- gentamicin) - allergy -> vanc staph - MSSA -> nafcillin or cefazolin - MRSA -> vanc or dapto - prosthetic valve -> add gentamicin AND rifampin to the above regimen - b-lactam allergy -> vancomycin enterococci - native or prosthetic valve -> penicillin or ampicillin + gentamicin or high dose CRO - vanc resistant -> linezolid or dapto - b-lactam allergy -> vanc + gentamicin

Answer 15

If the patient is at high risk (cardiac conditions) + dental work needed (ex. root canal) - artificial valve, hx of endocarditis, heart tx with abnormal heart valve function, some congenital heart defects Agents: *take as single dose 30-60mins prior to procedure* - 1st line - amoxicillin 2g PO - Unable to take PO -> ampicillin 2g IV/IM or cefazolin 1g IV/IM - Penicillin allergy -> azithromycin or clarithromycin 500mg PO or doxycycline 100mg PO

Answer 16

Common pathogens: Streptococci, Proteus, E. coli, Klebsiella Diagnosis: sx of infection (fever, inc. WBCs, AMS), ascites, abdominal pain/tenderness, ascitic fluid has > 250 cells/mm^3 PMNs (polymorphonuclear leukocytes) Empiric tx: duration of 5-7 days - 1st line: ceftriaxone or cefotaxime - if critically ill or risk of MDRs -> zosyn or meropenem

Answer 17

Criteria: prior episode of SBP or ascitic fluid protein <1.5 g/dL + impaired renal or hepatic function Therapy options: SMX/TMP or fluoroquinolone (cipro) Duration: indefinite or until liver transplant

Answer 18

Mild - local symptoms only Moderate - local and systemic signs (temp > 100.4ºF, HR >90, WBC > 12k or < 4k Severe - systemic signs + skin sloughing, fluid-filled blisters, hypotension, organ dysfunction, immunocompromised patients, or failed oral abx and/or I&D

Answer 19

Pathogens - S. pyogenes, S. aureus (likely MSSA) Presentation - honey-colored crusts Treatment - topical if limited/localized lesions: mupirocin - numerous, extensive lesions: cephalexin 250-500mg PO QID (or dicloxacillin)

Answer 20

Pathogens - S. aureus, including CA-MRSA Presentation - inflamed hairs Treatment - incision and drainage for large furuncles and carbuncles +/- antibiotics - SMX/TMP or doxycyline

Answer 21

Pathogens - **strep (s. pyogenes)**, staph aureus Presentation - unilateral Treatment: duration ~5 days - cephalexin 500mg PO QID - or dicloxacillin - allergy -> clindamycin Treatment if severe: duration 7-14 days *target MRSA* - vancomycin, dapto, or linezolid - can transition to PO once stable

Answer 22

Pathogens - MSSA, CA-MRSA Presentation - draining fluid - tend to be more localized Treatment if mild-mod: duration ~5 days - incision and drainage - PLUS SMX/TMP or doxycycline Treatment if severe: duration 7-14 days *target MRSA* - vancomycin, dapto, or linezolid - can transition to PO once stable

Answer 23

Pathogens - monomicrobial or polymicrobial - strep, staph, anaerobes, gram negatives Presentation - commonly affects extremities or perineal area - Often preceded by minor trauma Treatment - surgical debridement - clindamycin (anti-toxin) PLUS vancomycin or dapto PLUS beta-lactam (zosyn or meropenem)

Answer 24

Pathogens - polymicrobial - gram-pos: staph, strep, enterococci - gram-neg: E. coli, kleb, proteus - anaerobes: bacteroides spp. - may be at risk of rMRSA or pseudomonas Mild - treat like cellulitis Moderate to Severe - no concern for MRSA/pseudomonas: unasyn, ertapenem, moxifloxacin, or metronidazole + ceftriaxone - concern for pseudomonas: zosyn, meropenem, or metronidazole + cefepime, cipro, or levofloxacin - add MRSA coverage if needed as well duration: - 2-4 weeks if no bone involvement - 4-6 weeks for osteomyelitis - 2-5 days if amputation with no residual infection

Answer 25

WBCs - pyruia (WBCs > 10 cells/mm^3) indicates UTI RBCs - not specific to infection, but often present in UTIs Bacteria - contamination, colonization, or infection Leukocyte esterase - marker of WBCs and pyuria Nitrites - marker of nitrate reductase producing bacteria pH - marker of urease-producing bacteria

Answer 26

Pathogens - E. coli (most common) - Proteus, Klebsiella, staphylococcus saprophyticus Presentation - no systemic - pain, frequency urinating Treatment - nitrofurantoin 100mg PO BID x5 days (contraindicated if CrCL <60 mL/min) - fosfomycin 3g x1 dose - sulfamethoxazole/trimethoprim DS 1 tab PO BID x3 days (contraindicated in sulfa allergy)

Answer 27

Pathogens - E. coli (most common) - Proteus, Klebsiella, Enterobacter, Serratia, Pseudomonas, Enterococci Presentation - Systemic symptoms - Flank pain Outpatient treatment: PO - ciprofloxacin or levofloxacin - bactrim Inpatient treatment: IV - ceftriaxone - cipro or levo - zosyn or carbapenem if concerns for resistance (urinary instrumentation, prior isolation or culture, received broad spectrum abx in past)

Answer 28

Phenazopyridine (Rx: Pyridium, OTC: Azo Urinary Pain Relief) **only helps with symptoms, NOT the infection Adminstration - Max duration: 2 days - Take with 8oz of water with or immediately following food to minimize upset stomach Notes - Can cause red-orange coloring of the urine and other body fluids

Answer 29

beta-lactams are preferred - cephalexin - amox/clav alternatives if allergy - fosfomycin - nitrofurantoin (not preferred, potential fetal risk) - bactrim (not preferred, potential fetal risk) AVOID fluoroquinolones!! - fetal risk

Answer 30

Signs/sx: - at least 3 loose, watery stools in 24 hours - fever, abdominal pain, elevated WBC or impaired renal function - positive stool test (nucleic acid amplification test [NAAT], enzyme immunoassays) Nonsevere: WBC < 15k and SCr < 1.5 Severe: WBC ≥ 15k or SCr > 1.5 Fulminant: hypotension, shock, ileus, or toxic megacolon

Answer 31

Initial episode: - stop causative agents - fidaxomicin 200mg PO BID OR vancomycin 125mg PO QID - IF ABOVE UNAVAILABLE -> metronidazole 500mg PO TID - duration: 10 days Recurrence: - fidaxomicin 200mg PO BID x10 days - vancomycin PO + prolonged taper - 2+ recurrences: vanc PO + rifaximin x20 days - fecal microbiota transplantation Fulminant: - vancomycin 500mg PO/NG Q6H PLUS IV metronidazole - surgical evaluation for colectomy *adjunct **bezlotoxumab** (neutralizes toxin B) can be considered for high-risk patients (age ≥ 65, immuocompromised, severe, 2+ episodes in last 6 months), but **CAUTION for heart failure**

Answer 32

chlamydia - genital discharge or no symptoms gonorrhea - genital discharge or no symptoms genital warts - single or multiple pink/skin-tones lesions latent syphilis - asymptomatic primary syphilis - painless, smooth genital sores (chancre) bacterial vaginosis - vaginal discharge that has a fishy odor and pH > 4.5, little or no pain trichomoniasis - yellow/green, frothy vaginal discharge with pH > 4.5, foul odor pain with intercourse

Answer 33

diagnositic tests - nontreponemal test (VDRL, RPR) + treponemal assay Primary: chancre Secondary: rash, lymphadenopathy Early latent, acquired ≤ 1 year ago: asymptomatic Treatment the same for all!!! - **penicillin G benzathine (Bicillin L-A) 2.4 million units IM x1 dose** (this is for pregnant patients too) - alternative -> doxycycline 100mg PO BID x14 days - alternative if pregnant -> desensitization protocol followed by penicillin G

Answer 34

Late latent, acquired > 1 year ago: asymptomatic Tertiary: cardiovascular, CNS manifestations Treatment is the same for both!! - **penicillin G benzathine (Bicillin L-A) 2.4 million units IM weekly x 3 doses** (this is for pregnant patients too) - alternative -> doxycycline 100mg PO BID x28 days - alternative if pregnant -> desensitization protocol followed by penicillin G

Answer 35

neurosyphilis: altered mentation, motor/sensory dysfunction, symptoms of meningitis, abnormal CSF Treatment: - penicillin G aqueous 3-4 million units IV Q4H x10-14 days - allergy -> desensitization protocol followed by penicillin G

Answer 36

Treatment 1st line - ceftriaxone 500mg IM x1 (if <150kg) - ≥ 150 kg, 1g IM x1 Treatment the same for pregnant patients If chlamydia not excluded, add doxycycline

Answer 37

Treatment Doxycycline 100mg PO BID x7 days - pregnancy -> azithromycin 1g PO x1

Answer 38

Treatment - metronidazole 500mg PO x7 days - metronidazole 0.75% gel x5 days - clindamycin 2% cream x7 days

Answer 39

Females: metronidazole 500mg PO x7 days Males: metronidazole 2g PO x1

Answer 40

Human papillomavirus (HPV) strains 6 and 11 Treatment - imiquimod cream (immune activator) - podofilox solution or gel (causes wart necrosis)

Answer 41

Rocky Mountain spotted fever Symptoms - erythematous petechial rash that follows 3-5 days after fever/headache/pain Treatment - Doxycycline (even for pediatrics)

Answer 42

Lyme: bacterial - Erythema migrans: bull's eye rash - diagnosis: enzyme immunoassay (EIA) - treatment: doxycycline Ringworm: fungal - reddish, raised rings, can be itchy - treatment: clotrimazole or another topical antifungal