The ABC’s of Infections

Eleana M. Zamora, MD

Department of Internal Medicine

Division of Pulmonary/Critical Care/Sleep

Objectives

• Understand the difference between nosocomial and community-acquired

• Know where to find antibiogram data• Have a basic understanding of how to

approach common infections in the inpatient and outpatient setting

Overview• Community vs. nosocomial• Upper/Lower respiratory infections• C.difficile-associated diarrhea• Intra-abdominal infections• Skin-soft tissue infections• Bacteremia• Osteomyelitis, septic joints

Gram positives

Gram negatives

Urine Antibiogram

Objectives: Crash Course• Commonly encountered infections in

inpatient and outpatient settings– What bugs?– What drugs?

• Common clinical syndromes

Community vs. Nosocomial• Why important?

– Atypicals– MDRO– MRSA– Pseudomonas

• Broadened definition of “nosocomial”– SNF, OPAT, jail, community-living, homeless,

etc.

Common Outpatient Infections

• Upper respiratory• Lower respiratory• Sinusitis• Pharyngitis• UTI• SST

Upper Respiratory Infection

• Def’n:– Acute infxn which is typically viral– Sinus, pharngeal, or lower airway symptoms may

be present, but are not prominent• Abx are rarely indicated

– Although most “colds” have sinus symptoms, less than 2% have complication of acute bacterial sinusitis

– Presence of green mucus does not necessarily indicate bacterial infection

Acute Pharyngitis

• GAS causes 10% of adult pharyngitis– 90% are NOT GAS!– DDx: EBV, CMV (less likely), gonococcus, HSV,

HIV, Syphilis• ABX are rarely indicated for routine

pharyngitis– Use the Centor diagnostic criteria to decide who

to test– Treat only positive GAS rapid screens or

patients who have all 4 criteria

Centor Criteria• History of fever• Tonsillar exudates• No cough• Tender anterior cervical LAD

≥2 of the above = treat

Treatment of GAS Pharyngitis

• Treatment of choice: Penicillin V 500mg BID or 250mg QID x 10 days

• Alternatives– Benzathine PCN 1.2 MU IM x 1 dose (for

noncompliant patients)– 2nd gen cephalosporin: cefuroxime or cefprozil

500 mg qday, etc. etc– Azithro 500mg x1, then 250mg po day x 4d– If macrolide failure or pcn-allergy: FQ– Bactrim does not cover GAS

Acute Sinusitis

• Most cases of sinusitis are viral• Bacterial rhinosinusitis

– Sx lasting ≥7 d who have maxillary pain or tenderness in the face or teeth (esp. unilateral) and purulent nasal secretions

• Severe dz: dramatic symptoms of severe unilateral maxillary pain, swelling, and fever.

Sinusitis Guidelines: IDSA 2012

IDSA: Treatment

• First line = B-lactam (amox/clav)– Preferred over respiratory FQ– Doxycycline is equivalent to amox/clav– Not recommended to cover for MRSA

• Not recommended for use:– Macrolides, Bactrim

• Duration of tx: 5-7 days– Recommended over 10-14 days

Acute Sinusitis

• Etiology– Community-acquired from obstruction of ostia,

allergens, post-viral infxn:• S.pneumo 31%• H.influenzae 21%• M.catarrhalis 10%• S.aureus 4%

– Diabetic, neutropenic, IV iron therapy:• mucor/rhizopus, aspergillus

Etiology of Acute Sinusitis

– Nosocomial , NGT, or nasal intubation:• Gram neg (pseudomonas, acinetobacter) 47%• Staph aureus/gram pos 35%• Yeast 18%• Polymicrobial 80%

Chronic Sinusitis• Pathogenesis is multifactorial

– Smoking– Nasal polyps– Periodontitis

• Antibiotics are rarely effective– Refer to ENT– STOP SMOKING!

• Atypical pathogens– Prevotella, anaerobes, fusobacterium,

Pseudomonas, fungi/molds

URI

Non-Specific URI• Resistant Strep pneumoniae

– outpatient abx– Treating a viral URI with abx directly increases

the risk of resistant bug transmission

• Upper URI account for over 75% of outpatient RX each year

For URI Syndromes:Very strongly consider NO abx:• Adult uncomplicated

acute bronchitis– Not acute exacerbations of

chronic bronchitis)

• Acute sinusitis• Pharyngitis• Nonspecific URI

ABX should be used for:

• Documented GAS pharyngitis

• Severe sinusitis with fever, ptosis, etc.

• Pneumonia (LRI)

WHATUP!

Lower Respiratory

Lower Respiratory Infections

• Tracheitis – biggest airways• Bronchitis –large airways• Bronchiolitis – smallest airways, wheezing• Pneumonia – air space infection

– Basic concepts are the same for all

Stepwise Approach

• Decide viral, bacterial, atypical, other?–Not always so easy…sometimes more

than one–Rule of thumb: cover the top 3–Risk factors

• Smoking, travel, immunosuppression, diabetes

Pseudomonas?

• Community-acquired vs. nosocomial +/- aspiration– Hospitalized vs. non-hospitalized– Remember new broader risk categories for

MDRO– Pseudomonas and Acinetobacter longer

duration of tx

Powers of Pseudomonas Prediction

Common CAP Etiologies

IDSA CAP Guidelines 2007

Outpatient CAP Tx

To Hospitalize or not?• Pneumonia severity

index (PSI)• CURB-65• Your gut feeling

counts

• CURB-65• Confusion, Uremia, RR, low BP,

age>65• Score > 2admit

Severe CAP• IDSA Guidelines 2007

Inpatient, non-ICU CAP Tx

• UNMH Formulary1. Ceftriaxone + azithromycin/doxy

2. If β-lactam allergy: moxifloxacin1. Moxi not for UTI or Pseudomonas

Inpatient CAP, ICU

• UNMH Formulary1. Ceftriaxone + azithromycin

• Not doxy

2. If β-lactam allergy: moxifloxacin

Pseudomonal Risk Factors

• UNM: Know the antibiogram!– Available to you without ID consult: Zosyn (87%S), Cefepime (82%), Cipro (72%), Gent/Tobra

(85%)– ID Consult only: Meropenem (95%), amikacin (89%), doripenem, colistin

Infectious Diarrhea

Clostridium difficile• SHEA/IDSA Guidelines 2010• Who to test?• What to do?• How to treat?• When to take out of isolation?

The New CDAD• 4 x’s increase in cases over 13 year period • Increase in disease severity• Major risk factors for NAP1 strain

– Age > 65– Recent use of FQs

Severity assessment score

• ≥2 points classified as severe

• 1 point given for each of the following:

• Age > 60• Temp >38.3• WBC > 15K• Albumin < 2.5mg/dL• 2 points for

endoscopic evidence of CDAD– (Alternate: AKI)– (Alternate: sepsis,

ICU)

Case Definition

1. Presence of diarrhea (>3 unformed stools in 24 hours)

2. Stool test positive for Cdiff or its toxins

3. Colonoscopic evidence of Cdifficile

Who to test?

• Anyone with diarrhea?– Do not test asymptomatic patients– Only patients with diarrhea, not formed

• Unless toxic megacolon/ileus

• High risk:– SNF, jail, group home– Recent (<90d) abx– Recent (<30d) hospitalization– Known contact (2-3 days avg)– Severe, ICU intraabdominal source suspected

What test?• Previously used test for toxin• UNMH uses PCR confirmation

– A single test per episode of diarrheal illness is recommended

– No more than one test every 7 days– Do not need multiple tests to “rule-out”– Do not need test of cure

Understanding the test

• Stool tested for Antigen (Ag) and toxin (T)– Ag (+) T (+) positive C.diff (red)

– Ag (+) T (-) reflex to PCR (red) – Ag (-) T (+) reflex to PCR (red)

– Ag (-) T (-) negative C.diff

What to do?

• If you think it, patient must be in isolation– NEVER EVER order the test without putting

patient in isolation at same time– Never treat empirically without putting in

isolation at same time

• If patient is ill, empiric tx is ok

How to treat?Consider calling general surgery for severe disease!

Intra-Abdominal

Complicated Intra-abdominal Infections

• Examples:– Perf diverticulum– Complicated GB infection– Abscess– Peritonitis

• Location matters– Flora of upper small bowel vs. from beyond small

bowel vs. from beyond ileum vs. rectum

It’s All About Location!

• Upper GI, duodenum, biliary system, proximal small bowel– Peritonitis common– Gram pos, gram neg aerobic and facultative

organisms– Enterococcus is not a real concern

• Distal small bowel– Less GPC, more GNR (aerobes, facultative)– Often evolve into abscesses (not peritonitis)

Location, location, location• Colon

– Facultative (E.coli) and obligate anaerobes (B.frag), Streptococci (S.bovis)

• Abscesses– Abscesses, in general, should be drained– ABX have hard time getting into abscess

• Exception?

– ALWAYS send aspirate for anaerobic/aerobic culture

So, Why So Complicated?

• Location– Some drugs are inactive in abscesses– Some drugs are pH dependent

• Bugs– Some bugs are resistant

• B.frag vs. clinda/fq/cefotetan/cefoxitin

• Community-Acquired vs. Nosocomial?– Pseudomonas is less common in abscesses

Who to Treat?

• Bowel trauma that get surgically repaired within 12 hours, upper GI perf in the absence of antacids, or acute appendicitis– Abx used for <24h

• Acute uncomplicated cholecystitis = NO• Ascending cholangitis = YES• Acute pancreatitis = NO• Necrotizing pancreatitis = YES

What to give?

Note: Empiric coverage of Candida is NOT recommended.If candida is found, strongly consider if it needs therapy

Questions?

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