clostridium difficile: shifting sands of a pesky pathogen bob fader, ph.d. d (abmm) section chief,...

Clostridium difficile: Shifting Sands of a Pesky Pathogen

Bob Fader, Ph.D. D (ABMM)

Section Chief, Microbiology

Scott & White Memorial Hospital

Temple, TX

rfader@swmail.sw.org

Objectives

• Identify the reasons for the increase and severity of Clostridium difficile diarrhea

• List the methods of lab testing for C. difficile and discuss the pros and cons of each method

• Describe treatment modalities for C. difficile disease

• Discuss Infection Control processes required for containment of C. difficile in the health care setting

Clostridium difficile – The Basics

• Anaerobic Gram positive bacillus• Spore-former• Normal bowel flora

in 2 - 5% of population– Up to 20% in LTC facilities

• Infection most often associated with prior antibiotic therapy

• Originally strictly a hospital-acquired infection but now can also be seen in outpatients as well

C. difficile – Advanced Info• C. difficile diarrhea is a toxin-mediated

disease• Large increase in number and severity

of cases seen since 2004• Largely due to strain with deletion in

regulatory gene for toxin production– Results in 20-fold increase in toxin

production• Increasing number of strains also

resistant to the fluoroquinolones

APIC C. difficile SurveyNational Prevalence Study of Clostridium difficile

in U.S. Healthcare Facilities

• Health care institutions requested to collect data on C. difficile on any one day (May-August 2008)

• 648 facilities• 13 of every 1000 pts either infected or colonized• 6.5 - 20 times higher than previous estimates

So what happened?

• Appearance of a new strain of C. difficile in hospitals in Quebec

• Quickly spread south to the U.S. and over to Europe

• Strain is known as NAP1 (toxinotype III)

Spread of NAP1 strain of C. difficile

Deaths in the UK caused by C. difficile

C. difficile EpidemiologyNormal colon

Pseudo membranous

colitis

C. difficile Toxin Genes

Increased Toxin A Production in vitro

From Warny M, et al. Lancet. 2005;366:1079-1084.

In vitro production of toxins A and B by C. difficile isolates. Median concentration and IQRs are shown. C. difficile strains included 25 toxinotype 0 and 15 NAP1/027 strains (toxinotype III) from various locations.

Increased Toxin B Production in vitro

From Warny M, et al. Lancet. 2005;366:1079-1084.

In vitro production of toxins A and B by C. difficile isolates. Median concentration and IQRs are shown. C. difficile strains included 25 toxinotype 0 and 15 NAP1/027 strains (toxinotype III) from various locations.

Comparison of Molecular Characteristics of 2 C. difficile Isolates with Historical Standard-Type

Strains and a Recently Recognized Epidemic Strain, by Selected Characteristics, OH and PA, 2005

Characteristic

Standard Strain

Epidemic Strain

Ohio Strain

Pennsylvania Strain

Toxinotype

PFGE* pattern

Binary toxin

18 bp deletion in tcdC

0

< 80% related to NAP1†

_

_

III

NAP1

+

+

IX

85% related to NAP1

+

_

XIV/XV

64% related to NAP1

+

+

*Pulsed-field gel electrophoresis.† North American pulsed-field type 1.McDonald LC, Killgore GE, Thompson A, Owens RC Jr, Kazakova SV, Sambol SP, Johnson S, Gerding DN. An epidemic, toxin gene-variant strain of Clostridium difficile. N Engl J Med. 2005;353:2433-2441.CDC. MMWR. 2005;54:1201-1205.

Resistance of Current (after 2000) BI/NAP1 Isolates to Clindamycin and Fluoroquinolones Compared with Current Non-BI/NAP1 Isolates and Historic (before 2001) BI/NAP1 Isolates

No. (%) Intermediate or Resistant to:

Current BI/NAP1 Isolates n=24 (%)

Current non-BI/NAP1 Isolatesn=24 (%)

P-Value for BI/NAP1 vs. Non-BI/NAP1 Isolates

Historic BI/NAP1 Isolates n=14 (%)

P-Value for Current vs. Historic BI/NAP1 Isolates

Clindamycin 19 (79) 19 (79) 1.0 10 (71) 0.7

Levofloxacin 24 (100) 23 (96) 1.0 14 (100) 1.0

Gatifloxacin 24 (100) 10 (42) <0.001 0 <0.001

Moxifloxacin 24 (100) 10 (42) <0.001 0 <0.001

From McDonald LC, et al. N Engl J Med. 2005;353:2433-2441.

C. difficile-associated diseases (CDAD)

• Antibiotic-associated diarrhea

• Pseudomembranous colitis

• Toxic megacolon

• Perforations of the colon

• Sepsis

• Death (rarely)

C. difficile Clinical Symptoms

• Watery diarrhea

• Fever

• Loss of appetite

• Nausea

• Abdominal pain/tenderness

Risk factors for C. difficile

• Prior antibiotic exposure

• GI surgery/endoscopy

• Long LOS in health care setting

• Serious underlying illness

• Immunocompromising conditions

• Advanced age

• Proton pump inhibitors?

Changes in age-specific C. difficile associated disease 2000-2005

Zilberberg, M.D. et al. Increase in Adult Clostridium difficile-related hospitalizations and case-fatality rate, United States, 2000-2005. Emerg Infect Dis 2008 Vol 14 No 6

Stomach Acid-Suppressing Medications and Community-Acquired CDAD, England

From Dial S, et al. JAMA. 2005;294:2989-2995.

Severe CDAD in Populations Previously at Low Risk—Four States, 2005

• Recent reports to the Pennsylvania Department of Health and CDC– Young patients without serious underlying disease– C. difficile toxin-positive by routine diagnostic testing– Responded to CDAD-specific therapy

• Peripartum – Within 4 weeks of delivery– Reports from PA, NJ, OH, and NH

• Community-associated– No hospital exposure in prior 3 months– Reports from Philadelphia and 4 surrounding counties

CDC. MMWR. 2005;54:1201-1205.

Severe CDAD in Populations Previously at Low Risk—Four States, 2005 (2)

CDC. MMWR. 2005;54:1201-1205.

Characteristic,

No. (%)

Community

(N=23)

Peripartum

(N=10)

Total

(N=33)

Aged < 18 years 11 (48) 0 (0) 11 (33)

Female 15 (65) 10 (100) 25 (76)

Antimicrobial exposure 15 (65) 9 (90) 24 (73)

Bloody diarrhea 6 (26) 2 (20) 8 (24)

Hospitalization necessary

6 (26) 4 (40) 10 (24)

ER visit necessary 3 (13) 2 (20) 5 (15)

Relapse 8 (35) 5 (50) 13 (39)

• Transmission to close contacts in 4 cases• 8 cases without antimicrobial exposure

– 5 children; 3 required hospitalization– 3 had close contact with diarrheal illness

• Another 3 cases with < 3 doses of antimicrobials• Clindamycin most common exposure (10 cases)• Estimated minimum annual incidence of

community-associated disease– 7.6 cases per 100,000 population– 1 case per 5,000 outpatient antimicrobial prescriptions

Severe CDAD in Populations Previously at Low Risk—Four States, 2005

CDC. MMWR. 2005;54:1201-1205.

Laboratory Diagnosis of C. difficile

“A disease in search of a good diagnostic test”

C. difficile - Lab TestingGeneral Caveats

• Lab testing should only be performed on diarrheal stools (conform to the shape of the container)

• One or two specimens collected on consecutive days are sufficient for diagnosis

• No more than one specimen per day• Swab specimens are insufficient• Once pt positive, no further testing for at

least 2 weeks **No “Test of Cure”**

C. difficile - Lab testing Options

• Culture on CCFA agar (Cycloserine Cefoxitin Fructose agar)– Most sensitive and specific– If isolated still need to confirm

toxin production– 72-96 hour turn-around-time– Requires anaerobic culture

C. difficile – Lab Testing continued

• Latex agglutination – – originally marketed as toxin assay – now known to detect glutamate

dehydrogenase enzyme– present in C. difficile but also in other

organisms (C. sordellii)– Same day or next day results– Need to confirm positives with toxin

assay

C. difficile – Lab Testing continued

• Enzyme immunoassays– Detection of Toxin A only

• Will not detect ToxA negative/ToxB positive strains

– Detection of Toxins A&B • Better sensitivity than toxin A alone

– Microwell, lateral flow assay formats– Same day or next day results– Most popular (>90% of labs)– Sensitivities – 65-85%

Microwell enzyme immunoassay

Lateral flow EIA

C. difficile – Lab Testing continued

• Cell culture Cytotoxicity Assay –– Detects Toxin B (Cytotoxin) only

• Will not detect ToxA positive/ToxB negative strains

– Considered the “gold standard” for toxin testing

– Requires tissue culture capability– Costly, slow, and time consuming– 24-48 hour turn-around-time

C. difficile – Lab Testing continued

• Rapid enzyme EIA for glutamate dehydrogenase enzyme– Used as initial screen– If negative you can report out as negative

• Positive rapid test requires confirmation by cell culture cytotoxicity assay, EIA or PCR

• High specificity for negatives but still cannot provide a rapid result for a positive patient

C. difficile – Lab Testing continued

• Polymerase chain reaction

• BD GeneOhm Cdiff PCR assay has recently been FDA approved

• Targets the Toxin B gene• Fresh stool: Sensitivity 93.8%/Specificity 95.5%

• Frozen stool: Sensitivity 100%/Specificity 97.7%

• Evidence suggests a single negative is enough to rule out infection

C. difficile – Lab Testing continued

• Polymerase chain reaction for toxin A and toxin B (S&W)– Primers and probes for

Toxin A and B– 146 specimens– PCR picked up 7

additional positives

(37 vs 44)

EIA PCR

Sens 84% 100%

Spec 97.7% 100%

PPV 94.9% 100%

NPV 92.2% 100%

Smith, D, Hocker, K, Fader, B, Luna, RA, Versalovic, J, Rao, A. Rapid PCR screening strategy for hospital acquired infections including vancomycin-resistant Enterococci and Clostridium difficile in adult patients. (ASM Annual meeting, 2008)

C. difficile Treatment• Discontinue current antibiotics

– 23% cure rate

• Antibiotics – metronidazole

– oral vancomycin

– concern about selection of VRE 20% relapse rate

• Continue with metronidazole• 2nd relapse – switch to vancomycin

C. difficile Treatment continued

• “Severe disease” – Zar and CDC criteria– Vancomycin shown superior to metronidazole

• Toxic megacolon – direct installation of vancomycin + IV metronidazole

C. difficile Treatment continued

• Other antibiotics? (rifamixin, nitazoxinide)• Toxin binding compound was in

development– Recently stopped study

• Monoclonal antibodies• Vaccine in development• Probiotics – Saccharomyces boulardii and

Lactobacilli - questionable results– usually in combination with antibiotics

Treatment – Stool Transplant

• Reserved for severe pseudomembranous colitis and toxic megacolon

• Stool donated by healthy volunteer – usually family member– Fresh stool is homogenized, filtered through coffee

filter X2

• Administered by nasogastric tube or by enema• Usually 5 treatments to help restore normal flora

Recurrent Clostridium difficile Colitis: Case Series Involving 18 Patients Treated with Donor Stool Administered via a Nasogastric Tube. Johannes Aas, Charles E. Gessert, and Johan S. Bakken; Clin. Infect. Dis. 2003. 36:580-585

Infection Control Recommendations

• Conduct surveillance. Track positive numbers and outcomes

• Emphasize early diagnosis and treatment to physicians

• Enforce strict Infection Control policies– Contact precautions

• Hand washing with soap and water as opposed to alcohol-based hand rinse when caring for C. diff positive pts

Infection Control Recommendations

• Environmental cleaning and disinfection strategy (need sporicidal agent)– Terminal cleaning - Routine cleaning (Sani-

Master 4) vs (Dispatch) • SaniMaster 4 – ammonium chloride• Dispatch – sodium hypochlorite

– Sani-wipes for equipment and other items

• Glo-Germ® to evaluate cleaning

Surveillance - Should we Screen?

• Is C. difficile the next organism for active surveillance on inpatient admission?

• If so, should you also screen for Vancomycin- Resistant Enterococcus (VRE) with the same specimen?

• If nothing else, all positive C. difficile tests from the laboratory should be reported to Infection Control for tracking