Transcript RTS,S/AS Malaria Vaccine Candidate

A Closer Look at
Clostridium difficile Infections
Richard Allan Bettis, Fourth-Year
Pharm.D. Candidate
Preceptor: Dr. Ali Rahimi
University of Georgia College of
Pharmacy
Background

Clostridium species
>190 species identified
Gram-positive
Anaerobic
Spore forming bacilli
Releases exotoxins which
are associated with major
diseases in humans
C. difficile colitis results from
the ingestion of spores that
vegetate, multiply, and secrete
toxins
Background

Clostridium tetani
 Causes tetanus through spread of potent neurotoxin

Clostridium botulinum
 Causes botulism through spread of potent neurotoxins

Clostridium perfringens
 Causes gas gangrene through spread of necrotizing,
hemolytic exotoxin

Clostridium difficile
 Causes pseudomembranous colitis through production
of cytotoxin and enterotoxin
 Relatively resistant to most commonly used antibiotics
 Found in normal gut flora
of 2-10% of humans
Pathophysiology

Toxin A, the enterotoxin, causes:
 Damage to intestinal mucosa
 Intestinal fluid secretion
 Inflammation via actin disaggregation
 Intracellular calcium release
 Damage to neurons in the gut

Toxin B, the cytotoxin, causes:
 Depolymerization of filamentous actin
 More effective damage to colonic mucosa
Pathogenesis


Raised, yellowish-white
pseudomembranous plaques
Pseudomembranous
plaques formation resulting
in inflammation of mucosa
Enlargement and spread of
plaques through gut results
in clinical presentation
 Mild to severe diarrhea
 Mucosal necrosis
 Accumulation of inflammatory
cells and fibrin
Background


Clostridium difficile infection (CDI) is the
most common cause of infectious diarrhea in
hospitalized patients
Once antibiotics disrupt normal gut flora:
 C. difficile colonization occurs
 Toxins production results in manifestation of CDI
 Diarrhea and colitis results

CDI should be suspected in any patients with
diarrhea with recent history of antibiotic use
CDI Risk Factors

Clostridium difficile infections occur
most often in high risk groups:
 Elderly (>65 years old)
 Debilitated
 Immunocompromised
 Surgical patients
 Nasogastric tubes
 Frequent laxative use
 History of antibiotic use
CDI Risks



CDI can occur during, shortly after, or several
months after the use of broad spectrum
antimicrobial treatment
CDI should be suspect in any patients with
diarrhea with recent history of antibiotic use
within the past THREE MONTHS
Patients whose diarrhea began 72 HOURS
after hospitalization
CDI-Associated Antimicrobials

Broad spectrum antimicrobials
associated with CDIs:
 Clindamycin
 Ampicillin
 Flouroquinolones
 Ciprofloxacin, levofloxacin, moxifloxacin
 Cephalosporins (2nd & 3rd generation)
 Cefotaxime, ceftriaxone, cefuroxime, ceftazidime
 Aminoglycosides
 Erythromycin
 TMP-SMX
 Metronidazole
 Vancomycin
Used to
treat CDI!
Clinical Presentation

Patients with CDI often present with:
 Watery or perfuse diarrhea (as many as 20 bowel
movements per day)
 Leukocytosis (50%)
 Fever (28%)
 Abdominal pain (22%)
 Ileus (~20%)
 Pseudomembrane formation
 Malaise
 Nausea
 Anorexia
Clinical Presentation


Clinical diagnosis based
upon diarrhea onset during
or after antimicrobial use
Delay in diagnosis can
result in complications :
 Life-threatening toxic
megacolon
 Pseudomembranous
enterocolitis
Diagnosis

Pathogens most often responsible for
infectious diarrhea or enteritis:
 Shigella species
 Salmonella species
 Escherichia coli
 Yersinia species
 Vibrio species
 Clostridium difficile

Other etiologies less commonly seen or in
extreme cases of immunodeficiency
 Parasites (Entamoeba histolytica, Giardia lamlia)
 Viruses (Cytomegalovirus)
Differential Diagnosis

Stool cultures are crucial to making an
organism-specific diagnoses and determining
antimicrobial sensitivity
 Recommended in patients with inflammatory diarrhea
 Poor yield of positive cultures
 If negative, then a 2nd analysis is recommended
Diagnosis

Detection of toxins
 C. difficile toxins A or B

Enzyme assays for
 Glutamate dehydrogenase
(GDH)

Endoscopy
 Reserved when rapid
diagnosis is needed
 Used when ileus is present
 Stool samples are unavailable
 Differential diagnoses with
concurrent colonic diseases
Raised, yellowish-white
pseudomembranous plaques
characteristic of CDI
Prevention

Clostridium difficile can be cultured in rooms of
infected individuals UP TO 40 DAYS after discharge
 Strict hand washing
 Contact precautions
 Vaccines?
Clostridium difficile
can be cultured in
rooms of infected
individuals
UP TO 40 DAYS
after discharge
Is There A Problem?

Most frequently acquired exogenously from:
 Hospital
 Nursing home
 Long-term care facility

>20% fecal colonization among patients
hospitalized for >1 week
 C. difficile spores can persist for months on most surfaces
 Risk of colonization increases with length of stay

Other risk factors:
 Poor hand hygiene of hospital personnel
 Use of electronic rectal thermometers
 Enteral tube feeding
Why So Serious?



Both the incidence and severity of
Clostridium difficile infections have
increased significantly in the past decade
Clostridium difficile infection rates in U.S.
hospitals tripled between 2000 and 2005
CDI rates in Canada have quadrupled since 1997
 Increased rates directly attributed to an increase in
mortality from 1.7% to 6.9%
Why So Serious?

Causality attributed to emergence of specific straintypes of outbreaks known synonymously as:
 North American pulsed-field type (NAP-1)
 Toxinotype III
 REA type BI
 PCR ribotype 027

Emergence may be explained in part by patterns of
antibiotic use in hospitals
CDI Epidemic

North American pulsed-field type (NAP-1)
 Highly resistant to fluoroquinolones
 Carries deletion mutations in toxin regulatory gene
 Results in higher levels of toxin production
 16 to 23 times more toxin A and B!
 Results in significantly more serious disease
 More resistant to standard therapy
Fluoroquinolones


Most recent drug class implicated in hospital
outbreaks of C. difficile infections
Increasing fluoroquinolone resistance seen in:
 Campylobacter, Salmonella, Clostridium difficile
Treatment
Treatment
 Discontinue



offending agent
Diarrhea may resolve in up to 25% of patients
within 48 hours of discontinuation
Fluid and electrolyte replacement as necessary
Most patients will require antibiotics
 Vancomycin
 Metronidazole
Treatment

Metronidazole
 Drug of choice for mild to moderate CDI
 Less expensive

Vancomycin (Oral)
 IV does not achieve high enough gut concentrations
 Contraindications, intolerance, or poor response to
metronidazole
 Retention enema delivery if ileus or inability to reach
infection site
 Concerns of vancomycin resistant enterococci (VRE)
CDI Treatment Guidelines
Published by IDSA in 2010
 Metronidazole 500mg PO TID for 10-14 days

 For mild to moderate CDI

Vancomycin 125mg PO QID for 10-14 days
 For initial episode of severe CDI

Vancomycin +/- 500mg metronidazole IV
 For severe, complicated CDI
 Vancomycin dose is 500mg PO QID + 500mg IV in
100mL NS rectally
Treatment
Contraindicated Regimens

Drugs that inhibit peristalsis or slow gut transit
time should NOT be used in patients with fever
or bloody stool
 Diphenoxylate
 Loperamide

Evidence to support an increase risk for
development of hemolytic-uremic syndrome
due to delayed intestinal clearance and
increased toxin absorption
Recurrence
Treatments similar in diarrhea resolution, incidence
of side effects, and relapse rates
 Relapse occurs in approximately 20% of patients
 Relapse usually occurs within 1 to 2 weeks but can
be delayed for up to 12 weeks
 Frequency increases with subsequent recurrences

 One prior episode: >40% recurrence risk
 >2 prior episodes: >60% recurrence risk
Recurrence

Risk factors for recurrence:
History of recurrence
Advancing age
Additional antimicrobials
Inadequate immune
response to C. difficile toxins
Recurrence & Treatment


Optimal management of multiple relapses is unclear
Alternative regimens:
 Fecal transplantation
 Vancomycin + rifampin
 Vancomycin followed by rifaximin
 Nitazoxanide
 IVIG

Poor regimens
 Bacitracin, cholestyramine, colestipol, fusidic acid,
probiotics
Recurrence


There is more than
just C. difficile
amidst normal gut
flora
Further disruption of
gut flora only causes
susceptibility to
other infections
Where is the
selective
agent?
Treatment Failure &
Recurrence


Resistance to antimicrobials is rarely
the cause of relapse
Relapse occurs because treatment:
 Fails to eliminate C. difficile spores
 Makes patients vulnerable to another
infection by impairing normal flora
CDI Treatment Guidelines

Fidaxomicin?
Fidaxomicin (Dificid)







Narrow spectrum, macrocyclic antibiotic active against
gram-positive aerobes and anarobes
Lacks activity against gram-negative bacteria
Poor activity against normal gut flora
Relatively selective activity against C. difficile
Inhibits bacterial protein synthesis by binding to sigma
subunit of RNA polymerase
Negligible systemic absorption with oral administration
High fecal concentrations
Fidaxomicin (Dificid)




As effective as vancomycin and may be associated with
lower rates of relapse
1st antimicrobial FDA approved by the FDA for CDI
treatment in over 25 years
Orphan drug designation to all formulations for treatment
of CDI in pediatric patients <16 years and younger
Administered 200mg PO BID
Fidaxomicin versus Vancomycin
for Clostridium difficile Infection
Published in February 2011!
Study Design
Prospective, multi-centered, double-blind,
randomized, parallel-group trial
 Non-inferiority study
 All patients were enrolled at 52 sites in the
United States and 15 sites in Canada

Conducted from May 2006 to August 2008
Grading Recommendations
Eligibility Criteria
> 16 years of age
 Diagnosis of CDI

Presence of diarrhea defined as >3 unformed
bowel movements in a 24-hour period
Presence of C. difficile toxin A, B, or both in stool
sample obtained within 48 hours of
randomization

Could not be recipient of any potentially
effective concurrent CDI treatments
Oral bacitracin, fusidic acid, rifaximin
Exclusion Criteria

Patients receiving any potentially effective
concurrent CDI treatments
Oral bacitracin, fusidic acid, rifaximin

Patients with:
Life-threatening or fulminant CDI
Toxic megacolon
Previous exposure to fidaxomicin
History of ulcerative colitis or Crohn’s disease
>1 occurrence of CDI within 3 months before
study start
Efficacy Outcomes

Primary endpoint
Rate of clinical cure in the modified intentionto-treat and per-protocol populations at the end
of therapy or at the time of early withdrawal

Secondary endpoints
Recurrence of CDI during 28-day period after
the end of the course of therapy
Global cure in the modified intention-to-treat
and per-protocol populations
Treatment

Randomized into two groups
Vancomycin 125mg every 6 hours
Fidaxomicin 200mg every 12 hours
Dosing scheduled with placebo for q6h dosing
Both medications were over-encapsulated to
conceal identities
 Oral dosing for 10 days

Definitions

Modified intention-to-treat (MITT) population
 Patients with documented CDI who underwent
randomization and received at least one dose of study
medication

Per-protocol population
 Patients who received >1 dose of fidaxomicin who
received treatment for >3 days (treatment failure) or >8
days (clinical cure)
 Documented adherence to protocol
 Underwent end-of-therapy evaluation
Study Enrollment



629 patients enrolled and randomized
596 included in modified intention-to-treat
analysis (received > 1 dose of Dificid)
548 included in per-protocol analysis
Randomization
Follow-up
Follow-up
Assessed daily for clinical cure or
clinical failure
 Assessed weekly for 28 days after last
dose for recurrence

 Only patients who remained in the study and had
a follow-up assessment between days 36 and 40
after randomization
Patients


Adherence to medication similar in two groups
Did not differ significantly with baseline characteristics
Statistical Analysis

Rate of clinical cure (Primary endpoint)
 Non-inferiority margin of -10 percentage points
 If within 10-percentage points, then non-inferior

Recurrence and overall cure (Secondary endpoint)
 Post hoc hypothesis tests
 Based upon age, inpatient vs outpatient status, prior
occurrence, disease severity, and strain type

Time to resolution of diarrhea
 Kaplan-Meier method
 Gehan-Wilcoxon test for comparison of resolution times
Results
Primary Endpoint

Rate of clinical cure
Subgroup analyses based patient
characteristics showed no statistical
differences between treatments in either
treatment groups in both study populations
Secondary Endpoints

Recurrence of CDI
Treatment with fidaxomicin
Associated with a significantly lower rate of recurrence
Lower rates of recurrence with Non-NAP-1 strains
(69% relative reduction)
Treatment with vancomycin
Associated with a significantly higher recurrence
3.3 times higher rates with Non-NAP-1 strains
Secondary Endpoints

Global cure or resolution of diarrhea without recurrence


Fidaxomicin resulted in significantly higher global cure
rates than vancomycin
Median time to resolve diarrhea was shorter in the
fidaxomicin group than the vancomycin group

Not statistically significant
Overall Outcomes
Safety

Safety

No differences between either groups in regards to
rates of adverse events or serious adverse events
Study Conclusions


Treatment with fidaxomicin results in lower rates of
recurrence and correspondingly improved rate of
global cure
Rates of recurrence in non-NAP1 strains are lower
with fidaxomicin
Strengths




Study design
Study location
Data monitored and retrieved by a contract reasearch
organization (INC Research)
Data from study in regards to treatment of CDI with
NAP-1 strains, concurrent antibiotic therapy, and
clinical status resembled other studies
Additional Limitations







Sponsored by the manufacturers of Dificid
(Optimer Pharmaceuticals)
Data analyzed by Optimer Pharmaceuticals investigator
First draft of manuscript written by part-time employee
of Optimer Pharmaceuticals
Many definitions relied on subjective data
(symptomology and opinions) not lab data (GDH, C diff
toxins)
No mention about statistical significance of clinical cure
rates between the two agents in regards to more severe
infections
Data included similar factors attributing to secondary
endpoints of global cure and recurrence
Where were the author’s limitations?
REFERENCES
1.
2.
3.
4.
5.
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Retrieved January 27, 2013 from
http://www.accesspharmacy.com/content.aspx?aID=55830289.
Gerding DN, Johnson S. Chapter 129. Clostridium Difficile Infection,
Including Pseudomembranous Colitis. In: Fauci AS, Kasper DL, Jameson JL,
Longo DL, Hauser SL, eds. Harrison's Principles of Internal Medicine. 18th
ed. New York: McGraw-Hill; 2012.
http://www.accesspharmacy.com/content.aspx?aID=9119877. Accessed
January 29, 2013.
Jang J. Microbiology. In: McPhee SJ, Lu CM, Nicoll D, Pignone M, eds. Pocket
Guide to Diagnostic Tests. 5th ed. New York: McGraw-Hill; .
http://www.accesspharmacy.com/content.aspx?aID=3139168. Accessed
January 29, 2013.
Louie TJ, Miller MA, Mullane KM, et al. Fidaxomicin versus vancomycin for
Clostridium difficile infection. N Engl J Med 2011; 364: 422-31.
Martin S., Jung R. (2011). Chapter 122. Gastrointestinal Infections and
Enterotoxigenic Poisonings. In R.L. Talbert, J.T. DiPiro, G.R. Matzke, L.M.
Posey, B.G. Wells, G.C. Yee (Eds), Pharmacotherapy: A Pathophysiologic
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http://www.accesspharmacy.com/content.aspx?aID=8003383.
REFERENCES
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7.
8.
Morse SA, Brooks GF, Carroll KC, Butel JS, Mietzner TA. Chapter 11.
Spore-Forming Gram-Positive Bacilli: Bacillus & Clostridium
Species. In: Morse SA, Brooks GF, Carroll KC, Butel JS, Mietzner TA,
eds. Jawetz, Melnick, & Adelberg's Medical Microbiology. 25th ed.
New York: McGraw-Hill; 10.
http://www.accesspharmacy.com/content.aspx?aID=6427523.
Accessed January 28, 2013.
Morse SA, Brooks GF, Carroll KC, Butel JS, Mietzner TA. Chapter 21.
Infections Caused by Anaerobic Bacteria. In: Morse SA, Brooks GF,
Carroll KC, Butel JS, Mietzner TA, eds. Jawetz, Melnick, &
Adelberg's Medical Microbiology. 25th ed. New York: McGraw-Hill;
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http://www.accesspharmacy.com/content.aspx?aID=6428842.
Accessed January 28, 2013.
Olsen K.M., HUTCHINS G. . (2011). Chapter 38. Evaluation of the
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Thank you !
Definitions


Clinical cure defined as:
Resolution of diarrhea for 2 consecutive days
(<3 unformed stools)
Maintained resolution for duration of therapy
No further requirement for CDI treatment upon
2nd day (or 48 hours) after treatment end*
Patients with marked reduction in number of
unformed stools at end of treatment, but still had
mild abdominal discomfort were considered to
have met clinical cure provided no new CDI
treatment was required
Definitions

Clinical failure defined as:
Persistence of diarrhea
Need for additional therapy for CDI
Both of the above*

Global cure defined as:
Resolution of diarrhea without recurrence
Definitions

Clinical recurrence defined as:
Reappearance of >3 diarrheal stools in a 24hour period within 4-weeks after the cessation
of therapy
 C. difficile toxin A, B, or both, in stool
Need for retreatment for CDI
Disease Severity

Mild disease
 4-5 unformed BMs/day
 <12,000 white cell count

Moderate disease
 6-9 unformed BMs/day
 12,001-15,000 white cell count

Severe disease
 >10 unformed BMs/day
 >15,001 white cell count
Other Outcomes

Microbiologic evaluation
Fecal samples for toxins to verify CDI obtained
Microbiologic testing obtained at time of:
Screening or enrollment
Early termination
End-of-therapy visit due to clinical failure
Visits for the diagnosis and treatment of recurrence
Other Outcomes

Pharmacokinetic evaluation
Blood samples obtained before and 3-5 hours
after first dose of study medication on day 1 and
at conclusion of therapy
Fecal samples obtained at conclusion of therapy
Comparison