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Bacteriocidal versus Bacteriostatic: What Makes the Biggest Difference in VRE Bloodstream Infection?

An October 2018 publication in Critical Care Medicine by Chuang et al details a prospective study of adults in Taiwan, between 2010 -2015, aimed to assess all-cause mortality and rate of bloodstream clearance among patients with vancomycin-resistant enterococci (VRE) treated with daptomycin (bacteriocidal) versus linezolid(bacteriostatic). Patients were treated with conventional daptomycin (6 to < 9 mg/kg actual body weight), high-dose daptomycin(>9 mg/kg) or linezolid (600mg IV Q12 hours). The initial blood culture bacterial load was determined, followed by blood cultures daily for the first 4 days and then twice per week for a total of 2 weeks unless the patient was discharged or therapy discontinued prior to that. Blood cultures were assessed via traditional blood culture methodology and by a real-time quantitative PCR detecting vanA (no vanB documented in cohort).

108 patients were included in the analysis. 63(58.3%) received conventional dose daptomycin, 15 (13.9%) received high-dose daptomycin and 30(27.8%) received linezolid. There was no statistically significant difference between survivors and non-survivors in the initial bacterial load, however, survivors had a statistically significant higher rate of early bacterial clearance (p = 0.02). There was no statistically significant difference in bacterial clearance among those with empiric versus definitive treatment, however clearance was statistically significant in difference among the antimicrobial treatment arms. Early bacterial clearance was faster with high-dose daptomycin(p<0.001) and linezolid(p =0.043) as compared to conventional daptomycin, with no statistically significant difference between high-dose daptomycin and linezolid. A higher PITT bacteremia score and slower clearance of bacteremia were found to be independent predictors of mortality. PCR was more sensitive, and equally as specific, as traditional blood cultures.

The statistically significant differences in rate of bacterial clearance (and associated survivorship) between high-dose daptomycin and linezolid, compared to conventional daptomycin, suggests that higher doses of daptomycin or use of linezolid should be considered in VRE BSIs. Larger studies are needed to validate the results and validated determine clinical impact and optimal dosing.

Of note, the study is limited by smaller sample sizes, no vanB carrying VRE and the inability to report false positive PCRs. A formal RCT would be needed to determine optimal therapy. In addition, the average weight of patients was 60 kg, thus this data cannot be extrapolated necessarily to obese patients.  Further studies related to dosing weight and optimal dosing are also warranted.

Content originally written and adapted for the IDSA journal club. 


 

Saving SIRS? Discernment of Sepsis from Non-Infectious Syndromes in the ED

Upon patients’ arrival to the emergency department (ED), determining whether they do or do not have sepsis is difficult. Because of this, many patients receiving antibiotics ultimately are found to have a noninfectious cause of their syndrome. In order to try and improve detection of sepsis in the ED, Mearelli et al. completed a multicenter prospective study at five university hospitals in Italy and reported their results in a recent article in Critical Care Medicine.

The study included two cohorts: an inception cohort for the development of a predicted algorithm and a validation cohort to determine positive and negative predictive value of the algorithm based on pretest probability of infection with the aim to differentiate sepsis syndromes from noninfectious inflammatory states. Despite its faults, criteria for systemic inflammatory response syndrome (SIRS) were used to enroll patients and then categorize them based on whether an infectious diagnosis was ultimately identified. Biomarkers utilized in the algorithm included procalcitonin, soluble phospholipase A2 group IIA (sPLA2GIIA), presepsin, soluble interleukin-2 receptor α (sCD24), and soluble triggering receptor expressed on myeloid cells (sTREM-1).

The area under the curve (AUC) for the algorithm in the validation cohort was an impressive 0.95 (95 percent confidence interval [CI] 0.82-0.90). The primary impact of this study may be for ruling out sepsis and septic shock given that only five of 700 (0.7 percent) patients were misclassified when having sepsis or septic shock compared to the usual approach of clinical concern for infection, fever, leukocytosis, and increased C-reactive protein.

Although imperfect, the algorithm does appear to be better than current diagnostics used for determining if a patient has sepsis or septic shock. Primary concerns for future implementation of this are the few patients that had sepsis or septic shock with a negative SIRS screen, the feasibility of rapid multimodal test results for screening versus potential delay of therapy, and the overall cost of obtaining such labs.

(Mearelli et al. Crit Care Med. 2018;46(9):1421-1429.)

Content written by Dr. Kelly Cawcutt; originally posted for the IDSA journal club.


 

 

Skin Deep: A Closer Look at Treatment of Skin and Soft Tissue Infections

Current guidelines for management of Skin/Soft Tissue Infections (SSTIs) were published in 20141.  Nevertheless, management of SSTIs is variable, likely driven by the fact that culture data is often unavailable to direct clinical decision making. Treatment variability results in inappropriate antimicrobial use, highlighting the need for antimicrobial stewardship. Consequently, management of SSTIs is one area where more research has identified easy targets for improvement. This review describes two such studies.

The first, a systematic review conducted by Bowen et al.2, sought to answer the question: For which SSTIs should we use sulfamethoxazole-trimethoprim (SXT)? After identifying 196 potential studies, 10 randomized controlled trials (RCTs) and 5 observational studies underwent full-text review. The largest RCT of impetigo with 90% of isolates cultured as group A streptococci (GAS), found a nonsignificant difference in treatment success with 3-5 days of SXT vs benzathine penicillin. The authors therefore recommended a short course of SXT as treatment of choice for impetigo (when clinical situation dictates systemic therapy). The 2014 SSTI guidelines recommend covering S. aureus in impetigo, but only recommended it for situations where MRSA is suspected or confirmed.  The systematic review also highlighted newer RCTs demonstrating high grade evidence in favor of adding SXT to incision and drainage for abscesses vs incision and drainage alone.  The authors concluded that there was high grade evidence to support use of SXT monotherapy for SSTIs caused by GAS and S. aureus, including impetigo, purulent SSTIs and abscess (coupled with incision and drainage), and agreed that beta-lactams are treatment of choice for nonpurulent cellulitis, as MRSA coverage provides no additional benefit.

The second study conducted by Kamath et al.3, discovered that the majority of SSTI management was not compliant with guidelines. Their retrospective analysis looked at 240 patients who were diagnosed with purulent or nonpurulent SSTIs in a large VA Emergency Department. Patients seen in the ED for SSTI were either admitted to the hospital inappropriately (20%) or discharged from the ED inappropriately (34%). Patients were more likely to be hospitalized if they were alcoholics (OR 3.4, CI 1.3-8.5, p0.01), had SIRS (OR 3.98, CI 1.4-11, p 0.008), or had redness (OR 2.9, CI 1.06-4.2, p0.03).

More recent RCTs have again supported guideline recommendations to use beta-lactams for treatment of non-purulent cellulitis. Remarkably, (but unfortunately not surprisingly) only 30% of the time did treatment of nonpurulent cellulitis follow guidelines; most patients received some agent covering CA-MRSA. Compliance with guidelines improved slightly with management of purulent SSTIs (44% compliance). 88% of patients received antibiotics for management of mild skin abscess, and half of these underwent concurrent incision/drainage (I&D). Current guidelines indeed recommend I&D without antibiotics for mild abscess, however we do not know the size of the abscesses included in the study, and since the guidelines were published, new RCT data support adjunctive SXT after I&D for abscesses >2cm4, so perhaps these “noncompliant” clinicians were simply ahead of their time.   Finally, the authors looked at diagnostic testing. Current guidelines only recommend blood cultures in patients with severe nonpurulent infection, but 29% of patients with mild cellulitis had blood cultures obtained (only 1 positive).

Both of these studies identify clear targets for antibiotic (and diagnostic) stewardship with respect to SSTIs. Utilization of SXT in cases of impetigo could lead to more monotherapy and reduction of unnecessary “double coverage” antibiotic use; reinforcement of the need for only beta-lactams for non-purulent cellulitis is an important area for improvement; and avoidance of unnecessary blood cultures reduces the need for inappropriate antibiotic therapy for contaminants.

The preceding was previously posted by Dr. Marcelin to SHEA Journal Club published online in March 2018, and published on Medscape in June 2018. 

References:  

    1. Stevens DL, Bisno AL, Chambers HF, et al. Practice guidelines for the diagnosis and management of skin and soft tissue infections: 2014 update by the Infectious Diseases Society of America. Clin Infect Dis. 2014;59:e10-e52.
    2. Bowen AC Carapetis JR, Currie BJ, Fowler V Jr, Chambers HF, Tong SY. Sulfamethoxazole-trimethoprim (cotrimoxazole) for skin and soft tissue infections including impetigo, cellulitis, and abscess. Open Forum Infect Dis. 2017;4:ofx232.
    3. Kamath RS, Sudhakar D, Gardner JG, Hemmige V, Safar H, Musher DM. Guidelines vs actual management of skin and soft tissue infections in the emergency department. Open Forum Infect Dis. 2018;5:ofx188.
    4. Daum RS, Miller LG, Immergluck L, et al; DMID 07-0051 Team. A placebo-controlled trial of antibiotics for smaller skin abscesses. N Engl J Med. 2017;376:2545-2555.

Top 10 Things We Are Thankful for in ID – Letterman Style

Life is better with gratitude. Today, whether or not you celebrate Thanksgiving, we want to continue to show our gratitude and thankfulness to be able to help diagnose, prevent, treat, cure and even advance, the science of medicine. Now, let’s have a little fun!

We are grateful for:

10. Hand washing with those cute seasonal soaps – No one needs a real-life learning experience about Typhoid Mary.

9. Well-cooked Turkey – Salmonella was not invited to this dinner party.

8. Antibiotic-Free Agriculture  – This is not a rise of resistance anyone wants to endorse.

7. Improved monitoring and safety of herbicides – Did you know about The Great Cranberry Scare of 1959?

6. Separate cutting boards, so our spinach salad does not get introduced to Ecoli. Safety First, Food Safety!

5. Research & outbreak investigations that have taught us so many lessons about infections & foodborne pathogens like Listeria.

4. The potential antimicrobial effect of the honey on our roasted carrots – perhaps it is extra healthy?

3. The cinnamon in your pumpkin pie, may also have antimicrobial impact against. S. aureus & E. Coli.

2. Influenza vaccinations– saving lives every year during this season of celebrations and rising cases of influenza infection. It’s not too late you get yours!

  1. Finally, YOU! Colleague, patient, educator, advocate, researcher, funder, supporter. Without all of you, we simply would not be able to continue to provide the extraordinary care and education we strive to. Thank you! May you find your day full of gratitude and thankfulness.

 


 

Earrings In Healthcare Workers: Friend or Foe?

Ear piercing among people, including healthcare workers, is a common trend.

Katsuse et al, attempted to make a correlation between ear piercings and healthcare-associated infections. In order to prove this relationship, researchers sampled the earlobes and fingers of 200 nurses working at a university hospital. 128 of those nurses had pierced earlobes and 72 of the nurses sampled did not. When sampling the fingers, the fingers on the dominant hand were used for all nurses. The results are in the table below.

Pierced earlobes (128 nurses) Not Pierced (72 nurses)
Staphylococcus aureus on ears 24 7
Staphylococcus aureus on fingers and earlobes 12 3
MRSA isolates from earlobes 6 2
MRSA from fingers 5 1
MRSA from earlobes and fingers 3 1
Enterococcus faecalis 1 (earlobe and finger)
Morganella morganii 1 (ear lobe)
Pseudomonas aeruginosa 6 (fingers)
Acinetobacter species 6 (fingers)

 

The results showed that nurses with pierced ears were more likely to test positive for Staphylococcus aureus and MRSA on both their ears and fingers. The study concludes, based on these non-statistically significant numbers, that contamination and cross transmission can occur when fingers contact the earlobes. Since the same S aureus PFGE type was found on the earlobes and fingers, the authors deduced that pierced earlobes can be a source of hospital acquired infections.

They also concluded, that since more nurses with pierced ears also had MRSA isolates recovered, that pierced earlobes are a risk factor for MRSA carriage. The researches then used this information to determine that indirect transmission can occur when health care workers wear a name badge strap because removal of the strap may lead to contact with the earlobe and result in the spread of bacterial, although they could not prove this association.

Some comments from our journal club discussion included:

  1. There is no data to differentiate persons who are colonized vs transient carriage.
  2. There is also no consideration of other variables such as recent antibiotic use, current hygiene practices(including adequate hand hygiene with patient care, which should negate the risk of hand carriage), and frequency of earring changes and cleaning or a multitude of other factors that may affect isolation of organisms from body parts.
  3. The authors in this article drew conclusions, with inadequate evidence, that:
    1. Pierced ears may cause transmission when they come into contact with name badges
    2. Pierced ears may cause hospital associated infections.

Will we be changing policies regarding earrings based on this study – not at all. Earrings and piercings may have a relationship to MRSA coverage, but this study falls quite short of proving that. It also is unable to provide a clear increased risk of healthcare-associated infections relating to earring use.

Article chosen, presented and reported in this blog by Alisha Dorn, Infection Preventionist. Edited by Dr. Kelly Cawcutt. 


 

UNMC Infectious Diseases Fellows are Antibiotics Aware

The following was written by Dr. Raj Karnatak, 2nd year ID fellow at UNMC; a reflection of his current Antimicrobial Stewardship/Infection Control rotation:

The UNMC Infectious Diseases fellowship antimicrobial stewardship and infection control rotation provides robust training for fellows in both antimicrobial stewardship and infection control. Training is well designed with education in all the core elements of stewardship and infection control. Fellows attend dedicated lectures from the experts in the field of infection control and antimicrobial stewardship. Throughout the rotation fellows actively participate in hospital acquired infections (HAI) surveillance and infection prevention, and antimicrobial stewardship interventions. In the Infection control training, we learn about the role of healthcare epidemiology, surveillance and prevention of healthcare-associated infections including C. difficile, central-line associated bloodstream infections, multidrug-resistant organisms, ventilator-associated events, and surgical site infections.

Our antimicrobial stewardship training is concentrated on learning the CDC core elements of antimicrobial stewardship and implementing principles of antimicrobial stewardship in healthcare settings (Inpatient, outpatient, long-term care facility). Fellows actively engage in quality improvement in the infection control and antimicrobial stewardship and also work closely with our Stewardship Pharmacy Coordinator. Learning stewardship core elements present you to principles that can very well be applied to a wide variety of QI efforts. As fellows we are fully integrated into the stewardship team during our rotation, and besides attending key meetings where brainstorming stewardship issues occur and decisions are made, we actively participate in daily telephone audit-and-feedback. This gives us needed practice with communicating with prescribers, troubleshooting common problems and helps us to be better Infectious Disease Doctors.  We are also participating in the IDSA Antimicrobial Stewardship Curriculum pilot. In this formal training, our curriculum Directors Drs. Van Schooneveld and Marcelin meet with us regularly for case-studies, role playing and module reviews, where we discuss approaches to handling difficult situations as #Stewies.

As a part of my stewardship project, I am working on developing an institutional guidance document for antibiotic management of acute rhinosinusitis and pharyngitis in the outpatient setting. My other project is in infection control for the prevention of ventilator-associated events. I also had the opportunity to work with a larger multidisciplinary sepsis group for the development and implementation of institutional sepsis protocol. As a budding Infectious Diseases physician with particular interest in Critical Care Medicine, I know that Antimicrobial Stewardship is essential to any job I take post-fellowship, and I am thrilled to be at an institution that values it so highly.

How Nebraska ASAP is Making Everyone Antibiotic Aware

The following was written by Dr. Salman Ashraf, co-Medical Director of the Nebraska Antimicrobial Stewardship Assessment & Promotion Program (ASAP):

Antibiotic Resistance is one of the most urgent threats to the public health. Overuse and misuse of antibiotics allows the development of antibiotic-resistant bacteria. Unfortunately, a significant proportion of antibiotic use in various healthcare settings continues to be unnecessary or inappropriate. About a third (30%) of all antibiotic use in hospitals and outpatient setting and up to 75% of antibiotic use in long-term care facilities have been found to be inappropriate. Antimicrobial stewardship programs (ASP) have been shown to be effective in decreasing inappropriate antibiotic use in all of these settings. However, there is a shortage of infectious diseases (ID) trained physicians and pharmacists who can assist healthcare facilities in such efforts, especially in heavily rural states such as Nebraska. Additionally, many of these facilities may lack the resources necessary to effectively implement an ASP.

The Nebraska Antimicrobial Stewardship Assessment and Promotion Program (ASAP) is funded by the Nebraska Department of Health and Human Services, Healthcare-Associated Infection Team through a CDC grant. It is closely affiliated with the nationally recognized ASP at Nebraska Medicine. The ASAP program employs ID trained pharmacists, ID trained medical directors and infection preventionists with extensive experience in establishing and running successful infection control and antimicrobial stewardship programs. The goal of ASAP is to promote effective use of antimicrobials and improve patient outcomes throughout the state of Nebraska by collaborating with local clinicians, pharmacists, infection preventionists and other health care workers. The team is working diligently to establish effective ASP in all healthcare facilities, especially those that lack the expertise to develop or improve these programs on their own.

The highlights of Nebraska ASAP initiative include:

• Assessment of ASP in various health care facilities
• Identification of facility-specific gaps along with provision of recommendations for improvement
• Provision of ongoing support for antimicrobial stewardship efforts in recruited acute and long-term facilities through an innovative model of remote coaching (utilizing video-conferencing service)
• Development of tools and templates to facilitate implementation of ASP in various healthcare settings
• Development of patient and provider educational resources related to appropriate antibiotic use
• Collaboration with regional organizations and healthcare facilities on educational efforts to improve antibiotic prescribing practices in outpatient setting
• Provision of expert guidance related to ASP development and maintenance for all healthcare facilities that reach out with questions (in addition to assisting healthcare facilities in Nebraska, the team also answer questions sent to us by facilities and organizations from neighboring states or other parts of the country).

Notable achievements of Nebraska ASAP initiative include:

• Currently providing expert guidance to 24 facilities in the state (10 acute-care Hospitals and 14 long-term care facilities)
• Created a website focused on promoting ASP in healthcare facilities by providing tools and templates specific to the different healthcare settings
• Since its inception in August 2017, the Nebraska ASAP website has been visited by over 5000 users both nationally and internationally and has earned the reputation of a national resource for facilities looking into developing or improving their ASP
• Organized the inaugural “Antimicrobial Stewardship Summit” for the state of Nebraska on June 1st 2018 to provide education to ASP program leaders (over 250 healthcare workers attended the summit)
• Established the Nebraska ASAP YouTube Channel in February 2018 that hosts all the educational videos developed by the team (almost 2500 views of the videos have been reported in this short time frame).
• Shared our findings and experience with healthcare community at various national meetings (these presentations are available online here
• Piloted an educational intervention in 10 primary care clinics that resulted in a 25% decrease in antibiotic prescribing for acute bronchitis (further analysis is ongoing and the results will be shared with healthcare community soon)

Upcoming activities of Nebraska ASAP initiative include:
• Introducing a CME educational activity for providers of outpatient clinics and urgent care centers. The course will be launched in the next couple of months. Outpatient clinics and urgent care centers who want to partner with ASAP can reach out to us in advance to make sure they have a guaranteed spot when the activity goes live: Further information can be found at online here
• Organizing the 2019 Antimicrobial Stewardship Summit that will focus on the needs of acute-care, long-term care and ambulatory-care settings. The summit will not only provide guidance on how to establish ASP but also provide education on evidence-based management of common infections in various healthcare settings. To receive news on important new website contents or upcoming events sign up for updates here
• Continue to recruit for remote coaching on antimicrobial stewardship (only a few spots left). Healthcare facilities that are interested in partnering with antimicrobial stewardship experts to assist their local ASP team can find more information on the following link:

The Nebraska ASAP team

Nebraska Medicine is Proud to #BeAntibioticsAware

Our Antimicrobial Stewardship Program (ASP) at Nebraska Medicine has been in place since 2004. Over the years our program has changed and improved sought to expand and improve its approach with the goal of providing extraordinary care to our patients. Rather than an overly restrictive practice, our program has we have emphasized constant regular communication with our clinicians through a robust audit-and-feedback program. Physician medical directors are Drs. Trevor Van Schooneveld, Jasmine Marcelin and Erica Stohs, (who recently joined our program this summer). Our Pharmacy Coordinator is Scott Bergman PharmD.

Over the last year, our ASP team has collaborated with the microbiology laboratory, hospital clinical effectiveness team and sepsis taskforce to implement some changes with goals of improved patient care.  In June 2018, we hosted the inaugural Nebraska Antimicrobial Stewardship Summit, where experts spoke on various aspects of ASP.  This has led to multiple outreach conferences where members of our ASP team have been invited to speak and counsel medical centers on their ASP development.

Diagnostic stewardship has become an integral part of our ASP. We implemented a hard stop in the electronic medical record to prevent inappropriate ordering of the gastrointestinal pathogen panel and saw significant decreases in inappropriate use with associated cost savings (Presented at #IDWeek2018). Similar interventions are underway for decreasing inappropriate respiratory pathogen panel ordering and C. difficile testing.  A larger C. difficile reduction project is ongoing hospital-wide, and antimicrobial stewardship plays a significant role in this.  Additionally, we have updated several clinical guidance documents including alternatives to vancomycin + pipercillin/tazobactam combination therapy to avoid renal injury, skin & soft issue infections, and published an approach to inpatient allergy management.

We are also focusing efforts on Outpatient Antimicrobial Stewardship. While this program is still in its nascent stages, in collaboration with Nebraska ASAP we have developed a series of resources for antimicrobial stewardship in the outpatient setting including educational modules. The program goals are to reduce unnecessary antibiotic prescribing in the ambulatory setting throughout the Nebraska Medicine network.

Finally, the stewardship team has been working the Nebraska Medicine Sepsis Committee to assist in developing a management strategy for this common and highly lethal condition.  Initial work focused on sepsis recognition and implementation of screening to identify patients for early intervention.  This was highly successful with a 47% decrease in sepsis mortality at Nebraska Medicine between 2014 and 2016.  With the recent introduction of new sepsis definitions the Sepsis Committee elected to implement these new definitions to better focus aggressive care on those patients most likely to benefit from it. In addition, the current nurse screening protocol is being replaced this month with an advanced sepsis early warning model which mines large amounts of data available in our electronic record to more accurately identify patients at risk of developing sepsis.

Over the years the mission of the ASP at Nebraska Medicine has not changed, but our methods and activities have expanded to meet the challenges of our ever changing healthcare landscape.

Keep looking for updates to clinical guidance on our website!

Content courtesy Dr. Trevor Van Schooneveld and Dr. Jasmine Marcelin

Governor Ricketts Proclaims Antibiotic Awareness Week in Nebraska

Last year, Nebraska’s Governor Pete Ricketts signed a proclamation declaring Antibiotic Awareness Week in Nebraska, and he again signed a proclamation this year, declaring November 12-18 Antibiotic Awareness Week in our state. Once again, Dr. Maureen Tierney, leader of Nebraska’s Healthcare Associated Infections Program, championed the drafting of the proclamation and received support from the Governor for this observance.

Formerly known as Get Smart About Antibiotic Week, US Antibiotic Awareness Week is an annual observance designated by the CDC to bring awareness to healthcare professionals and the public on the threat of antibiotic resistance and the importance of using antibiotic appropriately.

The CDC has prepared a partner toolkit for institutions that want to participate in this event. The toolkit contains key messages, social media content (#AntibioticResistance, #USAAW18, #BeAntibioticsAware), graphics and more. Below is a sample of events that will be promoted during each day of the 2018 Antibiotic Awareness Week.

Monday, November 12

  • Special edition of the CDC Safe Healthcare Blog which will feature a story on successful implementation of antimicrobial stewardship program for veterans
  • Publication of an article that describes drivers of inappropriate antibiotic prescribing and potential interventions

Tuesday, November 13

Wednesday, November 14

Thursday, November 15

  • Kick-off of a global Twitter storm from 8am-9am CST with the hashtag #AntibioticResistance and the message “Antibiotic resistance is one of the most urgent global health threats. Everyone has a role to play in improving antibiotic use to help fight #AntibioticResistance”
  • New antimicrobial stewardship core elements for resource-limited settings

Friday, November 16

During this week, also look for blogposts from Nebraska ASAP and UNMC Division of Infectious Diseases on antibiotic stewardship and appropriate antibiotic prescribing.  We are excited for this year’s events and we hope you will participate in this important patient safety and public health initiative.

Content provided by Phil Chung PharmD and originally posted to the Nebraska ASAP website on November 6, 2018. 

Does the Clostridium Smell Diffy? Even the Dogs Disagree…

The C. difficile sniffing dogs are back! There are several prior reports of individual dogs being trained to “sniff out” C. difficile. In a novel approach, the authors of this study trained two dogs simultaneously, and then compared interrater reliability between sniff attempts. They used toxigenic C. difficile frozen stool samples (GDH EIA and PCR positive) and negative controls in an institution where prevalence of toxigenic C. difficile was 13.7%. A German Shepherd and Border Collie Pointer each trained with a reward based system, first detecting toxin-producing C. difficile then detecting negative samples (Click here for a cool training video). The dogs then sniffed 300 validation stool samples in identical boxes (30% positive 70% negative), with 10 random samples for each detection round.

The dogs had a moderate interrater reliability with a Cohen’s kappa of 0.52. Both dogs had about 85% specificity of toxigenic C. difficile detection but the German Shepherd’s sensitivity of detection out-sniffed the Border Collie Pointer (92% vs 78% respectively). Positive predictive value for both dogs was <50% and negative predictive value was >95% for both dogs. Interrater variability necessitates individualized dog training; and it is curious that two different species were used – could there be a genetic predisposition for “better” olfactory receptors in certain species?

Trained Giant African pouched rats can accurately sniff tuberculosis in Tanzania, and dogs have been trained to detect drugs and explosives for law enforcement, so why not C. difficile?Though the concept is exciting, this is miles away from mainstreaming due to effort and lack of generalizability.

If two different canine species could not agree on whether or not the stool smelled “diffy”, where does that leave humans, whose olfactory capabilities are thought to be 10,000- to 100,000-fold less sensitive than dogs? Perhaps when it comes to C. difficile, no nose knows better than conventional testing.

The preceding was previously posted by Dr. Marcelin to SHEA Journal Club published online in October. Article reviewed: Maureen T Taylor et al. Using Dog Scent Detection as a Point-of-Care Tool to Identify Toxigenic Clostridium difficile in Stool, Open Forum Infectious Diseases 

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