As presented at 112th General Meeting of the American Society for Microbiology, Session C-173 June 16 19, 2012, San Francisco, California

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1 As presented at 112th General Meeting of the American Society for Microbiology, Session C-173 June 16 19, 2012, San Francisco, California Evaluation of the Analytical Reactivity (Inclusivity) and Analytical Specificity (Cross-Reactivity) of the BD MAX Cdiff Assay A New Automated Molecular Assay. N. Paquette, I. Paradis, C. Lehouillier, R. Therrien, C. Roger-Dalbert GeneOhm Sciences Canada Inc. (BD Diagnostics), Quebec City, Quebec, CANADA ABSTRACT Objective: The BD MAX Cdiff Assay performed on the BD MAX System is an automated in vitro diagnostic test for the direct, qualitative detection of the Clostridium difficile toxin B gene (tcdb) in human liquid or soft stool specimens from patients suspected of having a C. difficile infection (CDI). The BD MAX Cdiff Assay is intended to aid in the diagnosis of CDI. The first objective of this study was to evaluate the analytical specificity (cross reactivity) of the BD MAX Cdiff Assay towards organisms found in stools. The second objective was to challenge the BD MAX Cdiff Assay with a large variety of toxigenic C. difficile strains in the analytical reactivity study (inclusivity). Methods: The analytical specificity testing has been performed with four non toxigenic C. difficile strains, two C. difficile strains of Toxinotype XI lacking tcdb gene and 30 other-clostridium strains (including four strains of Clostridium sordellii), along with 99 closely related organisms and other pathogenic and commensal flora found in the gut and stools (representing globally 90 species). All strains were tested at a concentration of 1X10 8 CFU/mL. Moreover, cross reactivity testing has been performed with seven viruses potentially present in stools. All viruses were tested at a concentration of 1X10 5 PFU/mL. The analytical reactivity testing has been performed on 64 toxigenic C. difficile strains (including 23 Toxinotypes), present in over 21 countries, from well-characterized clinical isolates or public collections. Some hypervirulent strains (NAP1) were also tested. C. difficile strains were tested at a concentration corresponding to 3 times the LoD95% of the assay. Results: None of the bacterial species or viruses used in the analytical specificity study tested positive with the BD MAX Cdiff Assay. The assay correctly identified all 64 C. difficile strains carrying the tcdb gene in the analytical sensitivity study. Conclusion: No cross reactivity has been observed with the BD MAX Cdiff Assay even with C. sordellii, which Lethal Toxin is genetically similar to C. difficile Toxin B. All toxigenic C. difficile strains tested from different geographical areas were successfully detected with the BD MAX Cdiff Assay. This new molecular assay for the detection of C. difficile tcdb gene demonstrated a high level of sensitivity and specificity. introduction C. difficile is the etiologic agent of a spectrum of diseases. Epidemiology studies demonstrate that an increased number of C. difficileassociated outbreaks have been reported worldwide 1, some with increased mortality and morbidity 2,3. Disease symptoms range from mild diarrhea to severe colitis, and even bowel perforation and death. This pathogen is the major cause of antibiotic-associated diarrhea (AAD) and pseudomembranous colitis. 4 The bacterium C. difficile, like the other bacteria comprising the intestinal flora, are killed by antibiotic therapy but not the C. difficile spores, which are insensitive to the majority of antibiotics. The BD MAX Cdiff Assay performed on the BD MAX System is an automated in vitro diagnostic test for the direct, qualitative detection of the Clostridium difficile toxin B gene (tcdb) in human liquid or soft stool specimens from patients suspected of having a C. difficile infection (CDI). The test, performed directly on the specimen, utilizes real-time polymerase chain reaction (PCR) for the amplification of C. difficile toxin B gene DNA and fluorogenic target-specific hybridization probes for the detection of the amplified DNA. The BD MAX Cdiff Assay is intended to aid in the diagnosis of CDI.

2 methods The objective of the analytical specificity (cross reactivity) study was to assess the analytical specificity of the BD MAX Cdiff Assay with isolates of phylogenetically related species (Clostridium other that C. difficile) and other organisms (bacteria and viruses) likely to be found in stool specimens. A total of 36 non toxigenic Clostridium species, as well as 98 other bacterial strains and seven viruses phylogenetically related to C. difficile or commonly found in human stools were tested. Human DNA was also tested. FIGURE 1. BD MAX System Bacterial strains were tested with the BD MAX Cdiff Assay at a concentration of 1X10 8 CFU/mL or 1X10 8 elementary bodies/ ml for intracellular bacteria. Viral suspension were tested at a concentration of 1X10 5 PFU/mL. Purified genomic DNA were tested at 1X10 5 cp/ Sample buffer tube. The objective of the analytical reactivity (inclusivity) study was to determine whether the BD MAX Cdiff Assay is able to detect different strains from various geographic origins, various toxinotypes 5, 6, 7, NAP1 outbreaks and various temporal diversities. A total of 64 toxigenic strains of Clostridium difficile were tested with the BD MAX Cdiff Assay, at a concentration equivalent to 3x LoD 95%. FIGURE 2. BD MAX reagents and consumable. A. Unitized Reagent Strip B. PCR Cartridge Tests were performed on BD MAX System (Figure 1) using Unitized reagent strip and cartridge (Figure 2) according to BD MAX Cdiff Assay workflow (Figure 3). FIGURE 1. BD MAX Cdiff Assay Workflow Steps 1 and 2. Recover and discharge stool Step 3. Load samples Step 4. Snap in reagents Step 5. Load PCR cartridge Step 6. Start run

3 results None of the bacterial species or viruses used in the analytical specificity study tested positive with the BD MAX Cdiff Assay (Table 1). TABLE 1. Analytical specificity (Cross-reactivity) Gender and Species Reference ID Assay Result Clostridium beijerinckii ATCC 8260 NEG Clostridium bifermentans NCTC 6929 NEG Clostridium bolteae BAA-613 NEG Clostridium butyricum CCRI NEG Clostridium chauvoei ATCC NEG Clostridium difficile 1 ATCC NEG Clostridium difficile 1 ATCC NEG Clostridium difficile 1 ATCC NEG Clostridium difficile 2 IS58 NEG Clostridium difficile 2 R11402 NEG Clostridium difficile 1 NCTC11206 NEG Clostridium fallax ATCC NEG Clostridium haemolyticum ATCC 9650 NEG Clostridium histolyticum ATCC NEG Clostridium innocuum CCRI-9927 NEG Clostridium nexile ATCC NEG Clostridium novyi ATCC NEG Clostridium orbiscindens ATCC NEG Clostridium paraputrificum ATCC NEG Clostridium perfringens ATCC NEG Clostridium ramosum ATCC NEG Clostridium scindens ATCC NEG Clostridium septicum ATCC NEG Clostridium sordellii ATCC 9714 NEG Clostridium sordellii NCCB NEG Clostridium sordellii CIP NEG Clostridium sordellii ATCC 9715 NEG Clostridium lavalense CCRI-9842 NEG Clostridium lavalense CCRI-9929 NEG Clostridium sphenoides ATCC NEG Clostridium spiroforme ATCC NEG Clostridium sporogenes ATCC NEG Clostridium symbiosum ATCC NEG Clostridium symbiosum CCRI-9928 NEG Clostridium tertium ATCC NEG Clostridium tetani ATCC NEG Abiotrophia defectiva ATCC NEG Acinetobacter baumannii ATCC NEG Acinetobacter lwoffii CDCF 3697 NEG Aeromonas hydrophila ATCC 7966 NEG Alcaligenes faecalis subsp. faecalis ATCC NEG Anaerococcus tetradius ATCC NEG Bacillus cereus ATCC NEG Gender and Species Reference ID Assay Result Bacillus cereus ATCC NEG Bacteroides caccae ATCC NEG Bacteroides stercoris ATCC NEG Bifidobacterium adolescentis ATCC NEG Bifidobacterium longum ATCC NEG Campylobacter coli ATCC NEG Campylobacter jejuni subsp. jejuni ATCC NEG Candida albicans ATCC NEG Candida catenulata ATCC NEG Cedecea davisae ATCC NEG Citrobacter amalonaticus ATCC NEG Citrobacter freundii ATCC 8090 NEG Citrobacter koseri ATCC NEG Citrobacter sedlakii ATCC NEG Collinsella aerofaciens ATCC NEG Corynebacterium genitalium LSPQ 3583 NEG Desulfovibrio piger ATCC NEG Edwardsiella tarda ATCC NEG Eggerthella lenta CCRI-9926 NEG Enterobacter aerogenes ATCC NEG Enterobacter cloacae subsp. cloacae ATCC NEG Enterococcus casseliflavus CCRI-1566 NEG Enterococcus cecorum ATCC NEG Enterococcus dispar ATCC NEG Enterococcus faecalis ATCC NEG Enterococcus faecium VanA ATCC NEG Enterococcus gallinarum CCRI-1561 NEG Enterococcus hirae ATCC 8043 NEG Enterococcus raffinosus ATCC NEG Escherichia coli Top10 NEG Escherichia coli ATCC NEG Escherichia coli ATCC NEG Escherichia fergusonii ATCC NEG Escherichia hermannii ATCC NEG Fusobacterium varium ATCC 8501 NEG Gardnerella vaginalis ATCC NEG Gemella morbillorum ATCC NEG Hafnia alvei ATCC NEG Helicobacter cinaedi NH 454 NEG Helicobacter pylori ATCC NEG Klebsiella oxytoca ATCC NEG Klebsiella oxytoca ATCC NEG Klebsiella pneumoniae subsp. pneumoniae ATCC NEG Lactobacillus acidophilus ATCC 4356 NEG

4 Gender and Species Reference ID Assay Result Lactobacillus reuteri ATCC NEG Lactococcus lactis subsp. lactis ATCC NEG Leminorella grimontii ATCC NEG Listeria grayi ATCC NEG Listeria innocua ATCC NEG Listeria monocytogenes L374 NEG Mitsuokella multacida ATCC NEG Mobiluncus curtisii subsp. holmesii ATCC NEG Moellerella wisconsensis ATCC NEG Morganella morganii subsp. morganii ATCC NEG Neisseria gonorrhoeae ATCC NEG Parabacteroides merdae ATCC NEG Peptoniphilus asaccharolyticus ATCC NEG Peptostreptococcus anaerobius ATCC NEG Plesiomonas shigelloides ATCC NEG Porphyromonas asaccharolytica ATCC NEG Prevotella melaninogenica ATCC NEG Proteus mirabilis ATCC NEG Proteus penneri ATCC NEG Providencia alcalifaciens ATCC 9886 NEG Providencia rettgeri ATCC 9250 NEG Providencia stuartii ATCC NEG Pseudomonas aeruginosa ATCC NEG Pseudomonas putida LCDC D7172 NEG Ruminococcus bromii ATCC NEG Salmonella enterica subsp. enterica ATCC NEG Salmonella enterica subsp. arizonae ATCC NEG Salmonella enterica subsp. enterica ATCC 7001 NEG Serratia liquefaciens ATCC NEG Gender and Species Reference ID Assay Result Serratia marcescens ATCC NEG Shigella boydii ATCC 9207 NEG Shigella dysenteriae 2933 NEG Shigella sonnei ATCC NEG Staphylococcus aureus subsp. aureus ATCC NEG Staphylococcus epidermidis ATCC NEG Stenotrophomonas maltophilia ATCC NEG Streptococcus agalactiae ATCC NEG Streptococcus dysgalactiae subsp. dysgalactiae ATCC NEG Streptococcus intermedius ATCC NEG Streptococcus uberis ATCC NEG Trabulsiella guamensis ATCC NEG Veillonella parvula ATCC NEG Vibrio parahaemolyticus ATCC NEG Yersinia bercovieri ATCC NEG Yersinia rohdei ATCC NEG Homo sapiens Hsap-25 NEG Vibrio cholerae CCRI NEG Adenovirus Type 14 CCRI NEG Rotavirus, strain WA NEG Norovirus group NEG Enterovirus CCRI NEG Echovirus 19 (Strain Burke) CCRI NEG Coxsackie virus B1 (Com-5) CCRI NEG Cytomegalovirus Strain AD NEG Chlamydia trachomatis Serovar D NEG 1 Non-toxigenic Clostridium difficile 2 Clostridium difficile XIa and XIb (lacking tcdb gene) The BD MAX Cdiff Assay detected (Table 2): -all the tested C. difficile toxinotypes (0, I, II, IIIa, IIIb, IV, V, VI, VII, VIII, IX, X, XII, XIII, XIV, XV, XVI, XVII, XVIII, XIX, XXI, XXIII, XXIV); -strains representing a NAP1 outbreak; -strains representing various temporal diversity -strains representing various geographic origins (21 countries).

5 TABLE 2: Analytical reactivity (Inclusivity) Country of origin Strain reference ID Toxin Expression Tox Assay result USA ATCC A+B+ 0 POS ND 3 ATCC A+B+ 0 POS USA ATCC A+B+ 0 POS Belgium ATCC A+B+ 0 POS Belgium ATCC A+B+ 0 POS Belgium ATCC A+B+ 0 POS Belgium ATCC A+B+ 0 POS ND 3 ATCC A+B+ 0 POS Switzerland ATCC BAA-1382 A+B+ 0 POS USA 141 NAv 1 ND 3 POS USA CD11 NAv 1 ND 3 POS France 301 NAv 1 ND 3 POS Canada CD 246 NAv 1 ND 3 POS New Zealand NCTC A+B+ ND 3 POS UK NCTC A+B+ ND 3 POS Turkey NI1 NAv 1 ND 3 POS Germany CI3 NAv 1 ND 3 POS Italy FI9 NAv 1 ND 3 POS Switzerland LI6 NAv 1 ND 3 POS Spain KI3 NAv 1 ND 3 POS The Netherlands GII1 NAv 1 ND 3 POS Poland HI1 NAv 1 ND 3 POS Ireland DII1 NAv 1 ND 3 POS UK QI1 NAv 1 ND 3 POS Sweden MI23 NAv 1 ND 3 POS Hungary EII1 NAv 1 ND 3 POS Greece PI2 NAv 1 ND 3 POS France AC008 A+B+ II POS France SE844 A+B+ IIIa POS Belgium A+B+ IV POS Belgium A+B+ VI POS Belgium A+B+ VII POS Belgium A+B+ IX POS UK 8864 A-B+ X POS USA CH6223 A+B+ XXI POS Canada M14614 A+B+ 0 POS Canada M39177 A+B+ 0 POS Canada M16256 A+B+ I POS Canada M25097 A+B+ IV POS Canada M30761 A+B+ VI POS Canada M46722 A+B+ IX POS Canada M40767 A+B+ IX POS Canada M26479 A+B+ XII POS Canada M13883 A+B+ XXI POS France SE881 A+B+ V POS Canada M14473 A+B+ III 2 POS

6 Country of origin Strain reference ID Toxin Expression Tox Assay result Canada M28681 A+B+ III 2 POS Canada M37992 A+B+ III 2 POS Canada M41124 A+B+ III 2 POS Canada M1137 A+B+ III 2 POS ND 3 IS25 A+B+ XII POS USA R9367 A+B+ XIII POS UK R10870 A+B+ XIV POS USA R9385 A+B+ XV POS Indonesia SUC36 A-B+ XVI POS Japan J9965 A-B+ XVII POS Korean K095 A+B+ XVIII POS Japan TR13 A+B+ XIX POS USA 8785 A+B+ XXIII POS Kuwait 597B A+B+ XXIV POS ND 3 ATCC A+B+ 0 POS ND 3 ATCC 9689 A+B+ 0 POS ND 3 ATCC BAA-1805 A+B+ IIIb 2 POS ND 3 ATCC A-B+ VIII POS 1 NAv: Non available 2 Strains identified as NAP1 and associated with CDI outbreaks 3 ND: Not Determined Conclusion The BD MAX Cdiff assay performed well in the presence of phylogenetically related species. No cross reactivity has been observed for the BD MAX Cdiff Assay with other phylogenetically related species or other organisms likely to be found in stool specimens A variety of clinically relevant toxigenic Clostridium difficile strains were included in this study taking into account geographic origin, toxinotypes, NAP1 outbreaks and temporal diversity. Sixty-four (64) strains including 23 toxinotypes and representing 21 countries were tested, including strains from public collections and from well-characterized clinical isolates. The assay correctly identified all tested toxigenic C. difficile strains. References 1 Cloud J and Kelly CP. Update on Clostridium difficile associated disease. Curr Opin Gastroenterol Jan; 23 (1): Warny M et al. Toxin production by an emerging strain of Clostridium difficile associated with outbreaks of severe disease in North America and Europe. The Lancet Sep 24-30; 366 (9491): Gould C V and McDonald L C. Bench-to-bedside review: Clostridium difficile colitis. Critical Care. 2008; 12 (1): Bartlett, John G. MD, Clostridium difficile: Old and New Observations. J of Clin Gastroent. May/June 2007; 41 Supplement 1:S24-S29. ACKNOWLEDGEMENTS C. difficile strains were kindly provided by: M. Rupnik, Institute of Public Health Maribor, SI-2000 Maribor, Slovenia F. Barbut, National Reference Laboratory for C. difficile, Paris, France M. Delmée, Université Catholique de Louvain, Brussels, Belgium J. Pepin, University of Sherbrooke, Sherbrooke, Quebec, Canada E. Frost, University of Sherbrooke, Sherbrooke, Quebec, Canada