Abstract
We (i) determined the prevalence of Clostridium difficile and their antimicrobial resistance to six antimicrobial classes, in a variety of fresh vegetables sold in retail in Ohio, USA, and (ii) conducted cumulative meta-analysis of reported prevalence in vegetables since the 1990s. Six antimicrobial classes were tested for their relevance as risk factors for C. difficile infections (CDIs) (clindamycin, moxifloxacin) or their clinical priority as exhaustive therapeutic options (metronidazole, vancomycin, linezolid, and tigecycline). By using an enrichment protocol we isolated C. difficile from three of 125 vegetable products (2.4%). All isolates were toxigenic, and originated from 4.6% of 65 vegetables cultivated above the ground (n = 3; outer leaves of iceberg lettuce, green pepper, and eggplant). Root vegetables yielded no C. difficile. The C. difficile isolates belonged to two PCR ribotypes, one with an unusual antimicrobial resistance for moxifloxacin and clindamycin (lettuce and pepper; 027-like, A+B+CDT+; tcdC 18 bp deletion); the other PCR ribotype (eggplant, A+B+ CDT−; classic tcdC) was susceptible to all antimicrobials. Results of the cumulative weighted meta-analysis (6 studies) indicate that the prevalence of C. difficile in vegetables is 2.1% and homogeneous (P < 0.001) since the first report in 1996 (2.4%). The present study is the first report of the isolation of C. difficile from retail vegetables in the USA. Of public health relevance, antimicrobial resistance to moxifloxacin/clindamycin (a bacterial-associated risk factor for severe CDIs) was identified on the surface of vegetables that are consumed raw.
Highlights
On September 16, 2013, the CDC declared in its Antimicrobial Resistance Threats Report spore-forming Clostridium difficile as a threat with “urgent” concern to public health in the USA [1] due to (i) the identification of antimicrobial resistance among human and food/animal derived C. difficile isolates to drugs commonly used in humans and (ii) their increased rates of associated patient mortality since the early 2000s [1]
Clostridium difficile was the only spore-forming organism considered as an antimicrobial threat, not because C. difficile infections (CDIs) are becoming difficult to treat with antiCDI-treatments, but because C. difficile have increasing resistance to antimicrobials commonly used to treat other medical conditions in humans, which allows C. difficile to grow in the gut opportunistically causing resilient and severe CDIs
One isolate had no match to our collection of C. difficile isolates of animal origin, but two isolates belonged to the same PCR ribotype and had an uncommon combination of antimicrobial resistance against moxifloxacin and clindamycin compared to our historic representative collection of food/animal derived isolates (Figure 2)
Summary
On September 16, 2013, the CDC declared in its Antimicrobial Resistance Threats Report spore-forming Clostridium difficile as a threat with “urgent” concern to public health in the USA [1] due to (i) the identification of antimicrobial resistance among human and food/animal derived C. difficile isolates to drugs commonly used in humans ( fluoroquinolones, e.g., moxifloxacin) and (ii) their increased rates of associated patient mortality since the early 2000s [1]. Because the same hypervirulent strains were isolated from animals and retail meats in 2006 [3, 4], concerns about food contamination and foodborne transmission have emerged. Antimicrobial resistance to fluoroquinolones in food/animal isolates emerged concurrently [5, 6]
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