Reviewed by: Rupak Datta, MD PhD, Yale School of Medicine; Emily S. Spivak, MD, MHS, University of Utah School of Medicine

Three articles this month aim to further our understanding of the role of food sources and the home environment in the transmission of extended-spectrum β-lactamase–producing (ESBL) Enterobacteriaceae.  

Day and colleagues aimed to identify foodborne reservoirs of ESBL-E coli contributing to human disease. In 5 UK regions, consecutive bloodstream ESBL-E coli isolates were collected from 2013-2014 from National Health Service laboratories, and human feces, sewage, farm slurry and retail foodstuffs were prospectively sampled. Samples were plated on CHROMagar ESBL and CHROMagar CTX chromogenic media.  Presumptive ESBL-E coli isolates from blood, feces, sewage, food, animals and slurry were screened for blaCTX-M, blaTEM, blaSHV and blaOXA by multiplex PCR. ESBL-E coli was confirmed with sequencing. 2157 (11%) of 20,243 human feces samples contained ESBL-E coli. ESBL-E coli were frequent in retail chicken (104 [65%] of 159 meat samples) but were rare in other meats and absent from plant-based foods. Sequence type (ST) 131 dominated among ESBL-E coli from human blood (188 [64%] of 293 isolates), feces (128 [36%] of 360), and sewage (14 [22%] of 65) but was rare among food and veterinary isolates (only two ST131 organisms recovered from 218 isolates). The authors conclude most human ESBL-E coli bacteremias in the UK involve human-associated strain types and non-human reservoirs likely contribute little to human disease.

Meijs and colleagues assessed whether vegetarians are at lower risk of carrying ESBL and plasmid-mediated AmpC (pAmpC)-producing E. coli and K. pneumoniae (ESBL-E/K) compared with persons who consume meat.  Dutch adults were recruited from 2015-2017 using news and social media to identify vegetarians.  Already identified vegetarians recruited non-vegetarians.  Vegetarians were included if their diet was meat-free for 6 months, and participation was limited to 1 person per household. Each participant received a detailed questionnaire and package to collect a stool sample. ESBL-E/K were cultured, and ESBL and pAmpC genes were analyzed using PCR and sequencing.  The risk of ESBL-E/K carriage according to diet type was assessed using multivariable logistic regression. Among 1542 participants, prevalence of ESBL-E/K was 8% in vegetarians (63/785), 7% in pescatarians (27/392), and 4% in non-vegetarians (14/365). The adjusted odds ratio for carriage of ESBL-E/K was 2.2 for vegetarians (95% CI 1.2–4.0) and 1.6 for pescatarians (95% CI 0.8–3.2) compared with non-vegetarians, suggesting that eating meat is not an important risk factor for ESBL-E/K carriage in the Netherlands.  

Martischang and colleagues performed a systematic review to evaluate the impact of home environment on patient’s carriage of ESBL-producing Enterobacteriaceae (ESBL-PE). Of 2,141 studies screened for eligibility, 13 were included. Co-carriage was defined as simultaneous carriage by 2 or more household members of a related ESBL-PE strain. Acquisition was defined as newly identified carriage of a related strain in another household member who was previously ESBL negative. When considering co-carriage of phenotypically-related pathogens, point prevalence of ESBL-PE co-carriage among household members was 8% to 27%. In the 9 studies assessing co-carriage of genotypically-related pathogens, including 817 household members of index cases colonized or infected by ESBL-PE, the proportion of co-carriage with a genotypically related strain ranged from 5.6% to 23%. Over 4-fold higher carriage was observed among household members of a colonized or infected index case compared to ESBL-PE carriage prevalence in the general population. Interestingly, co-carriage proportions decreased when considering only co-carriage of genotypically-related ESBL-PE, suggesting multiple sources of ESBL-PE introduction (e.g., food, travel) into households. 

References:

Day MJ, et al. Extended-spectrum β-lactamase-producing Escherichia coli in human-derived and food chain-derived samples from England, Wales, and Scotland: an epidemiological surveillance and typing study. Lancet Infect Dis. 2019 Dec; 19(12):1325-1335. https://www.sciencedirect.com/science/article/pii/S1473309919302737?via%3Dihub 

Meijs AP, et al. Do vegetarians less frequently carry ESBL/pAmpC-producing Escherichia coli/Klebsiella pneumoniae compared with non-vegetarians? J Antimicrob Chemother. 2019 Nov 25. pii: dkz483. https://academic.oup.com/jac/advance-article/doi/10.1093/jac/dkz483/5640478 

Martischang R, et al. (2019). Household carriage and acquisition of extended-spectrum β-lactamase–producing Enterobacteriaceae: A systematic review. Infect Control Hosp Epidemiol. 2019 Dec 11:1-9. https://www.ncbi.nlm.nih.gov/pubmed/31822301