The Household Resistome: Frequency of β-Lactamases, Class 1 Integrons, and Antibiotic-Resistant Bacteria in the Domestic Environment and Their Reduction during Automated Dishwashing and Laundering

Abstract

Households provide a habitat for bacteria originating from humans, animals, foods, contaminated clothes or other sources. Thus, bacteria carrying antibiotic resistance genes (ARGs) might be introduced via household members, animals or the water supply from these habitats into private households and vice versa. Since data on ABR in the domestic environment is limited, this study aimed to determine the abundance and correlation of β-lactamase, mobile colistin resistance and class 1 integron genes and to characterize phenotypic resistant strains in 54 private households in Germany. Additionally, the persistence of antibiotic resistant bacteria to automated dishwashing compared to laundering was assessed. Shower drains, washing machines and dishwashers were sampled and analyzed using quantitative real-time PCR. Resistant strains were isolated, followed by identification and antibiotic susceptibility testing using VITEK 2. The results show a significantly higher relative ARG abundance of 0.2367 ARG copies/16S rDNA copies in shower drains compared to dishwashers (0.1329 ARG copies/16S rDNA copies) and washing machines (0.0006 ARG copies/16S rDNA). blaCMY-2, blaACT/MIR and blaOXA-48 were the most prevalent ARG and intI1 occurred in 96.3% of the households while no mcr genes were detected. Several β-lactamase genes co-occurred and resistance of bacterial isolates correlated positively with genotypic resistance, with carbapenemase genes dominating across isolates. Antibiotic resistant bacteria were significantly reduced during automated dishwashing as well as laundering tests and did not differ from susceptible strains. Overall, the domestic environment might represent a potential reservoir of β-lactamase genes and β-lactam resistant bacteria with shower drains as the dominant source of ABR. Importance The abundance of antibiotic resistant bacteria and ARGs is steadily increasing and has been comprehensively analyzed in natural environments, animals, foods or wastewater treatment plants. In this respect, β-lactams and colistin are of particular interest due to the emergence of multidrug-resistant gram-negative bacteria. Despite of the connection of private households to these environments, only few studies focused on the domestic environment so far. Therefore, the present study further investigated the occurrence of ARGs and antibiotic resistant bacteria in shower drains, washing machines and dishwashers. The analysis of the domestic environment as a potential reservoir of resistant bacteria is crucial to determine whether households contribute to the spread of ABR or might be a habitat where resistant bacteria from the natural environment, humans, food or water are selected due to the use of detergents, antimicrobial products and antibiotics. Furthermore, ABR could limit treatment options of infections arising in the domestic environment.

Transmission Chains of Extended-Spectrum Beta-Lactamase-Producing Enterobacteriaceae at the Companion Animal Veterinary Clinic–Household Interface

“…Households have been previously described as a potential reservoir for ESBL-E [ 37 , 38 ]. Environmental contamination with ESBL-E in the household was extensive in household 1 with the persistently colonized dog but was undetectable in household 2 where only the owner was colonized, although hygiene habits seemed to be comparable in the two investigated households.…”

Distinct Resistomes and Microbial Communities of Soils, Wastewater Treatment Plants and Households Suggest Development of Antibiotic Resistances Due to Distinct Environmental Conditions in Each Environment

“…This is supported by the low bacterial diversity and significantly higher ARG richness compared to soil samples. Although no comparable data on HH are available so far, studies already determined the prevalence of ABR in households [ 35 , 36 , 37 ], suggesting that HH might be an under-investigated reservoir of ABR while WWTP and soil are analyzed more frequently. Despite the distinct structure of ABR and the bacterial community, the overlap of identified ARG and MGE in HH and WW highlights that domestic sewage represents an important component of WW.…”

“…Samples of the inner tubing of shower drains (SD), dishwasher sumps and sieves (DW), detergent trays and rubber door seals of washing machines (WM) were taken from households in the vicinity of Kleve, Germany, between September 2018 and June 2019 in a previous study [ 37 ]. All samples were taken in households from different apartment buildings or single-family houses.…”

“…53,035 households, WW from industries (5% of the WW) and the area includes three different clinics with a total of 1.280 beds. Samples were prepared as described in the previous studies [ 10 , 37 ], since the same samples were analyzed before using qPCR and a microbiological approach.…”

“…Anthropogenic pollution via wastewater used for irrigation or sewage sludge as fertilizer plays a key role in the transmission of ABR and MGE [ 29 , 30 , 31 , 32 ], and thus represents an important source of ARG in soil [ 33 ]. Moreover, a transfer of bacteria harboring ARG into private households via the water supply or as part of the human/animal microbiota and vice versa via domestic wastewater of washing machines, dishwashers and drains in natural environments seems possible, but the significance of the domestic area is comparatively less well understood [ 34 , 35 , 36 , 37 ]. However, domestic wastewater is a major component of the WWTP influent and thus might also play a role in the dissemination of ABR.…”