Investigating microbial dynamics and potential advantages of anaerobic co-digestion of cheese whey and poultry slaughterhouse wastewaters

Resource recovery and prevention of environmental pollution are key goals for sustainable development. It is widely reported that agro-industrial activities are responsible for the discharge of billions of liters of wastewater to the environment. Anaerobic digestion of these energy rich agro-industrial wastewaters can simultaneously mitigate environmental pollution and recover embedded energy as methane gas. In this study, an assessment of mono- and co-digestion of cheese whey wastewater (CWW) and poultry slaughterhouse wastewater (PSW) was conducted in 2.25-L lab-scale anaerobic digesters. Treatment combinations evaluated included CWW (R1), PSW (R2), 75:25 CWW:PSW (R3), 25:75 CWW:PSW (R4), and 50:50 CWW:PSW (R5). The digestion efficiencies of the mixed wastewaters were compared to the weighted efficiencies of the corresponding combined mono-digested samples. R4, with a mixture of 25% CWW and 75% PSW, achieved the greatest treatment efficiency. This corresponded with an average biodegradability of 84%, which was greater than for R1 and R2 at 68.5 and 71.9%, respectively. Similarly, R4 produced the highest average cumulative methane value compared to R1 and R2 at 1.22× and 1.39× for similar COD loading, respectively. The modified Gompertz model provided the best fit for the obtained methane production data, with lag time decreasing over progressive treatment cycles. PCoA and heatmap analysis of relative microbial abundances indicated a divergence of microbial communities based on feed type over the treatment cycles. Microbial community analysis showed that genus Petrimonas attained the highest relative abundance (RA) at up to 38.9% in the first two cycles, then subsequently decreased to near 0% for all reactors. Syntrophomonas was highly abundant in PSW reactors, reaching up to 36% RA. Acinetobacter was present mostly in CWW reactors with a RA reaching 56.5%. The methanogenic community was dominated by Methanothrix (84.3–99.9% of archaea). The presence of phosphate and Acinetobacter in CWW feed appeared to reduce the treatment efficiency of associated reactors. Despite Acinetobacter being strictly aerobic, previous and current results indicate its survival under anaerobic conditions, with the storage of phosphate likely playing a key role in its ability to scavenge acetate during the digestion process.

Prevalence and genetic diversity of Campylobacter spp. in the production chain of broiler chickens in Lebanon and its association with the intestinal protozoan Blastocystis sp

Campylobacter jejuni is recognized as the most common foodborne pathogen associated with human gastroenteritis worldwide. Broilers are frequently infected by the bacteria and are considered the main source of exposure to humans. However, despite its public health impact, no recent data are currently available in Lebanon about Campylobacter spp. in poultry and human population. Therefore, this study aimed to determine the prevalence and genetic diversity of Campylobacter spp. in 227 ceca and on 227 carcasses of broiler chickens collected in Lebanese slaughterhouses. Overall, the prevalence of Campylobacter was shown to reach 67.0% in ceca and 17.2% on carcasses of Lebanese poultry. The only 2 Campylobacter species identified were C. jejuni and C. coli, with a slightly higher prevalence of C. coli in ceca and of C. jejuni on carcasses. A high level of genetic diversity was reported among the 51 C. jejuni isolates selected, since 25 distinct profiles were identified according to the comparative genomic fingerprinting typing method based on a subset of 40 genes using the 90% similarity threshold. Predominant clusters observed in Lebanese poultry isolates were also frequently found among French human clinical cases, highlighting that broiler chickens represent a potential reservoir for human campylobacteriosis. In addition, a significantly higher prevalence of Campylobacter spp. was found in slaughterhouse workers than in a cohort of hospitalized patients with no contact with poultry, confirming that contaminated broiler chickens in slaughterhouse appeared to be a non-negligible source of Campylobacter spp. transmission. Interestingly, a significant association between Campylobacter spp. and Blastocystis sp. has been observed. This correlation suggested that the presence of Campylobacter spp. would be favored when Blastocystis sp. is present and, similarly, the absence of one would favor the absence of the other. This is the first large-scale investigation focusing on the impact of Campylobacter spp. in broiler chickens in Lebanon and confirmed the need to implement prevention and control measures in the poultry production to reduce the burden of campylobacteriosis in the human population.

First report on the prevalence and subtype distribution of Blastocystis sp. in dairy cattle in Lebanon and assessment of zoonotic transmission

Blastocystis sp. is frequently identified in a wide range of animal hosts, including bovids. Because of its burden and zoonotic potential, this parasite has been sought in domestic cattle from various countries, since this livestock may also represent a possible reservoir of human infection. However, epidemiological data regarding the prevalence and ST distribution of Blastocystis sp. in this animal group is lacking in Lebanon. Therefore, faecal samples were collected from a total of 254 dairy cattle raised on 55 farms located in the North Lebanon region and screened for the presence of the parasite by quantitative real-time PCR. The overall prevalence of Blastocystis sp. was shown to reach 63.4% in cattle livestock. Sequence analysis of positive samples indicated the presence of seven STs, with predominance of ST10 (44.0%) and ST14 (36.8%) and lower proportions of ST2 (8.0%), ST1 (7.2%), ST5 (2.4%), ST3 and ST7 (0.8% each). This survey was the first conducted worldwide reporting ST2 and ST7 in domestic cattle and confirmed that ST10 and ST14 represent cattle-adapted STs in view of their high prevalence. Faecal samples from in-contact dairy farmers and patients hospitalised in the same Lebanese governorate who reported no contact with cattle livestock were also analysed for the presence of Blastocystis sp. The same three STs were identified in both human cohorts, with predominance of ST3, followed either by ST1 or ST2 depending of the group. No other STs, including ST10 or ST14, have been reported. Moreover, even though ST1, ST2 and ST3 were found to be common to dairy cattle and farmers cohorts, only one ST3 isolate showed 100% sequence identity between both hosts. Consequently, the presence and low prevalence of ST1, ST2, ST3, ST5 and ST7 identified herein in domestic cattle, most of which exhibit low host specificity, could be derived from occasional direct exposure to faecal material from human and non-human hosts or by ingestion of contaminated drinking water or food in the enclosure of the farms. Together with the absence of ST10 and ST14 in the human population, these data suggest that cattle play a negligible role as zoonotic reservoirs of Blastocystis sp.

Prevalence and subtype distribution of Blastocystis sp. isolates from poultry in Lebanon and evidence of zoonotic potential

BACKGROUND

Blastocystis sp. is a common protozoan parasite frequently identified in the digestive tract of humans and a large variety of animal hosts worldwide, including birds. It exhibits a large genetic diversity with the identification of 17 subtypes (STs), most of them with low host specificity. ST6 and ST7 were identified in birds and suggested to represent avian STs only in the context of scarce small-scale epidemiological surveys. Moreover, these two STs also account for a significant proportion of human infections whose zoonotic origin has never been clearly confirmed. Therefore, molecular screening of Blastocystis sp. was conducted by quantitative real-time PCR for fecal samples from poultry farms and their in-contact humans from slaughterhouses in Lebanon. In parallel, a control group consisting of patients hospitalized in the same geographical area and reporting no contact with poultry was also screened for the presence of the parasite.

RESULTS

The overall prevalence of Blastocystis sp. was shown to reach around 32% in chicken samples and 65% in the farms screened. All the avian isolates were subtyped and belonged to either ST6 or ST7, with a large predominance of ST6. Fifty-four percent of slaughterhouse staff members were positive for Blastocystis sp. compared with a similar prevalence of 56% in hospitalized patients. ST3 was predominant in both human cohorts followed by either ST1 then ST2 among slaughterhouse staff or by ST2 then ST1 among hospitalized patients. ST6 was also identified in two slaughterhouse workers and not in the group of hospitalized patients. Gene sequence identity was observed between chicken and human ST6 isolates from the same slaughterhouse.

CONCLUSIONS

Our data revealed a high prevalence of Blastocystis sp. in chicken samples and confirmed that ST6 and ST7 represented avian-adapted STs. Among both human cohorts, Blastocystis sp. infection was shown to exceed 50% with a predominance of ST3. The identification of ST6 in slaughterhouse staff members confirmed the zoonotic transmission of this ST through repeated and direct contact between chickens and their handlers.