Occurrence and antimicrobial susceptibility patterns of Escherichia coli and Escherichia coli O157 isolated from cow milk and milk products, Ethiopia

Escherichia coli is a major foodborne pathogen worldwide. This study was conducted to assess the prevalence, risk factors, and antimicrobial susceptibility of E. coli and E. coli O157 in milk and milk products and hygienic practices in West Shoa, Oromia, Ethiopia. Five hundred fifty-six milk samples comprising 421 udder milk, 57 bulk tank milk, and 78 milk products were investigated. Moreover, a questionnaire was administered to 145 participants to assess hygienic practices. A standard microbiological procedure was used to detect E. coli and E. coli O157. The Kirby Bauer disc diffusion method was used to test the antimicrobial susceptibility of the isolates. Petri film plates were used to enumerate the coliform in raw bulk tank milk. Farm and animal-level E coli prevalence were estimated and association with risk factors was assessed. Escherichia coli was detected in 33.8% (95% confidence interval (CI) 29.9-37.9%) of the samples, of which only one isolate (0.2%) was E. coli O157. Escherichia coli contamination was higher in bulk tank samples (47.4%; 95% CI 34.0-61.0%) than in udder milk (34.7%; CI 30.1-39.4%), cottage cheese (27.0%; 95% CI 14.6-43.9%), and yoghurt 10.5% (95% CI 2.9-24.8%). For the animal-level E. coli contamination, only the study area was identified as a risk factor. Risk factors such as types of milk containers, udder washing practices, hygiene, and management systems were associated with both farm-level and milk products E. coli contamination. Most (59.0%) of the farmers practice udder washing only before milking and the remaining did not practice udder washing at all. The mean coliform count in raw bulk tank milk was higher than the international standard (4.09 log10 CFU/ml). All the 42 E. coli isolates tested were multidrug resistant. The occurrence of E. coli is high, while that of E. coli O157 is too low. The milk-handling practices are poor in the study areas. The high prevalence of E. coli, as well as the high coliform count and higher multi-drug resistance may pose risk to public health and food safety. Therefore, proper hygienic practices throughout the milk chain as well as rational drug use are advised.

Recent Progress of Surface-Enhanced Raman Spectroscopy for Bacteria Detection

There are various pathogenic bacteria in the surrounding living environment, which not only pose a great threat to human health but also bring huge losses to economic development. Conventional methods for bacteria detection are usually time-consuming, complicated and labor-intensive, and cannot meet the growing demands for on-site and rapid analyses. Sensitive, rapid and effective methods for pathogenic bacteria detection are necessary for environmental monitoring, food safety and infectious bacteria diagnosis. Recently, benefiting from its advantages of rapidity and high sensitivity, surface-enhanced Raman spectroscopy (SERS) has attracted significant attention in the field of bacteria detection and identification as well as drug susceptibility testing. Here, we comprehensively reviewed the latest advances in SERS technology in the field of bacteria analysis. Firstly, the mechanism of SERS detection and the fabrication of the SERS substrate were briefly introduced. Secondly, the label-free SERS applied for the identification of bacteria species was summarized in detail. Thirdly, various SERS tags for the high-sensitivity detection of bacteria were also discussed. Moreover, we emphasized the application prospects of microfluidic SERS chips in antimicrobial susceptibility testing (AST). In the end, we gave an outlook on the future development and trends of SERS in point-of-care diagnoses of bacterial infections.

Evaluation of the impact of formaldehyde fumigation during the hatching phase on contamination in the hatch cabinet and early performance in broiler chickens

Commercial hatch cabinet environments promote replication of microorganisms. These pathogenic or apathogenic microorganisms may serve as pioneer colonizers of the gastrointestinal tract (GIT) of poultry. Some of these pioneer colonizers, such as Escherichia coli and Enterococcus spp., are opportunistic pathogens that lead to reduced performance in commercial poultry. Effective hatchery sanitation is imperative to limit contamination of naïve neonatal chicks and poults. Formaldehyde fumigation has been traditionally used to reduce the pathogen load in commercial hatch cabinets. To investigate potential alternatives to formaldehyde fumigation, models to mimic the microbial bloom in a laboratory setting must be utilized. The purpose of the present study was to evaluate the impact of a multispecies environmental challenge model (PM challenge) with and without formaldehyde fumigation during the hatching phase on early performance in broiler chicks. Three experiments were conducted to evaluate microbial contamination in the hatch cabinet environment (air samples, fluff samples), enteric colonization at day-of-hatch (DOH), and 7-day performance. In all experiments, significantly (P < 0.05) more gram-negative bacteria were recovered from the GIT at DOH in the PM challenge control group as compared to the nonchallenged control (NC) group and the formaldehyde-treated group (PM + F). There were no statistical differences in 7-day body weight gain or feed conversion ratio between the PM challenge control group, the NC group or the PM + F group. These data suggest this model could be utilized to evaluate alternatives to formaldehyde fumigation for controlling the microbial load during the hatching phase in a laboratory setting.

Development of an environmental contamination model to simulate the microbial bloom that occurs in commercial hatch cabinets

Microbial blooms that emerge in commercial hatch cabinets consist of apathogenic and pathogenic microorganisms, including Escherichia coli, Enterococcus faecalis, and Aspergillus fumigatus. Objectives of the present study included the development of a multipathogen contamination model to mimic commercial conditions and optimization of sampling methods to quantify bacterial or fungal presence within the hatch cabinet. The pathogen challenge mix (PM) was recreated from select bacterial or fungal isolates recovered from an egg homogenate (EH) derived from the contents of infertile eggs and late embryonic mortalities. Isolates selected for PM included Enterococcus faecalis (∼10⁸ CFU/egg), Staphylococcus aureus (∼10⁷ CFU/egg), Staphylococcus chromogenes (∼10⁷ CFU/egg), Aspergillus fumigatus (∼10⁶ spores/egg), and 2 Escherichia coli (∼10⁸ CFU/egg) isolates. Challenge (100 μL of PM or EH) was administered using a sterile loop to a 28 mm area on the blunt end of the eggshell at day 19 of embryogenesis (DOE). In 3 experiments, microbiological data were collected from environmental hatcher samples (open-agar plate method), fluff samples, postmortem whole-body chick rinse samples, and gastrointestinal tract (GIT) samples to evaluate select bacteria and fungi circulating within the hatch cabinet and colonization of GIT. Cumulative bacterial and fungal recovery from the PM hatching environment from DOE20 to hatch was higher than the nonchallenged group (NC) and EH group at ∼860 and ∼1,730 CFU, respectively. Bacterial recovery from GIT, fluff, and chick rinse samples were similar for the PM and EH group in Exp. 1. However, Aspergillus fumigatus recovery from fluff and chick rinse samples for the PM group was significantly (P < 0.001) higher than the NC and EH group. In Exp. 2 and 3, PM challenge significantly (P < 0.05) increased Gram-negative bacterial recovery from the GIT, fluff and chick rinse samples compared to both the NC and EH group. These data suggest this innovative multispecies environmental contamination model using PM could be utilized to evaluate strategies to mitigate microbial contamination in commercial hatch cabinets in a laboratory setting.