Abstract
BackgroundPoultry houses are often highly contaminated with dust, which might contain considerable amounts of microorganisms and endotoxins. The concentrations of microorganisms and endotoxins in dust from laying hen houses in Egypt are unknown. However, to estimate the risks for birds, the environment, and people working in laying hen houses, it is important to gather information about the composition of these dusts. Here we report the microbial loads, the occurrence of antimicrobial-resistant bacteria, and endotoxin concentrations in dust samples from 28 laying hen farms in Dakahliya Governorate, Egypt, and discuss the results relevant to the literature.ResultsPooled settled dust samples (n = 28) were analyzed for total viable counts of bacteria and fungi (CFU/g), the occurrence of extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae, Salmonella spp., and methicillin-resistant Staphylococcus aureus (MRSA), and endotoxin concentrations (ng/g). The means and standard deviations of total viable counts were 7.10 × 108 ± 2.55 × 109 CFU/g for bacteria and 5.37 × 106 ± 7.26 × 106 CFU/g for fungi. Endotoxin levels varied from 2.9 × 104 to 6.27 × 105 ng/g. None of the tested samples contained Salmonella spp. or MRSA. In contrast, by direct plating, Enterobacteriaceae were found frequently (57%; n = 16), and suspected ESBL-producing Enterobacteriaceae occurred in 21% (n = 6) of the sampled barns. Using an enrichment method, the detection of Enterobacteriaceae and suspected ESBL-producing Enterobacteriaceae increased to 20 and 16 positive barns, respectively. Taking results from both methods into account, Enterobacteriaceae and suspected ESBL-producing Enterobacteriaceae were detected in 23 barns Overall, 100 ESBL suspected isolates (Escherichia coli, n = 64; Enterobacter cloacae, n = 20; and Klebsiella pneumoniae n = 16) were identified to species level by MALDI-TOF MS. Isolates from 20 barns (71% positive barns) were confirmed as ESBL producing Enterobacteriaceae by the broth microdilution test.ConclusionsDust in Egyptian laying hen houses contains high concentrations of microorganisms and endotoxins, which might impair the health of birds and farmers when inhaled. Furthermore, laying hens in Egypt seem to be a reservoir for ESBL-producing Enterobacteriaceae. Thus, farmers are at risk of exposure to ESBL-producing bacteria, and colonized hens might transmit these bacteria into the food chain.
Highlights
Poultry houses are often highly contaminated with dust, which might contain considerable amounts of microorganisms and endotoxins
The number of total mesophilic bacteria in settled dust samples varied from 9.07 × 106 colony-forming units (CFU)/g in flock 7 to 1.41 × 1010 counts of bacteria and fungi (CFU/g) in flock 26, with a mean ± standard deviation (SD) of 7.10 × ± 2.55 × CFU/g
Samples from three flocks [8, 9, 21] showed growth for Enterobacteriaceae with direct plating and no growth was observed after enrichment, resulting in a total of 23 positive samples that corresponded to a percentage of 82% positive flocks
Summary
Poultry houses are often highly contaminated with dust, which might contain considerable amounts of microorganisms and endotoxins. The amount and the composition of particles in poultry houses are affected by factors such as housed species, stocking density, age and fattening period of the birds, feeding system, antibiotic treatment, bedding material, humidity, ventilation system, and application of hygienic measures [3, 4] Respiratory diseases of both humans and animals have mainly multifactorial causes, and the quantity and quality of airborne dust play an important role [5]. Zoonotic Salmonella species (spp.) can occur and survive in dust from laying hen houses, and they can be transmitted horizontally via an airborne route [9] This might enhance the spread within a flock, and that can be associated with a higher risk of contaminated eggs [10]. A recent study showed that resistant Escherichia coli (E. coli) are able to survive for a considerable period of time in dust from livestock buildings [20]
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