Prevalence of Multidrug-Resistant Bacteria (Enteropathogens) Recovered from a Blend of Pig Manure and Pinewood Saw Dust during Anaerobic Co-Digestion in a Steel Biodigester

Abstract

South Africa adopts intensive livestock farming, embracing the employment of huge quantities of antibiotics to meet the increased demand for meat. Therefore, bacteria occurring in the animal products and manure might develop antibiotic resistance, a scenario which threatens public health. The study investigated the occurrence of Gram-negative bacteria from eighteen pooled samples withdrawn from a single-stage steel biodigester co-digesting pig manure (75%) and pine wood saw dust (25%). The viable counts for each bacterium were determined using the spread plate technique. The bacterial isolates were characterised based on cultural, morphological and biochemical characteristics, using the Analytical Profile Index 20 e test kit. In addition, isolates were characterised based on susceptibility to 14 conventional antibiotics via the disc diffusion method. The MAR index was calculated for each bacterial isolate. The bacterial counts ranged from 104 to 106 cfu/mL, indicating manure as a potential source of contamination. Overall, 159 bacterial isolates were recovered, which displayed diverse susceptibility patterns with marked sensitivity to amoxicillin (100% E. coli), streptomycin (96.15% for Yersinia spp.; 93.33% for Salmonella spp.) and 75% Campylobacter spp. to nitrofurantoin. Varying resistance rates were equally observed, but a common resistance was demonstrated to erythromycin (100% of Salmonella and Yersinia spp.), 90.63% of E. coli and 78.57% of Campylobacter spp. A total of 91.19% of the bacterial isolates had a MAR index > 0.2, represented by 94 MAR phenotypes. The findings revealed multidrug resistance in bacteria from the piggery source, suggesting they can contribute immensely to the spread of multidrug resistance; thus, it serves as a pointer to the need for the enforcement of regulatory antibiotic use in piggery farms. Therefore, to curb the level of multidrug resistance, the piggery farm should implement control measures in the study area.

Occurrence and Multidrug Resistance in Strains of Listeria monocytogenes Recovered from the Anaerobic Co-Digestion Sludge Contained in a Single Stage Steel Biodigester: Implications for Antimicrobial Stewardship

“…Viable counts ranged from 2.3 × 10 2 to 1 × 10 4 cfu/mL, indicating the potential of the manure to cause pollution. Details of the findings, describing the effect of time on the dynamics of the bacterium have been published, together with those of other organisms (Gram-negative bacteria) by Manyi-Loh and Lues [ 22 ]. The authors observed a 1 log reduction of L .…”

“…This somewhat contradicts the pre-existing idea that exposure to antibiotics over a prolonged period (as in pig farming) can provoke or exacerbate antibiotic resistance. This is because Manyi-Loh et al [ 22 ] published reported resistance to ampicillin (12.5–71.88%) and gentamicin (4.44–57.44%) by Gram-negative bacteria, including E . coli , Salmonella sp., Yersinia spp., and Campylobacter recovered from a co-digesting mixture of pinewood saw dust and pig manure.…”

“…Research findings demonstrated the possibility of contaminating foods with antibiotic resistant bacteria and genes during the continuum from farm to processing to retail to consumers [ 21 ]. According to a One Health approach, antibiotic and multidrug resistance originating from food animals can affect the health of humans and plants [ 22 ]. The authors demonstrated the presence of multidrug resistance amongst the 91.19% of zoonotic enteropathogens ( E .…”