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

Abstract

L. monocytogenes is a zoonotic foodborne pathogen with inherent adaptability to tolerate environmental and physiological stresses, thereby causing severe disease outbreaks. Antibiotic resistant foodborne pathogens are a challenge to the food industry. A total of 18 samples were pooled from a bio-digester co-digesting swine manure/pinewood sawdust, and evaluated for the occurrence of bacterium plus total viable counts using the spread plate method. The recovered bacterial isolates were presumptively identified by growth on selective medium and confirmed by biochemical characterisation, leading to the isolation of 43 L. monocytogenes. The isolates were characterized based on their susceptibility to antibiotics via the Kirby-Bauer disc diffusion technique against a panel of 14 antibiotics. Equally, the multiple antibiotic resistance (MAR) index was calculated, and MAR phenotypes generated. The bacterial counts were between 102 and104 cfu/mL. Complete susceptibility (100%) was demonstrated to ampicillin, gentamicin and sulfamethoxazole, which are the drugs of choice in the treatment of listeriosis. In addition, intermediate sensitivity occurred at 25.58% to cefotaxime, and the highest resistance (51.16%) was exhibited against nalidixic acid. The MAR index ranged from 0 to 0.71. Overall, 41.86% of the Listeria isolates displayed multidrug resistance, with 18 different MAR phenotypes, demonstrating CIP, E, C, TET, AUG, S, CTX, NA, AML, NI as the greatest MAR phenotype. It can be concluded that the isolates yielding MAR > 0.2 originated from the farm, where antibiotics had been in routine use. Therefore, strict monitoring of antibiotics use in the farm is crucial to mitigate further increase in antibiotic resistance amongst these bacterial isolates.

A review of the literature of Listeria monocytogenes in Africa highlights breast milk as an overlooked human source

“…Although there is a natural resistance, acquired resistance has increasingly emerged in foodborne and human strains. This resistance reportedly stems from the routine use of antibiotics in farms or livestock ( Kayode and Okoh, 2023 ; Manyi-Loh et al, 2023 ). This acquired resistance requires a constant surveillance to provide adequate treatment for listeriosis and control its spread.…”

The Use of Fungi of the <em>Trichoderma </em>Genus in Anaerobic Digestion: A Review

“…Lignocellulosic biomass is the group of most commonly generated waste in agricultural, agrifood, forestry and household production [22]. According to Paul and Dutta [57], the resulting byproducts can be classified as agricultural and forestry residues, as well as grass, energy crops and woody biomass.…”

“…In addition, a major technical challenge is the storage of surplus light and wind energy. Many years of research have shown that an ideal alternative to the problem in question, which is irrespective of weather conditions, is the production of energy in the form of biogas from plant waste biomass [21][22][23]. Majeed et al [2] estimate that bioenergy generated from biomass is capable of meeting almost 40% of global energy demand.…”

“…Moreover, plant biomass, which is waste, is used as a substrate for energy production. Thus, plant biomass does not compete with plants intended for the food sector [22,27].…”

“…Despite the fact that the final composition of biogas depends on many factors (for example, substrate type and properties, process conditions, type of installation) [34][35][36], it is estimated that the mixture consists of 55-70% of methane, 30-45% of carbon dioxide and, to a lesser extent, hydrogen sulphide, water vapour, nitrogen, oxygen and trace elements [25,30,37]. Biogas and biomethane are highly efficient sources not only of electricity and heat, but can also be used as biofuel in automotive motors [20,22,38,39].…”