Staphylococcus aureus in Intensive Pig Production in South Africa: Antibiotic Resistance, Virulence Determinants, and Clonality

Abstract

Although Staphylococcus aureus is a major threat to the veterinary, agricultural, and public health sectors because of its zoonotic potential, studies on its molecular characterisation in intensive animal production are rare. We phenotypically and genotypically characterised antibiotic-resistant S. aureus in intensive pig production in South Africa, using the farm-to-fork approach. Samples (n = 461) were collected from the farm, transport vehicles, and the abattoir using the World Health Organisation on Integrated Surveillance of Antimicrobial Resistance (WHO-AGISAR) sampling protocol. Bacteria were isolated using selective media and identified using biochemical tests and polymerase chain reaction (PCR). Phenotypic resistance was determined using the disk diffusion method. Selected resistance and virulence genes were investigated using PCR. Clonality among the isolates was determined using the repetitive element sequence-PCR. In all, 333 presumptive staphylococcal isolates were obtained, with 141/333 (42.3%) identified as staphylococci biochemically. Ninety-seven (97; 68.8%) were confirmed as S. aureus using PCR, 52.6% of which were identified as methicillin-resistant S. aureus (MRSA) through the mecA gene. All the 97 S. aureus isolates (100%) were resistant to at least one of the antibiotics tested, with the highest resistance observed against erythromycin and clindamycin (84.50% each), and the lowest observed against amikacin (2.10%); 82.47% (80/97) were multidrug-resistant with an average multiple antibiotic resistance index of 0.50. Most of the phenotypically resistant isolates carried at least one of the corresponding resistance genes tested, ermC being the most detected. hla was the most detected virulence gene (38.14%) and etb was the least (1.03%). Genetic fingerprinting revealed diverse MRSA isolates along the farm-to-fork continuum, the major REP types consisting of isolates from different sources suggesting a potential transmission along the continuum. Resistance to antibiotics used as growth promoters was evidenced by the high prevalence of MDR isolates with elevated multiple antibiotic resistance indices >0.2, specifically at the farm, indicating exposure to high antibiotic use environments, necessitating antibiotic stewardship and proper infection control measures in pig husbandry and intensive pig production.

Methicillin-Resistant Staphylococcus aureus from Peninsular Malaysian Animal Handlers: Molecular Profile, Antimicrobial Resistance, Immune Evasion Cluster and Genotypic Categorization

“…The S. aureus isolates in this study displayed a higher prevalence of ermC (4.5%; 7/155). This finding is in agreement with a study in South Africa where the ermC gene is the most frequently found macrolide–lincosamide resistance gene in pigs [ 36 ]. Nonetheless, it is observed that certain isolates did not harbour the antimicrobial resistance genes despite showing phenotypic resistance.…”

“…The tet K and tet L genes are responsible for the tetracycline efflux pump system, while tet M is involved in ribosomal protection [ 14 ]. Meanwhile, ermA , ermB and ermC genes are responsible for the ribosomal binding site modification to protect the S. aureus against erythromycin antibiotics, while the msrA gene encodes for an ATP-dependent efflux pump [ 36 ]. The S. aureus isolates in this study displayed a higher prevalence of ermC (4.5%; 7/155).…”

Efficiency of lactoferrin to eradicate multidrug resistant Staphylococcus aureus isolated from some dairy products

“…Determination of the multiple antibiotic resistance index (MARI) of the isolates shows that most of isolates were resistant to three or more antibiotics with over all mean value about 0.54. This is nearly agreed with previous work of [43,44] who cited that MARI was 0.61 and 0.48, respectively. On the other hand lesser index was reported by [45,42] as 0.23 and 0.3, respectively.…”

Beta hemolysin gene of Staphylococcus phage 3AJ_2017 genome is a suitable molecular marker for identification and characterization of pathogenic Staphylococcus aureus

“…S. aureus exist both in humans and animals either as a commensal or pathogenic bacteria causing diseases (Sineke et al, 2021) ranging from mild superficial skin infection to fatal cases such as toxic shock syndrome (Schmidt et al, 2017). Therefore, there is a need for the development of a specific and sensitive molecular method for detection and characterization of pathogenic S. aureus.…”

“…Mortality rate due to S. aureus infection ranges from about 15% to 40% (Schmidt et al, 2017) with an economical loss of about 30%-40% in livestock farming (Sineke et al, 2021). Accurate detection of pathogenic S. aureus is therefore of importance for effective management of infections (Chen et al, 2013;Tadros et al, 2013).…”