Isolation and Molecular Identification of Virulence, Antimicrobial and Heavy Metal Resistance Genes in Livestock-Associated Methicillin-Resistant Staphylococcus aureus

Abstract

Staphylococcus aureus is one of the most important pathogens of humans and animals. Livestock production contributes a significant proportion to the South African Gross Domestic Product. Consequently, the aim of this study was to determine for the first time the prevalence, virulence, antibiotic and heavy metal resistance in livestock-associated S. aureus isolated from South African livestock production systems. Microbial phenotypic methods were used to detect the presence of antibiotic and heavy metal resistance. Furthermore, molecular DNA based methods were used to genetically determine virulence as well as antibiotic and heavy metal resistance determinants. Polymerase chain reaction (PCR) confirmed 217 out of 403 (53.8%) isolates to be S. aureus. Kirby-Bauer disc diffusion method was conducted to evaluate antibiotic resistance and 90.8% of S. aureus isolates were found to be resistant to at least three antibiotics, and therefore, classified as multidrug resistant. Of the antibiotics tested, 98% of the isolates demonstrated resistance towards penicillin G. High resistance was shown against different heavy metals, with 90% (196/217), 88% (192/217), 86% (188/217) and 84% (183/217) of the isolates resistant to 1500 µg/mL concentration of Cadmium (Cd), Zinc (Zn), Lead (Pb) and Copper (Cu) respectively. A total of 10 antimicrobial resistance and virulence genetic determinants were screened for all livestock associated S. aureus isolates. Methicillin-resistant S. aureus (MRSA) isolates were identified, by the presence of mecC, in 27% of the isolates with a significant relationship (p < 0.001)) with the host animal. This is the first report of mecC positive LA-MRSA in South Africa and the African continent. The gene for tetracycline resistance (tetK) was the most frequently detected of the screened genes with an overall prevalence of 35% and the highest prevalence percentage was observed for goats (56.76%) followed by avian species (chicken, duck and wild birds) (42.5%). Virulence-associated genes were observed across all animal host species. The study reports the presence of luks/pv, a gene encoding the PVL toxin previously described to be a marker for community acquired-MRSA, suggesting the crossing of species between human and livestock. The high prevalence of S. aureus from the livestock indicates a major food security and healthcare threat. This threat is further compounded by the virulence of the pathogen, which causes numerous clinical manifestations. The phenomenon of co-selection is observed in this study as isolates exhibited resistance to both antibiotics and heavy metals. Further, all the screened antibiotic and heavy metal resistance genes did not correspond with the phenotypic resistance.

Essential Gene Clusters Involved in Copper Tolerance Identified in Acinetobacter baumannii Clinical and Environmental Isolates

“…In the present work, copper-tolerant A. baumannii could be detected in both clinical and natural environmental isolates. Previous studies reported that copper tolerance was found in pathogenic bacteria isolated from environmental, food, and clinical samples [11,31,32]. We found a narrow range of copper MIC values (5 and 10 mM) for 407 A. baumannii isolates, by using a rich growth medium (MHA).…”

Biofilm Production Ability, Virulence and Antimicrobial Resistance Genes in Staphylococcus aureus from Various Veterinary Hospitals

“…aureus has been considered as the most common causative pathogen in surgical site infections in recent years [13]. The ability of S. aureus to infect humans and animals poses a huge burden on the healthcare system [14]. Molecular typing methods such as pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), and Staphylococcus protein A (spa) typing have been widely used to track the sources and transmissions of pathogenic bacteria like S. aureus, thereby helping to establish the national and global epidemiological data [3].…”

“…If there will be no corresponding policy formulation, the global consumption of antibiotics in 2030 would be up to 200% higher than in 2015 [15]. However, a major cause for alarm is the drastic rise of antibiotic resistance of S. aureus with the increase in the use of antibiotics [14]. The World Health Organization (WHO) has identified antibiotic resistance as one of the biggest challenges to global health and classified S. aureus as a high priority superbug for which research and development of novel antibiotics are needed urgently [17,18].…”

“…S. aureus isolates can increase the pathogenicity by secreting many important virulence factors described as toxins interfering directly with the host cells, with Panton-Valentine Leucocidin (PVL) being one of the most essential, potent, and prevalent [14]. The biofilm described as toxins, toxic shock syndrome toxin (TSST), haemolysin, and staphylococcal enterotoxins (SEs) also played an important role in the life-threatening illness caused by S. aureus [21,28].…”

Nasal carriage of Staphylococcus aureus in livestock in North of Morocco

“…In Switzerland, the pathogen was isolated from only 1 % of calves and 0.3 % of adult cattle [16], whereas in Denmark, the rate exceeds 64% in goats [17]. Moreover, a recent study conducted by Dweba et al [19], in South African livestock production systems identified MRSA isolates in 27% with a significant relationship (p < 0.001) with the host animal.…”