Identification and characterization of Staphylococcus devriesei isolates from bovine intramammary infections in KwaZulu-Natal, South Africa

Detection of Staphylococcus Isolates and Their Antimicrobial Resistance Profiles and Virulence Genes from Subclinical Mastitis Cattle Milk Using MALDI-TOF MS, PCR and Sequencing in Free State Province, South Africa

Staphylococcus species are amongst the bacteria that cause bovine mastitis worldwide, whereby they produce a wide range of protein toxins, virulence factors, and antimicrobial-resistant properties which are enhancing the pathogenicity of these organisms. This study aimed to detect Staphylococcus spp. from the milk of cattle with subclinical mastitis using MALDI-TOF MS and 16S rRNA PCR as well as screening for antimicrobial resistance (AMR) and virulence genes. Our results uncovered that from 166 sampled cows, only 33.13% had subclinical mastitis after initial screening, while the quarter-level prevalence was 54%. Of the 50 cultured bacterial isolates, MALDI-TOF MS and 16S rRNA PCR assay and sequencing identified S. aureus as the dominant bacteria by 76%. Furthermore, an AMR susceptibility test showed that 86% of the isolates were resistant to penicillin, followed by ciprofloxacin (80%) and cefoxitin (52%). Antimicrobial resistance and virulence genes showed that 16% of the isolates carried the mecA gene, while 52% of the isolates carried the Lg G-binding region gene, followed by coa (42%), spa (40%), hla (38%), and hlb (38%), whereas sea and bap genes were detected in 10% and 2% of the isolates, respectively. The occurrence of virulence factors and antimicrobial resistance profiles highlights the need for appropriate strategies to control the spread of these pathogens.

Comparison of analytical approaches for identifying airborne microorganisms in a livestock facility

An intensive study, applied to a site characterized by multiple sources of microorganisms, was aimed at understanding the best approach to study bioaerosol. Culture-based, molecular biological, and chemical methods were applied to Particulate Matter (PM) samples collected in a livestock facility, during spring and autumn seasons, in two different outdoor areas. The first one was close to a place where feed was stored and handled and the second next to an open cowshed. Qualitative analysis of bacteria was performed by sequencing techniques applied to DNA extracted from both isolated culturable bacteria and particulate matter samples. Quantification of microorganisms was achieved through three distinct approaches. Microorganism colonies were counted, after incubation at 28 °C, and expressed as colony-forming units (CFU) per m³. Chemical method consisted in the identification of individual biomarkers, and their conversion to number of microorganisms per m³, using proper conversion factors. Finally, qPCR was applied to DNA extracted from PM samples, and the results were expressed as total amount of bacteria present in the bioaerosol (UG/m³). The presence of airborne sterols was also studied to broaden the knowledge of bioaerosol components in atmosphere. Small seasonal differences and major sampling site differences occurred. Obviously, culture-dependent method identified less and different bacteria, than culture-independent approach. The chemical approach and the culture independent metagenomic method were in good agreement. As expected, CFU/m³ accounted for not more than 0.3% of bacteria calculated as the average of chemical and culture independent metagenomic methods. The complexity of the obtained results shows that the different approaches are complementary to obtain an exhaustive description of bioaresol in terms of concentration, speciation, viability, pathogenicity.

Identification of bovine mastitis pathogens using MALDI-TOF mass spectrometry in Brazil

In this Research Communication we evaluate the use of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) to identify 380 bacteria isolated from cases of bovine mastitis in Brazil. MALDI-TOF MS identifications were compared to previous identifications by biochemical tests and 16S rRNA sequencing. MALDI-TOF MS achieved a typeability of 95.5%. The accuracy of MALDI-TOF MS for the identification of Staphylococcus isolates was 93.2%. The agreement between MALDI-TOF MS and biochemical identification of Streptococcus agalactiae was 96%, however, the agreement between these techniques for identifying other catalase-negative, Gram-positive cocci was lower. Agreement in identifying Gram-negative bacteria at the genus level was 90.5%. Our findings corroborate that MALDI-TOF MS is an accurate, rapid and simple technique for identifying bovine mastitis pathogens. The availability of this methodology in some research institutions would represent a significant step toward increasing the diagnosis and epidemiological studies of bovine mastitis and other animal infectious diseases in Brazil.

Review of Clinically and Epidemiologically Relevant Coagulase-Negative Staphylococci in Africa

Coagulase-negative staphylococci (CoNS) have engendered substantial interest in recent years as pathogenic causes of infections in both human and veterinary medicine, especially in the immunocompromised, critically ill, long-term hospitalized and in those harboring invasive medical devices such as catheters. They have been implicated in infections such as urinary tract infections, bloodstream infections, and invasive device-related infections, and are responsible for substantial economic losses in livestock production. The advancement of diagnostic techniques has increased our understanding of their molecular mechanisms of pathogenicity, even though distinguishing between innocuousness and pathogenicity is still challenging. The incidence of CoNS varied across the continent in humans and animals (mainly cattle), ranging from 6% to 68% in suspected human infections and from 3% to 61.7% in suspected animal infections, distributed across different geographic locations. Furthermore, there were varying antibiotic resistance patterns observed in CoNS isolates, with high methicillin resistance in some cases, leading to crossresistance against many antibiotics. Staphylococcus epidermidis, Staphylococcus haemolyticus, and Staphylococcus xylosus were most commonly reported in studies herein reviewed, while the enterotoxin C gene, atl E gene, ica gene, and hemolysin virulence factors were linked with enhanced pathogenicity. Advancement in identification and typing methods, including whole genome sequencing, virulence screening, and the assessment of the immune status of subjects in studies will help to thoroughly assess the true pathogenic potential of isolated CoNS species in developing countries. Careful antibiotic stewardship guidelines should be followed due to the ability of CoNS to develop multidrug resistance.