Genotypic and phenotypic characterization of biofilm production by Staphylococcus aureus strains isolated from bovine intramammary infections in Colombian dairy farms

Nasal carriage of Staphylococcus aureus in healthy dairy cows in Algeria: antibiotic resistance, enterotoxin genes and biofilm formation

BACKGROUND

Staphylococcus aureus can colonize and infect a variety of animal species. In dairy herds, it is one of the leading causes of mastitis cases. The objective of this study was to characterize the S. aureus isolates recovered from nasal swabs of 249 healthy cows and 21 breeders of 21 dairy farms located in two provinces of Algeria (Tizi Ouzou and Bouira).

METHODS

The detection of enterotoxin genes was investigated by multiplex PCRs. Resistance of recovered isolates to 8 antimicrobial agents was determined by disc-diffusion method. The slime production and biofilm formation of S. aureus isolates were assessed using congo-red agar (CRA) and microtiter-plate assay. Molecular characterization of selected isolates was carried out by spa-typing and Multi-Locus-Sequence-Typing (MLST).

RESULTS

S. aureus was detected in 30/249 (12%) and 6/13 (28.6%) of nasal swabs in cows and breeders, respectively, and a total of 72 isolates were recovered from positive samples (59 isolates from cows and 13 from breeders). Twenty-six of these isolates (36.1%) harbored genes encoding for staphylococcal enterotoxins, including 17/59 (28.8%) isolates from cows and 9/13 (69.2%) from breeders. Moreover, 49.1% and 92.3% of isolates from cows and breeders, respectively, showed penicillin resistance. All isolates were considered as methicillin-susceptible (MSSA). Forty-five (76.3%) of the isolates from cows were slime producers and 52 (88.1%) of them had the ability to form biofilm in microtiter plates. Evidence of a possible zoonotic transmission was observed in two farms, since S. aureus isolates recovered in these farms from cows and breeders belonged to the same clonal lineage (CC15-ST15-t084 or CC30-ST34-t2228).

CONCLUSIONS

Although healthy cows in this study did not harbor methicillin-resistant S. aureus isolates, the nares of healthy cows could be a reservoir of enterotoxigenic and biofilm producing isolates which could have implications in human and animal health.

Potential of phage EF-N13 as an alternative treatment strategy for mastitis infections caused by multidrug-resistant Enterococcus faecalis

Bovine mastitis is the most common and costly disease affecting dairy cattle throughout the world. Enterococcus faecalis is one of the environmental origin mastitis-causing pathogens. The treatment of bovine mastitis is primarily based on antibiotics. Due to the negative impact of developing antibiotic resistance and adverse effects on soil and water environments, the trend toward use of nonantibiotic treatments is increasing. Phages may represent a promising alternative treatment strategy. However, it is unknown whether phages have therapeutic effects on E. faecalis-induced mastitis. Thus, the objective of this study was to investigate the degree of protection conferred by a phage during murine mastitis caused by multidrug-resistant E. faecalis. Enterococcus faecalis was isolated from the milk of dairy cows with mastitis, and a phage was isolated using the E. faecalis isolates as hosts. The bactericidal ability of the phage against E. faecalis and the ability to prevent biofilm formation were determined in vitro. The therapeutic potential of the phage on murine mastitis was evaluated in vivo. We isolated 14 strains of E. faecalis from the milk of cows with mastitis, all of which exhibited multidrug resistance, and most (10/14) could form strong biofilms. Subsequently, a new phage (EF-N13) was isolated using the multidrug-resistant E. faecalis N13 (isolated from mastitic milk) as the host. The phage EF-N13 belongs to the family Myoviridae, which has short latent periods (5 min) and high bursts (284 pfu/cell). The genome of EF-N13 lacked bacterial virulence-, antibiotic resistance-, and lysogenesis-related genes. Furthermore, bacterial loading in the raw milk medium was significantly reduced by EF-N13 and was unaffected by potential IgG antibodies. In fact, EF-N13 could effectively prevent the formation of biofilm by multidrug-resistant E. faecalis. All of these characteristics suggest that EF-N13 has potential as mastitis therapy. In vivo, 1 × 105 cfu/gland of multidrug-resistant E. faecalis N13 resulted in mastitis development within 24 h. A single dose of phage EF-N13 (1 × 104, 1 × 105, or 1 × 106 pfu/gland) could significantly decrease bacterial counts in the mammary gland at 24 h postinfection. Histopathological observations demonstrated that treatment with phage EF-N13 effectively alleviated mammary gland inflammation and damage. This effect was confirmed by the lower levels of proinflammatory cytokines IL-6, IL-1β, and tumor necrosis factor-α in the mammary gland treated with phage EF-N13 compared with those treated with phosphate-buffered saline. Overall, the data underscored the potential of phage EF-N13 as an alternative therapy for bovine mastitis caused by multidrug-resistant E. faecalis.

On-farm epidemiology, virulence profiling, and molecular characterization of methicillin-resistant Staphylococcus aureus at goat farms

Antimicrobial resistance (AMR) becomes a challenging issue that limits the therapeutic options for both veterinary and public health professionals. The current study aimed to investigate the on-farm epidemiology, antibiotics resisting profiling, virulence analysis, and molecular detection of methicillin-resistant Staphylococcus aureus (MRSA) at the caprine-human interface. A total of 768 goat milk samples and 94 skin swabs from farm personnel were collected from 30 goat flocks and processed for isolation of S. aureus. The study isolates were confirmed as MRSA based on the oxacillin and cefoxitin disc diffusion test and the presence of mecA gene. MRSA isolates of goats and human origin were characterized and further evaluated for the presence of virulence genes responsible for intramammary infections and public health hazards. The results revealed 26.82 % and 27.79 % goat milk samples and human samples positive for S. aureus, respectively. A higher MRSA prevalence of 35.92 % and 10.71 % was found in goat and human isolates respectively. The phylogenetic analysis revealed a lesser extent of homology in mecA gene of S. aureus isolates at the caprine-human interface. Moreover, this study revealed strong evolutionary connection between the study isolates and MRSA isolates of Pakistani cattle and buffalo while the in-silico protein analysis showed that all sequences have the same protein motifs resembling penicillin binding protein 2a. The risk factors analysis revealed that teat length, drainage system, hygienic measures during milking, use of teat dip, teat injury, and veterinary services were significantly associated with subclinical mastitis in goats. A total of 43.24 % of local MRSA isolates showed multi-drug resistance (MDR). The isolates showed higher resistance to oxytetracycline followed by gentamicin and vancomycin while moxifloxacin, and linezolid were among the susceptible antibiotics. Local MRSA isolates carried virulence markers (nuc and coag genes) and biofilm-associated icaA (43.24 %) and icaD (29.73 %) genes which are responsible for the intramammary infection. The local isolates also carried the virulence genes of public health concern including the enterotoxin C (sec) gene (24.3 %), enterotoxins B (seb) gene (5.41 %), and enterotoxin D (sed) gene (2.7 %). Enterotoxins A (sea) and E (see) genes were not detected in any isolate. The study concluded that MRSA is an emerging and prevailing pathogen in dairy goats with a high potential to transmit to associated human beings. The presence of a variety of virulence factors as well as the associated antibiotic resistance makes MRSA a potential threat at animal-human interface and thus demands further research.

Evaluation of Virulence, Antimicrobial Resistance and Biofilm Forming Potential of Methicillin-Resistant Staphylococcus aureus (MRSA) Isolates from Bovine Suspected with Mastitis

Methicillin-resistant Staphylococcus aureus (MRSA) is a pathogen that poses a significant threat in cases of chronic mastitis in dairy animals. The ability of MRSA to persist in the host is attributed to various virulence factors, genes encoding surface adhesins, and determinants of antibiotic resistance, which provide it a survival advantage. This investigation focused to determine the virulence factors, antimicrobial resistance (AMR) profile and biofilm production potential of 46 MRSA isolates from 300 bovine mastitis milk samples. The AMR profile revealed a high level of resistance, with 46 and 42 isolates resistant to cefoxitin and oxacillin, respectively, followed by 24 and 12 isolates resistant to lomefloxacin and erythromycin, respectively. Only 2 isolates resistant to tetracycline and none were resistant to chloramphenicol. The study also evaluated various virulence factors such as coa (n = 46), nuc (n = 35) hlg (n = 36), pvl (n = 14), tsst-1(n = 28) spa (n = 39) and enterotoxin genes sea (n = 12) and seg (n = 28) and identified antibiotic resistance determinants mecA and blaZ in 46 and 27 isolates, respectively. Intercellular adhesion genes icaA and icaD were present in 40 and 43 isolates, respectively and surface adhesion genes ebps, fnbpA, eno, sasG, cna, and bap were found in 43, 40, 38, 26, 21 and 1 isolates, respectively. Microtiter plate (MTP) assay revealed that 29 MRSA isolates were capable of producing biofilms, whereas 17 were not. Biofilms producing MRSA isolates possessed adhesion genes, virulence factors, toxin genes and AMR genes that may act synergistically towards a chronic disease progression, illness and severe damage to the udder, which generally last for several months and very challenging to cure.

High genetic diversity and zoonotic potential of Staphylococcus aureus strains recovered from bovine intramammary infections in Colombians dairy herds

Genotyping of Staphylococcus aureus isolated from mastitis has become a fundamental tool to understand its complex epidemiology and to evaluate spillover events. The aim of this study was to describe the frequency of genotypes of the S. aureus strains isolated from intramammary infections by spa typing technique, and to evaluate the association between genotypes and the ability to form biofilm under in vitro conditions. Sixty-six strains of S. aureus recovered from bovines intramammary infections on 56 dairy herds located in 14 municipalities of the department of Antioquia were characterized. The majority of strains (65/66) were isolated from milk samples collected from dairy cows with subclinical intramammary infections. Nineteen different spa types were found in this study, t521 (19.70%), t267 (15.15%), and t605 (12.12%) being the most frequent. The strains from the t605 spa type showed the highest biofilm production. The high frequency of spa types with zoonotic potential found in this study, identified cattle as an important reservoir of theses clones for people in close proximity, such as milkers and consumers of unpasteurized dairy products.

Evaluation of three Staphylococcus aureus proteins involved in the adhesion process as antigens for the detection of bovine intramammary infections

Introduction. Fast and accurate diagnosis is one of the key strategies in the successful control of intramammary infections caused by Staphylococcus aureus. Immunoassays are one of the diagnostic tools that have been proposed for the detection of S. aureus infection because they offer an advantage in terms of cost and are fast and easy to use compared to other diagnostic tests.Gap statement. The main challenge of the immunoassays is to identify antigens or serological markers that allow accurate discrimination between infected and uninfected cows with S. aureus, since this bacterium can naturally colonize different areas of the animal body.Aim. To evaluate three S. aureus proteins (IsdA, ClfA, SdrD) involved in the adhesion process as antigens to detect indicator antibodies of bovine intramammary infections.Methodology. Ninety-six cows in lactation and not vaccinated against S. aureus were included. Forty-eight of these cows were infected with S. aureus, while the rest (n=48 cows) were uninfected. Blood and milk samples were collected from each animal to recover serum and whey. IgG titres against the three proteins individually and combined (Mix) were measured in each sample using an enzyme-linked immunosorbent assay (ELISA) test.Results. Significant differences in the IgG response against the proteins evaluated were observed, highlighting the antigenic potential of IsdA and demonstrating that some antigens can detect specific antibodies of infection better than others. According to receiver operating characteristic (ROC) curve analysis, the combined proteins showed the most remarkable capacity (sensitivity of 79 % and specificity of 77 %) to differentiate between infected and uninfected cows when blood samples were used. In addition, the combined proteins also showed the highest specificity (94 %) when using milk samples.Conclusion. Our findings provide information on the usefulness of three adhesion-associated S. aureus proteins in detecting serological markers of intramammary infections in bovines.

Persistence of Staphylococcus spp. in milk from cows undergoing homeopathy to control subclinical mastitis

Background

Mastitis is one of the major diseases in dairy cattle, as it causes great economic losses to producers due to the reduction of milk production and changes in the quality of the product. The disease is mainly caused by bacteria of the genus Staphylococcus spp., these microorganisms can express various virulence factors, such as biofilms for example. In herds with organic management, producers and technicians use unconventional ways to treat and control the disease, such as homeopathy. However, it is not known if this type of treatment is able to control pathogenic bacteria such as those of the genus Staphylococcus, of relevance to animal and human health. Thus, the objective of this study was to investigate the production of biofilm in vitro and its genes by Staphylococcus spp. isolated in the milk of cows treated with homeopathy, as well as the persistence of microorganisms in animals.

Methods

Ninety-nine isolates of Staphylococcus spp. from cows treated and not treated with homeopathy were identified by internal transcribed space-polymerase chain reaction and investigated for the presence of the icaABCD, bap, aap, atlE, and bhp genes and in vitro biofilm production using the adhesion method on polystyrene plates. The enzyme restriction profile was determined by Pulsed-Field Gel Electrophoresis. Clusters of S. aureus and S. epidermidis with three or more isolates had an isolate selected for Multilocus Sequence Typing.

Results

The frequency of S. aureus isolations was similar in treated and untreated cows, while 71.4% of the coagulase-negative identified were isolated in cows treated with homeopathy. The distribution of the operon ica genes was similar in animals with and without treatment, except for the icaD gene, more frequent in treated cows. Production of biofilm was associated with presence of one or more genes from the icaADBC operon. S. aureus revealed a greater diversity and greater dissemination in cows treated and not treated with homeopathy. Sequence Types ST1, ST5, and ST126 were identified in S. aureus.

Conclusions

The presence of biofilm-associated genes and the in vitro production of biofilms, combined with the persistence of clonal profiles of Staphylococcus spp. demonstrate other forms of control for bovine mastitis should be researched for organic production herds.

Diversity and pathogenesis of Staphylococcus aureus from bovine mastitis: current understanding and future perspectives

Staphylococcus aureus is a leading cause of bovine mastitis worldwide. Despite some improved understanding of disease pathogenesis, progress towards new methods for the control of intramammary infections (IMI) has been limited, particularly in the field of vaccination. Although herd management programs have helped to reduce the number of clinical cases, S. aureus mastitis remains a major disease burden. This review summarizes the past 16 years of research on bovine S. aureus population genetics, and molecular pathogenesis that have been conducted worldwide. We describe the diversity of S. aureus associated with bovine mastitis and the geographical distribution of S. aureus clones in different continents. We also describe studies investigating the evolution of bovine S. aureus and the importance of host-adaptation in its emergence as a mastitis pathogen. The available information on the prevalence of virulence determinants and their functional relevance during the pathogenesis of bovine mastitis are also discussed. Although traits such as biofilm formation and innate immune evasion are critical for the persistence of bacteria, the current understanding of the key host-pathogen interactions that determine the outcome of S. aureus IMI is very limited. We suggest that greater investment in research into the genetic and molecular basis of bovine S. aureus pathogenesis is essential for the identification of novel therapeutic and vaccine targets.

Virulence Factors in Staphylococcus Associated with Small Ruminant Mastitis: Biofilm Production and Antimicrobial Resistance Genes

Small ruminant mastitis is a serious problem, mainly caused by Staphylococcus spp. Different virulence factors affect mastitis pathogenesis. The aim of this study was to investigate virulence factors genes for biofilm production and antimicrobial resistance to β-lactams and tetracyclines in 137 staphylococcal isolates from goats (86) and sheep (51). The presence of coa, nuc, bap, icaA, icaD, blaZ, mecA, mecC, tetK, and tetM genes was investigated. The nuc gene was detected in all S. aureus isolates and in some coagulase-negative staphylococci (CNS). None of the S. aureus isolates carried the bap gene, while 8 out of 18 CNS harbored this gene. The icaA gene was detected in S. aureus and S. warneri, while icaD only in S. aureus. None of the isolates carrying the bap gene harbored the ica genes. None of the biofilm-associated genes were detected in 14 isolates (six S. aureus and eight CNS). An association was found between Staphylococcus species and resistance to some antibiotics and between antimicrobial resistance and animal species. Nine penicillin-susceptible isolates exhibited the blaZ gene, questioning the reliability of susceptibility testing. Most S. aureus isolates were susceptible to tetracycline, and no cefazolin or gentamycin resistance was detected. These should replace other currently used antimicrobials.

Klebsiella pneumoniae carbapenemase (KPC) in urinary infection isolates

Recently, emergence of carbapenem-resistance, in particular due to Klebsiella pneumoniae carbapenemase (KPC), was observed among K. pneumoniae causing urinary tract infections in Croatia. The aim of the study was to characterize, antimicrobial susceptibility, carbapenem resistance, virulence traits and plasmid types of the urinary KPC positive isolates of K. pneumoniae. The antimicrobial susceptibility to a wide range of antibiotics was determined by broth microdilution method. The transferability of meropenem resistance was determined by conjugation (broth mating method) employing Escherichia coli J63 strain resistant to sodium azide. Genes encoding broad and extended-spectrum β-lactamases, plasmid-mediated AmpC β-lactamases, group A and B carbapenemases, and carbapenem hydrolyzing oxacillinases (bla_OXA-48like), respectively, were determined by Polymerase chain reaction (PCR). In total 30 KPC-positive K. pneumoniae urinary isolates collected from different regions of Croatia were analysed. The isolates were uniformly resistant to all tested antibiotics except for variable susceptibility to gentamicin, sulphamethoxazole/trimethoprim, and colistin, respectively. Four isolates were resistant to colistin with MICs values ranging from 4 to 16 mg/L. All tested isolates were susceptible to ceftazidime/avibactam. Sixteen isolates transferred meropenem resistance to E. coli recipient strain by conjugation. Other resistance markers were not co-transferred. PCR was positive for bla_KPC and bla_SHV genes in all isolates whereas 13 isolates tested positive also for bla_TEM genes. PCR based replicon typing (PBRT) revealed the presence of FIIs in 13 and FIA plasmid in two strains. The study showed dissemination of KPC-producing K. pneumoniae in urinary isolates, posing a new epidemiological and treatment challenge. Sulphamethoxazole/trimethoprim, colistin, and ceftazidime/avibactam remain so far, as the therapeutic options.

Phenotypic Characterization and Whole Genome Analysis of a Strong Biofilm-Forming Staphylococcus aureus Strain Associated With Subclinical Bovine Mastitis in Colombia

Staphylococcus aureus represent a serious threat to public health due to food safety, antibiotic resistance, and the potential zoonotic transmission of strains between dairy cattle and humans. Biofilm formation by S. aureus results in chronicity of the infections which confers protection against the immune response and antibiotics. Likewise, biofilm allows the exchange of mobile genetic material among different strains through microbial interactions inside the matrix. In Colombia, where S. aureus continues to be one of the main pathogens isolated from bovine intramammary infections and where milking by hand is highly frequent, there are knowledge gaps on the zoonotic potential of the strains. Therefore, the aim of this work was to characterize genotypically and phenotypically the S. aureus Sa1FB strain with strong biofilm production and to perform genomic and phenotypic comparisons with other relevant S. aureus strains (native and references strains). These results show a highly productive strain of biofilm and a low ability of cell invasion compared to the other two native strains. In addition, high genomic similarity between S. aureus Sa1FB and the reference strains was observed, despite of the differences reported at the clinical level. However, Sa1FB exhibited special features in terms of mobile genetic elements, highlighting its ability to accept foreign genetic material. Indeed, this could increase mutation, pathogenesis, and adaptability to new hosts, representing a risk for people in contact with the milk obtained from animals infected with these strains. These results present the relevance of surveillance for early detection of emergent clones with zoonotic potential, which reduces the risk of occupational exposure and their spread in the community.

Phenotypic Characterization and Whole Genome Analysis of a Strong Biofilm-Forming Staphylococcus aureus Strain Associated With Subclinical Bovine Mastitis in Colombia

Staphylococcus aureus represent a serious threat to public health due to food safety, antibiotic resistance, and the potential zoonotic transmission of strains between dairy cattle and humans. Biofilm formation by S. aureus results in chronicity of the infections which confers protection against the immune response and antibiotics. Likewise, biofilm allows the exchange of mobile genetic material among different strains through microbial interactions inside the matrix. In Colombia, where S. aureus continues to be one of the main pathogens isolated from bovine intramammary infections and where milking by hand is highly frequent, there are knowledge gaps on the zoonotic potential of the strains. Therefore, the aim of this work was to characterize genotypically and phenotypically the S. aureus Sa1FB strain with strong biofilm production and to perform genomic and phenotypic comparisons with other relevant S. aureus strains (native and references strains). These results show a highly productive strain of biofilm and a low ability of cell invasion compared to the other two native strains. In addition, high genomic similarity between S. aureus Sa1FB and the reference strains was observed, despite of the differences reported at the clinical level. However, Sa1FB exhibited special features in terms of mobile genetic elements, highlighting its ability to accept foreign genetic material. Indeed, this could increase mutation, pathogenesis, and adaptability to new hosts, representing a risk for people in contact with the milk obtained from animals infected with these strains. These results present the relevance of surveillance for early detection of emergent clones with zoonotic potential, which reduces the risk of occupational exposure and their spread in the community.