Biofilm-Formation Ability and the Presence of Adhesion Genes in Coagulase-Negative Staphylococci Isolates from Chicken Broilers

Coagulase-negative staphylococci are the main causes of bacterial meningitis in duck

Since September 2018, serious meningitis has been found on some breeding-duck farms in Shandong Province, China. A large number of ducks exhibit severe neurological symptoms. The ducks were randomly selected for laboratory testing. Duck brain samples were collected using standard sterile techniques, and the staphylococci isolates were detected in 404 (70.14%) out of 576 brain samples. A total of 525 coagulase-negative staphylococci (CoNS) strains were isolated, including 6 species: Staphylococcus sciuri (S. sciuri) (67.24%, 353/525), Staphylococcus epidermidis (S. epidermidis) (9.71%, 51/525), Staphylococcus saprophyticus (S. saprophyticus) (8.38%, 44/525), Staphylococcus lentus (S. lentus) (7.62%, 40/525), Staphylococcus haemolyticus (S. haemolyticus) (2.48%, 13/525), and Staphylococcus xylosus (S. xylosus) (4.57%, 24/525). Mixed strain infections were detected in 121 (29.95%) infected presentations. The antimicrobial susceptibility testing indicated that 40.38% of the isolates exhibited multi-drug resistance, and 53.90% of the strains were methicillin-resistant strains by amplification of the methicillin resistance gene (mecA) gene. Through experimental reproduction of the disease, we determined that the CoNS strains were the leading pathogens causing bacterial meningitis in ducks. Although these CoNS strains does not directly cause the death of sick ducks, they still cause large economic losses due to the retarded growth and development of the sick ducks, lower feed returns, and lower grades of processed duck products. The results of this study will contribute to our understanding of the epidemiology and pathogenesis of CoNS and be helpful in the prevention and treatment of the infection.

Anatomical, pathological, and histological features of experimental respiratory infection of birds by biofilm-forming bacteria Staphylococcus aureus

Background and Aim

The pathogenesis of staphylococcal infections is mediated by virulence factors, such as enzymes, toxins, and biofilms, which increase the resistance of microorganisms to host immune system evasion. Testing and searching for standardized multi-level algorithms for the indication and differentiation of biofilms at the early stages of diagnosis will contribute to the development of preventive measures to control the critical points of technology and manage dangerous risk factors for the spread of infectious diseases. This research aimed to study the main stages of Staphylococcus aureus biofilm formation in in vitro experiments and to analyze the dynamics of respiratory syndrome development in chickens infected with these bacteria.

Materials and Methods

Experimental reproduction of the infectious process was performed using laboratory models: 10-day-old White Leghorn chickens (n = 20). Before the experiments, the birds were divided into two groups according to the principle of analogs: Group I (control, n = 10): the birds were intranasally inoculated with 0.5 cm3 of 0.9% NaCl solution; Group II (experiment, n = 10): the birds were intranasally inoculated with a suspension of S. aureus bacteria, 0.5 cm3, concentration 1 billion/cm3.

Results

Colonization of individual areas of the substrate under study in vitro occurred gradually from the sedimentation and adhesion of single motile planktonic cells to the attachment stage of microcolony development. Staining preparations with gentian violet due to the "metachromosia" property of this dye are a quick and fairly simple way to differentiate cells and the intercellular matrix of biofilms. Fixation with vapors of glutaraldehyde and osmium tetroxide preserves the natural architecture of biofilms under optical and scanning electron microscopy. Pure cultures of S. aureus microorganisms were isolated from the blood, lungs, small intestine, liver, kidneys, and spleen after 5-10 days during experimental infection of chickens. Clinical signs of respiratory syndrome developed within 5-6 days after infection. Acute and subacute serous-fibrinous airsacculitis, characterized by edema and thickening of the membranes of the air sacs and the presence of turbid, watery, foamy contents in the cavity, was the most characteristic pathomorphological sign. The signs of acute congestive hyperemia and one-sided serous-fibrinous pneumonia developed with significant thickening of fibrinous deposits. In Garder's gland, there was an increase in the number of secretory sections, indicating hypersecretion of the glands. In the lymphoid follicles of Meckel's diverticulum, leukocytes, usually lymphocytes, and pseudoeosinophils were detected.

Conclusions

Hydration and heteromorphism of the internal environment of biofilms determine the localization of differentiated cells in a three-dimensional matrix for protection against adverse factors. The most characteristic pathomorphological sign was the development of acute and subacute serous-fibrinous airsacculitis when reproducing the infectious process in susceptible models. There was a significant thickening of fibrinous deposits and signs of acute congestive hyperemia and one or two serous-fibrinous pneumonia developed.

mecA and fdh: markers of pathogenicity and commensalism in Staphylococcus epidermidis of pediatric origin from Pakistan

Staphylococcus epidermidis is an opportunistic bacterial pathogen. The study screened isolates of S. epidermidis of pediatric origin for genetic markers of discriminatory potential. 103 isolates (n = 75 clinical; n = 28 community) were screened for methicillin resistance (mecA), formate dehydrogenase (fdh) and an array of virulence factors through multiplex PCR and Congo red assay. The isolates were typed in four distinct categories, based on the presence of selected virulent factors. The type A clinical isolates carrying icaADBC operon (n = 22; 29.3%, P = 0.117) were not significantly differentiating the origin of isolates. The type B clinical isolates representing methicillin resistant S. epidermidis (MRSE) (n = 73; 97.3%, P < 0.00001) and the type C clinical isolates lacking formate dehydrogenase fdh (n = 62; 82.6%, P < 0.00001) were having significant discriminatory potential of clinical isolates, respectively. All type D community isolates were carrying fdh (n = 28; 100%, P < 0.00001). MecA and fdh are significant differential markers of pathogenicity and commensalism in S. epidermidis of pediatric origin.

Down-regulation of β-lactam antibiotics resistance and biofilm formation by Staphylococcus epidermidis is associated with isookanin

Introduction

Biofilm formation is the major pathogenicity of Staphylococcus epidermidis (S. epidermidis), which enhances bacterial resistance to antibiotics. Isookanin has potential inhibitory activity on biofilm.

Method

The inhibiting mechanisms of isookanin against biofilm formation through surface hydrophobicity assay, exopolysaccharides, eDNA, gene expression analysis, microscopic visualization, and molecular docking were explored. Additionally, the combination of isookanin and β-lactam antibiotics were evaluated by the broth micro-checkerboard assay.

Results

The results showed that isookanin could decrease the biofilm formation of S. epidermidis by ≥85% at 250 μg/mL. The exopolysaccharides, eDNA and surface hydrophobicity were reduced after treatment with isookanin. Microscopic visualization analysis showed that there were fewer bacteria on the surface of the microscopic coverslip and the bacterial cell membrane was damaged after treatment with isookanin. The down-regulation of icaB and up-regulation of icaR were observed after treatment with isookanin. Additionally, the RNAIII gene was significantly up-regulated (p < 0.0001) at the mRNA level. Molecular docking showed that isookanin could bind to biofilm-related proteins. This indicated that isookanin can affect biofilm formation at the initial attachment phase and the aggregation phase. The FICI index showed that the combination of isookanin and β-lactam antibiotics were synergistic and could reduce doses of antibiotics by inhibiting biofilm formation.

Discussion

This study improved the antibiotic susceptibility of S. epidermidis through inhibition of the biofilm formation, and provided a guidance for the treatment of antibiotic resistance caused by biofilm.

Multiple Antimicrobial Resistance and Heavy Metal Tolerance of Biofilm-Producing Bacteria Isolated from Dairy and Non-Dairy Food Products

Foodborne pathogens have acquired the ability to produce biofilms to survive in hostile environments. This study evaluated biofilm formation, antimicrobial resistance (AMR), and heavy metal tolerance of bacteria isolated from dairy and non-dairy food products. We aseptically collected and processed 200 dairy and non-dairy food specimens in peptone broth, incubated them overnight at 37 °C, and sub-cultured them on various culture media. Bacterial growth was identified with biochemical tests and API 20E and 20NE strips. The AMR of the isolates was observed against different antibacterial drug classes. Biofilm formation was detected with the crystal violet tube method. Heavy metal salts were used at concentrations of 250−1500 µg/100 mL to observe heavy metal tolerance. We isolated 180 (50.4%) bacteria from dairy and 177 (49.6%) from non-dairy food samples. The average colony-forming unit (CFU) count for dairy and non-dairy samples was 2.9 ± 0.9 log CFU/mL and 5.1 ± 0.3 log CFU/mL, respectively. Corynebacterium kutscheri (n = 74), lactobacilli (n = 73), and Staphylococcus aureus (n = 56) were the predominant Gram-positive and Shigella (n = 10) the predominant Gram-negative bacteria isolated. The correlation between biofilm formation and AMR was significant (p < 0.05) for most cephalosporins, aminoglycosides, and fluoroquinolones. Heavy metal tolerance tended to be higher in biofilm producers at different metal concentrations. The pathogens isolated from dairy and non-dairy food showed a high burden of AMR, high propensity for biofilm formation, and heavy metal tolerance, and pose an imminent threat to public health.

Characterization of Biofilm Producing Coagulase-Negative Staphylococci Isolated from Bulk Tank Milk

Coagulase-negative staphylococci (CoNS) are considered less virulent as they do not produce a large number of toxic enzymes and toxins; however, they have been increasingly recognized as an important cause of bovine mastitis. In particular, the ability to form biofilms appears to be an important factor in CoNS pathogenicity, and it contributes more resistance to antimicrobials. The aim of this study was to investigate the pathogenic potential by assessing the biofilm-forming ability of CoNS isolated from normal bulk tank milk using the biofilm formation assay and to analyze the biofilm-associated resistance to antimicrobial agents using the disc diffusion method. One hundred and twenty-seven (78.4%) among 162 CoNS showed the ability of biofilm formation, and all species showed a significantly high ability of biofilm formation (p < 0.05). Although the prevalence of weak biofilm formers (39.1% to 80.0%) was significantly higher than that of other biofilm formers in all species (p < 0.05), the prevalence of strong biofilm formers was significantly higher in Staphylococcus haemolyticus (36.4%), Staphylococcus chromogenes (24.6%), and Staphylococcus saprophyticus (21.7%) (p < 0.05). Also, 4 (11.4%) among 35 non-biofilm formers did not harbor any biofilm-associated genes, whereas all 54 strong or moderate biofilm formers harbored 1 or more of these genes. The prevalence of MDR was significantly higher in biofilm formers (73.2%) than in non-formers (20.0%) (p < 0.05). Moreover, the distribution of MDR in strong or moderate biofilm formers was 81.5%, which was significantly higher than in weak (67.1%) and non-formers (20.0%) (p < 0.05). Our results indicated that various CoNS isolated from bulk tank milk, not from bovine with mastitis, have already showed a high ability to form biofilms, while also displaying a high prevalence of MDR.

Multidrug-Resistant Methicillin-Resistant Coagulase-Negative Staphylococci in Healthy Poultry Slaughtered for Human Consumption

Coagulase-negative staphylococci are commensals that are known to be prevalent in most environments, and they are also an important reservoir of antimicrobial-resistant genes. Staphylococcal infections in animal husbandry are a high economic burden. Thus, we aimed to determine the prevalence and species diversity of methicillin-resistant coagulase-negative staphylococci (MRCoNS) in poultry slaughtered for human consumption and to study the antimicrobial resistance of the isolates. Swab samples were recovered from 220 commercial chickens, homebred chickens and quails. Species identification was performed using MALDI-TOF. Antimicrobial susceptibility testing was performed by the disc diffusion method against 14 antimicrobials. The presence of antimicrobial-resistant genes was investigated by polymerase chain reaction. Totals of 11 (19.6%), 13 (20.3%), and 51 (51%) MRCoNS were isolated from commercial chickens, homebred chickens and quails, respectively. S. lentus was isolated from all homebred chickens, whereas 11 S. lentus and 2 S. urealyticus were isolated from commercial chickens. As for quails, the most prevalent MRCoNS were S. urealyticus. Almost all isolates had a multidrug-resistant profile and carried the mecA gene. Most isolates showed resistance to erythromycin, clindamycin, penicillin, tetracycline, ciprofloxacin and fusidic acid and harbored the ermA, ermB, ermC, mphC tetK, tetL, tetM and tetO genes. This study showed a frequent occurrence of multidrug resistance in MRCoNS isolated from healthy poultry in Portugal.