Luk Genes Research Articles

Characterization of clinical and community acquired staphylococcus aureus, local isolates

It was found that 46.6% of S. aureus were collected from nose swaps followed by ear (41.6%) and catheter tubes (11.8%). Results showed the highest resistance 100% for both classes of Aminopenicillins (Amoxicillin), cephalosporins 3Gr (Cefotaxime, Ceftriaxone, and Cefexime, and Carboxypencillin, as well as one group as 93.5% for class the β-lactam combination agents (Amoxicillin/ clavulanic acid). Many virulence factors and antibiotics resistance genes also being considered in this study, including erm, luk, hlg, fbl, Sea, MecA, seb, vat and tet. The highest frequency was in MecA genes 53 (88%) followed by sea genes 20 (33%), hlg and seb genes 18 (30%) for each one, erm genes 14 (23.3%) and luk genes 2 (3.3%), genes fbI, vat and tet were not detected in any isolate. Results shows no correlation concerning age, gender or the site of infection with either antimicrobial resistance or virulence factors genes.

Survey on Methicillin Resistance and Panton Valentine Toxin of Staphylococcus aureus Strains Isolated from Raw Milk and Ice Cream: Molecular Study by Multiplex PCR

Staphylococcus aureus is a very important pathogenic bacterium that causes nosocomial and community-acquired infections in humans, and is also one of the leading pathogens that causes food-borne poisoning. The presence of S. aureus in raw milk and dairy products, and especially the presence of MRSA (Methicillin Resistance S. aureus) strains, poses a potential risk to public health. The aim of this study was to investigate the presence of methicillin resistance and Panton-Valentine Leucocidin (PVL) toxin in Staphylococcus aureus isolated and identified from raw milk and ice cream in Konya (Turkey) by multiplex PCR method. A total of 55 S. aureus were isolated 49 (18%) from 260 raw milk samples collected from various farms and 6 (4%) from 150 ice cream samples sold in patisseries. The obtained isolates were identified as S. aureus with conventional and genotypic methods. Multiplex PCR was performed to detect the 16S rRNA, mecA, femA and lukS genes. While no mecA gene was detected in any of the 49 S. aureus isolates obtained from raw milk samples, the presence of mecA gene was observed in one of the 6 S. aureus isolates isolated from ice cream samples. The PVL gene was not detected in any of the S. aureus isolates studied. S. aureus contamination is common in raw milk samples and ice cream samples. In order to avoid this, it is necessary to comply with the hygiene conditions and increase the precautions even more.

Epidemiology, resistance characteristics, virulence determinants, and treatment outcomes of Staphylococcus aureus bone and joint infections: a one-year prospective study at a tertiary care hospital in India

ABSTRACT Purpose The study was aimed to explore the differences between the Staphylococcus aureus osteosynthesis-associated infection (OAI) and non-implant related infections (NIRI) in terms of epidemiology, resistance characteristics, virulence determinants, treatment, risk factors, and outcome. Methods A prospective study was conducted from 2018 through 2019. The phenotypic and genotypic characterization of S. aureus, risk factors, treatment, and outcome were compared. Results A total of 60 patients were included. 50% had OAIs (70%) (p = .045). Overall, MRSA (OR 0.69; p = .020) and old age (OR 0.95; p = 0.035) were the important risk factors. Implanted patients presented with the features of chronic osteomyelitis (93.3%, p = 0.01). NIRI cases composed of only 66.7% of OM, and 55% of them were acute. OAI isolates were more frequently luk gene positives (50%) than isolates from the NIRI group (33.3%). Patients with OAI by luk positive isolates significantly had prolonged hospital stay (p = 0.043; OR-0.96, CI-0.91–1.0). Most of the NIRIs (60%) managed with antibiotics, but frequent surgical intervention (OR 10.68; p = .024) with prolonged systemic antibiotics (OR 1.07; p = .029) helped all OAIs to recover. Patients without implants were recovered in a higher number (83.3%). Conclusion Our study highlighted that the differences exist between the OAI and NIRI, specifically in terms of clinical features, distribution of luk genes, treatment approach, and outcome. Risk factors for both types of infection remained the same.

Unbiased Identification of Immunogenic Staphylococcus aureus Leukotoxin B-Cell Epitopes.

Unbiased identification of individual immunogenic B-cell epitopes in major antigens of a pathogen remains a technology challenge for vaccine discovery. We therefore developed a platform for rapid phage display screening of deep recombinant libraries consisting of as few as one major pathogen antigen. Using the bicomponent pore-forming leukocidin (Luk) exotoxins of the major pathogen Staphylococcus aureus as a prototype, we randomly fragmented and separately ligated the hemolysin gamma A (HlgA) and LukS genes into a custom-built phage display system, termed pComb-Opti8. Deep sequence analysis of barcoded amplimers of the HlgA and LukS gene fragment libraries demonstrated that biopannng against a cross-reactive anti-Luk monoclonal antibody (MAb) recovered convergent molecular clones with short overlapping homologous sequences. We thereby identified an 11-amino-acid sequence that is highly conserved in four Luk toxin subunits and is ubiquitous in representation within S. aureus clinical isolates. The isolated 11-amino-acid peptide probe was predicted to retain the native three-dimensional (3D) conformation seen within the Luk holotoxin. Indeed, this peptide was recognized by the selecting anti-Luk MAb, and, using mutated peptides, we showed that a particular amino acid side chain was essential for these interactions. Furthermore, murine immunization with this peptide elicited IgG responses that were highly reactive with both the autologous synthetic peptide and the full-length Luk toxin homologues. Thus, using a gene fragment- and phage display-based pipeline, we have identified and validated immunogenic B-cell epitopes that are cross-reactive between members of the pore-forming leukocidin family. This approach could be harnessed to identify novel epitopes for a much-needed S. aureus-protective subunit vaccine.

English

Staphylococcus aureus toxins represent a public health challenge all over the world. This study aims to analyze the prevalence of genes encoding the staphylococcal leukocidins and their correlation with antimicrobial susceptibility and the source of isolation. For this purpose, the susceptibility of 75 S. aureus isolates to 12 antimicrobial agents was investigated. The leukocidins genes (lukD, lukE, lukF and lukS) were detected by polymerase chain reaction (PCR). The ability to express these genes was assessed among 20 isolates by RT-PCR. The most prevalent luk genes were lukF gene (73.3%), followed by lukE (64%), lukD (44%) and lukS (34.7%). Expression of lukD, lukE and lukS genes were variable. lukF gene was not expressed by any of the tested isolates. A statistically significant association was found between lukF occurrence and burn isolates. Besides that, lukF gene was more prevalent among amoxicillin-clavulenic acid and amikacin resistant isolates, while lukE was predominant with gentamicin resistant isolates. High expression level of lukD was found in MRSA and MDR isolates. Key words: Staphylococcus aureus, leukocidins, antimicrobial sensitivity.

High rates of community-acquired, Panton-Valentine leukocidin (PVL)- positive methicillin-resistant S. aureus (MRSA) infections in adult outpatients in Greece

Staphylococcus aureus was isolated in 88 (30.8%) of 286 adult patients suffering from various skin and soft-tissue infections examined in the outpatient department of a 650 bed tertiary-care hospital of Athens, Greece between January 2006 and December 2007. Twenty-seven (30.7%) of the S. aureus infections were caused by methicillin-resistant S. aureus (MRSA). All MRSA isolates were also resistant to tetracycline, fucidic acid and kanamycin, but were sensitive to gentamicin and tobramycin, as well as to to cotrimoxazole, chloramphenicol, quinolones, clindamycin and erythromycin. All isolates belonged to staphylococcal cassette chromosome mec elements (SCCmec) type IV, and were found to carry the lukF-PV and lukS genes coding for Panton-Valentine leukocidin (PVL). Pulsed-field gel electrophoresis (PFGE) and spa-typing revealed high genetic similarity among all MRSA isolates and with the PFGE pattern of the well-described ST80 clone that seems to be spreading through Europe. The high prevalence of MRSA among S. aureus infections in the community signify that empiric therapy in Greece, when clinically indicated, should exclude beta-lactam antibiotics. Moreover, the establishment of an active screening for PVL-positive community-acquired (CA)-MRSA carriage and the adoption of a search and destroy strategy for CA-MRSA in all patients admitted with purulent skin and soft-tissue is of high priority in Greece as well as in all European countries which face high rates of CA-MRSA infection.

The gamma-hemolysin locus of Staphylococcus aureus comprises three linked genes, two of which are identical to the genes for the F and S components of leukocidin

The Staphylococcus aureus gamma-hemolysin comprises two polypeptides, whereas the gamma-hemolysin locus (hlg) contains three open reading frames. The hlgA and hlgB genes encode the gamma 1 and gamma 2 components, respectively. The HlgB protein (gamma 2) has 27% residue identity with S. aureus alpha-toxin. Surprisingly, hlgB and hlgC are 98.5 and 99.1% identical to the lukF and lukS genes, respectively, encoding the F and S components of the Panton-Valentine leukocidin.