Staphylococcus aureus is a dangerous gram positive bacterial pathogen which, not only evades the host’s immune system but also can destroy the leucocytes especially neutrophils. It has an embodiment of virulence fact...Staphylococcus aureus is a dangerous gram positive bacterial pathogen which, not only evades the host’s immune system but also can destroy the leucocytes especially neutrophils. It has an embodiment of virulence factors most of which are secreted. Staphylococcus aureus secretes a number of toxins which cause tissue damage and facilitate spreading and nutrients uptake. Among the toxins, hemolysins α, β, γ, δ and Panton Valentine Leukocidin (PVL) are unique that they drill pores in the membrane, leading to the efflux of vital molecules and metabolites. Hemolysins also help in the scavenging of iron, although many of them also have leucolytic properties. α-hemolysin, also known as α-toxin, is the most prominent cytotoxin which damages a wide range of host cells including epithelial cells, endothelial cells, erythrocytes, monocytes, keratinocytes and it damages cell membrane and induces apoptosis. β-Hemolysin significantly affects human immune cell function. It has Mg2+ dependent sphingomyelinase activity and degrades sphingomyelin of plasma membrane into phosphorylcholine and ceramides. The bi-component leukocidins, which include γ-hemolysin and PVL, attack human phagocytic cells and greatly contribute to immune evasion. Delta toxin is a low molecular weight exotoxin with a broad cytolytic activity. Virulence determinants, quorum sensing and biofilm synthesis provide some attractive targets for design and development of a new group of antimicrobial compounds. This review provides an update on the structure, biological functions of hemolysins and their role in quorum sensing/biofilm synthesis (if any) and as effective therapeutic targets for anti-virulence drug development. We have tried to bring together information available on various aspects of hemolysins and highlighted their distribution among all species of Staphylococcus and other bacteria. We have updated the status of development of candidate drugs targeting the hemolysins for anti-virulence therapy as it offers an additional strategy to reduce the severity of infection and which would, through quorum quenching, delay the development biofilms leading to drug resistance.展开更多
Phenotypic tests have limited discrimatory power to identify closely related members of genus Staphylococcus and particularly for identification of S. aureus. 157 isolates of S. aureus obtained from different clinical...Phenotypic tests have limited discrimatory power to identify closely related members of genus Staphylococcus and particularly for identification of S. aureus. 157 isolates of S. aureus obtained from different clinical specimens were included in our study. To present a demonstration of our method’s sensitivity and ability to correctly detect S. aureus from uncultured clinical specimen, 30 known S. aureus positive but leftover uncultured clinical specimens from clinical microbiology laboratory were processed by our protocol and analyzed. All the 30 clinical specimens were confirmed as S. aureus among which 26 specimen were identified as MRSA and the remaining 4 as MSSA. These 30 clinical specimens used in the study showed 100% correlation with coagulase test and Cefoxitin disc diffusion method. Though commercial molecular diagnostic kits are available for detecting MRSA from swabs, this is probably the first time that multiplex PCR is being demonstrated directly on a variety of uncultured clinical specimens.展开更多
Increase in prevalence of MRSA worldwide and hence the need for rapid detection, have led to use of molecular methods for confirmation of the species and also MRSA. Species specific markers like fem or nuc along with ...Increase in prevalence of MRSA worldwide and hence the need for rapid detection, have led to use of molecular methods for confirmation of the species and also MRSA. Species specific markers like fem or nuc along with the methicillin-resistance determinant, mecA, have been used by several investigators worldwide for the identification of MRSA. In the current study, we have screened 54 microbiologically confirmed (MRSA, MSSA and CoNS) isolates for the presence of mecA, 16S rRNA, femA and nuc markers. While mecAPCR and 16S rRNAPCR results were consistent with other studies, femA and nuc showed dramatic variation in detection rate (sensitivity) of S. aureus 29.6% and 53.7% respectively. Evidences are presented to demonstrate the absence of femA. Our attempt to amplify the complete femA gene using sequences flanking femA further confirmed these results and also indicated that variations exist even in the genomic sequences around femA. Our data reveals the need for exercising care while using primers designed on sequences of constitutive genes like femA and nuc for PCR based identification of S. aureus species. Though geographic variations in the genome of S. aureus have previously been reported from around the world, we present here evidence for the first time from India for absence of femA and also for probable variations in the sequences around the femA gene in clinical isolates of S. aureus.展开更多
文摘Staphylococcus aureus is a dangerous gram positive bacterial pathogen which, not only evades the host’s immune system but also can destroy the leucocytes especially neutrophils. It has an embodiment of virulence factors most of which are secreted. Staphylococcus aureus secretes a number of toxins which cause tissue damage and facilitate spreading and nutrients uptake. Among the toxins, hemolysins α, β, γ, δ and Panton Valentine Leukocidin (PVL) are unique that they drill pores in the membrane, leading to the efflux of vital molecules and metabolites. Hemolysins also help in the scavenging of iron, although many of them also have leucolytic properties. α-hemolysin, also known as α-toxin, is the most prominent cytotoxin which damages a wide range of host cells including epithelial cells, endothelial cells, erythrocytes, monocytes, keratinocytes and it damages cell membrane and induces apoptosis. β-Hemolysin significantly affects human immune cell function. It has Mg2+ dependent sphingomyelinase activity and degrades sphingomyelin of plasma membrane into phosphorylcholine and ceramides. The bi-component leukocidins, which include γ-hemolysin and PVL, attack human phagocytic cells and greatly contribute to immune evasion. Delta toxin is a low molecular weight exotoxin with a broad cytolytic activity. Virulence determinants, quorum sensing and biofilm synthesis provide some attractive targets for design and development of a new group of antimicrobial compounds. This review provides an update on the structure, biological functions of hemolysins and their role in quorum sensing/biofilm synthesis (if any) and as effective therapeutic targets for anti-virulence drug development. We have tried to bring together information available on various aspects of hemolysins and highlighted their distribution among all species of Staphylococcus and other bacteria. We have updated the status of development of candidate drugs targeting the hemolysins for anti-virulence therapy as it offers an additional strategy to reduce the severity of infection and which would, through quorum quenching, delay the development biofilms leading to drug resistance.
文摘Phenotypic tests have limited discrimatory power to identify closely related members of genus Staphylococcus and particularly for identification of S. aureus. 157 isolates of S. aureus obtained from different clinical specimens were included in our study. To present a demonstration of our method’s sensitivity and ability to correctly detect S. aureus from uncultured clinical specimen, 30 known S. aureus positive but leftover uncultured clinical specimens from clinical microbiology laboratory were processed by our protocol and analyzed. All the 30 clinical specimens were confirmed as S. aureus among which 26 specimen were identified as MRSA and the remaining 4 as MSSA. These 30 clinical specimens used in the study showed 100% correlation with coagulase test and Cefoxitin disc diffusion method. Though commercial molecular diagnostic kits are available for detecting MRSA from swabs, this is probably the first time that multiplex PCR is being demonstrated directly on a variety of uncultured clinical specimens.
文摘Increase in prevalence of MRSA worldwide and hence the need for rapid detection, have led to use of molecular methods for confirmation of the species and also MRSA. Species specific markers like fem or nuc along with the methicillin-resistance determinant, mecA, have been used by several investigators worldwide for the identification of MRSA. In the current study, we have screened 54 microbiologically confirmed (MRSA, MSSA and CoNS) isolates for the presence of mecA, 16S rRNA, femA and nuc markers. While mecAPCR and 16S rRNAPCR results were consistent with other studies, femA and nuc showed dramatic variation in detection rate (sensitivity) of S. aureus 29.6% and 53.7% respectively. Evidences are presented to demonstrate the absence of femA. Our attempt to amplify the complete femA gene using sequences flanking femA further confirmed these results and also indicated that variations exist even in the genomic sequences around femA. Our data reveals the need for exercising care while using primers designed on sequences of constitutive genes like femA and nuc for PCR based identification of S. aureus species. Though geographic variations in the genome of S. aureus have previously been reported from around the world, we present here evidence for the first time from India for absence of femA and also for probable variations in the sequences around the femA gene in clinical isolates of S. aureus.
