Staphylococcus aureus exfoliative toxins: How they cause disease

Exploring diflunisal as a synergistic agent against Staphylococcus aureus biofilm formation

Staphylococcus aureus is a bacterial pathogen of considerable significance in public health, capable of inducing a diverse range of infectious diseases. One of the most notorious mechanisms used by S. aureus to survive and colonize the site of infection is its ability to form biofilms. Diflunisal, a non-steroidal anti-inflammatory drug (NSAID), is a known inhibitor of the Agr system in S. aureus, which is key in regulating biofilm formation. This study evaluated the effect of broad-spectrum antibiotics in combination with diflunisal on S. aureus biofilm density. Eight antibiotics were tested independently at different concentrations and in combination with diflunisal to assess their effect on S. aureus biofilm formation. When using the antibiotics alone and with diflunisal, a significant control effect on biofilm formation was observed (p < 0.05), irrespective of diflunisal presence, but did not achieve a complete biofilm growth inhibition. Over time, diflunisal influenced biofilm formation; however, such an effect was correlated with antibiotic concentration and exposure time. With amikacin treatments, biofilm density increased with extended exposure time. In the case of imipenem, doripenem, levofloxacin, and ciprofloxacin, lower doses and absence of diflunisal showed higher control over biofilm growth with longer exposure. However, in all cases, diflunisal did not significantly affect the treatment effect on biofilm formation. In the absence of antibiotics, diflunisal significantly reduced biofilm formation by 53.12% (p < 0.05). This study suggests that diflunisal could be a potential treatment to control S. aureus biofilms, but it does not enhance biofilm inhibition when combined with antibiotics.

Molecular Characteristics of Methicillin-Resistant and Susceptible Staphylococcus aureus from Pediatric Patients in Eastern China

Staphylococcus aureus is an opportunistic pathogen that causes invasive infections in humans. In recent years, increasing studies have focused on the prevalence of S. aureus infections in adults; however, the epidemiology and molecular characteristics of S. aureus from Chinese pediatric patients remain unknown. The present study examined the population structure, antimicrobial resistance, and virulent factors of methicillin-resistant and -susceptible S. aureus isolated from Chinese pediatric patients from one medical center in eastern China. A total of 81 cases were screened with positive S. aureus infections among 864 pediatric patients between 2016 and 2022 in eastern China. Molecular analysis showed that ST22 (28.4%) and ST59 (13.6%) were the most typical strains, and associations between different clonal complex (CC) types/serotype types (ST) and the age of pediatric patients were observed in this study. CC398 was the predominant type in neonates under 1 month of age, while CC22 was mainly found in term-infant (under 1 year of age) and toddlers (over 1 year of age). Additionally, 17 S. aureus isolates were resistant to at least three antimicrobials and majority of them belonged to CC59. The blaZ gene was found in 59 isolates and mecA gene was present in 26 strains identified as methicillin-resistant. Numerous virulent factors were detected in S. aureus isolated from present pediatric patients. Remarkably, lukF-PV and lukS-PV were dominantly carried by CC22, tsst-1 genes were detected in CC188, CC7, and CC15, while exfoliative toxin genes were found only in CC121. Only 41.98% of the S. aureus isolates possessed scn gene, indicating that the sources of infections in pediatric patients may include both human-to-human transmissions as well as environmental and nosocomial infections. Together, the present study provided a phylogenetic and genotypic comparison of S. aureus from Chinese pediatric patients in Suzhou city. Our results suggested that the colonization of multi-drug resistant isolates of S. aureus may raise concern among pediatric patients, at least from the present medical center in eastern China.

Photodynamic inactivation of S. aureus with a water-soluble curcumin salt and an application to cheese decontamination

In this study, the optimal parameters for the photodynamic inactivation (PDI) of Staphylococcus aureus in bacterial suspensions and in cheese were assessed using a water-soluble curcumin salt as the photosensitizer (PS).

Genetic characterisation of methicillin-resistant Staphylococcus aureus and Staphylococcus pseudintermedius in pets and veterinary personnel in Iran: new insights into emerging methicillin-resistant S. pseudintermedius (MRSP)

OBJECTIVES

Methicillin-resistant staphylococci, including methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant Staphylococcus pseudintermedius (MRSP), pose a threat to animal and human health worldwide. Veterinary staff and pets may play a role in the spread of resistant clones.

METHODS

A total of 125 samples from veterinary staff (n=50), dogs (n=49) and cats (n=26) were investigated. Obtained isolates were tested for the methicillin resistance gene mecA and were subjected to multiplex PCR to differentiate coagulase-positive species. Following SCCmec and spa typing, isolates were tested for the presence of various toxin and virulence genes and phenotypic resistance to common antimicrobials.

RESULTS

Overall, 4 MRSA were isolated from two veterinarians and two dogs and 19 MRSP were found in eleven dogs (12 isolates) and five cats (7 isolates). The MRSA isolates possessed sea (2) and eta (3) virulence genes and the MRSP isolates possessed sea (6), expA (15), expB (1) and siet (19) genes. SCCmec type II and three spa types (t186, t1816 and t10897) were identified in the MRSA isolates. Most of the MRSP isolates belonged to SCCmec types II (2 isolates) and V (10 isolates); however, the remaining 7 isolates were untypeable and contained class C1 mec. The majority of isolates were multidrug-resistant (MDR).

CONCLUSION

These findings show that pets and veterinarians could be potential sources of MDR-MRSA and MDR-MRSP in Iran. Taken together, these findings warrant future investigations on the epidemiology and public-health significance of MDR-MRSA and MDR-MRSP both in veterinarians and companion animals in Iran.

Detección y expresión de superantígenos y de resistencia antimicrobiana en aislamientos obtenidos de mujeres portadoras de Staphylococcus aureus que cuidan y alimentan niños

Introducción. Staphylococcus aureus coloniza mucosas y piel, y causa graves infecciones en el hombre y los animales. Es importante establecer el estatus de portadoras de cepas enterotoxigénicas de este microorganismo en manipuladoras de alimentos, con el fin de prevenir intoxicaciones alimentarias.Objetivo. Establecer las correlaciones entre los genes de enterotoxinas clásicas, el gen tsst-1, la producción de toxinas en cultivo y la resistencia antimicrobiana en aislamientos de S. aureus provenientes de manipuladoras de alimentos que cuidan niños en sus comunidades.Materiales y métodos. Se cultivaron muestras de las fosas nasales y las yemas de los dedos de las manos, y se identificó S. aureus empleando las pruebas de rutina y métodos automatizados. La extracción de ADN se hizo mediante el método de bromuro de cetil-trimetil-amonio (Cetyl-Trimethyl-Ammonium Bromide, CTAB) modificado. Para la detección de superantígenos se emplearon pruebas de reacción en cadena de la polimerasa (PCR) simple y múltiple, y para la de toxinas, estuches comerciales.Resultados. Se encontró que el 22,0 % de los aislamientos correspondía a portadoras de S. aureus: 17,0 % en los aislamientos de fosas nasales; 5,0 % en los de las manos y 6,7 % simultáneamente en los dos sitios. La prevalencia de superantígenos fue de 73,7 %. El genotipo más frecuente fue el seatsst-1, con 10,0 %. La resistencia a un solo antibiótico fue de 74,7 % y, a cuatro antibióticos, de 3,2 %; de los aislamientos, el 93,7 % correspondía a cepas productoras de betalactamasas. La detección de genes clásicos y de tsst-1 mediante PCR fue de 48,4 % y la de toxinas en el sobrenadante, de 42,1 %,con una correlación de 95,7 %. Las mayores correlaciones se establecieron entre las toxinas TSST-1 (22/22) y SEA (17/18). La correlación del gen tsst-1 con la proteína y la resistencia fue de 100 %. Todos los aislamientos con el genotipo sea-tsst-1 t fueron resistentes y productores de las toxinas.Conclusión. La tasa de aislamientos de S. aureus toxigénicos y resistentes obtenidos de mujeres que cuidan y preparan alimentos para niños fue de más de 70 %, lo que demostró su gran virulencia y la consecuente necesidad de aplicar estrictamente las normas higiénicas y sanitarias vigentes para evitar el riesgo de intoxicación alimentaria.

Complete genome of Staphylococcus aureus Tager 104 provides evidence of its relation to modern systemic hospital-acquired strains

BACKGROUND

Staphylococcus aureus (S. aureus) infections range in severity due to expression of certain virulence factors encoded on mobile genetic elements (MGE). As such, characterization of these MGE, as well as single nucleotide polymorphisms, is of high clinical and microbiological importance. To understand the evolution of these dangerous pathogens, it is paramount to define reference strains that may predate MGE acquisition. One such candidate is S. aureus Tager 104, a previously uncharacterized strain isolated from a patient with impetigo in 1947.

RESULTS

We show here that S. aureus Tager 104 can survive in the bloodstream and infect naïve organs. We also demonstrate a procedure to construct and validate the assembly of S. aureus genomes, using Tager 104 as a proof-of-concept. In so doing, we bridged confounding gap regions that limited our initial attempts to close this 2.82 Mb genome, through integration of data from Illumina Nextera paired-end, PacBio RS, and Lucigen NxSeq mate-pair libraries. Furthermore, we provide independent confirmation of our segmental arrangement of the Tager 104 genome by the sole use of Lucigen NxSeq libraries filled by paired-end MiSeq reads and alignment with SPAdes software. Genomic analysis of Tager 104 revealed limited MGE, and a νSaβ island configuration that is reminiscent of other hospital acquired S. aureus genomes.

CONCLUSIONS

Tager 104 represents an early-branching ancestor of certain hospital-acquired strains. Combined with its earlier isolation date and limited content of MGE, Tager 104 can serve as a viable reference for future comparative genome studies.

Proteomic analysis of the proteins released from Staphylococcus aureus following exposure to Ag(I)

The silver ion (Ag(I)) has well established antimicrobial properties and is widely used in a variety of anti-bacterial ointments and plasters for the control of wound infections. Wounds are frequently colonised by the bacterium Staphylococcus aureus and the aim of the work presented here was to establish how S. aureus responded following exposure to Ag(I). Exposure of S. aureus to Ag(I) resulted in the release of a range of proteins from cells. Analysis of proteins released revealed a number of proteins associated with the stress response (e.g. alkaline shock protein, methionine sulfoxide reductase), virulence (e.g. signal transduction protein) and metabolism (e.g. lipase, acetate kinase, phosphoglycerate mutase). The release of toxins (e.g. α-hemolysin, bifunctional autolysin, leucocidin F) was decreased. These results indicated that, while silver is a potent antimicrobial agent, exposure of S. aureus to this metal results in the release of a variety of proteins from the cell. Many of the proteins showing increased release were antigenic and would have the potential to induce an inflammatory response at the site of infection and thus delay healing.

Toxins and Antibiotic Resistance in Staphylococcus aureus Isolated from a Major Hospital in Lebanon

Molecular characterization of Staphylococcus aureus is of both clinical and infection control importance. Virulence determinants using PCR and multiple drug resistance profiles were studied in 130 S. aureus isolates. PCR-RFLP analysis of the 16S-23S DNA spacer region was done to investigate the level of 16S-23S ITS (internal transcribed spacer) polymorphism. Methicillin-resistant S. aureus (MRSA), which represented 72% of the studied isolates, showed multiple drug resistance with 18% being resistant to 10-18 of the drugs used compared to a maximum resistance to 9 antibiotics with the methicillin sensitive S. aureus (MSSA) isolates. Exfoliative toxin A (ETA) was more prevalent than B (ETB) with virulent determinants being additionally detected in multiple drug-resistant isolates. 16S-23S ITS PCR-RFLP combined with sequencing of the primary product was successful in generating molecular fingerprints of S. aureus and could be used for preliminary typing. This is the first study to demonstrate the incidence of virulent genes, ACME, and genetic diversity of S. aureus isolates in Lebanon. The data presented here epitomize a starting point defining the major genetic populations of both MRSA and MSSA in Lebanon and provide a basis for clinical epidemiological studies.

Molecular detection of enterotoxins E, G, H and I in Staphylococcus aureus and coagulase-negative staphylococci isolated from clinical samples of newborns in Brazil

AIMS

The objective of this study was to investigate the detection of SEE, SEG, SEH and SEI in strains of Staphylococcus aureus and coagulase-negative staphylococci (CNS) using RT-PCR.

METHODS AND RESULTS

In this study, 90 Staph. aureus strains and 90 CNS strains were analysed by PCR for the detection of genes encoding staphylococcal enterotoxins (SE) E, G, H and I. One or more genes were detected in 54 (60%) Staph. aureus isolates and in 29 (32.2%) CNS isolates. Staphylococcus epidermidis was the most frequently isolated CNS species (n = 64, 71.1%), followed by Staphylococcus warneri (n = 8, 8.9%) and other species (Staphylococcus haemolyticus, Staphylococcus hominis, Staphylococcus lugdunensis, Staphylococcus simulans, Staphylococcus saprophyticus and Staphylococcus xylosus: n = 18, 20%). The genes studied were detected in Staph. epidermidis, Staph. warneri, Staph. haemolyticus, Staph. hominis, Staph. simulans and Staph. lugdunensis. The highest frequency of genes was observed in Staph. epidermidis and Staph. warneri, a finding indicating differences in the pathogenic potential between CNS species and highlighting the importance of the correct identification of these micro-organisms. RT-PCR used for the detection of mRNA revealed the expression of SEG, SEH and/or SEI in 32 (59.3%) of the 90 Staph. aureus isolates, whereas expression of some of these genes was observed in 10 (34.5%) of the 90 CNS isolates.

CONCLUSIONS

Staphylococcus epidermidis was the most toxigenic CNS species. Among the other species, only Staph. warneri and Staph. lugdunensis presented a positive RT-PCR result. PCR was efficient in confirming the toxigenic capacity of Staph. aureus and CNS.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study permitted to confirm the toxigenic capacity of CNS to better characterize the pathogenic potential of this group of micro-organisms. In addition, it permitted the detection of SEG, SEH and SEI, enterotoxins that cannot be detected by commercially available immunological methods.

Mobile genetic elements of Staphylococcus aureus

Bacteria such as Staphylococcus aureus are successful as commensal organisms or pathogens in part because they adapt rapidly to selective pressures imparted by the human host. Mobile genetic elements (MGEs) play a central role in this adaptation process and are a means to transfer genetic information (DNA) among and within bacterial species. Importantly, MGEs encode putative virulence factors and molecules that confer resistance to antibiotics, including the gene that confers resistance to beta-lactam antibiotics in methicillin-resistant S. aureus (MRSA). Inasmuch as MRSA infections are a significant problem worldwide and continue to emerge in epidemic waves, there has been significant effort to improve diagnostic assays and to develop new antimicrobial agents for treatment of disease. Our understanding of S. aureus MGEs and the molecules they encode has played an important role toward these ends and has provided detailed insight into the evolution of antimicrobial resistance mechanisms and virulence.

Identification of first exfoliative toxin in Staphylococcus pseudintermedius

Staphylococcus aureus, Staphylococcus hyicus, and Staphylococcus chromogenes are known to cause skin infections in human or animals by producing exfoliative toxins (ETs). Staphylococcus pseudintermedius can also cause canine pyoderma, but no exfoliative toxins or similar toxins have been reported. PCR with degenerate primers targeted to the conserved regions in ETA, ETB, and ETD from S. aureus and SHETB from S. hyicus, and subsequent chromosome walking identified a novel gene, designated as exi (exfoliative toxin of pseudintermedius) in S. pseudintermedius. EXI had significant homologies with the exfoliative toxins (43-68% identity), particularly with ETB (67.1%), ETD (67.9%), and SHETB (65.1%). Phylogenetic analysis showed close relation between EXI and ETB with a bootstrap value of 80%. Neonatal mice injected with the crude proteins from the culture supernatant or recombinant EXI showed gross blisters and/or characteristic skin exfoliation. The prevalence of exi assessed by dot-blot hybridization was 23.3% (10/43) in S. pseudintermedius isolates from canine pyoderma. The EXI reported herein is the first exfoliative toxin identified in S. pseudintermedius.

Transduction of the plasmid encoding antiseptic resistance gene qacB in Staphylococcus aureus

The plasmid-borne qacA and qacB genes encode a multidrug efflux protein. The proteins encoded by qacA and qacB mediate efflux of cationic antiseptic agents such as quaternary ammonium compounds. In methicillin-resistant Staphylococcus aureus (MRSA), qacA and qacB are widely prevalent and decrease antiseptic susceptibility. However, it is difficult to find the plasmids encoding qacA or qacB in community-associated MRSA (C-MRSA) isolated from patients with impetigo. Most MRSA, the strains causative of impetigo, carry the plasmid-borne exfoliative toxin-producing gene etb. To find the reason for the paucity of qacA or qacB in MRSA isolated from patients with impetigo, we performed transfer experiments of the plasmid pTZ2162qacB encoding qacB. The pTZ2162qacB was transferred to S. aureus strain RN4220 by transduction, although no pTZ2162qacB was transferred by conjugation. Additionally, pTZ2162qacB was transduced to MRSA carrying etb, and was coexistence with the plasmid encoding etb. Our results showed that pTZ2162qacB was horizontally transferred by transduction and was compatible with the plasmid encoding etb. Consequently, there will be risk of the emergence of C-MRSA with decreased antiseptic susceptibility among patients with impetigo.

[Primary cutaneous infections due to Staphylococcus and Streptococcus]

Pyodermitis constitutes a very important chapter in dermatological practice. Its pathogenesis, in special the one caused by S. aureus, has improved due to the knowledge of the role developed by the host defensins, quorum-sensing signaling and the Panton-Valentine leucocidin gene among others. As well, exfoliative toxins and enterotoxins responsible for the staphylococal scalded skin syndrome (SSSS) and toxic shock syndrome, respectively, have been cloned. Also, it has been seen that bullous impetigo, SSSS and pemphigus foliaceus share a common target: desmoglein-1. The Panton-Valentine leucocidin gene has been related to the appearance of abscesses, necrotic cutaneous lesions and furuncles in young persons caused by meticillin resistant S. aureus, with its epidemiological implications. Finally, some atypical forms of erysipelas suppose a diagnostic challenge for the dermatologist.

Multiplex PCR for detection of three exfoliative toxin serotype genes in Staphylococcus aureus

Rapid and specific detection of exfoliative toxin (ET)-producing Staphylococcus aureus strains by multiplex polymerase chain reaction (PCR) was used for identification of exfoliative toxin genes in a diverse set of 115 clinical S. aureus strains isolated in 14 Czech cities between 1998 and 2004. Fifty-nine wild-type ET-positive isolates of which 40 strains were the causative agents of toxic epidermolysis in neonates were classified into 4 PCR types. The genes coding for ETA, ETB or ETD were not detected in any of non-ET-producing isolates. The PCR method using the multiplex and specific primer set was shown to be reliable in rapid identification of the exfoliative toxin producing S. aureus and can be used as a convenient tool for hospital epidermolytic infection control.

Antimicrobial agent of susceptibilities and antiseptic resistance gene distribution among methicillin-resistant Staphylococcus aureus isolates from patients with impetigo and staphylococcal scalded skin syndrome

The susceptibilities to antimicrobial agents of and distributions of antiseptic resistance genes in methicillin-resistant Staphylococcus aureus (MRSA) strains isolated between 1999 and 2004 in Japan were examined. The data of MRSA strains that are causative agents of impetigo and staphylococcal scalded skin syndrome (SSSS) were compared with those of MRSA strains isolated from patients with other diseases. The susceptibilities to antiseptic agents in MRSA isolates from patients with impetigo and SSSS were higher than those in MRSA isolates from patients with other diseases. The distribution of the qacA/B genes in MRSA strains isolated from patients with impetigo and SSSS (1.3%, 1/76) was remarkably lower than that in MRSA strains isolated from patients with other diseases (45.9%, 95/207). Epidemiologic typings of staphylococcal cassette chromosome mec (SCCmec) and pulsed-field gel electrophoresis (PFGE) showed that MRSA strains isolated from patients with impetigo and SSSS had type IV SCCmec (75/76), except for one strain, and 64.5% (49/76) of the strains had different PFGE types. In addition, the patterns of restriction digestion of all tested qacA/B plasmid in MRSA isolates having different PFGE types were identical. The results showed that a specific MRSA clone carrying qacA/B was not prevalent, but qacA/B was spread among health care-associated MRSA strains. Therefore, it was concluded that the lower distribution rate of qacA/B resulted in higher susceptibilities to cationic antiseptic agents in MRSA isolated from patients with impetigo and SSSS.