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

Abstract

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.

Staphylococcus haemolyticus strains target mitochondria and induce caspase-dependent apoptosis of macrophages

“…They reported that 18 of 35 strains were toxin positive and some of them produced more than one toxin. The most prevalent staphylococcal enterotoxins (SE) were SED and SEH, whilst two strains produced exfoliative toxin A. Vasconcelos et al (2011) observed that 40 % of S. haemolyticus strains that originated from newborns hospitalized at a neonatal unit contained staphylococcal enterotoxins G (SEG) genes. High cytotoxic activity (more than 50 %) to keratinocytes has also been observed for 7 of 35 of Staphylococcus aureus clinical isolates (Krut et al 2003).…”

VISLISI trial, a prospective clinical study allowing identification of a new metalloprotease and putative virulence factor from Staphylococcus lugdunensis

“…In addition, S. lugdunensis encodes a streptolysin S-like toxin system and iron-regulated surface determinant similar to S. aureus in terms of organization and sequence. Genes for enterotoxins G and I were identified from clinical samples [8]. The clinical presentation of severe S. lugdunensis infection may be caused by virulence factor production.…”

Expression of superantigens and the agr system in Staphylococcus epidermidis

“…Cunha et al [21] investigated the presence of enterotoxin A and D and TSST-1 genes in Staphylococcus strains isolated from clinical samples of newborns seen at the same hospital as the present study by PCR and found that 40% of the CoNS isolates were positive for at least one of the genes. The authors also observed that 32.2% of the same CoNS isolates carried at least one of the following genes: see, seg, seh, and sei [22].…”