Diverse Enterotoxin Gene Profiles among Clonal Complexes of Staphylococcus aureus Isolates from the Bronx, New York

Abstract

Staphylococcal enterotoxins (SE) can cause toxin-mediated disease, and those that function as superantigens are implicated in the pathogenesis of allergic diseases. The prevalence of 19 enterotoxin genes was determined by PCR in clinical S. aureus strains derived from wounds (108) and blood (99). We performed spa typing and multilocus sequence typing (MLST) to determine clonal origin, and for selected strains staphylococcal enterotoxin B (SEB) production was measured by enzyme-linked immunosorbent assay. Strains carried a median of five SE genes. For most SE genes, the prevalence rates among methicillinresistant and methicillin-sensitive S. aureus isolates, as well as wound-and blood-derived isolates, did not differ. At least one SE gene was detected in all except two S. aureus isolates (>99%). Complete egc clusters were found in only 11% of S. aureus isolates, whereas the combination of sed, sej, and ser was detected in 24% of clinical strains. S. aureus strains exhibited distinct combinations of SE genes, even if their pulsed-field gel electrophoresis and MLST patterns demonstrated clonality. USA300 strains also showed considerable variability in SE content, although they contained a lower number of SE genes (mean, 3). By contrast, SE content was unchanged in five pairs of serial isolates. SEB production by individual strains varied up to 200-fold, and even up to 15-fold in a pair of serial isolates. In conclusion, our results illustrate the genetic diversity of S. aureus strains with respect to enterotoxin genes and suggest that horizontal transfer of mobile genetic elements encoding virulence genes occurs frequently.As a commensal, Staphylococcus aureus colonizes the nasal mucosa of 20 to 40% of humans (54), and as a pathogen it causes pyogenic diseases and toxin-mediated diseases (38). S. aureus produces many different virulence factors, including enterotoxins (SEs), which can cause defined toxic shock syndromes (4). The characterization of some of these toxins led to the discovery of superantigens (41), which bind to major histocompatibility complex class II molecules and V␤ chains of T-cell receptors, resulting in the activation of large numbers of T cells (20 to 30%) and massive cytokine production (10, 18). These superantigen-induced "cytokine storms" are responsible for the toxic effects seen in staphylococcal entertoxin B (SEB)-and toxic shock syndrome toxin (TSST)-associated shock syndromes in S. aureus infections (13, 40, 47). To date, 19 SEs have been identified based on sequence homologies, and studies have reported enterotoxin genes in up to 80% of all S. aureus strains (4, 21). Although many new enterotoxins have been identified, i.e., seg ser and seu (33,37,44,49), their precise functions have not been characterized yet. The majority of experimental work with SEs is still done with SEB, toxic shock syndrome toxin 1, and SEA (27, 31), because these toxins are commercially available. Most SEs are located on mobile elements in bacterial genomes such as plasmids or pathogenicity islands and can thu...

Mechanisms Mediating Enhanced Neutralization Efficacy of Staphylococcal Enterotoxin B by Combinations of Monoclonal Antibodies

“…ϳ0.75 Å). Our data identify 17 residues of SEB that bind 20B1 Fab , which are conserved among SEBs derived from diverse clinical methicillin-sensitive and -resistant Staphylococcus aureus strains (49). Interestingly, of those 17 residues, 14 are identical in SEC1, and 11 are identical in SEC2 and SEC3, and 10 are identical in SSA.…”

Detection and Measurement of Staphylococcal Enterotoxin-Like K (SEl-K) Secretion by Staphylococcus aureus Clinical Isolates

“…Epidemiological studies have demonstrated the SEl-K-encoding genes to be among the most common SE genes in S. aureus clinical isolates (10-14). Additionally, SEl-K is the only SE gene to our knowledge that is significantly associated with community-acquired methicillin-resistant S. aureus (CA-MRSA) strains of several clonal lineages (10,15,16). Interestingly, the neighboring SEl-Q enterotoxin is not significantly associated with MRSA (10).…”

Frequency of Panton-Valentine Leukocidin-Producing Methicillin-Sensitive Staphylococcus Strains in Patients with Complicated Skin and Soft Tissue Infection in Bronx, New York

“…In this study, we compared the prevalences of PVL in MSSA and MRSA strains from patients with skin and soft tissue infections (SSTIs) and compared the clinical presentations. S. aureus isolates from wound (n ϭ 108) and blood (n ϭ 99) were collected by the microbiology laboratory of Montefiore Medical Center as described previously (9). Detection of enterotoxin genes (staphylococcal enterotoxin A [SEA], SEB, SEC, and toxic shock syndrome toxin [TSST] genes), multilocus sequence typing (MLST), and spa typing were done in the context of a previously published study (9).…”

“…S. aureus isolates from wound (n ϭ 108) and blood (n ϭ 99) were collected by the microbiology laboratory of Montefiore Medical Center as described previously (9). Detection of enterotoxin genes (staphylococcal enterotoxin A [SEA], SEB, SEC, and toxic shock syndrome toxin [TSST] genes), multilocus sequence typing (MLST), and spa typing were done in the context of a previously published study (9). For this study, detection of PVL in MSSA isolates was performed by real-time PCR targeting the lukF-PV gene (7).…”