Global Analysis of the Staphylococcus aureus Response to Mupirocin

Abstract

In the present study, we analyzed the response of S. aureus to mupirocin, the drug of choice for nasal decolonization. Mupirocin selectively inhibits the bacterial isoleucyl-tRNA synthetase (IleRS), leading to the accumulation of uncharged isoleucyl-tRNA and eventually the synthesis of (p)ppGpp. The alarmone (p)ppGpp induces the stringent response, an important global transcriptional and translational control mechanism that allows bacteria to adapt to nutritional deprivation. To identify proteins with an altered synthesis pattern in response to mupirocin treatment, we used the highly sensitive 2-dimensional gel electrophoresis technique in combination with mass spectrometry. The results were complemented by DNA microarray, Northern blot, and metabolome analyses. Whereas expression of genes involved in nucleotide biosynthesis, DNA metabolism, energy metabolism, and translation was significantly downregulated, expression of isoleucyl-tRNA synthetase, the branched-chain amino acid pathway, and genes with functions in oxidative-stress resistance (ahpC and katA) and putative roles in stress protection (the yvyD homologue SACOL0815 and SACOL1759 and SACOL2131) and transport processes was increased. A comparison of the regulated genes to known regulons suggests the involvement of the global regulators CodY and SigB in shaping the response of S. aureus to mupirocin. Of particular interest was the induced transcription of genes encoding virulence-associated regulators (i.e., arlRS, saeRS, sarA, sarR, sarS, and sigB), as well as genes directly involved in the virulence of S. aureus (i.e., fnbA, epiE, epiG, and seb). Staphylococcus aureus is both a colonizer and a human pathogen. Due to its ability to express an impressive arsenal of different virulence factors, S. aureus is able to cause a variety of diseases ranging from mild skin infections to more severe and life-threatening conditions, such as osteomyelitis, endocarditis, and sepsis. With the emergence of multiresistant strains, antimicrobial therapy of S. aureus infections has become an increasing challenge.Mupirocin (pseudomonic acid A) was first isolated from Pseudomonas fluorescens NCIB 10586 and has since proven its value as a topical agent in the treatment of S. aureus-associated wound infections. Furthermore, recent studies have shown that nasal decolonization of S. aureus carriers significantly reduces the risk of S. aureus infections after surgery (16, 28). However, the emergence of resistance to mupirocin after common use has increasingly hampered its use as the topical agent of choice for the elimination of methicillin-resistant Staphylococcus aureus (MRSA) carriage (6,37,75,100,112,119).Although the chemical structure of mupirocin is significantly different from that of isoleucyl-adenylate (Ile-AMP) (23), it was demonstrated that it is a structural analogue of Ile-AMP and competes with Ile-AMP for overlapping binding sites of the eubacterial and archaeal isoleucyl-tRNA synthetases (IleRSs) (66,67,91,120). As a consequence, addition of mupirocin blocks the ...

Two Small (p)ppGpp Synthases in Staphylococcus aureus Mediate Tolerance against Cell Envelope Stress Conditions

“…However, one can assume that under more physiological conditions, the impact of the enzymes may differ substantially. This is supported by the observation that the cell wall stress stimulon (27,28) has little overlap with the stringent response imposed by amino acid limitation or mupirocin (23,44,45). Thus, whether there is a quantitative or qualitative difference between the outcomes of RSH versus RelP/Q activity in S. aureus needs further evaluation.…”

ω-Hydroxyemodin Limits Staphylococcus aureus Quorum Sensing-Mediated Pathogenesis and Inflammation

“…In contrast, the expression of the enterotoxin gene set7 decreased with OHM in LAC but not LAC⌬agr, and OHM had no effect on the expression of the saeR component of the SaeRS virulence regulator. Likewise, the transcription of genes involved in the stress response (asp23, crtM, and clpB) was not altered by OHM, suggesting that OHM does not induce a general stress response in LAC under the conditions tested (50)(51)(52)(53)(54). Among the metabolism genes examined, OHM had no significant effect on the transcription of the genes involved in electron transport (atpG and sdhA).…”

Deep sternal wound infection after cardiac surgery: Evidences and controversies

“…The Society of Thoracic Surgeons practice guidelines upon antimicrobial prophylaxis recommend routine 5-d mupirocin 2% nasal administration for all patients undergoing cardiac surgery in the absence of a documented negative testing for staphylococcal colonization [41] . However, concerns still remain about the extensive use of mupirocin because of lack of efficacy, risk of widespread high-level resistance, and costs [42][43][44] . A systematic review of the literature and meta-analysis by Kallen et al [45] demonstrated a 45% reduction in surgical site infections (SSIs) caused by Staphylococcus aureus with the use of preoperative mupirocin among cardiac surgery patients known to be colonized with Staphylococcus aureus.…”