Following a change in surgical practice, we noted that the rate at which Staphylococcus lugdunensis was isolated from samples from the plastic surgery unit of our hospital increased considerably. We investigated the sources of these S. lugdunensis strains, and we found that in the case of drain colonization or surgical site infection, the strain was more likely to have come from the patient's skin bacteria when the pubic site had been shaved preoperatively. To test the hypothesis of pubic site colonization, we evaluated the prevalence of S. lugdunensis carriage among the cutaneous flora of the inguinal area. We found that 22% of 140 incoming patients carried S. lugdunensis in this area and that carriage at both inguinal folds was frequent (68% of carriers). A study of the genetic structure of the total population, including the clinical (n ؍ 18) and the commensal (n ؍ 53) strains, revealed that the diversity of the species was low and that the population was composed of two major groups that diverged at a distance of 35%. No particular characteristics made it possible to distinguish between clinical and commensal strains. Only isolates producing -lactamase were homogeneous; six of the eight -lactamase-positive strains displayed the same pulsed-field gel electrophoresis pattern.Staphylococcus lugdunensis is a coagulase-negative Staphylococcus (CoNS) that was first described by Freney et al. (9) in 1988 and that has the potential to be an opportunistic pathogen. S. lugdunensis is an unusually virulent CoNS and can cause many types of infection, ranging from superficial skin infections to life-threatening endocarditis. Most laboratory isolates are collected from colonized patients or patients with primary skin infections or minor postoperative wound infections. Nevertheless, S. lugdunensis has been shown to be associated with serious infections such as breast abscesses (18, 34), peritonitis (19, 28), infected joint prostheses (26, 35), osteomyelitis (22), discitis (2), septic arthritis (12), and pacemaker infections (1,3,16). Unlike S. epidermidis, which usually results in indolent subacute infections, S. lugdunensis results in acute infections, similar to S. aureus. S. lugdunensis infections typically resemble S. aureus infections in terms of the virulence of the organism and the clinical course of infection, which is often highly destructive (28, 31, 33).S. lugdunensis can act as an etiologic agent of infective endocarditis. It may infect both prosthetic and native valves (31). Patel et al. (24) found that S. lugdunensis accounted for 18% of CoNS strains causing infective endocarditis and 44% of CoNS strains causing native valve endocarditis. The mortality rate as a result of endocarditis caused by S. lugdunensis is high (7,15,31). Few studies have looked at the epidemiology and ecology of S. lugdunensis. Similar to other CoNS strains, S. lugdunensis is considered part of the resident flora of the entire surface of the human skin and mucous membranes (11). No detailed studies have been carried out on the d...