S lugdunensis

S. lugdunensis NVE requires special mention because of its reputed aggressive nature. S. lugdunensis was first described by Freney et al. in 1988 [282], deriving its species name from Lyon (Latin adjective of Lugdunum), the French city where it was first isolated [283]. As with other CoNS, it is commonly found on the skin [283]. S. lugdunensis, however, is particularly common in the perineal area, which was felt to be the source of NVE in 10 of 21 cases where a portal of entry was known [284].

The identification of S. lugdunensis in the microbiology laboratory can be made difficult because some strains may test positive on the slide coagulase test (see above) [285]. As such, such isolates may be misidentified as S. aureus. This misidentification can be overcome by performing the tube coagulase test, which is negative for S. lugdunensis. Other features suggestive of S. lugdunensis include the production of ornithine decarboxylase and pyrrolidonyl ary-lamidase [282]. The correct identification of S. lugdunensis is critical because of the severe disease associated with it, which may be anticipated or preempted with early speciation.

S. lugdunensis NVE is uncommon, with a recent review of the English literature identifying 48 reported cases [284]. Of these, a ful minant course with symptoms < 3 weeks in duration was reported in 74% of cases. Cardiac complications were particularly common: intracardiac abscess formation (23%), perforation, and destruction of a valve (21%), and large vegetations (11%). Systemic emboli with metastatic foci of infection occurred in 32% of cases.

S. lugdunensis is generally susceptible in vitro to P-lactams [284,286]. In a study of 59 clinically significant isolates of S. lugdunensis, 76% were P-lactamase negative, and all strains were susceptible to oxacillin, cephalothin, gentamicin, rifampin, and vancomycin [287]. Therapy should be guided by susceptibility data, and in most instances, a P-lactam plus rifampin or gen-tamicin is adequate therapy [288]. Because the MICs of penicillin are usually > 2 dilutions lower than that of oxacillin, penicllin intravenously may be the drug of choice once antimicrobial suscepbility testing confirms it as an option [284,289].

Unfortunately, because of the destructive nature of this pathogen, surgical intervention is almost always necessary, despite "adequate antimicrobial coverage." In particular, S. lugdunensis NVE is characterized by a shorter, more aggressive clinical history, perivalvular abscess formation, and a high mortality rate. In a review by Vandenesch et al. in 1993 [290], the mortality rate from this disease was 70%, and only 35% of the cases underwent surgery. After 1993, with early cardiac surgery occurring in 64% of cases, the mortality rate was 18% [284]. Although the numbers are small, it is felt that the decrease in mortality is attributed directly to early surgical intervention.

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