tailieunhanh - Chapter 130. Streptococcal and Enterococcal Infections (Part 6)

Impetigo contagiosa is a superficial streptococcal or Staphylococcus aureus infection consisting of honey-colored crusts and erythematous weeping erosions. Occasionally, bullous lesions may be seen. (Courtesy of Mary Spraker, MD.) The classic presentation of impetigo usually poses little diagnostic difficulty. Cultures of impetiginous lesions often yield S. aureus as well as GAS. In almost all cases, streptococci are isolated initially and staphylococci appear later, presumably as secondary colonizing flora. In the past, penicillin was nearly always effective against these infections. However, an increasing frequency of penicillin treatment failure suggests that S. aureus may have become more prominent as a cause of impetigo | Chapter 130. Streptococcal and Enterococcal Infections Part 6 Figure 130-3 3eu Fluil AS PL brtunvald e. Hjvitr ẸL Lonpo PL Jamtion JI Loictlie Ji h rĩìỉữrì ỉ rH2jỹ hi r ữf ỉnt rĩĩ J 17th Editiani httpi ww aoc rxtTi d dn .cpm CopVHflht Th Co-mpiRitt ns. All Hghtí uUítdâíĩCỈ Impetigo contagiosa is a superficial streptococcal or Staphylococcus aureus infection consisting of honey-colored crusts and erythematous weeping erosions. Occasionally bullous lesions may be seen. Courtesy of Mary Spraker MD. The classic presentation of impetigo usually poses little diagnostic difficulty. Cultures of impetiginous lesions often yield S. aureus as well as GAS. In almost all cases streptococci are isolated initially and staphylococci appear later presumably as secondary colonizing flora. In the past penicillin was nearly always effective against these infections. However an increasing frequency of penicillin treatment failure suggests that S. aureus may have become more prominent as a cause of impetigo. Bullous impetigo due to S. aureus is distinguished from typical streptococcal infection by more extensive bullous lesions that break down and leave thin paper-like crusts instead of the thick amber crusts of streptococcal impetigo. Other skin lesions that may be confused with impetigo include herpetic lesions either those of orolabial herpes simplex or those of chickenpox or zoster. Herpetic lesions can generally be distinguished by their appearance as more discrete grouped vesicles and by a positive Tzanck test. In difficult cases cultures of vesicular fluid should yield GAS in impetigo and the responsible virus in Herpesvirus infections. Streptococcal Impetigo Treatment Treatment of streptococcal impetigo is the same as that for streptococcal pharyngitis. In view of evidence that S. aureus has become a relatively frequent cause of impetigo empirical regimens should cover both streptococci and S. aureus. For example either dicloxacillin or cephalexin can be given at a