Nasal, axillary, and perineal carriage of Staphylococcus aureus among women: identification of strains producing epidermolytic toxin

Nasal carriage of Staphylococcus aureus: epidemiology, underlying mechanisms, and associated risks

Staphylococcus aureus has long been recognized as an important pathogen in human disease. Due to an increasing number of infections caused by methicillin-resistant S. aureus (MRSA) strains, therapy has become problematic. Therefore, prevention of staphylococcal infections has become more important. Carriage of S. aureus appears to play a key role in the epidemiology and pathogenesis of infection. The ecological niches of S. aureus are the anterior nares. In healthy subjects, over time, three patterns of carriage can be distinguished: about 20% of people are persistent carriers, 60% are intermittent carriers, and approximately 20% almost never carry S. aureus. The molecular basis of the carrier state remains to be elucidated. In patients who repeatedly puncture the skin (e.g., hemodialysis or continuous ambulatory peritoneal dialysis [CAPD] patients and intravenous drug addicts) and patients with human immunodeficiency virus (HIV) infection, increased carriage rates are found. Carriage has been identified as an important risk factor for infection in patients undergoing surgery, those on hemodialysis or CAPD, those with HIV infection and AIDS, those with intravascular devices, and those colonized with MRSA. Elimination of carriage has been found to reduce the infection rates in surgical patients and those on hemodialysis and CAPD. Elimination of carriage appears to be an attractive preventive strategy in patients at risk. Further studies are needed to optimize this strategy and to define the groups at risk.

Demonstration of mother-to-infant transmission of Staphylococcus aureus by pulsed-field gel electrophoresis

We assessed mother-to-infant transmission of Staphylococcus aureus. Anterior nares swabs of 466 pregnant women, vaginal swabs of 305 of these women and anterior nares swabs of 305 6-day-old infants were examined for the presence of S. aureus. The results showed that 7.5% of the vaginal swabs from the pregnant women and 10.1% of the anterior nares swabs from the infants were positive for S. aureus. Six of the 466 pregnant women (1.3%) and 12 of the 305 infants (3.9%) carried methicillin-resistant S. aureus (MRSA) in the anterior nares site, but none of the vaginal specimens were positive for MRSA. Analysis of SmaI digested chromosomal DNA analysis using pulsed-field gel electrophoresis (PFGE) showed that methicillin-sensitive S. aureus (MSSA) strains obtained from four pairs of pregnant women and their infants were completely identical, which strongly suggests [correction of suggesting] mother-to-infant transmission of S. aureus.

CONCLUSION

This study elucidated the prevalence of S. aureus carriage among pregnant women and newborn infants. Mother-to-infant infection of S. aureus was demonstrated phenotypically and genetically. PFGE is a useful tool to detect infection routes including mother-to-infant infection.

Epidemiological analysis of strains of methicillin-resistant Staphylococcus aureus (MRSA) infection in the nursery; prognosis of MRSA carrier infants

Forty-five neonates who carried methicillin-resistant Staphylococcus aureus (MRSA) were studied. Retrospective molecular analysis using pulsed-field gel electrophoresis showed three separate MRSA epidemics in the nursery. Strains of MRSA isolated from the neonates were also isolated from the hospital environment and health care providers. Clinical manifestations included skin pustules (eight patients), conjunctivitis (four patients), or other minor infections (two patients). No neonate developed systemic infection. The prevalence of MRSA decreased with age. At one year, three (14.3%) of 21 infants that had carried MRSA at six days remained carriers and only two (1.1%) of 180 infants in a control 'S. aureus-negative at six days' group carried MRSA.

Staphylococcal scalded skin syndrome in an adult. Influence of immune and renal factors

We report a case of staphylococcal scalded skin syndrome in a 77-year-old man with an infected surgical wound. The patient was immunocompetent and had only mildly impaired renal function. The pathogenic and aetiological factors of the condition are discussed.

Impetigo: an overview

This article reviews in detail the pathogenesis, clinical characteristics and management of impetigo in children. Impetigo is the most common bacterial skin infection of children. Most cases of nonbullous impetigo and all cases of bullous impetigo are caused by Staphylococcus aureus. The remainder of cases of nonbullous impetigo are due to group A beta hemolytic streptococci (GABHS). GABHS colonize the skin directly by binding to sites on fibronectin that are exposed by trauma. In contrast, S. aureus colonizes the nasal epithelium first; from this reservoir, colonization of the skin occurs. Patients with recurrent impetigo should be evaluated for carriage of S. aureus. Superficial, localized impetigo may be treated successfully in more than 90% of cases with topical application of mupirocin ointment. Impetigo that is widespread or involves deeper tissues should be treated with a beta-lactamase-resistant oral antibiotic. The choice of antibiotics is affected by the local prevalence of resistance to erythromycin among strains of S. aureus, antibiotic cost and availability, and issues of compliance.

Skin microflora of atopic eczema in first time hospital attenders

The bacterial flora of the skin was assessed quantitatively in 50 children with eczema, aged 6 months to 14 years, referred to the hospital for the first time. Twenty nonatopic controls with an unrelated non-infective disorder were also studied. Cotton-tipped swabs and contact agar discs were taken from the worst affected area of eczema and from an uninvolved site in patients and from the forearm in controls. Swabs were also taken from the nose, axilla and groin in all children. Bacterial colonization of the skin was consistently more common and greater in amount from patients compared with controls. Staphylococcus aureus was the most common pathogen isolated from patients only; from the worst affected area of eczema in 74% of patients and from an uninvolved skin site in 30% of patients. Quantitative assessment showed that the density of colonization was proportional to the severity of eczema. The most common S. aureus phage group was group II accounting for 32% of strains. Resistance to penicillin was present in 88% of strains and to two or more antibiotics in 38% of strains. No relationship was noted between the pattern of resistance and phage group.