Outbreaks of Serratia marcescens in neonatal and pediatric intensive care units: clinical aspects, risk factors and management.

The following recommendations are derived from a systematic analysis of 34 Serratia marcescens outbreaks described in 27 publications from neonatal and pediatric intensive care units (NICU, PICU), in which genotyping methods were used to confirm or exclude clonality. The clinical observation of two or more temporally related cases of nosocomial S. marcescens infection should raise the suspicion of an outbreak, particularly in the NICU or PICU setting. Since colonized or infected patients represent the most important reservoir for cross transmission, hygienic barrier precautions (contact isolation/cohortation, the use of gloves and gowns in addition to strictly performed hand disinfection, enhanced environmental disinfection) should immediately be implemented and staff education given. Well-planned sampling of potential environmental sources should only be performed when these supervised barrier precautions do not result in containment of the outbreak. The current strategy of empiric antibiotic treatment should be reevaluated by a medical microbiologist or an infectious disease specialist. Empiric treatment of colonized children should use combination therapy informed by in vitro susceptibility data; in this context the high propensity of S. marcescens to cause meningitis and intracerebral abscess formation should be considered. In vitro susceptibility patterns do not reliably prove or exclude the clonality of the outbreak isolate. Genotyping of the isolates by pulse-field gel electrophoresis or PCR-based methods should be performed, but any interventions to interrupt further nosocomial spread should be carried out without waiting for the results.

Group G streptococcal bacteraemia: an opportunistic infection associated with immune senescence.

The number of cases of group G streptococcal bacteraemia reported worldwide is increasing. Twenty-six cases of group G streptococcal bacteraemia were identified during a 70-month period at a single university teaching hospital in Sheffield, UK. These cases represented 20% of all bacteraemias due to beta-hemolytic Streptococci, a higher proportion than previously reported. The median age of these cases was 72 y and although medical comorbidities were common only cutaneous ulceration was clearly linked to the presenting syndromes. The skin was the source of infection in 16 cases (62%) and the most frequent clinical presentations were cellulitis in 13 cases (50%) and endovascular infection in 5 (19%). Eight (31%) of the cases died during the period of follow-up but only 2 deaths were related to the streptococcal infection. Immunosenescence represents the major risk factor for group G streptococcal infection in this population and comorbidities, including carcinoma, may be markers of the senescent immune system rather than direct contributing factors to group G streptococcal bacteraemia.