Septic pseudarthrosis caused by Serratia plymuthica

Serratia infections: from military experiments to current practice

Serratia species, in particular Serratia marcescens, are significant human pathogens. S. marcescens has a long and interesting taxonomic, medical experimentation, military experimentation, and human clinical infection history. The organisms in this genus, particularly S. marcescens, were long thought to be nonpathogenic. Because S. marcescens was thought to be a nonpathogen and is usually red pigmented, the U.S. military conducted experiments that attempted to ascertain the spread of this organism released over large areas. In the process, members of both the public and the military were exposed to S. marcescens, and this was uncovered by the press in the 1970s, leading to U.S. congressional hearings. S. marcescens was found to be a certain human pathogen by the mid-1960s. S. marcescens and S. liquefaciens have been isolated as causative agents of numerous outbreaks and opportunistic infections, and the association of these organisms with point sources such as medical devices and various solutions given to hospitalized patients is striking. Serratia species appear to be common environmental organisms, and this helps to explain the large number of nosocomial infections due to these bacteria. Since many nosocomial infections are caused by multiply antibiotic-resistant strains of S. marcescens, this increases the danger to hospitalized patients, and hospital personnel should be vigilant in preventing nosocomial outbreaks due to this organism. S. marcescens, and probably other species in the genus, carries several antibiotic resistance determinants and is also capable of acquiring resistance genes. S. marcescens and S. liquefaciens are usually identified well in the clinical laboratory, but the other species are rare enough that laboratory technologists may not recognize them. 16S rRNA gene sequencing may enable better identification of some of the less common Serratia species.

Serratia infections in a general hospital: characteristics and outcomes

We aimed to present our experience regarding infections caused by Serratia spp. in a region with relatively high antimicrobial resistance rates. We retrospectively reviewed the databases of the microbiological laboratory of the University Hospital of Heraklion, Crete (2/2004-12/2009). A total of 77 patients [67.5% men, mean age ± standard deviation (SD) = 56.9 ± 24.5 years) were identified; 37.7% were outpatients. Sixty-five (84.4%) of the 77 included patients had a Serratia marcescens isolate; the remaining 12 patients had a non-marcescens Serratia spp. The most frequently observed infections were respiratory tract infection (32.5%) and keratitis/endophthalmitis (20.8%). Seventy-three (94.9%) patients were cured. Four deaths were observed; three of them were considered as attributed to the Serratia infection. No difference was found regarding the characteristics and outcomes between patients with Serratia marcescens and non-marcescens infections. In addition, antipseudomonal penicillins and their combinations with beta-lactamase inhibitors, as well as carbapenemes, and fluoroquinolones exhibited high antimicrobial activity against both the tested Serratia marcescens and non-marcescens isolates. Our study adds useful information regarding the characteristics and outcomes of patients with Serratia infection, as well as the susceptibilities of the respective Serratia marcescens and non-marcescens isolates, in a region with relatively high levels of antimicrobial resistance.

Antibiotic susceptibility profiles of uncommon bacterial species causing severe infections in Italy

This study presents the results of the italian "Severe infections project" involving bacteria that can be considered rare causes of disease. we isolated 30 uncommon human pathogens from a total of 60 strains (1.2% of all the isolates). The most frequent sources of uncommon human pathogens were primary bloodstream infections (48.3%) and pneumonia (20%). Species such as Comamonas testosteroni, Enterococcus hirae, Kluyvera ascorbata, Kluyvera cryocrescens, Leclercia adecarboxylata and Ochrobactrum anthropi were recovered from bacteremia patients. Clinically useful antimicrobial agents were tested against each isolate. Resistance to 4 or more antibiotics tested was found in Achromobacter xylosoxidans, O. anthropi, Pseudomonas stutzeri, Citrobacter braakii, Enterobacter sakazakii, K. ascorbata, Proteus penneri and Serratia plymuthica. About 16% of the Gram-negative species were resistant to third-generation cephalosporins and 28.6% of the staphylococci were oxacillin-resistant. the results from this study offer indications for empirical therapy for severe infections from uncommon human pathogens.