Antibody reactivity of a standardized human serum protein solution against a spectrum of microbial pathogens and toxins: comparison with fresh frozen plasma

Genotypic and phenotypic characteristics of Escherichia coli involved in transfusion-transmitted bacterial infections: implications for preventive strategies

BACKGROUND

Transfusion-transmitted bacterial infections (TTBIs) are the main residual infectious complications of transfusions. Escherichia coli and platelet (PLT) concentrates may be epidemiologically associated, leading to severe, if not lethal, TTBIs. We investigated the genotypic and phenotypic reasons for this clinically deleterious combination.

STUDY DESIGN AND METHODS

We investigated a French national E. coli strain collection related to six independent episodes of TTBIs. Their phenotypic characterizations included antibiotic susceptibility testing, growth testing under different culture conditions, serum survival assays, and virulence in a sepsis mouse model. Their genotypic characterizations included polymerase chain reaction phylotyping, whole genome sequencing, and a subsequent in silico analysis.

RESULTS

We highlighted a selection process of highly extraintestinal virulent strains, mainly belonging to the B2 phylogroup, adapted to the hostile environment (high citrate concentration and a bactericidal serum effect) of apheresis-collected platelet concentrates (PCs). Compared to controls, the E. coli TTBI strains grew faster in the PCs due to a superior ability to capture iron. The in vitro growth performances were highly compatible with blood-derived product real-life conditions, including storage conditions and delays. The consistent serum resistance of TTBI strains promotes their survival in both the donor's and the receiver's blood and in the PCs.

CONCLUSION

This study pointed out that E. coli strains responsible for TTBI exhibit very specific traits. They belong to the extraintestinal pathogenic phylogroups and have a high intrinsic virulence. They can be resistant to complement, capture iron, and grow in the apheresis-collected PCs. These findings therefore support the reinforcement of the postdonation information.

Transcriptional Profiling of C. albicans in a Two Species Biofilm with Rothia dentocariosa

Biofilms on silicone rubber voice prostheses are the major cause for frequent failure and replacement of these devices. The presence of both bacterial and yeast strains has been suggested to be crucial for the development of voice prosthetic biofilms. Polymicrobial biofilms that include Candida albicans and Rothia dentocariosa are the leading cause of voice prosthesis failure. An in vitro biofilm comprising these two organisms was developed on silicone rubber, a material used for Groningen button voice prosthesis. We found that this biofilm environment was not conducive for C. albicans growth or differentiation. Global transcriptional analyses of C. albicans biofilm cells grown with R. dentocariosa revealed that genes with functions related to cell cycle progression and hyphal development were repressed >2-fold. The mixed species biofilms were more compact and less robust compared to C. albicans mono-species biofilms, even when developed under conditions of continuous nutrient flow. Under these conditions R. dentocariosa also significantly inhibited C. albicans biofilm dispersal. Preferential adherence of R. dentocariosa to candidal hyphae was mediated by the adhesin Als3.

Treatment of Staphylococcus aureus Infections

Staphylococcus aureus, although generally identified as a commensal, is also a common cause of human bacterial infections, including of the skin and other soft tissues, bones, bloodstream, and respiratory tract. The history of S. aureus treatment is marked by the development of resistance to each new class of antistaphylococcal antimicrobial drugs, including the penicillins, sulfonamides, tetracyclines, glycopeptides, and others, complicating therapy. S. aureus isolates identified in the 1960s were sometimes resistant to methicillin, a ß-lactam antimicrobial active initially against a majority S. aureus strains. These MRSA isolates, resistant to nearly all ß-lactam antimicrobials, were first largely confined to the health care environment and the patients who attended it. However, in the mid-1990s, new strains, known as community-associated (CA-) MRSA strains, emerged. CA-MRSA organisms, compared with health care-associated (HA-) MRSA strain types, are more often susceptible to multiple classes of non ß-lactam antimicrobials. While infections caused by methicillin-susceptible S. aureus (MSSA) strains are usually treated with drugs in the ß-lactam class, such as cephalosporins, oxacillin or nafcillin, MRSA infections are treated with drugs in other antimicrobial classes. The glycopeptide drug vancomycin, and in some countries teicoplanin, is the most common drug used to treat severe MRSA infections. There are now other classes of antimicrobials available to treat staphylococcal infections, including several that have been approved after 2009. The antimicrobial management of invasive and noninvasive S. aureus infections in the ambulatory and in-patient settings is the topic of this review. Also discussed are common adverse effects of antistaphylococcal antimicrobial agents, advantages of one agent over another for specific clinical syndromes, and the use of adjunctive therapies such as surgery and intravenous immunoglobulin. We have detailed considerations in the therapy of noninvasive and invasive S. aureus infections. This is followed by sections on specific clinical infectious syndromes including skin and soft tissue infections, bacteremia, endocarditis and intravascular infections, pneumonia, osteomyelitis and vertebral discitis, epidural abscess, septic arthritis, pyomyositis, mastitis, necrotizing fasciitis, orbital infections, endophthalmitis, parotitis, staphylococcal toxinoses, urogenital infections, and central nervous system infections.

Staphylococcal scalded skin syndrome: diagnosis and management in children and adults

Staphylococcal scalded skin syndrome is a potentially life-threatening disorder caused most often by a phage group II Staphylococcus aureus infection. Staphylococcal scalded skin syndrome is more common in newborns than in adults. Staphylococcal scalded skin syndrome tends to appear abruptly with diffuse erythema and fever. The diagnosis can be confirmed by a skin biopsy specimen, which can be expedited by frozen section processing, as staphylococcal scalded skin syndrome should be distinguished from life threatening toxic epidermal necrolysis. Histologically, the superficial epidermis is detached, the separation level being at the granular layer. The diffuse skin loss is due to a circulating bacterial exotoxin. The aetiological exfoliating toxin is a serine protease that splits only desmoglein 1. The exfoliative toxins are spread haematogenously from a localized source of infection, causing widespread epidermal damage at distant sites. Sepsis and pneumonia are the most feared complications. The purpose of this review is to summarize advances in understanding of this serious disorder and provide therapeutic options for both paediatric and adult patients. Recent epidemiological studies have demonstrated that paediatric patients have an increased incidence of Staphylococcal scalded skin syndrome during the summer and autumn. Mortality is less than 10% in children, but is between 40% and 63% in adults, despite antibacterial therapy. Previously, intravenous immunoglobulin had been recommended to combat Staphylococcal scalded skin syndrome, but a recent study associates its use with prolonged hospitalization.

Severe staphylococcal scalded skin syndrome in children

Staphylococcal scalded skin syndrome (SSSS) is a rare toxin-mediated condition caused by Staphylococcus aureus, which causes blistering and desquamation of the skin. Between November 2005 and April 2006, four children were admitted to critical care beds in the South West Regional Paediatric Burns Unit because of SSSS affecting more than 50% of the body surface area. Details of these cases are presented, highlighting the potential severity of the condition. The cases also illustrate that fluid overload is a common complication of the condition, despite hypovolaemia being the more obvious risk, and that both hyponatraemia and leukopenia are frequent findings. These summaries clearly demonstrate the need for paediatric critical care in a tertiary burns unit for children with SSSS affecting a large proportion of the body surface area. The cluster of admissions prompted us to write a management protocol for children with severe SSSS and a summary of this is provided. Most children with SSSS will initially present to general paediatric units, where mild cases will be managed, but severe cases should be promptly referred to a tertiary paediatric burns unit for multi-disciplinary care in a critical care environment.