Infections cutanées causées par des mycobactéries à croissance rapide [Skin infections due to rapid-growing mycobacteria].

Rapid-growing mycobacteria (e.g. M. abscessus and M. chelonae) are emerging pathogens with various clinical manifestations. Among immunocompetent individuals, rapid-growing mycobacteria may be responsible of pulmonary, cutaneous, osteoarticular and postoperative infections, as well as lymphadenitis and catheter-associated infections. Among immunocompromised patients, disseminated infections are also observed. Diagnosis relies on specific microbiological investigations to confirm etiology and guide antibiotic treatment. The treatment requires a multi-disciplinary approach that includes specific long-term antibiotic treatment, surgical debridement and reduction of immunosuppression whenever possible.

New and emerging treatment of Staphylococcus aureus infections in the hospital setting.

Methicillin-resistant Staphylococcus aureus (MRSA), both hospital-acquired and community-acquired, is a dangerous pathogen that is involved in an increasing number of serious infections with high risk for morbidity and mortality. Community-acquired MRSA strains have epidemic potential and can be particularly virulent. Vancomycin has been the standard hospital treatment for the past 40 years, but vancomycin-resistant isolates of S. aureus have emerged in the USA, and vancomycin-intermediate isolates are increasingly being reported worldwide. New antimicrobial agents with activity against multidrug-resistant S. aureus and other resistant pathogens are urgently needed. Despite great strides, further advances in our understanding of the molecular and biochemical mechanisms responsible for antimicrobial resistance are still required. Several agents have been recently approved for the treatment of serious Gram-positive infections, including linezolid, daptomycin, and tigecycline. The novel investigational cephalosporin, ceftobiprole, is one of the first penicillinase-resistant agents to target penicillin-binding protein 2a (or PBP2a), an acquired PBP with low beta-lactam-affinity that confers intrinsic beta-lactam resistance to S. aureus and other staphylococci. This mechanism of PBP binding, including inhibition of PBP2a, confers broad-spectrum activity against clinically important Gram-negative and Gram-positive pathogens, including MRSA. Phase III clinical trials comparing ceftobiprole with vancomycin alone and in combination with ceftazidime for the treatment of complicated skin and skin structure infections showed ceftobiprole to have efficacy similar to the efficacy of these comparators as evidenced by non-inferior clinical cure and microbiological eradication rates.

The efficacy of amoxycillin/clavulanate (Augmentin) in the treatment of severe staphylococcal infections.

The experimental and clinical values of amoxycillin/clavulanate in severe Staphylococcus aureus infections are reviewed. Experimentally, amoxycillin/clavulanate was highly effective in the treatment of acute endocarditis due to methicillin-sensitive isolates of S. aureus (MSSA) in rats. In addition, high doses of amoxycillin/clavulanate also cured experimental endocarditis due to methicillin-resistant strains of S. aureus (MRSA) in the animal model. In the clinical setting, a review of 86 patients with either community- or hospital-acquired bacteraemia due to MSSA showed that intravenous treatment with amoxycillin/clavulanate was adequate for empirical (and apparently also long-term) therapy of such severe infections. However, the retrospective nature of the analysis did not allow assessment of the relative efficacy of amoxycillin/clavulanate as compared with standard anti-staphylococcal drugs, such as flucloxacillin or vancomycin. Further prospective studies are warranted to address this issue. Thus, amoxycillin/clavulanate appears to be a good candidate for empirical treatment of severe infections that may be caused by MSSA. Usage of amoxycillin/clavulanate against MRSA is, however, still experimental and is not currently advocated for the treatment of MRSA infections in humans.

Efficacy of trovafloxacin in treatment of experimental staphylococcal or streptococcal endocarditis.

The efficacy of trovafloxacin against Staphylococcus aureus and viridans group streptococci was investigated in vitro and in an experimental model of endocarditis. The MICs at which trovafloxacin and ciprofloxacin inhibited 90% of clinical isolates of such bacteria (MIC90s) were (i) 0.03 and 2 mg/liter, respectively, for 30 ciprofloxacin-susceptible S. aureus isolates, (ii) 32 and 128 mg/liter, respectively, for 20 ciprofloxacin-resistant S. aureus isolates, and (iii) 0.25 and 8 mg/liter, respectively, for 28 viridans group streptococci. Rats with aortic vegetations were infected with either of two ciprofloxacin-susceptible but methicillin-resistant S. aureus strains (strains COL and P8), one penicillin-susceptible Streptococcus sanguis strain, or one penicillin-resistant Streptococcus mitis strain. Rats were treated for 3 or 5 days with doses that resulted in kinetics that simulated those achieved in humans with trovafloxacin (200 mg orally once a day), ciprofloxacin (750 mg orally twice a day), vancomycin (1 g intravenously twice a day), or ceftriaxone (2 g intravenously once a day). Against the staphylococci, the activities of both trovafloxacin and ciprofloxacin were equivalent to that of vancomycin, and treatment of endocarditis with these drugs was successful (P < 0.05). However, ciprofloxacin selected for resistant derivatives in vitro and in vivo, whereas trovafloxacin was 10 to 100 times less prone than ciprofloxacin to select for resistance in vitro and did not select for resistance in vivo. Against the two streptococcal isolates, trovafloxacin significantly (P < 0.05) decreased bacterial counts in the vegetations but was less effective than the control drug, ceftriaxone. Thus, a simulated oral dose of trovafloxacin (200 mg per day) was effective against ciprofloxacin-susceptible staphylococci and was less likely than ciprofloxacin to select for resistance. The simulated oral dose of trovafloxacin also had some activity against streptococcal endocarditis, but optimal treatment of infections caused by such organisms might require higher doses of the drug.

Surgery and granulocyte transfusions for life-threatening infections in chronic granulomatous disease.

We report two patients with chronic granulomatous disease (CGD) and life-threatening infections: a 10 10/12-year-old boy had Aspergillus fumigatus spondylitis with destruction of the 11th vertebral body and paravertebral abscess formation, and an 8 5/12-year-old boy had multiple Staphylococcus aureus hepatic abscesses with subphrenic abscess formation. Both patients failed to respond to intense antimicrobial therapy but showed a remarkable recovery following surgical drainage combined with granulocyte transfusions. These results suggest that antimicrobial therapy and surgical drainage followed by granulocyte transfusions may be the ideal mode of treatment for severe infections in patients with CGD.

Pursestring closure of the stoma site leads to fewer wound infections: results from a multicenter randomized controlled trial.

BACKGROUND: Surgical site infection after stoma reversal is common. The optimal skin closure technique after stoma reversal has been widely debated in the literature. OBJECTIVE: We hypothesized that pursestring near-complete closure of the stoma site would lead to fewer surgical site infections compared with conventional primary closure. DESIGN: This study was a parallel prospective multicenter randomized controlled trial. SETTINGS: This study was conducted at 2 university medical centers. PATIENTS: Patients (N = 122) presenting for elective colostomy or ileostomy reversal were selected. INTERVENTIONS: Pursestring versus conventional primary closure of stoma sites were compared. MAIN OUTCOME MEASURES: Stoma site surgical site infection within 30 days of surgery, overall surgical site infection, delayed healing (open wound for >30 days), time to wound epithelialization, and patient satisfaction were the primary outcomes measured. RESULTS: The pursestring group had a significantly lower stoma site infection rate (2% vs 15%, p = 0.01). There was no difference in delayed healing or patient satisfaction between groups. Time to epithelialization was measured in only 51 patients but was significantly longer in the pursestring group (34.6 ± 20 days vs 24.1 ± 17 days, p = 0.02). LIMITATIONS: This study was limited by the variability in procedures and surgeons, the limited follow-up after 30 days, and the inability to perform blinding. CONCLUSION: Pursestring closure after stoma reversal has a lower risk of stoma site surgical site infection than conventional primary closure, although wounds may take longer to heal with the use of this approach. REGISTRATION NUMBER: NCT01713452 (www.clinicaltrials.gov).

Clinical consensus conference: survey on Gram-positive bloodstream infections with a focus on Staphylococcus aureus.

The increased incidence over the past decade of bloodstream infections (BSIs) caused by gram-positive bacteria, particularly methicillin-resistant Staphylococcus aureus, highlights the critical need for a consistent approach to therapy. However, there is currently no international consensus on the diagnosis and management of gram-positive BSIs. The Clinical Consensus Conference on Gram-Positive Bloodstream Infections was convened as a session at the 9th International Symposium on Modern Concepts in Endocarditis and Cardiovascular Infections held in 2007. Participants discussed various aspects of the practical treatment of patients who present with gram-positive BSI, including therapeutic options for patients with BSIs of undefined origin, the selection of appropriate empirical therapy, and treatment of complicated and uncomplicated BSIs. The opinions of participants about these key issues are reflected in this article.

Dermatophyte identification in skin and hair samples using a simple and reliable nested polymerase chain reaction assay.

BACKGROUND: Dermatophyte identification in tinea capitis is essential for choosing the appropriate treatment and in tinea infections to identify the possible source. The failure of fungi to grow in cultures frequently occurs, especially in cases of previous antifungal therapy. OBJECTIVES: To develop a rapid polymerase chain reaction (PCR) sequencing assay for dermatophyte identification in tinea capitis and tinea corporis. MATERIAL AND METHODS: Fungal DNA was extracted from hair and skin samples that were confirmed to be positive by direct mycological examination. Dermatophytes were identified by the sequence of a 28S ribosomal DNA subunit amplicon generated by nested PCR. RESULTS: Nested PCR was found to be necessary to obtain amplicons in substantial amounts for dermatophyte identification by sequencing. The results agreed with those of classical mycological identification in 14 of 23, 6 of 10, and 20 of 23 cases of tinea capitis, tinea corporis and tinea pedis, respectively, from which a dermatophyte was obtained in culture. In seven of the 56 cases, another dermatophyte was identified, revealing previous misidentification. A dermatophyte was identified in 12 of 18, three of five, and four of nine cases of tinea capitis, tinea corporis and tinea pedis, respectively, in cases in which no dermatophyte grew in culture. CONCLUSIONS: Although the gold standard dermatophyte identification from clinical samples remains fungal cultures, the assay developed in the present study is especially suitable for tinea capitis. Improved sensitivity for the identification of dermatophyte species was obtained as it is possible to identify the dermatophyte when the fungus fails to grow in cultures.

Antibiotic lock technique combined with systemic antimicrobial therapy for management of port-related bloodstream infections in onco-haematological patients without catheter removal

Background : Port-related bloodstream infection (PRBSI) is a common complication associated with long-term use of ports systems. Systemic antimicrobial therapy (ST) and removal of the device is the standard management of PRBSI. However, a conservative management combining ST with antibiotic lock therapy (ALT) without port removal has been suggested as an alternative management option for infections due to gram-positive skin colonizers with low virulence.¦Objectives : i) to assess the frequency of management of PRBSI in onco-hematological patients by combining the ALT with ST, without catheter removal and ii) to analyze the efficacy of such an approach.¦Methods : Retrospective observational study over a 6-year period between 2005 and 2010, including patients who where diagnosed with PRBSI and who were treated with ST and ALT. PRBSI diagnosis consisted in clinical signs of bacteremia with blood cultures positive for gram-positive skin colonizers. The primary endpoint was failure to cure the PRBSI.¦Results : 61 port infections were analysed, of which 23 PRBSI met the inclusion criteria. All the patients were suffering from haematological conditions and 75% were neutropenic at the time of PRBSI diagnosis. S. epidermidis was responsible for 91% of PRBSI (21/23). The median duration of ST was 14 days (range 7-35) and the median duration of ALT was 15 days (range 8-41). Failure to cure the PRBSI requiring port removal was observed in 4 patients, but was not associated with severe infectious complications. Kaplan-Meier analysis showed a success rate in port salvage at day 180 (6 months) of 78% (95%CI 59-97%).¦Conclusion : The success rate observed in the present study suggests that combining ST and ALT is an effective option to conservatively treat PRBSI caused by pathogens of low virulence such as S. epidermidis.

Plasmacytoid dendritic cells sense skin injury and promote wound healing through type I interferons.

Plasmacytoid dendritic cells (pDCs) are specialized type I interferon (IFN-α/β)-producing cells that express intracellular toll-like receptor (TLR) 7 and TLR9 and recognize viral nucleic acids in the context of infections. We show that pDCs also have the ability to sense host-derived nucleic acids released in common skin wounds. pDCs were found to rapidly infiltrate both murine and human skin wounds and to transiently produce type I IFNs via TLR7- and TLR9-dependent recognition of nucleic acids. This process was critical for the induction of early inflammatory responses and reepithelization of injured skin. Cathelicidin peptides, which facilitate immune recognition of released nucleic acids by promoting their access to intracellular TLR compartments, were rapidly induced in skin wounds and were sufficient but not necessary to stimulate pDC activation and type I IFN production. These data uncover a new role of pDCs in sensing tissue damage and promoting wound repair at skin surfaces.

VARIABILITY OF PHENOTYPIC, PROTEOMIC AND TRANSCRIPTOMIC EXPRESSION OF STAPHYLOCOCCUS AUREUS SURFACE ADHESINS

Staphylococcus aureus is a highly successful pathogen responsible of a wide variety of diseases, from minor skin infection to life-threatening sepsis or infective endocarditis, as well as food poisoning and toxic shock syndrome. This heterogeneity of infections and the ability of S. aureus to develop antibiotic-resistance to virtually any available drugs reflect its extraordinary capacity to adapt and survive in a great variety of environments. The pathogenesis of S. aureus infection involves a wide range of cell wall-associated adhesins and extracellular toxins that promote host colonization and invasion. In addition, S. aureus is extremely well equipped with regulatory systems that sense environmental conditions and respond by fine tuning the expression of metabolic and virulence determinants. Surface adhesins referred to MSCRAMMs - for Microbial Surface Component Recognizing Adherence Matrix Molecules - mediate binding to the host extracellular matrix or serum components, including fibrinogen, fibronectin, collagen and elastin, and promote tissue colonization and invasion. Major MSCRAMMs include a family of surface-attached proteins covalently bound to the cell wall peptidoglycan via a conserved LPXTG motif. Genomic analyses indicate that S. aureus contain up to 22 LPXTG surface proteins, which could potentially act individually or in synergy to promote infection. In the first part of this study we determined the range of adherence phenotypes to fibrinogen and fibronectin among 30 carriage isolates of S. aureus and compared it to the adherence phenotypes of 30 infective endocarditis and 30 blood culture isolates. Overall there were great variations in in vitro adherence, but no differences were observed between carriage and infection strains. We further determined the relation between in vitro adherence and in vivo infectivity in a rat model of experimental endocarditis, using 4 isolates that displayed either extremely low or high adherence phenotypes. Unexpectedly, no differences were observed between the in vivo infectivity of isolates that were poorly and highly adherent in vitro. We concluded that the natural variability of in vitro adherence to fibrinogen and fibronectin did not correlate with in vivo infectivity, and thus that pathogenic differences between various strains might only be expressed in in vivo conditions, but not in vitro. Therefore, considering the importance of adhesins expression for infection, direct measurement of those adhesins present on the bacterial surface were made by proteomic approach. 5 In the second series of experiments we assessed the physical presence of the LPXTG species at the staphylococcal surface, as measured at various time points during growth in different culture media. S. aureus Newman was grown in either tryptic soy broth (TSB) or in Roswell Park Memorial Institute (RPMI) culture medium, and samples were removed from early exponential growth phase to late stationary phase. Experiments were performed with mutants in the global accessory-gene regulator (agr), surface protein A (Spa) and clumping factor A (ClfA). Peptides of surface proteins were recovered by "trypsin-shaving" of live bacteria, and semi-quantitative proteomic analysis was performed by tandem liquid-chromatography and mass-spectrometry (LC-MS). We also determined in parallel the mRNA expression by microarrays analysis, as well as the phenotypic adherence of the bacteria to fibrinogen in vitro. The surface proteome was highly complex and contained numerous proteins theoretically not belonging to the bacterial envelope, including ribosomal proteins and metabolic enzymes. Sixteen of the 21 known LPXTG species were detected, but were differentially expressed. As expected, 9 known agr-regulated proteins (e.g. including Spa, FnBPA, ClfA, IsdA, IsdB, SasH, SasD, SasG and FmtB) increased up to the late exponential growth phase, and were abrogated in agr-negative mutants. However, only Spa and SasH modified their proteomic and mRNA profiles in parallel in the parent and its agr negative mutant, while all other LPXTG proteins modified their proteomic profiles independently of their mRNA. Moreover, ClfA became highly transcribed and active in in vitro fibrinogen adherence tests during late growth (24h), whereas it remained poorly detected by proteomics. Differential expression was also detected in iron-rich TSB versus iron-poor RPMI. Proteins from the iron-regulated surface determinant (isd) system, including IsdA, IsdB and IsdH were barely expressed in iron-rich TSB, whereas they increased their expression by >10 time in iron-poor RPMI. We conclude that semi-quantitative proteomic analysis of specific protein species is feasible in S. aureus and that proteomic, transcriptomic and adherence phenotypes demonstrated differential profiles in S. aureus. Furthermore, peptide signatures released by trypsin shaving suggested differential protein domain exposures in various environments, which might be relevant for antiadhesins vaccines. A comprehensive understanding of the S. aureus physiology should integrate all these approaches.

New infectious mammary tumor virus superantigen with V beta-specificity identical to staphylococcal enterotoxin B (SEB).

Only few infectious mouse mammary tumor viruses (MMTV) have been characterized which induce a potent superantigen response in vivo. Here we describe the characterization of an MMTV which was isolated from milk of the highly mammary tumor-prone SHN mouse strain. Exposure of newborn mice to milk-borne MMTV (SHN) results in a very slow deletion of V beta 7, 8.1, 8.2 and 8.3 expressing peripheral T cells. Subcutaneous injection of adult mice with this virus induces a rapid and strong stimulation of all four affected V beta-subsets in vivo. Besides the strong T cell effect we observed an early proliferation and activation of the local B cell pool leading to the initial secretion of IgM followed by preferential secretion of IgG2a by day 6. Sequence comparison of the polymorphic C terminus with known open reading frames revealed high homology to the endogenous provirus Mtv-RCS. This is the first report of a virus having a complete overlap in V beta-specificity with a bacterial superantigen stimulating as many as 35% of the whole CD4+ T cell repertoire including V beta 8.2.

Impact of chlorhexidine-impregnated sponges on catheter-related infections rate

INTRODUCTION. Multimodal strategy targeted at prevention of catheter-related infection combine education to general measures of hygiene with specific guidelines for catheter insertion and dressing (1). OBJECTIVES. In this context, we tested the introduction of chlorhexidine(CHX)-impregnated sponges (2). METHODS. In our 32-beds mixed ICU, prospective surveillance of primary bacteremia and of microbiologically documented catheter-related bloodstream infections (CRBSI) is performed according to standardized definitions. New guidelines for central venous catheter (CVC) dressing combined a CHX-impregnated sponge (BioPatch_) with a transparent occlusive dressing (Tegaderm _) and planning for refection every 7 days. To contain costs, Biopatch_ was used only for internal jugular and femoral sites. Other elements of the prevention were not modified (overall compliance to hand hygiene 65-68%; non coated catheters except for burned patients [173 out of 9,542 patients];maximal sterile barriers for insertion; alcoholic solution ofCHXfor skin disinfection). RESULTS. Median monthly CVC-days increased from 710, to 749, 855 and 965 in 2006, 2007, 2008 and 2009, respectively (p\0.01). Following introduction of the new guidelines (4Q2007), the average monthly rate of infections decreased from 3.7 (95% CI: 2.6-4.8) episodes/1000 CVC-days over the 24 preceding months to 2.2 (95% CI: 1.5-2.8) over the 24 following months (p = 0.031). Dressings needed to be changed every 3-4 days. The decrease of catheter-related infections we observed in all consecutive admitted patients is comparable to that recently showed in a placeborandomized trial2. Further generalization to all CVC and arterial catheters access may be justified. CONCLUSIONS. Our data strongly suggest that combined with occlusive dressings, CHXimpregnated sponges for dressing of all CVC catheters inserted in internal jugular and/or femoral sites, significantly reduces the rate of primary bacteremia and CRBSI. REFERENCES. (1) Eggimann P, Harbarth S, Constantin MN, Touveneau S, Chevrolet JC, Pittet D. Impact of a prevention strategy targeted at vascular-access care on incidence of infections acquired in intensive care. Lancet 2000; 355:1864-1868. (2) Timsit JF, Schwebel C, Bouadma L, Geffroy A, Garrouste-Org, Pease S et al. Chlorhexidine- impregnated sponges and less frequent dressing changes for prevention of catheter-related infections in critically ill adults: a randomized controlled trial. JAMA 2009; 301(12):1231-1241.

Pathogenesis of streptococcal and staphylococcal endocarditis.

Although streptococcal and S. aureus IE share the same primary site of infection, their pathogenesis and clinical evolution present several major differences. Streptococci adhere to cardiac valves with pre-existing endothelial lesions. In contrast, S. aureus can colonize either damaged endothelium or invade physically intact endothelial cells. These interactions are mediated by multiple surface adhesins, some of which have been only partially characterized. Streptococci produce surface glucans (gtf and ftf), ECM adhesins (e.g., fibronectin-binding proteins, FimA), and platelet aggregating factors (phase I and phase II antigens, pblA, pblB, and pblT), all of which have been.