Céline Dupieux

Actinomycosis: etiology, clinical features, diagnosis, treatment, and management

Actinomycosis is a rare chronic disease caused by Actinomyces spp., anaerobic Gram-positive bacteria that normally colonize the human mouth and digestive and genital tracts. Physicians must be aware of typical clinical presentations (such as cervicofacial actinomycosis following dental focus of infection, pelvic actinomycosis in women with an intrauterine device, and pulmonary actinomycosis in smokers with poor dental hygiene), but also that actinomycosis may mimic the malignancy process in various anatomical sites. Bacterial cultures and pathology are the cornerstone of diagnosis, but particular conditions are required in order to get the correct diagnosis. Prolonged bacterial cultures in anaerobic conditions are necessary to identify the bacterium and typical microscopic findings include necrosis with yellowish sulfur granules and filamentous Gram-positive fungal-like pathogens. Patients with actinomycosis require prolonged (6- to 12-month) high doses (to facilitate the drug penetration in abscess and in infected tissues) of penicillin G or amoxicillin, but the duration of antimicrobial therapy could probably be shortened to 3 months in patients in whom optimal surgical resection of infected tissues has been performed. Preventive measures, such as reduction of alcohol abuse and improvement of dental hygiene, may limit occurrence of pulmonary, cervicofacial, and central nervous system actinomycosis. In women, intrauterine devices must be changed every 5 years in order to limit the occurrence of pelvic actinomycosis.

The High Diversity of MRSA Clones Detected in a University Hospital in Istanbul

Background: To characterize the methicillin-resistant Staphylococcus aureus (MRSA) clones present in Istanbul, 102 MRSA isolates collected during a 5-year period at the Istanbul Medical Faculty Hospital were characterized using microarray analysis and phenotypic resistance profiles. Methods: Resistance to methicillin was detected with a cefoxitin disk diffusion assay and confirmed with a MRSA-agar and MRSA detection kit. Antimicrobial susceptibility testing was performed by a disk diffusion assay and interpreted according to the 2012 guidelines of the Antibiogram Committee of the French Society for Microbiology. Decreased susceptibility to glycopeptides was confirmed using the population analysis profile-area under the curve (PAP-AUC) method. The presence of the mecA gene was detected by polymerase chain reaction. Bacterial DNA was extracted according to the manufacturers recommended protocol using commercial extraction kits. Strains were extensively characterized using the DNA microarray. Results: Isolates were grouped into six clonal complexes. The most frequently detected clone was the Vienna/Hungarian/Brazilian clone (ST239-MRSA-III), which accounted for 53.9% of the isolates. These isolates were resistant to multiple antibiotics, particularly penicillin, tetracycline, rifampicin, kanamycin, tobramycin, gentamicin, levofloxacin, erythromycin, lincomycin and fosfomycin. Furthermore, three isolates were detected by population analysis profile as heterogeneous vancomycin-intermediate S. aureus (hVISA). The UK-EMRSA-15 clone (ST22-MRSA-IV PVL negative) was detected in 9.8% of the isolates and was mainly susceptible to all anti-staphylococcal antibiotics. Seven isolates (6.9%) were positive for PVL genes and were assigned to the CC80-MRSA-IV clone (European CA-MRSA clone, three isolates), ST8-MRSA-IV clone (USA300 clone, two isolates, one ACME-positive) or ST22-MRSA-IV clone (“Regensburg EMRSA” clone, two isolates). All other clones were detected in one to six isolates and corresponded to well-known clones (e.g., Pediatric clone, Dublin EMRSA clone, WA MRSA-54/63, WA MRSA-1/57). Conclusions: This work highlighted both the high prevalence of ST239-MRSA-III clone and the large diversity of the other MRSA clones detected in a university hospital in Istanbul.

Emergence and dissemination of a linezolid-resistant Staphylococcus capitis clone in Europe

Objectives We investigated the epidemiological, clinical, microbiological and genetic characteristics of linezolid-resistant (LZR) Staphylococcus capitis isolates from French ICUs, and compared them with LZR S. capitis isolates from other European countries. Methods All LZR isolates were subjected to antimicrobial susceptibility testing (AST) and the presence of cfr and optrA genes as well as mutations in the 23S rRNA and ribosomal proteins were investigated using specific PCR with sequencing. The genetic relationship between isolates was investigated using PFGE and WGS. Epidemiological data concerning LZR S. capitis were collected retrospectively in French microbiology laboratories. Results Twenty-one LZR isolates were studied: 9 from France, 11 from Greece and 1 from Finland. All were resistant to methicillin and aminoglycosides. In addition, this unusual AST profile was identified in S. capitis isolates from seven French hospitals, and represented up to 12% of the S. capitis isolates in one centre. A G2576T mutation in 23S rRNA was identified in all isolates; cfr and optrA genes were absent. All isolates belonged to the same clone on the basis of their PFGE profiles, whatever their geographical origin. WGS found at most 212 SNPs between core genomes of the LZR isolates. Conclusions We identified and characterized an LZR S. capitis clone disseminated in three European countries, harbouring the same multiple resistance and a G2576T mutation in the 23S rRNA. The possible unrecognized wider distribution of this clone, belonging to a species classically regarded as a low-virulence skin colonizer, is of major concern not least because of the increasing use of oxazolidinones.

Rapid bench identification of methicillin-sensitive and methicillin-resistant Staphylococcus aureus: A multicenter comparative evaluation of Alere PBP2a Culture Colony Test (Alere) Versus Slidex MRSA detection (bioMérieux)

Using 30 clinical isolates of Staphylococcus aureus representative of the most prevalent clones circulating in France, the performance of the Alere™ PBP2a Culture Colony Test (CCT) and the Slidex(®) MRSA detection kit (SMD) were compared in 5 different labs. CCT demonstrated better performance and was easier to conduct in routine.

Population pharmacokinetics and probability of target attainment of ertapenem administered by subcutaneous or intravenous route in patients with bone and joint infection

Background Ertapenem is a therapeutic option in patients with Gram-negative bone and joint infection (BJI). The subcutaneous (sc) route of administration is convenient in the outpatient setting and has shown favourable pharmacokinetics (PK), but available data on ertapenem are limited. Objectives To perform population PK analysis and pharmacokinetic/pharmacodynamic (PK/PD) simulation of ertapenem administered by the intravenous (iv) or sc route to patients with BJI. Patients and methods This was a retrospective analysis of PK data collected in patients with BJI who received iv or sc ertapenem. Measured ertapenem concentrations were analysed with a non-parametric population approach. Then, simulations were performed based on the final model to investigate the influence of ertapenem route of administration, dosage and renal function on the probability of achieving a pharmacodynamic (PD) target, defined as the percentage of time for which free plasma concentrations of ertapenem remained above the MIC (fT>MIC) of 40%. Results Forty-six PK profiles (13 with iv and 33 with sc ertapenem) with a total of 133 concentrations from 31 subjects were available for the analysis. A two-compartment model with linear sc absorption and linear elimination best fitted the data. Creatinine clearance was found to significantly influence ertapenem plasma clearance. Simulations showed that twice daily dosing, sc administration and renal impairment were associated with an increase in fT>MIC and target attainment. Conclusions Our results indicate that 1 g of ertapenem administered twice daily, by the iv or sc route, may optimize ertapenem exposure and achievement of PK/PD targets in patients with BJI.

Intraosteoblastic activity of daptomycin in combination with oxacillin and ceftaroline against MSSA and MRSA

Background The Staphylococcus aureus intracellular reservoir is associated with bone and joint infection (BJI) chronicity. As daptomycin is increasingly prescribed in BJI, strategies for improving its reduced intracellular activity should be promoted. Objectives Based on the known in vitro synergy of daptomycin with β-lactams, the aim of the present study was to evaluate the intracellular activity of these combinations in an ex vivo osteoblast infection model. Methods Osteoblastic cells infected with an MRSA strain or its isogenic MSSA counterpart were incubated for 24 h with daptomycin, oxacillin or ceftaroline alone or in combination using usual intraosseous therapeutic concentrations. Intracellular bacteria were quantified by plating cell lysates. MICs for MSSA and MRSA were determined using the chequerboard method at pH 5 to mimic conditions expected within lysosomes, the foremost S. aureus intracellular location. Results Daptomycin failed to reduce the intracellular MSSA inoculum, and was weakly active against MRSA compared with untreated cells (-27.6%; P < 10-3). Oxacillin and ceftaroline revealed significant intracellular activity, including oxacillin against MRSA-infected cells (-43.2%; P < 10-3). The daptomycin/oxacillin combination was significantly more active against intracellular MSSA and MRSA compared with daptomycin and oxacillin alone (-44.4% and -57.2%, respectively; P < 0.05). In contrast, daptomycin/ceftaroline was not more efficient than ceftaroline alone. Interestingly, oxacillin MICs for MRSA decreased in vitro from >256 to 0.023 mg/L when the pH decreased from 7 to 5, and chequerboards showed an additive effect of the daptomycin/oxacillin combination against MRSA at pH 5. Conclusions In acidic intracellular conditions, oxacillin enhances daptomycin activity against the intraosteoblastic reservoir of S. aureus, including MRSA.

Implant-associated ESBL-Klebsiella pneumonia producing small colony variant bone and joint infection in a healthy 40-year-old man.

A 40-year-old man underwent a bifocal fracture of the left leg in Senegal. An intramedullar rod was implanted to obtain consolidation. At 7 months, the patient was admitted to our institution as the distal fracture had not consolidated (figure 1A). There was no clinical sign of infection. A 1-stage exchange of the rod was performed. No abscess or suspected tissue was detectable during the surgery. Systematic peroperative test of samples were performed, and revealed Klebsiella pneumonia producing extended-spectrum β-lactamase (ESBL), and some colonies expressed the small colony variant (SCV) phenotype in the culture (with the same antibiotic susceptibility), which was also identified to be K. pneumonia (figure 1 B and C). An early new intervention was required due to local abscess formation, the rod was explanted, the tibia was immobilised with a cruro-pedal cast and negative pressure therapy on the skin defect was instaured. …

Innovations for the treatment of a complex bone and joint infection due to XDR Pseudomonas aeruginosa including local application of a selected cocktail of bacteriophages

found a high prevalence of ESBL producers, but no CPE. In conclusion, we report two temporally and geographically linked patients with community-onset urinary tract infection caused by the same OXA-48-producing E. coli clone. The association between OXA-48 and Cambodia in NZ suggests the Cambodian patient may have acquired the organism during recent travel and indirectly transmitted to the second patient via unknown community transmission pathways. It is possible that OXA-48-positive CPE are under-recognized in NZ due to the challenges of laboratory detection. Screening with adequate selective media for CPE is highly recommended. The forthcoming national response plan to CPE in NZ has potential to help address some of these issues.

Diagnostic des infections ostéo-articulaires

Resume Le diagnostic microbiologique des infections osteo-articulaires est complexe et necessite une collaboration forte entre orthopedistes, infectiologues et biologistes. Il est obligatoire de realiser des prelevements dans les conditions les plus strictes d’asepsie au bloc chirurgical avec un acheminement rapide au laboratoire de bacteriologie. La multiplication des prelevements facilite l’interpretation des resultats. Une fois au laboratoire, ces prelevements doivent etre traites dans des conditions d’asepsie pour eviter toute contamination. L’incubation des milieux geloses doit etre prolongee (minimum 14 jours) pour permettre la culture de toutes les bacteries. L’identification et les antibiogrammes sur tous les types de colonies bacteriennes sont d’ailleurs indispensables. La biologie moleculaire est utile en cas de forte suspicion d’infection alors que les cultures sont negatives ou systematiquement en cas d’arthrite septique de l’enfant de moins de 4 ans.