Microbiologic profile of Staphylococci isolated from osteoarticular infections: evolution over ten years.

BACKGROUND: Staphylococci, especially coagulase-negative staphylococci (CoNS) represent the most frequent micro-organism associated with osteoarticular infections (OAIs), especially those involving orthopedic devices. The antibiotic susceptibility profile of the bacteria mostly responsible for OAIs is therefore crucial information for choosing the appropriate antibiotic regimen administered during the removal procedure until the first results of the conventional culture. METHODS: The antibiotic susceptibility profile of staphylococci isolated from OAIs in a referent center for osteoarticular infection was studied over a 10-y period to adapt antibiotic protocols to the ecology. RESULTS: From 2002 to 2011, the resistance of Staphylococcus aureus to methicillin and rifampicin decreased (27.9% versus 20.6% and 13% versus 1%, respectively); the resistance to fluoroquinolones (FQ) was stable (24% on average), and all the isolates were susceptible to glycopeptides. For CoNS, the resistance to methicillin, rifampicin, and FQ increased (30.4% versus 43.9%, 13% versus 18.5%, and 20.3% versus 34.1%, respectively) over the same period. Resistance of the CoNS to vancomycin was observed in 2011 for the first time (2.3%), and 3.8% were resistant to teicoplanin in 2002 compared with 22% in 2011, with 3.5% resistant to linezolid in 2011. CONCLUSION: The sensibility of bacteria over 10 y remained stable, except for CoNS. The increase of the resistances for CoNS led us to exclude teicoplanin from the first-line empiric antibiotic treatment, to avoid linezolid, and to prefer vancomycin or daptomycin.

Ruminococcus gnavus: an unusual pathogen in septic arthritis.

Ruminococcus gnavus is an anaerobic Gram positive coccus that can be found in the gastrointestinal tract of animals and humans. We report a case of septic arthritis caused by R. gnavus that was identified by mass spectrometry and confirmed by 16S rRNA sequencing.

Psychrobacter sanguinis: an unusual bacterium for nosocomial meningitis.

We report the first case of postneurosurgical meningitis due to Psychrobacter sanguinis, identified only by 16S rRNA analysis. Psychrobacter spp. usually live in deep sea environments and cold habitats. Despite a strict questioning of the patient and the medical staff, we did not find the source of this bacterium.

Difficulty with Gordonia bronchialis identification by Microflex mass spectrometer in a pacemaker-induced endocarditis.

INTRODUCTION: This report describes the first case, to the best of our knowledge, of pacemaker-induced endocarditis due to Gordonia bronchialis. PRESENTATION: Pacemaker-induced endocarditis due to G. bronchialis infection was determined in a 92-year old man. This Gram-positive bacillus failed to be identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry technology, whereas the taxon was indexed in the database. 16S rRNA and rpoB gene sequencing were required to determine the correct strain identity. CONCLUSION: Infections caused by G. bronchialis remain a rare phenomenon affecting immunocompromised patients and/or medical device carriers. Molecular tools may be necessary to ensure accurate identification.

PCR-electrospray ionization time-of-flight mass spectrometry: a new tool for the diagnosis of infective endocarditis from heart valves.

A polymerase chain reaction with an injection of the amplicons in an electrospray ionization mass spectrometry (PCR-ESI-MS) technique was evaluated for the diagnosis of bacterial and yeast pathogens on 13 cardiac valves with suspected endocarditis. At the moment of surgery, 3/13 PCR-ESI-MS results matched with microbiological documentation. Nine PCR-ESI-MS results correlated with Duke's criteria, leukocytes, C-reactive protein and blood cultures before surgery. The PCR-ESI-MS result of the last valve failed to confirm the blood culture result obtained fifteen days before. With speed and accuracy, this method may be useful to assert microbiological identification and adapt treatment.

CHROMagar Yersinia, a new chromogenic agar for screening of potentially pathogenic Yersinia enterocolitica isolates in stools.

CHROMagar Yersinia (CAY) is a new chromogenic medium for the presumptive detection of virulent Yersinia enterocolitica in stools. Based on a comparative analysis of 1,494 consecutive stools from hospitalized patients, CAY was found to be just as sensitive as the reference medium (cefsulodin-irgasan-novobiocin agar) but was significantly more specific and had a very low false-positive rate. CAY reduces the workload (and thus costs) for stool analysis and can therefore be recommended for routine laboratory use.

Evaluation of rapid mecA gene detection versus standard culture in staphylococcal chronic prosthetic joint infections.

In case of periprosthetic joint infections, the antibiotic treatment administered intraoperatively entails consequences on bacterial ecology with potential secondary effects. This study evaluates the rapid detection of methicillin-resistant staphylococci (MRS) by Xpert® technology directly on intraoperative samples. Xpert® technology was compared to conventional culture for 104 clinical specimens performed on 30 patients. The performance of the test expressed in terms of sensitivity, specificity, positive predictive value, and negative predictive value was, respectively, 87.1%, 100%, 100%, and 94.5% for the 104 specimens, and 92.3%, 100%, 100%, and 94.4% for the 30 patients. With the rapid detection of MRS, the use of vancomycin was limited for 17 of these 30 patients. In conclusion, this technique would allow the implementation of first-line antibiotic treatment adapted to the presence of MRS or not within approximately 1 h and would strongly reduce the use of broad-spectrum antibiotics.

Usefulness of real-time PCR for the diagnosis of sepsis in ICU-acquired infections.

Real-time PCR methods are able to rapidly detect a wide panel of microorganisms. These methods are of interest in critically ill patients to determine the presence of bacteria in the blood and other biological samples, especially in those patients with prior antimicrobial treatment. In intensive care unit (ICU), the LightCycler SeptiFast (LC-SF) Test provides 1.5 to 2 fold higher positivity rate compared with conventional blood cultures. Although identification of the bacterium by LC-SF is rapid and sensitive, susceptibility test could not be performed using this technique, except the methicillin- resistance for Staphylococci. The conventional cultures remain necessary for samples in ICU because of the high incidence of multidrug-resistant bacteria and the need for antimicrobial susceptibility of the bacterium to treat the patient correctly. A negative result for a Gram positive or negative bacterium allows deescalating the initial antimicrobial treatment, and decreasing the pressure of selection. Moreover, it is necessary to understand and interpret a DNA signal knowing that a dead bacterial material may be detected in a patient without any infection. What is the clinical relevance of bacterial DNA present in the blood and does the DNAemia found reflect true infection? Cost-effectiveness of the real-time PCR should be determined. Meanwhile, this test should be restricted to severe clinical situations, especially ICU patients with severe sepsis. In the future, real-time PCR tests should include more pathogens and antimicrobial resistant targets.

Daily serum piperacillin monitoring is advisable in critically ill patients.

The aim of the present study was to evaluate the benefit of monitoring serum piperacillin concentrations in critically ill patients. This was an 11-month, prospective, observational study in a 30-bed Intensive Care Unit in a teaching hospital, involving 24 critically ill patients with evidence of bacterial sepsis. All patients received a 66 mg/kg intravenous bolus of piperacillin in combination with tazobactam (ratio 1:0.125) followed by continuous infusion of 200mg/kg/24h. The dosage was adjusted when the serum piperacillin concentration either fell below 4x the drug's minimum inhibitory concentration (MIC) for the causative agent or exceeded the toxic threshold of 150 mg/L. With the initial regimen, serum piperacillin concentrations were within the therapeutic target range in only 50.0% of patients (n=12). This proportion increased to 75.0% (18 patients) (P=0.006) following dosage adjustment. For patients with low initial serum piperacillin concentrations (n=8), the percentage of time during which the concentration remained above 4x MIC (%T>4x MIC) was 7.1+/-5.9% before dosage adjustment and 27.3+/-8.6% afterwards. In conclusion, in critically ill patients, monitoring and adjustment of serum piperacillin levels is required to prevent overdosing and might also help to correct underdosing, an important cause of antibiotic therapy failure.

Paracoccus yeei: a new unusual opportunistic bacterium in ambulatory peritoneal dialysis.

Paracoccus yeei was identified as the etiologic agent of peritonitis in an ambulatory peritoneal dialysis patient. While the old biochemical identification kits are not able to identify this species, the new colorimetric VITEK 2 GN card correctly identified this isolate in 7hours. Its identity was confirmed by sequencing of the 16S rRNA gene.

Isolation of Helcococcus kunzii from plantar phlegmon in a vascular patient.

Helcococcus kunzii has previously been considered to belong to the normal skin flora of podiatry patients. Here, H. kunzii was isolated in abundance from a pus specimen collected by incision and drainage of plantar phlegmon. This fastidious Gram-positive species was unambiguously identified with the colorimetric VITEK 2 GP card identification system. This suggests that this phenotypic identification system is able to identify promptly H. kunzii, which should be considered a potential pathogen.

Molecular diagnosis of a bilateral panuveitis due to Borrelia burgdorferi sensu lato by cerebral spinal fluid analysis.

The present paper describes a case of bilateral panuveitis due to Borrelia burgdorferi sensu lato diagnosed by a PCR approach using cerebral spinal fluid. Since the culture of B. burgdorferi takes a long time to grow and the accuracy of serological tests is doubtful in patients, the PCR method of amplifying a B. burgdorferi flagellin could be suitable to make a positive diagnosis in a case of atypical clinical history of Lyme disease.

Bacteriological analysis of meshes removed for complications after surgical management of urinary incontinence or pelvic organ prolapse.

The aim of this study is to examine the role of bacterial infection in complications following surgical management of urinary incontinence and genital prolapse using meshes. There were sixteen prostheses removed. Eight were monofilament polypropylene-knitted meshes, one was a silicone-coated polypropylene mesh, another was a collagen-coated polypropylene mesh, four were silicone-coated polyester meshes and two were polyester meshes. The most frequent cause for removal was symptomatic vaginal erosion (62%). Cultures were performed under aerobic, anaerobic and enrichment conditions. Infection was multimicrobial for 31% of meshes. When only one bacteria was found, it was Proteus mirabilis in 25% of cases. Forty-three per cent of bacterial quantifications were under 10(3) colony-forming units per millilitre. Bacterial contamination was found in all meshes, quantification was often low, and therefore, its exact role is not yet clear.

First case of osteomyelitis caused by "Staphylococcus pettenkoferi".

"Staphylococcus pettenkoferi" (proposed name) was identified as an unusual agent of osteomyelitis in a diabetic foot infection. The phenotypical tests used failed to give a good identification. Molecular 16S rRNA gene and rpoB sequencing allowed us to correctly identify this new species of coagulase-negative staphylococcus responsible for this chronic infection.

First isolation of Clostridium amygdalinum from a patient with chronic osteitis.

We describe a case of osteitis caused by a new and unusual Clostridium species, Clostridium amygdalinum, an environmental, moderately thermophilic bacterium. This is the first documented report of human infection caused by this organism.

Evaluation of VITEK 2 colorimetric cards versus fluorimetric cards for identification of yeasts.

The new colorimetric VITEK 2 yeast cards (YST) were evaluated versus the fluorimetric yeast cards (ID-YST). Of the 172 clinical isolates belonging to 19 taxa, 161 (93.6%) and 144 (83.7%) strains were correctly identified with the ID-YST and YST cards, respectively.

Against all odds: molecular confirmation of an implausible case of bone tuberculosis.

We report the use of typing based on a variable number of tandem repeats of genetic elements called "mycobacterial interspersed repetitive units" to clarify a puzzling situation involving a patient with an exceptional case of spondylodiskitis that initially led to the suspicion of a possible event of laboratory cross-contamination with Mycobacterium tuberculosis.