[An atypical case of necrotizing staphylococcal pneumonia]

INTRODUCTION

Some strains of Staphylococcus aureus produce a toxin known as Panton-Valentine leukocidin. These strains notably cause a necrotizing pneumonia which is associated with a high mortality.

OBSERVATION

A 70-year-old woman presented with sub-acute onset dyspnea, low-grade fever, and hemoptysis after a trip to Dubai and New Zealand. Computed tomography showed bilateral necrotizing pneumonia, suggesting the diagnosis of pneumonia caused by S. aureus producing Panton-Valentine toxin. It was confirmed by microbiological investigation. The rapid initiation of adequate antimicrobial therapy including an effective antitoxin was essential for successful treatment, without the need for ventilatory support.

CONCLUSION

Necrotizing pneumonia caused by S. aureus producing Panton-Valentine leukocidin usually occurs in young subjects without comorbidities. Typical symptoms are a combination of hypoxemia, high fever, hemoptysis, leukopenia, and a rapidly worsening condition. Panton-Valentine leukocidin should not be discarded if not all the symptoms are typical. Antibiotic therapy including an antitoxin drug such as linezolid or clindamycin should be initiated promptly.

Management of emerging multidrug-resistant tuberculosis in a low-prevalence setting

Multidrug-resistant (MDR) tuberculosis (TB) is an emerging concern in communities with a low TB prevalence and a high standard of public health. Twenty-three consecutive adult MDR TB patients who were treated at our institution between 2007 and 2013 were reviewed for demographic characteristics and anti-TB treatment management, which included surgical procedures and long-term patient follow-up. This report of our experience emphasizes the need for an individualized approach as MDR TB brings mycobacterial disease management to a higher level of expertise, and for a balance to be found between international current guidelines and patient-tailored treatment strategies.

Efficient applications of capillary electrophoresis-tandem mass spectrometry to the analysis of adrenoreceptor antagonist enantiomers using a partial filling technique

Throughout the separation of chiral basic drugs by capillary electrophoresis (CE) with neutral hydroxypropyl-beta-cyclodextrin (HP-beta-CD) as chiral selector, the sensitivity of detection can be improved by using tandem mass spectrometric (MS-MS) detection with a partial filling technique rather than with UV spectrometric detection. Prior to sample injection. the capillary was partly filled with HP-beta-CD dissolved in volatile ammonium formate buffer (pH 4, ionic strength 50 mM). The effects of modifying the HP-beta-CD concentration in the selector zone and the length of the separation zone on the enantioresolution and the signal-to-noise ratio of the pseudo-molecular MH+ ion were investigated. For a given selector zone length, as the concentration of the neutral cyclodextrin increases, the resolution between enantiomers becomes higher (the opposite of the behavior of the signal-to-noise ratio) and then reaches an optimum value. The decrease of the selector zone length lowered the resolution between the enantiomers but increased peak efficiencies and signal-to-noise ratio values. Accordingly, partial capillary filling at 80% (v/v) and 10 mM concentration of HP-beta-CD was selected as a suitable compromise between resolution and sensitivity of MS detection. Limits of detection for each adrenoreceptor antagonist enantiomer were 5 ng/ml (0.02 microM) in CE-MS-MS instead of 150 ng/ml (0.60 microM) in CE-UV, which enhances sensitivity by a factor of 30.

Analysis of sulfobutyl ether-beta-cyclodextrin mixtures by ion-spray mass spectrometry and liquid chromatography-ion-spray mass spectrometry

The analysis of two commercial and two home-made sulfobutyl ether beta-cyclodextrin (SBE-beta-CD) samples by ion-spray (IS) mass spectrometry and by liquid chromatography-mass spectrometry coupling (LC-MS) is investigated in a negative ion mode. SBE-beta-CD fragmentation was first investigated by direct infusion. In IS, the best conditions for SBE-beta-CD ionization consisted of ammonium acetate added to an acetonitrile/water mixture as sample solvent. These conditions allowed simplification of the mass spectrum, mainly by the formation of dicharged species [M-2H]2-, thus limiting the production of multicharged fragments. IS-MS permits fast and simple measurement of the substitution pattern and determination of the global degree of substitution for SBE-beta-CD mixtures. A complementary method using LC-MS was developed for the analysis of these mixtures. The substitution patterns obtained by LC-MS are in good agreement with those determined by direct MS analysis. The LC-MS coupling enabled separation of the mixtures versus the charge in anion-exchange chromatography (AEC) whereas no separation of the different substitution isomers potentially present in the SBE-beta-CD mixture was displayed. The AEC methodology described can be successfully used for fractionation of SBE-beta-CD derivatives at the semi-preparative scale.

Characterization of sulfobutyl ether-beta-cyclodextrins mixtures by anion-exchange chromatography using evaporative light scattering detection

An analytical method based on anion-exchange chromatography (AEC) using volatile eluent ion and evaporative light scattering detection was developed for the analysis of mixtures of sulfobutyl-ether-beta-cyclodextrins (SBE-beta-CDs). A systematic investigation of the retention mechanism of pure SBE-beta-CD standards has been studied on a silica quaternary ammonium exchanger (Vydac 302 IC column). The influence of the nature and concentration of volatile anions (acetate, formate, trifluoroacetate), the addition of the organic modifier in the mobile phase as well the nature of the stationary phase have been evaluated under isocratic elution conditions. Satisfactory analysis of two commercial and two home-made SBE-beta-CD samples was achieved on the Vydac 302 IC column by using ammonium acetate as ion eluent in water-acetonitrile (70:30) under a salt concentration gradient mode. This method provides for SBE-beta-CD samples, an efficient and characteristic liquid chromatography fingerprint which depicts the mixture complexity and determines an average degree of substitution (DS) for each sample.

Enhancement of second-migrating enantiomer peak symmetry of basic drugs by using dual-cyclodextrin system in capillary electrophoresis

Today, chiral separations of cationic drugs by capillary electrophoresis are generally carried out by adding negatively charged cyclodextrins (CDs) to the running buffer while anionic or neutral drug separations require the use of dual-CD systems (mixtures of neutral and charged CDs). Chiral separation of some basic drugs (idazoxan, efaroxan, milnacipran) has been studied by using mixtures of sulfated-beta-CD (S-beta-CD) and hydroxypropyl-gamma-CD (HP-gamma-CD). The influence of the following parameters (nature and concentration of neutral CD, concentration of S-gamma-CD) on many separation factors (electrophoretic mobility, selectivity, efficiency, asymmetry factor, resolution) demonstrated that dual-CD systems are useful for chiral separation of basic drugs in order to improve the symmetry of the second-migrating enantiomer. Indeed, the neutral CD reduces the extent of electromigration dispersion by mobility tuning. Finally, the 0.5 mg/mL S-beta-CD/5 mg/mL HP-gamma-CD dual system has allowed the chiral separation of idazoxan, efaroxan and milnacipran enantiomers in less than 9 min.