Jorgelina Smayevsky

Vaginal microflora associated with bacterial vaginosis in nonpregnant women: reliability of sialidase detection

Objective: To determine the prevalence of Gardnerella vaginalis, anaerobic bacteria and Mycoplasma hominis in vaginal specimens of women with and without bacterial vaginosis (BV) as well as to determine the sensitivity and specificity of the direct sialidase assay of vaginal fluid as a rapid test for diagnosing this syndrome. Methods: Vaginal cultures were obtained from 109 nonpregnant women (mean age 33 ± 7.1 years), 47 of them with clinical signs of BV (BV+) and 62 of them without BV (BV- ). In addition, we determined the vaginal sialidase activity in both groups, which may serve as a feature of this syndrome. Results: Anaerobic bacteria were isolated in 91% and 18% of the BV+and BV- groups, respectively (p < 0.001). Peptostreptococcus spp., Prevotella bivia and Porphyromonas spp. were strongly associated with BV. P. bivia and Prevotella spp. represented 44% of all the anaerobes isolated in the BV+ group. All the isolated P. bivia strains presented sialidase activity. G. vaginalis and M. hominis were isolated in 76% and 42% of the BV+ and 1% and 0% of the BV- women, respectively (p < 0.001). Mobiluncus morphotypeswere observed in 34% of the BV+and 0% of BV- women. Sensitivity, specificity, positive predictive value and negative predictive value of sialidase activity were 81%, 94%, 90% and 86%, respectively. Conclusions: Our data demonstrate a strong association between G. vaginalis, M. hominis, and P. bivia and BV. Sialidase activity and Gram stain of vaginal fluid represent accurate methods for diagnosing BV.

Outbreak of OXY-2-Producing Klebsiella oxytoca in a Renal Transplant Unit

ABSTRACT We describe a Klebsiella oxytoca infection outbreak in a renal transplant unit that involved seven patients. All strains belonged to a single pulsed-field gel electrophoresis pattern and were resistant to amoxicillin-clavulanate, cefuroxime, piperacillin-tazobactam, and aztreonam but susceptible to ceftriaxone, ceftazidime, cefepime, and imipenem. Chromosomal β-lactamase hyperproduction was caused by a point mutation in the blaOXY-2 gene promoter region.

Comparative in vitro bactericidal activity between cefepime and ceftazidime, alone and associated with amikacin, against carbapenem-resistant Pseudomonas aeruginosa strains

Fifteen unique isolates of carbapenem-resistant Pseudomonas aeruginosa were selected for time-kill studies to assess the bactericidal activity of cefepime (CFP) and ceftazidime (CZD) (at 4 and 16 microg/mL), alone and associated with amikacin (AMK) (4 microg/mL). CFP proved more active than CZD (p < 0.05, Students t test). Bactericidal activity after 24-h incubation was only achieved by the combination of CFP (16 microg/mL) plus AMK. The higher in vitro activity of cefepime over that of ceftazidime against imipenem-resistant P. aeruginosa strains highlights the differences of these drugs beyond Enterobacterspp. and Staphylococcus aureus.

Activity of gatifloxacin compared to those of seven agents against bacteria recovered from outpatients with respiratory tract infection.

The in vitro activity of gatifloxacin and levofloxacin, ciprofloxacin, penicillin, ampicillin, ampicillin-sulbactam, ceftriaxone and clarithromycin was evaluated against 173 S. pneumoniae strains (128, penicillin-susceptible strains; 32, intermediate penicillin- resistant strains and 13, penicillin-resistant strains), 163 H. influenzae strains (128, beta-lactamase non-producer; 35, beta-lactamase producers), 111 M. catarrhalis (9, beta-lactamase non-producer; 102, beta-lactamase producers), 95 Streptococcus pyogenes and 116 S. aureus strains (96, methicillin-susceptible; 20, methicillin-resistant) recovered from outpatients with respiratory tract infection. Based upon the MICs at which 50% and 90% of the isolates were inhibited we concluded that gatifloxacin proved to be the most active antibiotic against respiratory pathogens, including all the penicillin-resistant pneumococci and H. influenzae or M. catarrhalis producing beta-lactamase. Furthermore, their MICs against S. pneumoniae and methicillin-resistant S. aureus were lower than those of levofloxacin and ciprofloxacin.Therefore, this new fluoroquinolone displayed in vitro features that make it suitable for treating community-acquired respiratory tract infections.

A Pharmacodynamic Model to Support a 12-Hour Dosing Interval for Amoxicillin/Sulbactam, a Novel Oral Combination, in the Treatment of Community-Acquired Lower Respiratory Tract Infections

Abstract We evaluated, by time-kill studies, the pharmacodynamics of amoxicillin/sul-bactam (AMX/SUL, 875 mg/125 mg), a novel oral combination, against the major respiratory pathogens in 12 volunteers receiving a single dose. The sera corresponding to 50% of a 12-h dosing interval displayed either bactericidal or inhibitory activity against both a penicillin-susceptible and a penicillin-intermediate Streptococcus pneumoniae strain (penicillin MIC of 0.03 and 0.25 μg/ml, respectively), as well as against a β-lactamase-positive Moraxella catarrhalis and a β-lactamase-negative Haemophilus influenzae strain. Both the peak samples and those corresponding to 4 h after dose (i.e. 33% of a 12-h dosing interval) proved active against both a penicillin-resistant S. pneumoniae (MIC, 2 μg/ml) and a β-lactamase-positive H. influenzae strain. The AMX-SUL formulation evaluated in this study showed pharmacodynamic features that support clinical trials to assess its efficacy in the treatment of lower respiratory tract infections with a 12-h dosing interval regimen.

Saksenaea erythrospora infection following a serious sailing accident

Saksenaea erythrospora is a species of the order Mucorales recently described and reported as a cause of human mucormycosis. We report a case of S. erythrospora in a man involved in a serious sailing accident causing deep skin and soft tissue contamination with soil and water. Direct microscopic examination of the clinical sample with Giemsa stains showed hyaline and non-septate hyphae belonging to the order Mucorales. Fungal identification was performed by culture of biopsy material on SDA, and identification of species by floating an agar block containing the fungus in a nutritionally deficient medium consisting of sterile distilled water supplemented with 0.05 % yeast extract; and by sequencing the ITS region of the rDNA. This is the first report to our knowledge of infection with S. erythrospora in Argentina, confirming the presence of this fungus in this country.

Rationale for Treating Community-Acquired Lower Respiratory Tract Infections with Amoxicillin/Sulbactam Combination Through Pharmacodynamic Analysis in the Setting of Aminopenicillin-Resistant Organisms

Abstract In order to establish a rationale for treating community-acquired lower respiratory tract infections, we assess here the pharmacodynamics of amoxi-cillin/sulbactam, 500mg/500mg, a formulation marketed in Argentina since 1988 and currently available in 17 countries, against the major pathogens, in comparison with that of a novel formulation (875mg/125mg, see J Chemother 2000; 12: 223-227). In time-kill studies, both bactericidal and inhibitory activity were seen in the 1.5- and 6-h sera, obtained from 12 volunteers after a single oral dose, against both a penicillin-susceptible and an -intermediate Streptococcus pneumoniae strain, as well as against Moraxella catarrhalis and a β-lactamase-negative Haemophilus influenzae strain. Only the 1.5-h sera proved bactericidal against a penicillin-resistant S. pneumoniae strain (MIC, 2 μg/ml) and a β-lactamse-positive H. influenzae isolate. This study suggests that amoxicillin/sulbactam (500mg/500mg) is still a suitable option for treating community-acquired lower respiratory tract infections, allowing a b.i.d. dosing schedule. Caution should be taken with pneumonia caused by β-lacta-mase-positive H. influenzae or penicillin-resistant (MIC >2 μg/ml) S. pneumoniae isolates. Either shorter dosing intervals (t.i.d.) or a higher amoxicillin content in the formulation (i.e. 875 mg) may be required in these situations.

The susceptibility to tigecycline of Acinetobacter spp. may vary depending on the methodology used

Healthcare-associated infections caused by multidrug-resistant (MDR) Acinetobacter spp. have increased substantially worldwide, including in Latin America. This is a major challenge, as several isolates are only susceptible to polymyxins. Tigecycline provides a new therapeutic option against this microorganism. Therefore, surveillance of susceptibility to this drug is critical to detect changes in its activity profile. Regarding the medium used for susceptibility testing, recent publications have suggested that the susceptibility of Acinetobacter spp. isolates to tigecycline may vary according to the commercial Mueller–Hinton agar (MHA) used in the disk diffusion test. This could be because of the elevated manganese concentration in MHA and may increase the reported differences in minimum inhibitory concentration (MIC) values obtained by different methodologies. We performed susceptibility testing on 60 MDR Acinetobacter spp. isolates obtained from hospitalized patients at two teaching hospitals in Buenos Aires city, Argentina, over the course of two time periods: 2002–2003 and 2006–2008. In vitro susceptibility was assayed in parallel by the broth microdilution, agar dilution, and disk diffusion method with a 15 mg tigecycline disk (Difco MHA, Difco Laboratories, Detroit, MI, USA), as per the guidelines of the Clinical and Laboratory Standards Institute (CLSI). Susceptibility was inferred using the breakpoint suggested by the US Food and Drug Administration (FDA) for Enterobacteriaceae (Tygacil package insert (June 2005), Wyeth Pharmaceuticals Inc., Philadelphia, PA, USA). A comparative analysis between methods by scattergram correlation and analysis of MICs and diameter zones around the disk was performed. Staphylococcus aureus ATCC 29213, S. aureus ATCC 25923, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853 and Enterococcus faecalis ATCC 29212 were used as controls. A positive lineal correlation was found between methodologies. Using the FDA Enterobacteriaceae susceptibility breakpoint for tigecycline of <2 mg/ml and >19 mm, an acceptable minor error

Bacteriemia por Vibrio cholerae no-O1, no-O139 en un paciente en hemodiálisis crónica

Resumen es: Vibrio cholerae no-O1, no-O139 es un agente poco frecuente como causal de bacteriemias y no hay informes que documenten su presencia en pacientes en hemo...

Utilidad de la espectrometría de masas MALDI-TOF en la identificación de bacterias anaerobias

Resumen El analisis de espectrometria de masas mediante la metodologia hoy conocida como MALDI-TOF MS (Matrix-assited laser desorption/ionization time-of-flight mass spectrometry) se ha convertido en un recurso de referencia para la identificacion de microorganismos en microbiologia clinica. No obstante, los datos relativos a algunos grupos de microorganismos son todavia controvertidos. El objetivo del presente estudio fue determinar la utilidad del MALDI-TOF MS para la identificacion de aislamientos clinicos de bacterias anaerobias. Se analizaron 106 aislamientos de bacterias anaerobias mediante MALDI-TOF MS y por pruebas bioquimicas convencionales. En aquellos casos en los que la identificacion por metodologia convencional no era aplicable o frente a una discordancia de resultados entre las metodologias citadas, se realizo la secuenciacion del gen 16S del ARNr. El metodo convencional y el MALDI-TOF MS coincidieron a nivel de genero y especie en un 95,3 % de los casos considerando la totalidad de los aislamientos estudiados. Al considerar solo el conjunto de los bacilos gram negativos, la coincidencia fue del 91,4 %; entre los bacilos gram positivos, fue del 100 %; los 8 aislados de cocos gram positivos estudiados coincidieron y tambien hubo coincidencia en el unico coco gram negativo incluido. Los datos obtenidos en este estudio demuestran que el MALDI-TOF MS ofrece la posibilidad de llegar a una adecuada identificacion de bacterias anaerobias.The analysis by MALDI-TOF MS (Matrix-assited laser desorption/ionization time-of-flight mass spectrometry) has become a reference method for the identification of microorganisms in Clinical Microbiology. However, data on some groups of microorganisms are still controversial. The aim of this study is to determine the utility of MALDI-TOF MS for the identification of clinical isolates of anaerobic bacteria. One-hundred and six anaerobic bacteria isolates were analyzed by MALDI-TOF MS and by conventional biochemical tests. In those cases where identification by conventional methodology was not applicable or in the face of discordance between sequencing methodologies, 16 S rRNA gene sequence analysis was performed. The conventional method and MALDI-TOF MS agreed at genus and species level by 95.3 %. Concordance in gram-negative bacilli was 91.4% and 100% among gram-positive bacilli; there was also concordance both in the 8 isolates studied in gram-positive cocci and in the single gram-negative cocci included. The data obtained in this study demonstrate that MALDI-TOF MS offers the possibility of adequate identification of anaerobic bacteria.