Comparison of antibiotic resistance and virulence factors in pigmented and Non-pigmented Pseudomonas aeruginosa / Comparación de la resistencia antibiótica y los factores de virulencia en las Pseudomonas aeruginosa pigmentadas y no pigmentadas

OBJECTIVES: Pseudomonas aeruginosa produces multiple virulence factors that have been implicated in pathogenesis and quorum sensing. The aim of this study was to determine differences in the virulence factors of pigmented and non-pigmented P aeruginosa isolates. METHODS: Associations were assessed between pigment production (pyocyanin and pyoverdin) and production of DNase, elastase, lipase, protease, siderophore, twitching motility, antibiotic resistance patterns and virulence-associated genes in 57 non-duplicate P aeruginosa isolates from wounds, sputum, urine, high vaginal swab (HVS), ear, eye and respiratory tract swabs and aspirates of peritoneum and ulcers. RESULTS: Most (82.5%) of the isolates produced either pigment. Pigmented isolates produced more frequently and significant more (p < 0.05) DNase, elastase, lipase protease, and siderophore. Imipenem was the only antibiotic to which all isolates were susceptible (p < 0.05), while 93% and 32% were resistant to tetracycline and norfloxacin, respectively. There was however no significant difference between pigmented and non-pigmented isolates when antibiotic resistance was compared. While isolates had multiple virulence-associated genes, exoS (51%), rhlA (37%) and rhlB (46%) were the predominant genes detected. Except for exoY, genes were present in pigmented isolates more frequently than in non-pigmented isolates. CONCLUSION: The results of this study suggest that antibiotic resistance per se might not be associated with the pigment production in P aeruginosa. However, pigment production appeared to be more significantly associated with multi-drug resistance, presence ofvirulence-associated genes, and expression ofcertain virulence factors, most notably elastase, protease, siderophore and DNase activity. Since pigment production is easy to determine, this might to be a good starting point to identify the virulence status ofan isolate.

OBJETIVO: Pseudomonas aeruginosa produce múltiples factores de virulencia que han estado implicados en patogénesis y detección de quórum (quorum sensing). El objetivo de este estudio fue determinar las diferencias en los factores de virulencia de aislados de P aeruginosa pigmentada y no pigmentada. MÉTODO: Se evaluaron las asociaciones entre la producción de pigmentos (piocianina y pioverdina) y la producción de Dnasa, elastasa, lipasa, proteasa, sideróforos, motilidad asociada a superficies (twitching), patrones de resistencia antibiótica, y genes asociados con virulencia en 57 aislados de P aeruginosa no duplicados, de heridas, esputo, orina, exudado vaginal, exudados de oídos, ojos, y vías respiratorias, y aspirados de peritoneo y úlceras. RESULTADOS: La mayor parte (82.5%) de los aislados produjeron uno de los pigmentos. Los aislados pigmentados produjeron con mayor frecuencia y más significativamente (p < 0.05). Dnasa, elastasa, lipasa, proteasa, y siderósforos. Imipenem fue el único antibiótico al que todos los aislados eran susceptibles (p < 0.05), mientras que el 93% y el 32% fueron resistentes a la tetraciclina y a la norfloxacina, respectivamente. Sin embargo, no hubo diferencia significativa entre los aislados pigmentados y los no pigmentados cuando se comparaba la resistencia antibiótica. Si bien los aislados tenían múltiples genes asociados con la virulencia, exoS (51%), rhlA (37%) y rhlB (46%) fueron los genes predominantes detectados. Con excepción de exoY, los genes estuvieron presentes en aislados pigmentados con mayor frecuencia que en los aislados no pigmentados. CONCLUSIÓN: Los resultados de este estudio sugieren que la resistencia antibiótica per se podría no estar asociada con la producción de pigmentos en P aeruginosa. Sin embargo, la producción de pigmentos parecía estar asociada más significativamente con la resistencia a las multidrogas, la presencia de genes asociados con la virulencia, y la expresión de ciertos factores de virulencia, en particular la actividad de la elastasa, la proteasa, los sideróforos, y la Dnasa. Puesto que la producción de pigmentos es fácil de determinar, esto podría ser un buen punto de partida para identificar el estado de virulencia de un aislado.

The emergence of qnr-mediated quinolone resistance among Enterobacteriaceae in Jamaica / Surgimiento de la resistencia a las quinolonas mediada por qnr entre las Enterobacteriaceae en Jamaica

OBJECTIVE: Quinolone resistance is usually caused by various chromosomal mutations, but has been more recently associated with plasmids which carry the qnr determinant. The aim of this study is to investigate the prevalence of qnr genes in clinical isolates of Enterobacteriaceae in Jamaica. METHODS: A total of 255 non-duplicate fluoroquinolone-resistant Enterobacteriaceae clinical isolates, comprising 232 Escherichia coli, 20 Klebsiella species and three Enterobacter spp were collected between October 2007 and November 2008 from hospitalized patients in Jamaica. The presence of the qnr gene was screened by PCR using specific primers for qnrA, qnrB and qnrS in extracted plasmid DNA. RESULTS: Eighty-three (32.5%) of these isolates were qnr-positive, of which 47.0% housed the qnrA gene only, 1.2% qnrB and 9.6% qnrS only. Another 36.1% possessed both qnrA and qnrS genes. Approximately 30% of the quinolone-resistant E coli isolates harboured the qnr gene while 50% Klebsiella spp and all Enterobacter spp were positive. CONCLUSION: The emergence of qnr-mediated quinolone resistance among clinical Enterobacteriaceae isolates is described for the first time in Jamaica.

OBJETIVO: La resistencia a la quinolona es generalmente causada por varias mutaciones cromosomáticas, pero más recientemente ha sido asociada con plásmidos portadores del determinante qnr. El objetivo de este estudio fue investigar la prevalencia de genes qnr en los aislados clínicos de Enterobacteriaceae en Jamaica. MÉTODOS: Un total de 255 aislados clínicos no duplicados de Enterobacteriaceae resistentes a la fluoroquinolona, incluyendo 232 de Escherichia coli, 20 especies de Klebsiella y tres Enterobacter spp, fueron recogidos entre octubre de 2007 y noviembre de 2008, de pacientes hospitalizados en Jamaica. La presencia del gen qnr fue tamizada mediante marcadores PCR, usando primers específicos para qnrA, qnrB y qnrS en el ADN plásmido extraído. RESULTADOS: Ochenta y tres (32.5%) de éstos aislados fueron qnr-positivos. De ellos, 47.0% alojaban solamente el gen qnrA, 1.2% el qnrB y 9.6% el qnrS solamente. Otro 36.1% poseía tanto genes qnrA cuanto genes qnrS. Aproximadamente 30% de los aislados E. coli resistentes a la quinolona, albergaban el gen qnr mientras que 50% de Klebsiella spp y todas las Enterobacter spp fueron positivas. CONCLUSIÓN: Se describe por primera vez el surgimiento de la resistencia a las quinolonas mediada por qnr en Jamaica.

Pathogenesis of Urinary Tract Infection: the Role of Sexual Behavior and Sexual Transmission.

Acute urinary tract infection (UTI) is an extremely common clinical entity that affects almost half of all women in the United States, and accounts for more than 7 million physician visits, annually, in this country. Sexual behavior and UTI history are the most important predictors of UTI risk among sexually active young women. Whether sexual behavior has similar impact on UTI risk in older women is unknown. Postcoital prophylaxis has been investigated as a strategy for the prevention of recurrent UTI in sexually active women. There are conflicting data regarding the role of voiding habits in relation to sexual intercourse and the risk of UTI. Finally, there are interesting epidemiologic studies suggesting that uropathogenic Escherichia coli may be transmitted between sex partners. We review the recent literature regarding these different areas, and comment on the potential role of sexual transmission in UTI.

Origin of Threefold Periodicity in High-Resolution Transmission Electron Microscopy Images of Thin Film Cubic SiC.

: High-resolution transmission electron microscopy (HRTEM) images of the [1-10] zone of cubic SiC layers grown by molecular beam epitaxy (MBE) often reveal regions of material exhibiting an unusual threefold periodicity. The same contrast was found in earlier works of Jepps and Page, who attributed this contrast in HRTEM images of polycrystalline SiC to the 9R-SiC polytype. In this report we demonstrate by HRTEM image simulations that the model of the 9R polytype and an alternative twinning model can fit qualitatively the experimental HRTEM images. However, by comparing the fast Fourier transform (FFT) patterns of the experiments and the simulations, as well as by using dark-field imaging, we show unambiguously that only the model of overlapping twinned 3C-SiC crystals fully agrees with the experiments.

Community-Acquired Pneumonia: An Overview.

Community-acquired pneumonia (CAP) accounts for a significant number of hospitalizations and outpatient visits, as well as substantial health care expenditures. CAP is particularly common among the elderly who account for more than 90% of deaths due to pneumonia. Streptococcus pneumoniae is believed to be the most common microbial etiology of CAP, but recent studies suggest that the atypical pathogens may be more common than previously thought, particularly among ambulatory patients. Recent studies have provided data regarding risk of mortality and process of care and outcomes. Increasing resistance among strains of S. pneumoniae has impacted the approach to the empiric therapy of CAP. The Infectious Diseases Society of America published guidelines for the evaluation and management of CAP this past year. Pathogen-specific therapy guided by the results of sputum gram stain and culture is emphasized. Despite enthusiasm for practice guidelines and clinical pathways, there remains insufficient published data to determine their impact on quality and cost of care in patients with CAP.

Antibiotic Selection for Urinary Tract Infection: New Microbiologic Considerations.

Urinary tract infection (UTI) is an extremely common clinical condition, especially among women, half of whom will have at least one episode of acute cystitis at some point during adult life. An estimated one quarter of these women will have frequent, recurrent UTI. The microbiology of uncomplicated UTI is very predictable, with the vast majority of cases attributed to Escherichia coli. Recent reports from the United States and Europe have shown that resistance among uropathogens to agents that have traditionally been recommended as firstline therapy for uncomplicated UTI is on the rise. Although resistance to fluoroquinolone antibiotics among community-acquired uropathogens remains very low in the United States, fluoroquinolone resistance in community-acquired UTI isolates from other parts of the world has been increasingly described. Very low levels of resistance to nitrofurantoin among uropathogens has revived interest in this agent. The effect of in vitro resistance in uropathogens on the clinical response to treatment of acute cystitis is not well studied. The implications of emerging resistance among the causative agents of this extremely common infection for therapy of UTI are discussed.