Impact of quinolone-resistance acquisition on biofilm production and fitness in Salmonella enterica.

OBJECTIVES: To investigate the potential relationship between quinolone resistance and biofilm production in a collection of Salmonella enterica clinical isolates and in S. enterica serovar Typhimurium serial mutants with increasing resistance to ciprofloxacin. METHODS: Nalidixic acid susceptibility and biofilm formation were assessed in a collection of 122 S. enterica clinical isolates. An in vitro quinolone-resistant mutant, 59-64, was obtained from a biofilm-producing and quinolone-susceptible clinical isolate, 59-wt, in a multistep selection process after increasing ciprofloxacin concentrations. The quinolone resistance mechanisms [target gene and multidrug resistance (MDR) regulatory mutations, MICs of several antibiotics, cell envelope protein analysis, real-time PCR and ciprofloxacin accumulation] were characterized for mutant strains. In addition, analysis of fitness, biofilm formation, rdar morphotype and expression of biofilm-related genes by real-time PCR were also determined. RESULTS: Nalidixic acid-susceptible S. enterica strains were more prevalent in producing biofilm than the resistant counterparts. Strain 59-64 acquired five target gene mutations and showed an MDR phenotype. AcrAB and acrF overexpression were ruled out, whereas TolC did show increased expression in 59-64, which, in addition, accumulated less ciprofloxacin. Consistently, increased ramA expression was seen in 59-64 and attributed to a mutation within its promoter. Reduced biofilm production related to diminished csgB expression as well as reduced fitness was seen for 59-64, which was unable to form the rdar morphotype. CONCLUSIONS: Quinolone resistance acquisition may be associated with decreased production of biofilm due to lower csgB expression. Efflux, biofilm production and fitness seem to be interrelated.

Repression of invasion genes and decreased invasion in a high-level fluoroquinolone-resistant Salmonella typhimurium mutant.

BACKGROUND: Nalidixic acid resistance among Salmonella Typhimurium clinical isolates has steadily increased, whereas the level of ciprofloxacin resistance remains low. The main objective of this study was to characterize the fluoroquinolone resistance mechanisms acquired in a S. Typhimurium mutant selected with ciprofloxacin from a susceptible isolate and to investigate its invasion ability. METHODOLOGY/PRINCIPAL FINDINGS: Three different amino acid substitutions were detected in the quinolone target proteins of the resistant mutant (MIC of ciprofloxacin, 64 microg/ml): D87G and G81C in GyrA, and a novel mutation, E470K, in ParE. A protein analysis revealed an increased expression of AcrAB/TolC and decreased expression of OmpC. Sequencing of the marRAB, soxRS, ramR and acrR operons did not show any mutation and neither did their expression levels in a microarray analysis. A decreased percentage of invasion ability was detected when compared with the susceptible clinical isolate in a gentamicin protection assay. The microarray results revealed a decreased expression of genes which play a role during the invasion process, such as hilA, invF and the flhDC operon. Of note was the impaired growth detected in the resistant strain. A strain with a reverted phenotype (mainly concerning the resistance phenotype) was obtained from the resistant mutant. CONCLUSIONS/SIGNIFICANCE: In conclusion, a possible link between fluoroquinolone resistance and decreased cell invasion ability may exist explaining the low prevalence of fluoroquinolone-resistant S. Typhimurium clinical isolates. The impaired growth may appear as a consequence of fluoroquinolone resistance acquisition and down-regulate the expression of the invasion genes.

Characterization of the enzyme aac(3)-id in a clinical isolate of Salmonella enterica serovar Haifa causing traveler's diarrhea

Introducciónel objetivo de este estudio fue identificar el mecanismo de sensibilidad disminuida a gentamicina en un aislamiento clínico de Salmonella, lo que nos condujo a la detección de un gen que codifica una acetiltransferasa modificante de aminoglucósidos localizada en un integron tipo 1.Métodosla cepa multiresistente de Salmonella fue aislada de las heces de un viajero a Egipto. La susceptibilidad a 12 agentes antimicrobianos se determinó mediante Kirby-Bauer. La presencia de integron clase 1 se realizó mediante PCR. El producto de PCR amplificado del integrón fue recuperado y secuenciado para conocer los genes que contenía dicho integrón. Además se determinó la susceptibilidad a gentamicina C1a, gentamicina C1, sisomicina, neomicina, dibekacina, kanamicina, tobramicina, amikacina, netilmicina, apramicina, dactimicina, espectinomicina, estreptomicina, lividomicina y butirosina. El kit de expresión Champion™ pET101 Directional TOPO® fue utilizado para clonar y expresar el gen aac(3)-I.Resultadosel aislamiento fue identificado como Salmonella enterica serovariedad Haifa, el cual presentaba resistencia al ácido nalidixico, tetraciclina y sensibilidad disminuida a gentamicina. Se observó la presencia de un integron tipo 1 con un tamaño de 1,500bp en el que se encontraron dos genes (aac(3)-Id y aadA7). El análisis de la sensibilidad a diferentes aminoglucósidos de la cepa de E. coli TOP10F’ transformada con el vector que contenia el gen aac(3)-Id demostró resistencia a gentamicina C1a, gentamicina C1, y dactimicina, en concordancia con la presencia del enzima pero era susceptible a sisomicina. La secuencia de aminoácidos presentaba un 100% de identidad con el enzima AAC(3)-Id.Conclusiónla presencia del enzima AAC(3)-Id ha sido descrita por primera vez en S. Haifa(AU)

IntroductionThe objective of this investigation was to identify the mechanism of decreased susceptibility to gentamicin in a Salmonella clinical isolate, leading to the detection of a aminoglycoside acetyltransferase gene found in a class 1 integron.MethodsA multidrug-resistant Salmonella strain was recovered from feces of a traveler to Egypt. The antimicrobial susceptibility test to 12 antimicrobial agents was performed with the Kirby-Bauer method. The presence of class 1 integron was determined by PCR. The amplified product was recovered and sequenced in order to establish the genes carried. In addition, susceptibility to gentamicin C1a, gentamicin C1, sisomicin, neomycin, dibekacin, kanamycin, tobramycin, amikacin, netilmicin, apramycin, dactimicin, spectinomycin, streptomycin, lividomycin and butirosin, was established. The Champion™ pET101 Directional TOPO® Expression Kit was used to clone and express the aac(3)-I gene.ResultsThe isolate was identified as Salmonella enterica serovar Haifa, showing resistance to nalidixic acid, tetracycline and decreased susceptibility to gentamicin. One integron with a size circa 1,500bp, encoding an aac(3)-Id plus aadA7 genes was observed. The analysis of the susceptibility to different aminoglycosides in the E. coli TOP10F’ transformed with the vector carrying aac(3)-Id gene showed resistance to gentamicin C1a, gentamicin C1, and dactimicin, in accordance with the presence of this enzyme but, was susceptible to sisomicin. The homology of the amino acid and nucleotide sequences with the AAC(3)-Id enzyme was of 100%.ConclusionThe presence of the AAC(3)-Id enzyme was described for the first time in a S. Haifa(UA)

Characterization of the enzyme aac(3)-Id in a clinical isolate of Salmonella enterica serovar Haifa causing traveler's diarrhea.

INTRODUCTION: The objective of this investigation was to identify the mechanism of decreased susceptibility to gentamicin in a Salmonella clinical isolate, leading to the detection of a aminoglycoside acetyltransferase gene found in a class 1 integron. METHODS: A multidrug-resistant Salmonella strain was recovered from feces of a traveler to Egypt. The antimicrobial susceptibility test to 12 antimicrobial agents was performed with the Kirby-Bauer method. The presence of class 1 integron was determined by PCR. The amplified product was recovered and sequenced in order to establish the genes carried. In addition, susceptibility to gentamicin C1a, gentamicin C1, sisomicin, neomycin, dibekacin, kanamycin, tobramycin, amikacin, netilmicin, apramycin, dactimicin, spectinomycin, streptomycin, lividomycin and butirosin, was established. The Champion pET101 Directional TOPO Expression Kit was used to clone and express the aac(3)-I gene. RESULTS: The isolate was identified as Salmonella enterica serovar Haifa, showing resistance to nalidixic acid, tetracycline and decreased susceptibility to gentamicin. One integron with a size circa 1,500 bp, encoding an aac(3)-Id plus aadA7 genes was observed. The analysis of the susceptibility to different aminoglycosides in the E. coli TOP10F' transformed with the vector carrying aac(3)-Id gene showed resistance to gentamicin C1a, gentamicin C1, and dactimicin, in accordance with the presence of this enzyme but, was susceptible to sisomicin. The homology of the amino acid and nucleotide sequences with the AAC(3)-Id enzyme was of 100%. CONCLUSION: The presence of the AAC(3)-Id enzyme was described for the first time in a S. Haifa.

Quinolone-resistant uropathogenic Escherichia coli strains from phylogenetic group B2 have fewer virulence factors than their susceptible counterparts.

The prevalence of 31 virulence factors was analyzed among nalidixic acid-susceptible and -resistant Escherichia coli strains from phylogenetic group B2. Hemolysin, cytotoxic necrotizing factor 1, and S and F1C fimbriae genes were less prevalent among nalidixic acid-resistant E. coli strains. Quinolone resistance may be associated with a decrease in the presence of some virulence factors.

A double mutation in the gyrA gene is necessary to produce high levels of resistance to moxifloxacin in Campylobacter spp. clinical isolates.

The aim of this study was to compare different fluoroquinolones against Campylobacter spp., analysing the molecular mechanisms of resistance. Moxifloxacin exhibited the greatest activity of the quinolones tested, being active against isolates carrying a single mutation in the gyrA gene. High resistance levels to moxifloxacin were related to the presence of a double gyrA mutation.

Extended virulence genotypes and phylogenetic background of Escherichia coli isolates from patients with cystitis, pyelonephritis, or prostatitis.

Molecular analysis of 63 Escherichia coli urine isolates showed that pyelonephritis (n=23) and prostatitis (n=17) isolates exhibited more virulence factors (VFs) among the 35 sought than did cystitis isolates (n=23). Several nontraditional VFs--including bmaE (M fimbriae), gafD (G fimbriae), fyuA (yersiniabactin receptor), ireA and iroN (novel siderophore receptors), cvaC (colicin [microcin] V), traT (serum-resistance associated), ibeA (invasion of brain endothelium), ompT (outer membrane protease T), and malX (pathogenicity island marker)--either differentiated significantly between syndromes (despite small numbers of isolates and possible multiple-comparison artifacts) or were broadly prevalent. Thus, interventions that target conserved uro-VFs may be possible, despite the likely existence of syndrome-specific pathogenetic mechanisms and/or host defense systems.

Mechanism of resistance to several antimicrobial agents in Salmonella Clinical isolates causing traveler's diarrhea.

The evolution of antimicrobial resistance in Salmonella isolates causing traveler's diarrhea (TD) and their mechanisms of resistance to several antimicrobial agents were analyzed. From 1995 to 2002, a total of 62 Salmonella strains were isolated from stools of patients with TD. The antimicrobial susceptibility to 12 antibiotics was determined, and the molecular mechanisms of resistance to several of them were detected as well. The highest levels of resistance were found against tetracycline and ampicillin (21 and 19%, respectively), followed by resistance to nalidixic acid (16%), which was mainly detected from 2000 onward. Molecular mechanisms of resistance were analyzed in 16 isolates. In these isolates, which were resistant to ampicillin, two genes encoding beta-lactamases were detected: oxa-1 (one isolate) and tem-like (seven isolates [in one strain concomitantly with a carb-2]). Resistance to tetracycline was mainly related to tetA (five cases) and to tetB and tetG (one case each). Resistance to chloramphenicol was related to the presence of the floR and cmlA genes and to chloramphenicol acetyltransferase activity in one case each. Different genes encoding dihydrofolate-reductases (dfrA1, dfrA12, dfrA14, and dfrA17) were detected in trimethoprim-resistant isolates. Resistance to nalidixic acid was related to the presence of mutations in the amino acid codons 83 or 87 of the gyrA gene. Further surveillance of the Salmonella spp. causing TD is needed to detect trends in their resistance to antimicrobial agents, as we have shown in our study with nalidixic acid. Moreover, such studies will lead to better treatment and strategies to prevent and limit their spread.

In vitro activity of gemifloxacin against clinical isolates of Neisseria gonorrhoeae with and without mutations in the gyrA gene.

The MIC of gemifloxacin and five other quinolones was tested against 31 clinical isolates of Neisseria gonorrhoeae; strains were analyzed for the presence of mutations in both the gyrA and parC genes. Only seven strains were resistant to nalidixic acid due to a mutation in the gyrA gene but not in the parC gene, with six and two considered intermediate to ciprofloxacin and levofloxacin, respectively. The activity of gemifloxacin was similar to that of trovafloxacin and moxifloxacin, but was more active than nalidixic acid, ciprofloxacin or levofloxacin against the gyrA mutant strains. Gemifloxacin is a valid therapeutic alternative to treat infections with N. gonorrhoeae, retaining its activity against strains already presenting a mutation in gyrA.

Distribution of beta-lactamases in Acinetobacter baumannii clinical isolates and the effect of Syn 2190 (AmpC inhibitor) on the MICs of different beta-lactam antibiotics.

The distribution of beta-lactamases in a group of 20 epidemiologically well defined Acinetobacter baumannii clinical isolates and the in vitro activity of Syn 2190, a novel beta-lactamase AmpC inhibitor, were determined. Twenty-five per cent of the strains carried and expressed a TEM-type beta-lactamase, whereas 35% had an OXA-type beta-lactamase. In nine out of 11 (82%) ceftazidime-resistant and four out of 13 (30.7%) cefepime-resistant strains, the MIC of these beta-lactam antibiotics decreased when determined in the presence of Syn 2190. Thus, our results suggest that in a high percentage of A. baumannii clinical isolates the increased production of AmpC, in combination or not with other resistance mechanisms, contributes to the resistance pattern in A. baumannii to beta-lactams.

In vitro activity of clinafloxacin in comparison with other quinolones against Stenotrophomonas maltophilia clinical isolates in the presence and absence of reserpine.

A total of 33 Stenotrophomonas maltophilia clinical isolates were tested for their susceptibility to clinafloxacin in comparison with ciprofloxacin, levofloxacin, moxifloxacin, nalidixic acid, norfloxacin, sparfloxacin and trovafloxacin. The MIC(50) and MIC(90) were as follows: ciprofloxacin 4 and 64 microg/mL; clinafoxacin 0.5 and 4 microg/mL; levofloxacin 2 and 32 microg/mL; moxifloxacin 1 and 8 microg/mL; nalidixic acid 8 and 128 microg/mL; norfloxacin 64 and 256 microg/mL; sparfloxacin 1 and 16 microg/mL; and trovafloxacin 1 and 8 microg/mL. Clinafloxacin was the most active quinolone, with only a 15.1% of strains showing resistance. When the MICs were determined in the presence of 25 microg/ml of reserpine, the MIC(90) of trovafloxacin and moxifloxacin did not change, whereas decreased 2-fold for clinafloxacin, levofloxacin, sparfloxacin and nalidixic acid, and 4- and 8-fold for ciprofloxacin and norfloxacin respectively. No clinafloxacin-resistant strains were observed when the MIC was performed in the presence of reserpine. Therefore, clinafloxacin shows the better "in vitro"activity against these 33 strains of S.maltophilia.

Activity of clinafloxacin, compared with six other quinolones, against Acinetobacter baumannii clinical isolates.

The in vitro activity of clinafloxacin was studied in comparison with ciprofloxacin, levofloxacin, moxifloxacin, nalidixic acid, sparfloxacin and trovafloxacin against Acinetobacter baumannii clinical isolates. Clinafloxacin showed a MIC(90) of 4 mg/L, whereas the remaining quinolones showed a MIC(90) equal to or higher than 16 mg/L. MIC(50) determination in the presence of reserpine resulted in a two-fold decrease, except for trovafloxacin, which decreased four-fold, and for moxifloxacin and nalidixic acid, which did not change. The effect of reserpine was most pronounced among strains with a low level of resistance to quinolones. The MIC of clinafloxacin for strains with no mutation in either gyrA or parC genes ranged from 0.008 to 0.25 mg/L. In strains with a single mutation at amino acid codon Ser83 of the gyrA gene, the MIC of clinafloxacin ranged from 0.12 to 1 mg/L, whereas strains with a double mutation, one in the gyrA gene and another in the parC gene, showed a range of MIC of clinafloxacin from 1 to 8 mg/L. Therefore, clinafloxacin shows good activity against strains carrying a single mutation in the gyrA gene, and hence a second mutation is required for the microorganism to express resistance.

Seroprevalencia de la toxoplasmosis en mujeres en edad fértil (1992-1999) / Seroprevalence of toxoplasmosis in women of childbearing age (1992-1999)

Fundamento: Averiguar si es necesario el cribado prenatal de la toxoplasmosis en nuestro hospital desde un punto de vista seroepidemiológico. Pacientes y métodos: Se ha analizado retrospectivamente la prevalencia de IgG anti-T. gondii en 7.090 mujeres en edad fértil visitadas en el Hospital Clínic de Barcelona desde febrero de 1992 hasta abril de 1999. Se ha comprobado la asociación entre la seroprevalencia y las variables año, edad, lugar de nacimiento (provincia de Barcelona/otras provincias) y de residencia (urbano/rural). Resultados: Se observó una tendencia decreciente de la prevalencia a lo largo del tiempo (p < 0,001), siendo actualmente menor de 40 por ciento en el conjunto de mujeres entre 15 y 45 años. La infección también estuvo directamente relacionada con la edad (p < 0,001) y el nacimiento fuera de la provin cia de Barcelona (p = 0,001). No se encontró asociación entre el lugar de residencia y la seroprevalencia. Conclusiones: Es aconsejable realizar el cribado prenatal de la toxoplasmosis por la alta tasa de mujeres seronegativas expuestas a la infección y la existencia de un número elevado de primoinfecciones en el período fértil de la vida. (AU)

Datación de igm anti-toxoplasma en el embarazo con métodos VIDAS-ELFA / Datation of IgM anti-Toxoplasma in pregnancy with VIDAS-ELFA methods

Fundamentos: Estudiar la utilidad de la titulación de anticuerpos IgG e IgM, y de la avidez de las IgG para la datación de IgM frente a Toxoplasma gondii. Métodos: Se usaron las pruebas VIDAS Toxo IgG, VIDAS Toxo IgM y VIDAS Toxo IgG Avidity. Se analizaron 64 sueros con IgM e IgG anti-T. gondii, 32 de ellos pertenecientes a 12 individuos con una infección de menos de 40 semanas (grupo I), y el resto pertenecientes a 17 individuos con una infección de más de 40 semanas (grupo II). Resultados: Un índice de IgM 12 semanas. Un índice de avidez > 0,164 excluyó el 100 por ciento de infecciones ó 12 semanas. Con índices de avidez > 0,26 y 0,45 se pudieron excluir infecciones ó 20 y ó 40 semanas, respectivamente. Conclusiones: Los métodos serológicos utilizados para el estudio son capaces de identificar correctamente anticuerpos IgM anti-T. gondii residuales y, por tanto, en muchas ocasiones hacen innecesario una segunda extracción para analizar la cinética de las IgG en pacientes embarazadas. (AU)