Acquisition of plasmids from Shiga toxin-producing Escherichia coli strains had low or neutral fitness cost on commensal E. coli.

Although it has been hypothesized that the acquisition of plasmids-especially those bearing virulence factors and antimicrobial resistance genes-increases the energetic burden and reduces the fitness of a bacterium in general, some results have challenged this view, showing little or no effect on fitness after plasmid acquisition, which may lead to change in the view that there are evolutionary barriers for a wide spread of such plasmids among bacteria. Here, to evaluate the fitness impact of plasmid-encoded antibiotic resistance and virulence genes, plasmids from O26:H11, O111:H8, and O118:H16 Shiga toxin-producing Escherichia coli (STEC) human and bovine isolates were transferred to the non-virulent E. coli HS and K-12 MG1655 strains. Sequencing and PCR were used to characterize plasmids, and to identify the presence of antimicrobial resistance and/or virulence genes. The fitness impact of plasmids encoding virulence and antimicrobial resistance upon bacterial hosts was determined by pairwise growth competition. Plasmid profile analysis showed that STEC strains carried one or more high and low molecular weight plasmids belonging to the B/O, F, I, K, P, Q, and/or X incompatibility groups encoding virulence genes (SPATE-encoding genes) and/or antimicrobial resistance genes (aadA1, strAB, tetA, and/or tetB). Competition experiments demonstrated that the biological cost of carriage of these plasmids by the commensal E. coli strain HS or the laboratory strain E. coli K-12 MG1655 was low or non-existent, ranging from - 4.7 to 5.2% per generation. This suggests that there are few biological barriers-or, alternatively, it suggests that there are biological barriers that we were not able to measure in this competition model-against the spread of plasmid encoding virulence and resistance genes from STEC to other, less pathogenic E. coli strains. Thus, our results, in opposition to a common view, suggest that the acquisition of plasmids does not significantly affect the bacteria fitness and, therefore, the theorized plasmid burden would not be a significant barrier for plasmid spread.

Pharmacodynamic profiling of commonly prescribed antimicrobial drugs against Escherichia coli isolates from urinary tract

Since antimicrobial resistance among uropathogens against current first line agents has affected the management of severe urinary tract infection, we determined the likelihood that antibiotic regimens achieve bactericidal pharmacodynamic exposures using Monte Carlo simulation for five antimicrobials (ciprofloxacin, ceftriaxone, piperacillin/tazobactam, ertapenem, and meropenem) commonly prescribed as initial empirical treatment of inpatients with severe community acquired urinary tract infections. Minimum inhibitory concentration determination by Etest was performed for 205 Brazilian community urinary tract infection Escherichia coli strains from 2008 to 2012 and 74 E. coli bloodstream strains recovered from a surveillance study. Pharmacodynamic exposure was modeled via a 5000 subject Monte Carlo simulation. All isolates were susceptible to ertapenem and meropenem. Piperacillin/tazobactam, ceftriaxone and ciprofloxacin showed 100%, 97.5% and 83.3% susceptibility among outpatient isolates and 98.6%, 75.7% and 64.3% among inpatient isolates, respectively. Against outpatient isolates, all drugs except ciprofloxacin (82.7% in aggressive and 77.6% in conservative scenarios) achieved high cumulative fraction of response: car-bapenems and piperacillin/tazobactam cumulative fraction of responses were close to 100%, and ceftriaxone cumulative fraction of response was 97.5%. Similar results were observed against inpatients isolates for carbapenems (100%) and piperacillin/tazobactam (98.4%), whereas ceftriaxone achieved only 76.9% bactericidal cumulative fraction of response and ciprofloxacin 61.9% (aggressive scenario) and 56.7% (conservative scenario) respectively. Based on this model, standard doses of beta-lactams were predicted to deliver sufficient pharmacodynamic exposure for outpatients. However, ceftriaxone should be avoided for inpatients and ciprofloxacin empirical prescription should be avoided in both inpatients and outpatients with complicated urinary tract infection.

Pharmacodynamic profiling of commonly prescribed antimicrobial drugs against Escherichia coli isolates from urinary tract.

Since antimicrobial resistance among uropathogens against current first line agents has affected the management of severe urinary tract infection, we determined the likelihood that antibiotic regimens achieve bactericidal pharmacodynamic exposures using Monte Carlo simulation for five antimicrobials (ciprofloxacin, ceftriaxone, piperacillin/tazobactam, ertapenem, and meropenem) commonly prescribed as initial empirical treatment of inpatients with severe community acquired urinary tract infections. Minimum inhibitory concentration determination by Etest was performed for 205 Brazilian community urinary tract infection Escherichia coli strains from 2008 to 2012 and 74 E. coli bloodstream strains recovered from a surveillance study. Pharmacodynamic exposure was modeled via a 5000 subject Monte Carlo simulation. All isolates were susceptible to ertapenem and meropenem. Piperacillin/tazobactam, ceftriaxone and ciprofloxacin showed 100%, 97.5% and 83.3% susceptibility among outpatient isolates and 98.6%, 75.7% and 64.3% among inpatient isolates, respectively. Against outpatient isolates, all drugs except ciprofloxacin (82.7% in aggressive and 77.6% in conservative scenarios) achieved high cumulative fraction of response: carbapenems and piperacillin/tazobactam cumulative fraction of responses were close to 100%, and ceftriaxone cumulative fraction of response was 97.5%. Similar results were observed against inpatients isolates for carbapenems (100%) and piperacillin/tazobactam (98.4%), whereas ceftriaxone achieved only 76.9% bactericidal cumulative fraction of response and ciprofloxacin 61.9% (aggressive scenario) and 56.7% (conservative scenario) respectively. Based on this model, standard doses of beta-lactams were predicted to deliver sufficient pharmacodynamic exposure for outpatients. However, ceftriaxone should be avoided for inpatients and ciprofloxacin empirical prescription should be avoided in both inpatients and outpatients with complicated urinary tract infection.

A virulência de Escherichia coli patogênica extra-intestinal (ExPEC) em relação à idade e ao sexo do hospedeiro / La virulencia de Escherichia coli (ExPEC) patogénica intraintestinal en relación a la edad y al sexo del hospedero / Extraintestinal Pathogenic Eschericia coli (ExPEC) virulence regarding host age and sex

A Escherichia coli é, entre os bacilos Gram-negativos, o principal agente etiológico de infecções da corrente sanguínea, seja comunitárias seja as nosocomiais. Uma vez que são poucos os trabalhos que pesquisaram a virulência de amostras de E. coli isoladas de bacteremia no Brasil, este trabalho teve por objetivo investigar os fatores de virulência frequentes em amostras isoladas de seres humanos hospitalizados bem como a origem filogenética destas amostras, relacionando essas características bacterianas com características dohospedeiro como sexo e idade. A pesquisa da origem filogenética das amostras foi realizada utilizando-se a técnica da PCR e a pesquisa de fatores de virulência por hibridação de colônias com sondas radioativas. O resultado obtido com a pesquisa de 20 fatores de virulência demonstrou que os fatores relacionados à fimbria tipo 1, ao sistema yersiniabactina de aquisição de ferro e à produção de cápsula, foram os mais frequentes nas amostras estudadas. Além disso, a grande maioria das amostras foi classificada nos grupos filogenéticos B2 e D. Em relação às características do hospedeiro, foi possível estabelecer uma relação positiva entre amostras mais virulentas e infecções em pacientes do sexo feminino. Contudo, não houve diferença na virulência das amostras em relação à idade do hospedeiro. Estes dados sugerem que as amostras que causam infecções extra-intestinais em pacientes do sexo feminino são, em geral, mais virulentas do que aquelas que causaminfecções nos pacientes do sexo masculino. Por outro lado, a idade não parece ter correlação com a virulência da amostra infectante. (AU)

Escherichia Coli es, entre los bacilos gram negativos, el agente etiológico principal de infecciones de la cadena sanguínea, sean comunitarias o nosocomiales. Como son pocos los trabajos que han estudiado la virulencia de muestras de Escherichia Coli aisladas de bacteremia en Brasil, este trabajo tiene el objetivo de investigar los factores frecuentes de virulencia en muestras aisladas de seres humanoshospitalizados así bien el del filogenética de estas muestras, relacionando estas características bacterianas con las características sexo y edad del hospedero. La investigación del origen filogenética de las muestras fue realizada utilizando la técnica de reacción en cadena de polimerasa y la investigación de factores de factores de virulencia mediante hibridación de colonias con sondas radioactivas. El resultado conseguido con la investigación de 20 factores de virulencia demostró que los factores relacionados a las fimbrias tipo 1, al sistema yersiniabactinade adquisición del hierro y a la producción de cápsula fueran los más frecuentes en las muestras estudiadas. Por otra parte, se clasificaron a la gran mayoría de las muestras en los grupos filogenéticos B2 y D. En lo referente a las características del hospedero,fue posible establecer una relación positiva entre muestras más virulentas e infecciones en pacientes del sexo femenino. Sin embargo,no hubo diferencia en la virulencia de las muestras en lo referente a la edad del hospedero. Estos datos sugieren que las muestras que causan las infecciones extraintestinales en pacientes del sexo femenino son generalmente más virulentas que las que causan infeccionesen pacientes del sexo masculino. Por otra parte, la edad no parece tener correlación con la virulencia de la muestra infectante. (AU)

E. coli is the Gram-negative rod most important cause of bacteremia both in the community and in the hospital environment. Since the reports on virulence of E. coli isolated from the bloodstream are rare in Brazil, this work aimed to investigate isolates from hospitalized patients in regard to the frequency of their virulence factors, and phylogeny, as well as their relationship with the sex and age of the patients. The analysis of phylogenetic relationship was done by PCR, and the search for virulence factors by colony hybridization. Most of the strains were classified in phylogenetic groups B2 and D. Among 20 virulence traits searched, the most frequent were related to Type1 fimbriae, yersiniabactin iron acquisition system, and capsule. The most virulent strains were found in the female gender, while age seemed not to have any connection with the virulence of the isolates. These data suggest that E. coli strains causing bacteremia in female patients are more virulent than those able to cause the same infection in man. The same is not seen in regard to the age of the patients. (AU)