ABSTRACT
Virulence profiles and innate immune responses were studied in Acinetobacter baumannii from nosocomial infections collected over one year in a tertiary care hospital in Mexico. A. baumannii were identified by VITEK 2 System followed by susceptibility tests. Carbapenemase genes, active efflux mechanism to imipenem and meropenem and outer membrane proteins profile were analyzed to evaluate their role on the activity of carbapenem resistance. All isolates were genotyped by pulsed field gel electrophoresis. The ability to form biofilm was determined on a polystyrene surface. The resistance to complement was determined with a pooled human normal serum and TNFα release by infected macrophages was determined by ELISA. The 112 isolates from this study were associated with a 52% of mortality. All were resistance to ß-lactams, fluoroquinolones, and trimethroprim-sulfamethoxal, 96 and 90% were resistant to meropenem and imipenem, respectively, but with high susceptibility to polymyxin B, colistin and tigecyclin. Isolates were classified in 11 different clones. Most isolates, 88% (99/112), were metallo-ß-lactamases and carbapenemases producers, associated in 95% with the presence of blaOXA-72 gene. Only 4/99 and 1/99 of the carbapenem-resistant isolates were related to efflux mechanism to meropenem or imipenem resistance, respectively. The loss of expression of 22, 29, and/or 33-36-kDa proteins was detected in 8/11 of the clinical isolates with resistance to carbapenem. More than 96% (108/112) of the isolates were high producers of biofilms on biotic surfaces. Finally, all isolates showed variable resistance to normal human serum activity and were high inductors of TNFα release by macrophages. In summary, these results suggest that multidrug-resistant A. baumannii can persist in the hospital environment through its ability to form biofilms. The high mortality observed was due to their ability to survive normal human serum activity and capability to induce potent inflammatory immune response making this nosocomial pathogen a serious threat to hospitalized patients.
Subject(s)
Acinetobacter Infections/drug therapy , Acinetobacter baumannii/isolation & purification , Cross Infection/drug therapy , Immunity, Innate , Acinetobacter Infections/metabolism , Acinetobacter baumannii/drug effects , Acinetobacter baumannii/pathogenicity , Anti-Bacterial Agents/pharmacology , Anti-Bacterial Agents/therapeutic use , Carbapenems/metabolism , Cross Infection/metabolism , Drug Resistance, Multiple, Bacterial/drug effects , Drug Resistance, Multiple, Bacterial/genetics , Humans , Mexico , Microbial Sensitivity Tests , Tertiary Care Centers , Tumor Necrosis Factor-alpha/metabolism , Virulence , beta-Lactamases/metabolismABSTRACT
Nine Acinetobacter strains from patients and hospital environment were analyzed for virulence markers, quorum sensing signal production, and the presence of luxI and luxR genes. The strains had several properties in common: growth in iron limited condition, biofilm formation, and no active protease secretion. Significantly higher catechol production was determined in patient isolates (P < 0.03), but other invasiveness markers, such as lipase secretion, amount of biofilm, cell motility, antibiotic resistance, and hemolysin production, showed large variability. Notably, all members of the so-called A. calcoaceticus-A. baumannii complex, regardless of whether the source was a patient or environmental, secreted mediumto long-chain N-acyl homoserine lactones (AHL) and showed blue light inhibition of cell motility. In these strains, a luxI homologue with a homoserine lactone synthase domain and a luxR putative regulator displaying the typical AHL binding domain were identified.
Subject(s)
Acinetobacter Infections/microbiology , Acinetobacter/pathogenicity , Cross Infection/microbiology , Acinetobacter/genetics , Acinetobacter/metabolism , Acinetobacter Infections/metabolism , Acyl-Butyrolactones/metabolism , Amino Acid Sequence , Bacterial Proteins/genetics , Bacterial Proteins/metabolism , Base Sequence , Biofilms/growth & development , Cross Infection/metabolism , DNA, Bacterial/chemistry , DNA, Bacterial/genetics , Humans , Molecular Sequence Data , Phylogeny , Polymerase Chain Reaction , Quorum Sensing/physiology , RNA, Ribosomal, 16S/chemistry , RNA, Ribosomal, 16S/genetics , Repressor Proteins/genetics , Repressor Proteins/metabolism , Sequence Alignment , Sequence Analysis, DNA , Trans-Activators/genetics , Trans-Activators/metabolism , Transcription Factors/genetics , Transcription Factors/metabolism , VirulenceABSTRACT
AIMS: To assess the different phenotypes and mechanisms of fluoroquinolone (FQ) resistance in clinical and environmental isolates of Escherichia coli. METHODS AND RESULTS: We compared FQ-resistant E. coli isolates, measuring minimal inhibitory concentrations (MIC) of ciprofloxacin, along with susceptibility to other antibiotics. We also searched for the presence of efflux pumps, using efflux inhibitors, and for plasmid-borne FQ-resistance by PCR. We found that, aside from the higher FQ-resistance prevalence among clinical strains, environmental ones resist much lower concentrations of ciprofloxacin. Efflux pumps mediate fluoroquinolone resistance as frequently among environmental isolates than in clinical strains. Plasmid-borne qnrA genes were not detected in any resistant strain. CONCLUSIONS: Environmental FQ-resistant strains may have a nonclinical origin and/or a selective pressure different from the clinical use of FQs. SIGNIFICANCE AND IMPACT OF THE STUDY: The identification of the source of low-level FQ-resistant strains (ciprofloxacin MIC c. 8 microg ml(-1)) in the environment could be important to curb the rapid emergence and spread of FQ-resistance in clinical settings, as these strains can easily become fully resistant to FQ concentrations achievable in fluids and tissues during therapy.
Subject(s)
Anti-Infective Agents/pharmacology , Ciprofloxacin/pharmacology , Drug Resistance, Bacterial/physiology , Escherichia coli Proteins/metabolism , Escherichia coli/isolation & purification , Escherichia coli/metabolism , Cross Infection/genetics , Cross Infection/metabolism , Cross Infection/microbiology , Dose-Response Relationship, Drug , Drug Resistance, Bacterial/drug effects , Escherichia coli/genetics , Escherichia coli Proteins/genetics , Humans , Mexico , Plasmids/genetics , Plasmids/metabolismABSTRACT
En América Latina (AL) son trascendentes los productores de betalactamasas de espectro extendido (BLEE) en infecciones hospitalarias. Los datos de API y SENTRY revelan una incidencia del 22 a 55. En AL y frecuentemente en el Cono Sur predominan las BLEE de la familia CTX-M contrariamente a EUA y Europa donde prevalecen las derivadas de TEM. Las CTX-M afectan cefotaxima, ceftriaxona y cefepima con más frecuencia que ceftacidima. El tratamiento depende del empleo de carbapenemes con el riesgo de seleccionar resistencia en bacilos gram negativos no fermentadores. El uso de otros betalactámicos particularmente cefepima no es aconsejable por las frecuentes fallas observadas en nuestro medio debido al efecto inóculo por aislados productores de CTX-M-2. Describimos un brote por Klebsiella pneumoniae (Kp) ocurrido entre junio-julio 2004. En el período previo, sólo un paciente presentó una infección debida a Kp productora de BLEE y en el posterior, lo presentaron dos pacientes Se determinó la CIM por microdilución en agar. El fenotipo BLEE se sospechó por ensayo del efecto del clavulanato unido a cefalosporinas de 3ª generación (C3G). Se determinó el punto isoeléctrico (pI) y la detección por PCR del tipo molecular por métodos convencionales. Se comprobaron dos bandas pI 5.4 y 8.2 con ampicilina y ceftriaxona en todas las cepas excepto en dos. Todas las cepas revelaron producción de CTX-M-2 excepto en dos cepas que se identificaron como productoras de SHV-5. Los estudios clonales se correspondieron con los moleculares identificándose dos clones. El brote se resolvió usando dos importantes medidas: 1) lavado de manos y otras medidas de barrera y 2) restringiendo el uso de C3G y ciprofloxacina