Acinetobacter baumannii infections in a tertiary care hospital in Mexico over the past 13 years.

BACKGROUND: Acinetobacter baumannii has evolved from an opportunistic pathogen into a common and persistent nosocomial bacterium capable of causing severe infections during endemic and epidemic periods. METHODS: The study period extended from January 1999 to December 2011 and involved patients hospitalized at the Hospital Civil de Guadalajara, Fray Antonio Alcalde, Jalisco, Mexico. From each patient, a single isolate was obtained, and a total of 3,680 unique isolates were collected. Susceptibility tests were performed according to the guidelines of the Clinical and Laboratory Standards Institute. RESULTS: A. baumannii has disseminated throughout the Hospital Civil de Guadalajara, Fray Antonio Alcalde, since 1999. A. baumannii isolates obtained from patients treated in the adult intensive care unit represent the majority of the isolates that have been collected. In addition, A. baumannii was isolated from the adult neurosurgical ward and the adult internal medicine ward, and these isolates were frequently obtained from secretions. A persistent decrease in the susceptibility of A. baumannii isolates to meropenem (92% in 1999 to 12% in 2011), imipenem and amikacin has been observed. CONCLUSIONS: A. baumannii became an endemic nosocomial pathogen during the study period at the Hospital Civil de Guadalajara, Fray Antonio Alcalde, and has exhibited a persistent decrease in susceptibility to all categories of antimicrobial agents over the past 13 years.

Klebsiella pneumoniae 35 and 36 kDa porins are common antigens in different serotypes and induce opsonizing antibodies.

BACKGROUND: Klebsiella pneumoniae is a major cause of neonatal sepsis and nosocomial infections in Mexico. Antibiotic therapy is the first choice for treatment but the increase in multiple resistance strains has forced scientists to look for alternative treatments, such as immunotherapy. In this work, we propose that porins could be a common antigen among four different capsular serotypes of Klebsiella pneumoniae for the production of immune sera with opsonizing capacity. METHODS: The 35 and 36 kDa porins from four different serotypes of the bacteria were isolated by the Nikaido method followed by purification in Sephacryl column chromatography. The 36 kDa of serotype K8 was further purified by electroelution. The 35 and 36 kDa porins were used to obtain rabbit polyclonal antibodies (PolyAb) to the four serotypes and the 36 kDa from K8 for the production of monoclonal antibodies (MoAb). Antigenic reactivity of PolyAb and MoAb were analyzed by ELISA and WB and their opsonizing capacity for human PMN was measured by chemiluminescence (CL) using capsulated and non-capsulated bacteria. RESULTS: Porins from the four strains showe electrophoretic homology and cross reaction by ELISA and WB. CL assays indicated that PolyAb opsonized heterologous strains and that MoAb perform this in the absence of capsule. CONCLUSIONS: K.pneumoniae 35 and 36 kDa porins are common antigens for the four serotypes studied and induce opsonizing antibodies.

[Capsular polysaccharide of Klebsiella pneumoniae. II. Immunogenic properties]. / Polisacárido capsular de Klebsiella pneumoniae. II. Propiedades inmunogénicas.

It has been considered that the polysaccharide capsular material from microorganisms such as Klebsiella pneumoniae induces mainly thymus-independent humoral immunity, nevertheless studies done with Bacteroides fragilis have shown the participation of cellular immune effector mechanisms. Works done to define the immunogenic role of the capsular polysaccharide of Klebsiella pneumoniae indicate that both active and passive immunization with these antigens confer protection against infections with this bacteria. Several studies propose the use of vaccines prepared with one or various capsular serotypes of Klebsiella pneumoniae in immunoprophylaxis or immunotherapy.

Opsonic capacity of a hyperimmune serum against outer membrane proteins of Klebsiella pneumoniae.

The opsonic capacity of a hyperimmune rabbit serum against a porin-rich outer membrane protein preparation of a strain of K. pneumoniae was evaluated. By immunoblot, the antiserum recognized mainly the porins from an outer membrane protein preparation. Using an ELISA, the titer of anti-porin antibodies was determined. Through a chemiluminescence assay, the increase in the respiratory burst of murine hyperimmune serum was recorded. These data correlate with the results of the microbicidal assays and with the electron microscopy preparations obtained where a great number of bacteria were seen within the macrophages. The in vitro data show that there is a greater bacterial killing when the macrophage is infected with bacteria opsonized with the hyperimmune serum.