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The murine immune response to Escherichia coli O6:K-alone or pre-exposed to 0.1 x MIC of aztreonam was investigated. Relative to mice immunized with untreated bacteria, mice immunized with antibiotic-treated microorganisms presented a significantly enhanced protection towards a challenge of 100 x LD50 of viable E. coli O6:K-. Previous injection of 0.1 mL of serum drawn from mice immunized with treated and untreated bacteria protected non-immunized mice towards a challenge of 10 x LD50 of viable E. coli O6:K--. Serum from mice immunized with treated bacteria also protected non-immunized mice towards a lethal challenge of E. coli O111. The antiserum contained high titre of IgG antibodies that cross-reacted with lipopolysaccharide isolated from smooth and rough Gram-negative bacteria. Immunoblotting showed additional bands of reactivity to the untreated E. coli O6:K-. Immunization with antibiotic-treated bacteria led to the production of type specific and cross reactive antibodies that protected animals against viable homologous and heterologous lethal challenges. [ABSTRACT FROM AUTHOR]

OBJECTIVE: To evaluate the feasibility of using 16S rDNA universal primer PCR (followed by sequencing) and 65-kDa heat shock Mycobacterium tuberculosis protein gene PCR as a method to determine a bacterial etiology in culture---negative cerebrospinal fluid (CSF) samples. METHODS: One hundred and forty-nine CSF samples from 128 patients were processed. DNA was extracted from the CSF samples and amplified with the eubacterial 16S rDNA primers P11E and P13B, and with the 65-kDa heat shock protein gene mycobacterial primers. The amplicons were identified by sequencing and specific oligoprobe hybridization. RESULTS: Overall, a microbiological diagnosis was made in 11 of 125 ultimately culture-negative cases. The use of 65-kDa heat shock protein gene PCR was needed to improve the diagnosis of tuberculous meningitis; in four patients, prospectively studied, the outcome of antituberculous therapy could also be followed. CONCLUSIONS: In culture-negative bacterial meningitis it is possible to improve the microbiological diagnosis by use of 16S rDNA amplification and sequencing, together with amplification of a more specific gene in mycobacteria.