Prolonged application of closed in-line suction catheters increases microbial colonization of the lower respiratory tract and bacterial growth on catheter surface.

BACKGROUND: Microorganisms become attracted to polymer surfaces for a number of reasons including positive charge of biomaterial or concentration of nutrients on the biomaterial surface. Many bacteria additionally possess specific receptors for the interaction with extracellular host protein components that adhere on the biomaterial surface. Several authors suggest that application of closed in-line polypropylene suction catheters (CISC) in intubated patients for more than 24 h is safe and can reduce the costs associated with mechanical ventilation. Therefore, we evaluated the possible role of prolonged application of CISC to cause enhanced colonization of both the biomaterial and the lower respiratory tract. MATERIALS AND METHODS: The prospective, randomized study included 23 mechanically ventilated patients. The CISC tips, adjacent segments and tracheobronchial aspirates of each patient were examined for microbial growth. RESULTS: Application for 72 h significantly enhanced the microbial growth on the CISC tips and on the adjacent catheter segment. Usage for 3 days led to a significant increase in colonization in the lower respiratory tract. CONCLUSION: Normal saline instillation in conjunction with endotracheal suctioning may lead to a dispersion of microorganisms into the lower respiratory tract. More effective self-cleaning mechanisms are necessary to decontaminate the CISC surface after suctioning.

Short report: high prevalence and imbalanced age distribution of the Plasmodium falciparum dihydrofolate reductase gene Asn108 mutation in an area of low pyrimethamine usage in Nigeria.

Resistance of Plasmodium falciparum to pyrimethamine is associated with a non-silent point mutation of the parasite dihydrofolate reductase (DHFR) gene (Ser108 --> Asn108). Wide-scale use of antimalarials is thought to contribute to the emergence of drug resistance. In 131 P. falciparum-infected children in rural Nigeria, the frequency of the resistant Asn108 genotype was assessed by enzymatic restriction digestion of polymerase chain reaction-amplified DHFR sequences and compared with residual pyrimethamine blood levels. The prevalence of the Asn108 variant was 41.2%. In 18.3% of the isolates, both the Asn108 and the wild-type alleles were present. In contrast to the high prevalence of resistant genotypes, residual pyrimethamine blood levels were detected in only 4%. Furthermore, age was found to be a determinant of the parasite genotype since the proportion of Asn108 variants decreased with age (P < 0.05). These findings indicate that additional, unidentified factors, rather than selection by residual drug levels alone, might be responsible for the emergence of pyrimethamine-resistant parasite genotypes.

The ClpB protein from Campylobacter jejuni: molecular characterization of the encoding gene and antigenicity of the recombinant protein.

The ClpB heat-shock protein is necessary for the survival of Escherichia coli cells upon sudden increase of temperature. Using a PCR-based genomic walking method, the nucleotide sequence of a clpB homolog from Campylobacter jejuni was determined. The clpB gene encodes a protein of 857 amino acid (aa) residues, with a predicted molecular mass of 95.3kDa. Alignment of the deduced aa sequence with other known bacterial ClpB proteins revealed overall identity from 47% (E. coli) to 61% (Helicobacter pylori). Within the clpB promoter region, as indicated by primer extension analysis, we identified a sequence identical to the E. coli sigma70 consensus promoter. Northern blot analysis confirmed that clpB is heat-inducible in C. jejuni. The ClpB protein, fused to a 6xHis tag, was synthesized in E. coli and purified by metal-affinity and size exclusion chromatography. In ELISA studies, IgA levels reactive to recombinant ClpB were significantly higher in sera of patients with prior C. jejuni infections than in sera obtained from healthy control persons.

Cloning and expression of the dnaK gene of Campylobacter jejuni and antigenicity of heat shock protein 70.

Campylobacter jejuni is a leading cause of infectious diarrhea throughout the world. In addition, there is growing evidence that Guillain-Barré syndrome, an inflammatory demyelinating disease of the peripheral nervous system, is frequently preceded by C. jejuni infection. In the present study, the hrcA-grpE-dnaK gene cluster of C. jejuni was cloned and sequenced. The dnaK gene consists of an open reading frame of 1,869 bp and encodes a protein with a high degree of homology to other bacterial 70-kDa heat shock proteins (HSPs). The overall percentages of identity to the HSP70 proteins of Helicobacter pylori, Borrelia burgdorferi, Chlamydia trachomatis, and Bacillus subtilis were calculated to be 78.1, 60.5, 57.2, and 53. 8%, respectively. Regions similar to the Escherichia coli sigma70 promoter consensus sequence and to a cis-acting regulatory element (CIRCE) are located upstream of the hrcA gene. Following heat shock, a rapid increase of dnaK mRNA was detectable, which reached its maximum after 20 to 30 min. A 6-His-tagged recombinant DnaK protein (rCjDnaK-His) was generated in E. coli, after cloning of the dnaK coding region into pET-22b(+), and purified by affinity and gel filtration chromatography. Antibody responses to rCjDnaK-His were significantly elevated, compared to those of healthy individuals, in about one-third of the serum specimens obtained from C. jejuni enteritis patients.

Cloning and expression of the Campylobacter jejuni lon gene detected by RNA arbitrarily primed PCR.

Fingerprinting of RNA by arbitrarily primed PCR was used to identify a heat-inducible gene in Campylobacter jejuni. Comparing RNA fingerprints from C. jejuni cells before and after 20 min of heat shock at 48 degrees C, a differentially amplified PCR product was identified which displayed a high degree of homology to bacterial lon genes. By screening C. jejuni genomic libraries, the entire lon gene was cloned and sequenced. It encodes a protein of 791 amino acids with a calculated molecular mass of 90.2 kDa. Alignment of the Lon amino acid sequence with that of other bacterial species revealed an overall identity of up to 56.6% (Helicobacter pylori). Northern and RNA dot blot experiments confirmed heat induction of the C. jejuni lon gene, revealing a maximum 6-8-fold increase in the level of specific mRNA.