Hemagglutinin, urease, and hemolysin production by Proteus mirabilis from clinical sources

Proteus mirabilis, a common cause of urinary tract infection, can lead to serious complications including pyelonephritis. Adherence factors, urease, and hemolysin may be virulence determinants. These factors were compared for bacteria cultured from 16 patients with acute pyelonephritis and 35 with catheter-associated bacteriuria and for 20 fecal isolates. Pyelonephritis isolates were more likely (P less than .05) to express the mannose-resistant/Proteus-like (MR/P) hemagglutinin in the absence of mannose-resistant/Klebsiella-like (MR/K) hemagglutinin than were catheter-associated or fecal isolates. Pyelonephritis isolates produced urease activity of 63 +/- 27 (mean +/- SD) mumol of NH3/min/mg of protein, not significantly different from catheter-associated or fecal isolates. Hybridization of Southern blots of P. mirabilis chromosomal DNA with two urease gene probes demonstrated that urease gene sequences were conserved in all isolates. Geometric mean of reciprocal hemolytic titers for pyelonephritis isolates was 27.9; for urinary catheter isolates, 18.0; and for fecal isolates, 55.7 (not significantly different, P greater than .1). Although in vivo expression of urease and hemolysin may not be reliable indexes of virulence, MR/P hemagglutination in the absence of MR/K hemagglutination may be necessary for development of pyelonephritis.     

Analysis of acetylcholinesterase synthesis and transport in the rat hippocampus: recovery of acetylcholinesterase activity in the septum and hippocampus after administration of diisopropylfluorophosphate

The site and rate of synthesis, as well as the transport dynamics, of newly synthesized acetylcholinesterase (AChE) has been studied in the septum and hippocampus of the rat. Histochemical and biochemical techniques were employed to study time-dependent changes in AChE activity of the medial septal nucleus and hippocampus following systemic administration of the anticholinesterase diisopropyl-fluorophosphate. In both septum and hippocampus, an initially rapid phase of recovery was followed by a slower recovery with similar rate constants for the two regions. Analysis of AChE synthesis in the septo-hippocampal system revealed that recovery of activity in the septum(t_1/2for recovery= 140h) preceded that in the hippocampus(t_1/2for recovery= 400h). The data suggested that the bulk of septal AChE in the hippocampus is transported via the slow component of axoplasmic flow (about 2 mm/day). A fast component may exist, but the experimental arrangement did not permit the clear demonstration of any rapid axoplasmic flow.     

Expression of type 1 fimbriae may be required for persistence of Escherichia coli in the catheterized urinary tract.

Long-term urinary catheterization results in polymicrobial bacteriuria and is complicated by fever, bacteremia, acute pyelonephritis, and death. Escherichia coli is a common urine isolate from catheterized patients and can persist for months. We hypothesized that fimbria-mediated adherence contributes to its persistence. For 1 year, urine specimens were collected from 51 patients greater than or equal to 65 years of age who were catheterized for greater than or equal to 30 days. E. coli was isolated at greater than or equal to 10(5) CFU/ml from 447 (36%) of 1,230 weekly urine specimens from 26 patients. Week 1 isolates from 52 definable episodes were tested for hemagglutination, hybridization with gene sequences from the pil and pap operons, in vitro adherence to catheter material, binding of 125I-labeled Tamm-Horsfall protein, hemolysin and colicin V production, and serum resistance. The proportions of isolates of short (1 week only), medium (2 to 11 weeks) and long (greater than or equal to 12 weeks) episodes of bacteriuria which expressed type 1 fimbriae as assayed by mannose-sensitive hemagglutination were 59, 65, and 92%, respectively. Isolates with the pil operon (the genome for type 1 fimbriae) from episodes lasting greater than 1 week expressed mannose-sensitive hemagglutination more frequently (P = 0.011) than pil-positive isolates from episodes of less than or equal to 1 week. Isolates from episodes of greater than 1 week also bound significantly more Tamm-Horsfall protein than isolates from episodes of less than or equal to 1 week (P = 0.044). Although nearly half of the isolates produced P fimbriae, an important virulence factor for the development of pyelonephritis, no correlation with persistence could be made. Overall, the E. coli isolates expressed traits similar to those of strains that caused cystitis. Type 1 fimbriae appear to be important for the persistence of E. coli in the long-term-catheterized urinary tract.     

Internalization of Proteus mirabilis by human renal epithelial cells.

Proteus mirabilis, a common agent of bacteriuria in humans, causes acute pyelonephritis and bacteremia. Renal epithelium provides a barrier between luminal organisms and the renal interstitium. We have hypothesized that P. mirabilis may be internalized into renal epithelium. To test this hypothesis, we added suspensions of three P. mirabilis strains (10(8) CFU) to confluent monolayers of primary cultures of human renal proximal tubular epithelial cells (HRPTEC) and, after 3 h, found the bacteria internalized within membrane-bound vacuoles by light and electron microscopy. Internalization of bacteria by HRPTEC was corroborated by using the gentamicin protection assay. Cytolysis of HRPTEC by the HpmA hemolysin, however, was a confounding factor in this assay, and therefore a hemolysin-negative hpmA mutant was used in subsequent experiments. The nonhemolytic mutant WPM111 did not disrupt the monolayer and was recovered in numbers that were 10- to 100-fold higher than those of the hemolytic parent BA6163. Cytochalasin D (20 micrograms/ml) inhibited internalization of Salmonella typhimurium but not that of P. mirabilis, suggesting that the latter species enters HRPTEC by a mechanism that is not dependent on actin polymerization. We suggest that HpmA hemolysin-mediated cytotoxicity and internalization of bacteria by HRPTEC may play a role in the development of Proteus pyelonephritis.