The effect of bacterial toxins on levels of intracellular adenosine nucleotides and human ciliary beat frequency.

Toxins that slow ciliary beat are virulence determinants of bacteria that infect or invade ciliated epithelial surfaces. We have previously shown that the effect of the Pseudomonas aeruginosa toxin pyocyanin on ciliary beat is associated with a fall in intracellular cAMP and ATP. We have now investigated whether reduction in intracellular adenosine nucleotides might be a common mechanism of action of other bacterial toxins which slow ciliary beat. Two other P. aeruginosa toxins, 1-hydroxyphenazine (1-HP) and rhamnolipid, and two Haemophilus influenzae fractions produced by gel filtration of broth cultures were tested. The effect on human nasal epithelium ciliary beat frequency (CBF), and intracellular cAMP and ATP were measured, and the effect of two pharmacological agents, dibutyryl cAMP and salmeterol, on these changes was assessed. 1-HP, rhamnolipid and the two H. influenzae fractions slowed CBF before there was significant release of lactate dehydrogenase from the cells. The toxins also caused a fall in intracellular cAMP and ATP. Dibutyryl cAMP and salmeterol at the concentrations used do not increase baseline CBF, but diminished the fall in CBF and intracellular adenosine nucleotides. The cAMP and ATP levels in these studies were combined with those previously obtained with pyocyanin. there was a good correlation between cAMP and ATP levels and CBF. Bacterial toxins which slow CBF may act by causing a fall in intracellular adenosine nucleotides, and agents which stimulate cAMP may prevent toxin-induced slowing of ciliary beat.

Efficacy and safety of long-term ciprofloxacin in the management of severe bronchiectasis.

The efficacy and safety of long-term ciprofloxacin therapy in the management of severe bronchiectasis were retrospectively assessed in patients who had taken oral ciprofloxacin continuously for at least 90 days. The drug was well tolerated, with only one reported side effect. Treatment resulted in a symptomatic improvement in seven of the ten patients and significant improvements in peak expiratory flow rate and residual volume. There was a decrease in the number of infective exacerbations from 6.2 +/- 2.9 during 365 days to 0.5 +/- 0.53 during 412 days. Resistance to ciprofloxacin developed in 2 patients with Pseudomonas aeruginosa infection and this was associated with clinical deterioration, but in a further two patients with P. aeruginosa the pathogen was eradicated. Two patients had persistent Streptococcus pneumoniae cultured from sputum but this was not associated with clinical deterioration. The study suggests that ciprofloxacin is effective and safe in the long-term treatment of chronic bronchial sepsis due to bronchiectasis, but emergence of P. aeruginosa resistance is of some concern.

Haemophilus influenzae infection of human respiratory mucosa in low concentrations of antibiotics.

We examined the effects of 0.25 and 0.5 minimal inhibitory concentrations (MIC) of amoxicillin, loracarbef, and ciprofloxacin on the interaction of a clinical isolate of nontypable Haemophilus influenzae (NTHi) with human adenoid organ culture. Adenoid tissue was embedded in agar so that only the mucosal surface was exposed. Minimum essential medium containing NTHi with or without antibiotics was added to the organ culture and incubated with 5% CO2 at 37 degrees C for 24 h. The organ cultures (n = 6) were assessed for several parameters by light microscopy (LM) and transmission electron microscopy (TEM). Bacterial viable counts after 24 h were not significantly different in all organ cultures. Compared with uninfected controls at 24 h, infection with NTHi caused significant (p < 0.05) damage to epithelium as assessed by LM: reduced ciliary beat frequency (CBF), disruption of epithelium integrity, and reduced number of ciliated sites. TEM showed extrusion of cells from the epithelial surface, loss of cilia from ciliated cells, cytoplasmic blebbing, and mitochondrial damage. In the presence of 0.25 and 0.5 MIC of all three antibiotics, the mucosal damage was significantly less (p < 0.05). We conclude that in the presence of sub-MIC levels of amoxicillin, loracarbef, and ciprofloxacin, NTHi infection causes less functional (CBF) and structural damage.

A study of macrophage-mediated initiation of fibrosis by asbestos and silica using a diffusion chamber technique.

Several cellular interactions have been identified as potentially important in fibrogenesis induced by mineral dusts. Evaluation of their relative importance in vivo remains a problem. Sealed diffusion chambers limited by Nuclepore membranes and implanted into mouse peritoneal cavities provide a means of assessing different stages of fibrogenesis by separating initiating mechanisms (dust-macrophage-lymphocyte combinations inside the chamber) from the target tissue. Fibrous reactions surrounding the chambers were quantitated by macroscopic and histological scoring, and by measurement of 14C glycine incorporated at the reaction site. Using this model the fibrogenicity of Rhodesian A chrysotile asbestos, DQ12 quartz and haematite were compared. Whereas asbestos-macrophage ratios of between 6 . 6 and 900 micrograms/10(6) mouse peritoneal macrophages (MPM) produced fibrosis, an equivalent response was obtained with 0.05 micrograms silica/10(6) MPM. Silica in amounts greater than this produced macrophage cytotoxicity without fibrogenesis. Haematite-macrophage combinations produced no significant fibrosis. It was confirmed that a direct dust-macrophage interaction forms the essential first step in fibrogenesis by both asbestos and silica and that the fibrogenicity is mediated by diffusible factor(s). Prior stimulation of host mice with Freund's complete adjuvant modified the fibrogenic response to some dust-cell combinations, suggesting an important role for host responses in determining the outcome of fibrogenic stimuli.