Potentiation by salicylate and salicyl alcohol of cadmium toxicity and accumulation in Escherichia coli

Effects of Acetyl Salicylate and Ibuprofen on Fluoroquinolone MICs onSalmonella entericaSerovartyphimurium In Vitro

In this study, the effects of acetylsalicylate and ibuprofen at 2, 4 and 8 mM concentration were investigated on ofloxacin, ciprofloxacin, levofloxacin and pefloxacin minimum inhibitory concentrations (MICs) for 14 Salmonella enterica serovar typhimurium clinical isolates, one standard strain (SZH KUEN 557), SH7616 (acr mutant), SH5014 (parent strain of acr mutant) and PP120 (soxRS mutant) strains. All isolates were susceptible to the 4 fluoroquinolones. In the presence of 2, 4 and 8 mM acetylsalicylate and ibuprofen, 2- to 8-fold increases were observed in fluoroquinolone MICs. This rise was higher, especially in the presence of acetylsalicylate. In spite of this rise, none of the MICs were in the range of resistance limits in vitro. Except for a 2-fold increase in levofloxacin MICs, we did not observe any difference in MICs of ofloxacin, ciprofloxacin, and pefloxacin in the presence of 2, 4 and 8 mM acetylsalicylate and ibuprofen for SH7616 and PP120 strains. According to the in vitro results of this study, it can be suggested that use of acetylsalicylate or ibuprofen together with clinical treatment of bacteria, especially bacteria which show intermediate resistance, will cause resistance. However, since clinical data are insufficient, further studies are needed.

Impact of metals on the biodegradation of organic pollutants

Forty percent of hazardous waste sites in the United States are co-contaminated with organic and metal pollutants. Data from both aerobic and anaerobic systems demonstrate that biodegradation of the organic component can be reduced by metal toxicity. Metal bioavailability, determined primarily by medium composition/soil type and pH, governs the extent to which metals affect biodegradation. Failure to consider bioavailability rather than total metal likely accounts for much of the enormous variability among reports of inhibitory concentrations of metals. Metals appear to affect organic biodegradation through impacting both the physiology and ecology of organic degrading microorganisms. Recent approaches to increasing organic biodegradation in the presence of metals involve reduction of metal bioavailability and include the use of metal-resistant bacteria, treatment additives, and clay minerals. The addition of divalent cations and adjustment of pH are additional strategies currently under investigation.

Aspirin inhibits the growth of Helicobacter pylori and enhances its susceptibility to antimicrobial agents

BACKGROUND AND AIM

The role of Helicobacter pylori and aspirin in peptic ulcer formation and recurrence remains an important clinical topic. The interaction between aspirin and H pylori in vitro is also not clear. We investigated the effect of aspirin on the growth of H pylori and on the susceptibility of H pylori to antimicrobials.

METHODS

Time killing studies of H pylori were performed with different concentrations of aspirin and salicylate. Growth of bacteria was assessed spectrophotometrically and by viable colony count. The effects of aspirin on the efficiency of colony formation and on metronidazole induced mutation to rifampicin resistance in H pylori were determined. Minimal inhibitory concentrations (MICs) of aspirin and metronidazole were tested by the standard agar dilution method. MICs of amoxycillin and clarithromycin were determined by the E test method.

RESULTS

Aspirin and salicylate inhibited the growth of H pylori in a dose dependent manner and bactericidal activity was due to cell lysis. Aspirin 400 micro g/ml caused a 2 logs decrease in colony forming units/ml at 48 hours, and suppressed the normal ability of metronidazole to induce new mutations to rifampicin. The IC(90) of aspirin was 512 micro g/ml. Increased susceptibility of amoxycillin, clarithromycin, and metronidazole to H pylori was observed at 1 mM (180 micro g/ml) aspirin.

CONCLUSIONS

Aspirin inhibited the growth of H pylori, suppressed the mutagenic effect of metronidazole, and enhanced the susceptibility of H pylori to antimicrobial agents. This mechanism is important in future drug development for effective clearing and overcoming resistance.

The effects of salicylate on bacteria

Salicylate and related compounds, such as aspirin, have a variety of effects in eucaryotic systems and are well known for their medicinal properties. Salicylate also has numerous effects on bacteria, yet only a handful of individuals within the scientific community appreciate these findings. From a bacterial viewpoint, growth in the presence of salicylate can be both beneficial and detrimental. On one hand, growth of certain bacteria in the presence of salicylate can induce an intrinsic multiple antibiotic resistance phenotype. On the other hand, growth in the presence of salicylate can reduce the resistance to some antibiotics and affect virulence factor production in some bacteria. This review provides an overview of the effects salicylate has on various bacterial species.

Salicylate induction of antibiotic resistance in Escherichia coli: activation of the mar operon and a mar-independent pathway

Since the growth of wild-type Escherichia coli in salicylate results in a multiple antibiotic resistance phenotype similar to that of constitutive mutants (Mar) of the chromosomal mar locus, the effect of salicylate on the expression of the marRAB operon was investigated. The amount of RNA hybridizing with a mar-specific DNA probe was 5 to 10 times higher in wild-type cells grown with sodium salicylate (5.0 mM) than in untreated controls. Untreated Mar mutants had three to five times more mar-specific RNA than wild-type cells did. When a Mar mutant was treated with salicylate, a 30- to 50-fold increase of mar-specific RNA was seen. In wild-type cells bearing a mar promoter-lacZ fusion on the chromosome, salicylate increased beta-galactosidase activity by sixfold. Thus, salicylate induces transcription of the marRAB operon. Other inducers of phenotypic multiple antibiotic resistance, e.g., benzoate, salicyl alcohol, and acetaminophen, but not acetate, also increased transcription from the mar promoter but to a lesser extent than did salicylate. Both in wild-type and mar-deficient strains, growth in salicylate resulted in increased antibiotic resistance, decreased permeation of the outer membrane to cephaloridine, increased micF transcription, and decreased amounts of OmpF. However, the magnitude of these changes was generally greater in wild-type (mar-containing) cells. Thus, salicylate and other compounds can induce transcription of the mar operon and, presumably, give rise to multiple antibiotic resistance via this pathway. However, salicylate can also activate an unidentified, mar-independent pathway(s) which engenders multiple antibiotic resistance.