In vitro activity of a novel compound, the metal ion chelating agent AQ+, against clinical isolates of Staphylococcus aureus.
OBJECTIVE
To determine the efficacy of a novel antimicrobial compound, AQ+, against a genetically heterogeneous collection comprising 213 Staphylococcus aureus isolates from global sources. AQ+ is an aqueous preparation containing 0.5% 8-hydroxyquinoline.


METHODS
MICs were found for all the isolates tested using the BSAC microdilution method. Time-kill studies were performed according to NCCLS guidelines. Transmission electron microscopy (TEM) was used to view the ultrastructural effects of AQ+.


RESULTS
AQ+ was shown to strongly inhibit the growth of all isolates with a median MIC of 0.25% at a pH optimum of 9.2. Lowering the pH to 7.5 gave an approximately 4-fold reduction in efficacy and at pH 5.5 there was an approximately 8-fold reduction in efficacy. Methicillin-resistant S. aureus (MRSA) as well as vancomycin-intermediate S. aureus were shown to be as equally susceptible to AQ+ as methicillin-susceptible S. aureus. Time-kill curves for AQ+ were similar to those for gentamicin. TEM showed that AQ+ actively disrupts the cell wall of S. aureus leading to cell lysis.


CONCLUSIONS
These results suggest that AQ+ has strong antimicrobial activity and may be useful in preparations to reduce nasal and skin carriage of MRSA.
Short
Benjamin R D
BR
Department of Infectious Disease Epidemiology, Faculty of Medicine, Imperial College London, Old Medical School Building, St Mary's Hospital, Norfolk Place, London W2 1PG, UK.
Vargas
Miguel A
MA
Thomas
Jonathan C
JC
O'Hanlon
Simon
S
Enright
Mark C
MC
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002614:Chelating Agents / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial / Q000187:drug effects; D006863:Hydrogen-Ion Concentration; D008670:Metals; D008826:Microbial Sensitivity Tests; D046529:Microscopy, Electron, Transmission; D015125:Oxyquinoline / Q000494:pharmacology*; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000254:growth & development / Q000302:isolation & purification / Q000648:ultrastructure; D013997:Time Factors
D000900:Anti-Bacterial Agents; D002614:Chelating Agents; D008670:Metals; D015125:Oxyquinoline