Multidrug resistant Psudomonas aeruginosa infections complicating surgical wounds and the potential challenges in managing post–operative wound infections: University of Calabar Teaching Hospital experience

Prevalence of multi-drug resistant <em>Pseudomonas aeruginosa</em> isolated from selected residential sewages in Dutsin-Ma, Katsina State, Nigeria

The global surge in Multidrug resistant (MDR) bacteria is an issue of great concern. Pseudomonas aeruginosa has been impli- cated in several nosocomial infections, where it has caused grave complications in immunocompromised patients. This is the first study to report the prevalence of MDR P. aeruginosa isolated from residential sewage in Dutsin-Ma, Katsina State, Nigeria. Pseudomonads count, isolation, biochemical characterization and antibiogram were carried out using standard microbiological pro- cedures. This study examined sixty (60) samples from selected res- idential sewage in the study site collected at different intervals between July and September 2021. A total of 40 (66.7%) P. aeruginosa were isolated from the analyzed sewage samples. The high- est (2.84x104) pseudomonad count was recorded from sewage samples collected from Kadangaru. Pseudomonas aeruginosa isolates from this sample site showed the highest (100%) resistance to cephalosporins (cefuroxime) and nitrofurantoin. Similarly, isolates from Miami area also demonstrated the highest (95%) resistance to a cephalosporin (ceftazidime). All (100%) isolates used in this study showed MDR resistance to tested antibiotics. The occurrence of MDR P. aeruginosa from a residential sewage site that may con- taminate drinking water sources in the study area is of public health threat to the inhabitants. Surveillance and molecular epi- demiology of antibiotics resistant bacteria are urgently needed in the study area.

Antimicrobial and Antibiofilm Activity of Synergistic Combinations of a Commercially Available Small Compound Library With Colistin Against Pseudomonas aeruginosa

Biofilm-associated Pseudomonas aeruginosa infections remain a significant clinical challenge since the conventional antibiotic treatment or combination therapies are largely ineffective; and new approaches are needed. To circumvent the major challenges associated with discovery of new antimicrobials, we have screened a library of compounds that are commercially available and approved by the FDA (Prestwick Chemical Library) against P. aeruginosa for effective antimicrobial and anti-biofilm activity. A preliminary screen of the Prestwick Chemical Library alone did not yield any repositionable candidates, but in a screen of combinations with a fixed sub-inhibitory concentration of the antibiotic colistin we observed 10 drugs whose bacterial inhibiting activity was reproducibly enhanced, seven of which were enhanced by more than 50%. We performed checkerboard assays of these seven drugs in combination with colistin against planktonic cells, and analysis of their interactions over the complete combination matrix using the Zero Interaction Potency (ZIP) model revealed interactions that varied from highly synergistic to completely antagonistic. Of these, five combinations that showed synergism were down-selected and tested against preformed biofilms of P. aeruginosa. Two of the five combinations were active against preformed biofilms of both laboratory and clinical strain of P. aeruginosa, resulting in a 2-log reduction in culturable cells. In summary, we have identified synergistic combinations of five commercially available, FDA-approved drugs and colistin that show antimicrobial activity against planktonic P. aeruginosa (Clomiphene Citrate, Mitoxantrone Dihydrochloride, Methyl Benzethonium Chloride, Benzethonium Chloride, and Auranofin) as well as two combinations (Auranofin and Clomiphene Citrate) with colistin that show antibiofilm activity.