Background: According to the Center for Disease Control (CDC), antibiotic resistance is one of the largest public health challenges facing modern society. It has been estimated that 2.8 million people each year in the US are infected with an antibiotic-resistant organism, resulting in gt;35,000 deaths. One of the multi-drug resistant microbes listed on the CDC’s urgent threats list is Acinetobacter. The Acinetobacter calcoaceticus–Acinetobacter baumannii complex (ACB complex) is a group of clinically relevant Acinetobacter species that can cause pneumonia, urinary tract, skin and soft tissue infections. Although a lot of work has focused on antibiotic resistance in A. baumannii, the resistance of A. calcoaceticus is underexplored. To address this gap in knowledge, we obtained three commercially available A. calcoaceticus strains and four clinical isolates. We hypothesized that clinical isolates of A. calcoaceticus would be well adapted to withstand traditional antibiotics. Methods amp;
Results: To test this hypothesis, we grew commercially available and clinical isolates of A. calcoaceticus in a fully defined bacterial media, termed ZMB1, which was then seeded into Biolog plates (12B) containing beta-lactams (penicillin G, carbenicillin, oxacillin), tetracyclines (tetracycline, penimepicycline), aminoglycosides (polymyxin B, paromomycin, sisomicin, tobramycin, spectinomycin), glycopeptides (vancomycin), sulfonamides (sulfamethazine, sulfadiazine, sulfathiazole, sulfa-methoxazole), aminocoumarins (novobiocin), pteridines (2,4-diamino-6,7- diisopropyl- pteridine), biocides (benzethonium chloride), macrolides (spiramycin), antimycobacterials (rifampicin), amphiphiles (dodecyltrimethyl ammonium bromide), and acids (D,L-Serine hydroxamate, 5-fluoroorotic acid, L-aspartic-β- hydroxamate). All A. calcoaceticusstrains were resistant to penicillin G, tetracycline, carbenicillin, and sisomicin. Interestingly, although our commercially available strains were sensitive to sulfamethazine, we observed that all of our clinical isolates were resistant to this antibiotic. We also identified that 2 of our isolates were resistant to polymyxin B and one isolate was highly resistant to dodecyltrimethyl ammonium bromide. These data suggest significant differences in antibiotic resistance between strains.
Conclusions: Collectively, these data demonstrate reveal a profile of resistance for A. calcoaceticus. This data also indicates that clinical isolates of A. calcoaceticus are much more resistant to antibiotics than lab adapted strains and should be incorporated into experimental study design.
