1278. Testing the Synergistic Effect of Ceftazidime-Avibactam Plus Aztreonam on Metallobetalactamase-Producing Non-Fermenting Gram-negative Bacteria

Abstract

s • OFID 2021:8 (Suppl 1) • S727 Figure 1a) Phage titers in PFU/ml obtained from each bacterial isolate via agar overlay method. 1b) Representative agar plate demonstrating lytic plaques from OMS1 and OMS2 on a Staphylococcus aureus LVAD isolate. 1c) Biofilm biomass of Staphylococcus aureus isolates alone (SA) or with individual phage (SA+OMSA1 and SA=OMS2) assessed by optical density readings at 570 nm; error bars represent standard error of the mean. Conclusion. We demonstrated in vitro lytic and anti-biofilm activity of 2 S. aureus phages against clinical S. aureus isolates from patients with LVAD infection. Our data suggests that phage susceptibility measured with agar overlay does not always correlate with phage susceptibility of S. aureus biofilms, suggesting that more than one method should be used to assess in vitro activity. We plan to assess for synergistic activity with the phage combination. Session: P-72. Resistance Mechanisms Background. Characterization of antimicrobial-resistant organism (ARO) colon-ization is critical to understand transmission dynamics and infection risk, however data in resource-limited settings are scare. We estimated the prevalence of Enterobacterales colonization with extended-spectrum cephalosporin-resistance (ESCrE), carbapen-em-resistance (CRE) and methicillin-resistant Staphylococcus aureus (MRSA) among community residents and hospitalized patients in rural (Siaya County) and urban (Kibera) Kenya. Methods. Community-dwelling adults and children were enrolled via cluster rand-omized sampling. Inpatients of all ages were enrolled by simple random sampling. Stool/ rectal and nasal swabs were collected and screened for ESCrE, CRE and MRSA, respectively , using HardyChrom™ media. Vitek2 ® was used for isolate confirmation and antibiotic susceptibility testing. Fisher's exact tests were used to compare prevalence of AROs. Results. The prevalence of ESCrE was higher for the urban hospital (69.8%, 263/377) compared to rural hospitals (62.7%, 298/475, P=0.04); a similar pattern was