Carbapenemase gene-positive (CP) Gram-negative bacilli are of significant clinical and public health concern. Their rapid detection and containment are critical to preventing their spread and additional infections they can cause. To this end, CDC developed the Antibiotic Resistance Laboratory Network (AR Lab Network), in which public health laboratories across all 50 states, several cities, and Puerto Rico characterize clinical isolates of carbapenem-resistant Enterobacterales (CRE), Pseudomonas aeruginosa (CRPA), and Acinetobacter baumannii (CRAB), and conduct colonization screens to detect the presence of mobile carbapenemase genes. In its first three years, the AR Lab Network tested 76,887 isolates and 31,001 rectal swab colonization screens. Targeted carbapenemase genes (bla(KPC), bla(NDM), bla(OXA-48-like), bla(VIM), or bla(IMP)) were detected by PCR in 35% of CRE, 2% of CRPA, <1% of CRAB, and 8% of colonization screens tested, respectively. bla(KPC) and bla(VIM) were the most common CP-CRE and CP-CRPA, respectively, but regional differences in the frequency of carbapenemase genes detected were apparent. In CRE and CRPA isolates tested for carbapenemase production and the presence of the targeted genes, 97% had concordant results; 3% of CRE and 2% of CRPA were carbapenemase production-positive but PCR-negative for those genes. Isolates harboring bla(NDM) showed the highest frequency of resistance across the carbapenems tested and those harboring bla(IMP) and bla(OXA-48-like) genes showed the lowest frequency of carbapenem resistance. The AR Lab Network provides a national snapshot of rare and emerging carbapenemase genes, delivering data to inform public health actions to limit the spread of these antibiotic resistance threats.

Aztreonam-avibactam is a drug combination pending phase 3 clinical trials and is suggested for treatment of severe infections caused by metallo-beta-lactamase (MBL)-producing Enterobacterales by combining ceftazidime-avibactam and aztreonam. Beginning in 2019, four Antibiotic Resistance Laboratory Network regional laboratories offered aztreonam-avibactam susceptibility testing by broth microdilution. For 64 clinical isolates tested, the MIC(50) and MIC(90) of aztreonam-avibactam were 0.5/4 μg/mL and 8/4 μg/mL, respectively. Aztreonam-avibactam displayed potent in vitro activity against the MBL-producing Enterobacterales tested.