Comparative Analysis of Commercially Available Typhoid Point-of-Care Tests: Results of a Prospective and Hybrid Retrospective Multicenter Diagnostic Accuracy Study in Kenya and Pakistan.

Blood and bone marrow cultures are considered the gold standard for the diagnosis of typhoid, but these methods require infrastructure and skilled staff that are not always available in low- and middle-income countries where typhoid is endemic. The objective of the study is to evaluate the sensitivity and specificity of nine commercially available Salmonella Typhi rapid diagnostic tests (RDTs) using blood culture as a reference standard in a multicenter study. This was a prospective and retrospective multicenter diagnostic accuracy study conducted in two geographically distant areas where typhoid is endemic (Pakistan and Kenya; NCT04801602). Nine RDTs were evaluated, including the Widal test. Point estimates for sensitivity and specificity were calculated using the Wilson method. Latent class analyses were performed using R to address the imperfect gold standard. A total of 531 serum samples were evaluated (264 blood culture positive; 267 blood culture negative). The sensitivity of RDTs varied widely (range, 0 to 78.8%), with the best overall performance shown by Enterocheck WB (72.7% sensitivity, 86.5% specificity). In latent class modeling, CTK IgG was found to have the highest sensitivity (79.1%), while the highest overall accuracy was observed with Enterocheck (73.8% sensitivity, 94.5% specificity). All commercially available Salmonella Typhi RDTs evaluated in the study had sensitivity and specificity values that fell below the required levels to be recommended for an accurate diagnosis. There were minimal differences in RDT performances between regions of endemicity. These findings highlight the clear need for new and more-accurate Salmonella Typhi tests.

Frequency and diversity of carbapenemase-producing Enterobacterales recovered from untreated wastewater impacted by selective media containing cefotaxime and meropenem in Ohio, USA.

As safe agents of last resort, carbapenems are reserved for the treatment of infections caused by multidrug-resistant organisms. The impact of ß-lactam antibiotics, cefotaxime, and meropenem on the frequency and diversity of carbapenemase-producing organisms recovered from environmental samples has not been fully established. Therefore, this methodological study aimed at determining ß-lactam drugs used in selective enrichment and their impact on the recovery of carbapenemase-producing Enterobacterales (CPE) from untreated wastewater. We used a longitudinal study design where 1L wastewater samples were collected weekly from wastewater treatment plant (WWTP) influent and quarterly from contributing sanitary sewers in Columbus, Ohio USA with 52 total samples collected. Aliquots of 500 mL were passed through membrane filters of decreasing pore sizes to enable all the water to pass through and capture bacteria. For each sample, the resulting filters were placed into two modified MacConkey (MAC) broths, one supplemented with 0.5 µg/mL of meropenem and 70 µg/mL of ZnSO4 and the other supplemented with 2 µg/mL cefotaxime. The inoculated broth was then incubated at 37° C overnight, after which they were streaked onto two types of correspondingly-modified MAC agar plates supplemented with 0.5 µg/mL and 1.0 µg/mL of meropenem and 70 µg/mL of ZnSO4 and incubated at 37°C overnight. The isolates were identified based on morphological and biochemical characteristics. Then, up to four distinct colonies of each isolate's pure culture per sample were tested for carbapenemase production using the Carba-NP test. Matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry (MS) MALDI-TOF MS was used to identify carbapenemase-producing organisms. In total 391 Carba-NP positive isolates were recovered from the 52 wastewater samples: 305 (78%) isolates had blaKPC, 73 (19%) carried blaNDM, and 14 (4%) harbored both blaKPC and blaNDM resistance genes. CPE genes of both blaKPC and blaNDM were recovered in both types of modified MAC broths, with 84 (21%) having a blaKPC gene, 22 (6%) carrying blaNDM and 9 (2%) harbored both a blaKPC and blaNDM of isolates recovered from MAC medium incorporated with 0.5ug/mL meropenem and 70ug/mL ZnSO4. The most prevalent isolates were Klebsiella pneumoniae, Escherichia coli, and Citrobacter spp.