Development of a PCR-dipstick DNA chromatography-based tool for the detection of CTX-M- and TEM-producing Escherichia coli and Klebsiella pneumoniae isolated from patients in Kafue and Katete districts of Zambia

In Zambia, 40% of clinical Gram-negative bacteria are either Escherichia coli or Klebsiella pneumoniae , with a high third-generation cephalosporin (3GC) resistance prevalence. Therefore, 3GC resistance surveillance is a crucial indicator for guiding focused intervention policies. However, the lack of genotypic diagnostic tools limits the ability to elucidate trends, especially in peri-urban and rural areas of developing countries. This study aimed to develop a rapid, cost-effective tool for the genotypic surveillance of 3GC resistance. Here, 900 stool samples collected from patients in Kafue (peri-urban, n = 400) and Katete (rural, n = 500) districts of Zambia were used for bacterial isolation on MacConkey agar supplemented with 1 μg/ml cefotaxime. Isolated 3GC-resistant strains were characterized by sequencing the 16S rRNA gene and screening for bla CTX-M and bla TEM genes using single polymerase chain reaction (PCR). Furthermore, selected 3GC-resistant strains were subjected to whole-genome sequencing (WGS) using MiSeq/HiSeq ( n = 34) and MinION ( n = 1). Using the data from this and other previous studies, we developed a rapid PCR-dipstick DNA chromatography-based tool for detecting bla CTX-M , bla TEM , E. coli -specific yaiO, and K. pneumoniae -specific khe genes. The prevalence of isolated 3GC resistant strains was 15.4% (139/900), dominated by E. coli (102/139, 73.4%). On PCR, the bla CTX-M gene was detected in 72.7% (101/139) of the isolates, while bla TEM was found in 46.8% (65/139) of the strains. The developed tool displayed a high level of agreement with WGS and single PCR/Sanger sequencing, with sensitivity and specificity ≥ 95% and Kappa ≥ 0.95 for each of the four target genes. We envisage that the simplicity and adaptability of this tool will be a significant advantage for the surveillance of 3GC resistance in Zambia and elsewhere.