# Association of the existence of CRISPR-Cas system and antimicrobial resistance in multi-drug resistant Klebsiella pneumoniae in Egypt

## TL;DR

This study explores the link between CRISPR-Cas systems and antibiotic resistance in Klebsiella pneumoniae isolates from Egypt.

## Contribution

The study investigates the association between CRISPR-Cas systems and antimicrobial resistance in Egyptian MDR K. pneumoniae isolates.

## Key findings

- 65.9% of isolates were positive for CRISPR-Cas systems.
- No general significant correlation was found between AMR and CRISPR-Cas presence.
- Significant correlations were found for imipenem, colistin, and chloramphenicol resistance with CRISPR-Cas presence.

## Abstract

The CRISPR-Cas systems are supposed to be associated with antibiotic susceptibility. Klebsiella pneumoniae (K. pneumoniae) is a major multidrug-resistant (MDR) pathogen that may cause severe infections. This study aimed to detect the antimicrobial resistance (AMR) of K. pneumoniae isolates in addition to determine the association between the existence of CRISPR-Cas systems and the presence of AMR in Egypt. The antibiotic susceptibility patterns of 100 K. pneumoniae isolates were determined using the Kirby Bauer disc diffusion and broth microdilution methods. The frequency of carbapenem resistance encoding genes (blaKPC, blaOXA, blaIMP,
blaNDM, and blaVIM), ESBLs encoding genes (blaTEM), aminoglycoside resistance encoding genes (aac(3)-Ia, aac(3)-IIa, colistin resistance encoding genes (mcr-1, mcr-2) and tetracycline resistance encoding genes (tetB) were determined using polymerase chain reaction (PCR). The presence or absence of CRISPR-Cas systems was determined by detection of Cas genes (Cas1 or Cas3) in conjunction with one of CRISPR arrays 1, 2 or 3. Kirby Bauer disc diffusion revealed that 95% of isolates were MDR. The resistance rates of K. pneumoniae isolates to amikacin, meropenem, and colistin were 76%, 67%, and 41% respectively by broth microdilution assay. Among selected 41 K. pneumoniae, the frequency of ESBLs; blaTEM was 92.7%, while the frequency of blaNDM
blaOXA
blaVIM
blaIMP and blaKPC was 95.1%, 95.1%, 39%, 19.5% and 14.6% respectively. The frequency of mcr-1 and mcr-2 was 70.7% and 65.9%. Additionally, the frequency of aac(3)-Ia was 12.2%, and aac(3)-IIa was 87.8%, while the frequency of tetB was 100%. Our isolates exhibited varied profiles for CRISPR-Cas systems, where 65.9% were positive for CRISPR-Cas system. No general significant positive correlation between AMR and the presence ofCRISPR-Cas system was detected; however, a significant difference is present for imipenem, colistin and chloramphenicol phenotypic resistance andfor aac(3)-IIa and mcr-1 genes (P value > 0.1). A significant positive correlation was detected between AMR for imipenem, colistin and chloramphenicol and for aac(3)-IIa and mcr-1 genes and thepresence of CRISPR-Cas system.

The online version contains supplementary material available at 10.1038/s41598-025-26706-6.