BackgroundKlebsiella pneumoniaeis one of the main pathogens of clinical isolation and nosocomial infections, asK. pneumoniaeshow broad-spectrum resistance to β-lactam and carbapenem antibiotics. It is emerging clinical need for a safe and effective drug to anti-K. pneumoniae. At present,Achromobactermainly focused on its degradation of petroleum hydrocarbons, polycyclic aromatic hydrocarbons, assisting insects to decompose, degrade heavy metals and utilize organic matter, but there were few reports on the antibacterial activity of the secondary metabolites ofAchromobacter.ResultsIn this study, a strain WA5-4-31 from the intestinal tract ofPeriplaneta americanaexhibited strong activity againstK. Pneumoniaethrough preliminary screening. The strain was determined to beAchromobacter sp.through the morphological characteristics, genotyping and phylogenetic tree analysis, which is homologous toAchromobacter ruhlandiiby 99%, its accession numbe in GenBank at National Center for Biotechnology Information (NCBI) is MN007235, and its deposit number was GDMCC NO.1.2520. Six compounds (Actinomycin D, Actinomycin X2, Collismycin A, Citrinin, Neoechinulin A and Cytochalasin E) were isolated and determined by activity tracking, chemical separation, nuclear magnetic resonance (NMR) and mass spectrometry (MS) analysis. Among them, Actinomycin D, Actinomycin X2, Collismycin A, Citrinin and Cytochalasin E showed a good effect on anti-K. pneumoniae, with MIC values of 16–64 µg/mL.ConclusionsThe study reportedAchromobacter, which was from the intestinal tract ofPeriplaneta americanawith the activity againstK. Pneumoniae, can produce antibacterial compounds for the first time. It lays the foundation for development of secondary metabolites of insect intestinal microorganisms.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12866-023-02909-7.