Acinetobacter baumannii Strains Deficient in the Clp Chaperone-Protease Genes Have Reduced Virulence in a Murine Model of Pneumonia

Pyrogallol downregulates the expression of virulence-associated proteins in Acinetobacter baumannii and showing anti-infection activity by improving non-specific immune response in zebrafish model

Acinetobacter baumannii, a virulent uropathogen with widespread antibiotic resistance, has arisen as a critical scientific challenge, necessitating the development of innovative therapeutic agents. This is the first study reveal the proteomic changes in A. baumannii upon pyrogallol treatment for understanding the mechanisms using nano-LC-MS/MS-based quantitative proteomics and qPCR analysis. The obtained results found that pyrogallol treatment dramatically downregulated the expression level of several key proteins such as GroEL, DnaK, ClpB, SodB, KatE, Bap, CsuA/B, PgaA, PgaC, BfmR, OmpA, and SecA in A. baumannii, which are involved in chaperone-mediated oxidative stress responses, antioxidant defence system, biofilm formation, virulence enzyme production, bacterial adhesion, capsule formation, and antibiotic resistance. Accordingly, the pyrogallol dramatically enhanced the lifespan of A. baumannii-infected zebrafish by inhibiting bacterial colonization, demonstrating the anti-infective potential of pyrogallol against A. baumannii. Further, the histopathological results also demonstrated the disease protection efficacy of pyrogallol against the pathognomonic sign of A. baumannii infection. In addition, the pyrogallol treatment effectively improved the immune parameters such as serum myeloperoxidase activity, leukocyte respiratory burst activity, and serum lysozyme activity in zebrafish against A. baumannii infection. Based on the results, the present study strongly proposes pyrogallol as a promising therapeutic agent for treating A. baumannii infection.

ESKAPE Pathogens: Looking at Clp ATPases as Potential Drug Targets

Bacterial antibiotic resistance is rapidly growing globally and poses a severe health threat as the number of multidrug resistant (MDR) and extensively drug-resistant (XDR) bacteria increases. The observed resistance is partially due to natural evolution and to a large extent is attributed to antibiotic misuse and overuse. As the rate of antibiotic resistance increases, it is crucial to develop new drugs to address the emergence of MDR and XDR pathogens. A variety of strategies are employed to address issues pertaining to bacterial antibiotic resistance and these strategies include: (1) the anti-virulence approach, which ultimately targets virulence factors instead of killing the bacterium, (2) employing antimicrobial peptides that target key proteins for bacterial survival and, (3) phage therapy, which uses bacteriophages to treat infectious diseases. In this review, we take a renewed look at a group of ESKAPE pathogens which are known to cause nosocomial infections and are able to escape the bactericidal actions of antibiotics by reducing the efficacy of several known antibiotics. We discuss previously observed escape mechanisms and new possible therapeutic measures to combat these pathogens and further suggest caseinolytic proteins (Clp) as possible therapeutic targets to combat ESKAPE pathogens. These proteins have displayed unmatched significance in bacterial growth, viability and virulence upon chronic infection and under stressful conditions. Furthermore, several studies have showed promising results with targeting Clp proteins in bacterial species, such as Mycobacterium tuberculosis, Staphylococcus aureus and Bacillus subtilis.

Expression and function of clpS and clpA in Xanthomonas campestris pv. campestris

ATP-dependent proteases (FtsH, Lon, and Clp family proteins) are ubiquitous in bacteria and play essential roles in numerous regulatory cell processes. Xanthomonas campestris pv. campestris is a Gram-negative pathogen that can cause black rot diseases in crucifers. The genome of X. campestris pv. campestris has several clp genes, namely, clpS, clpA, clpX, clpP, clpQ, and clpY. Among these genes, only clpX and clpP is known to be required for pathogenicity. Here, we focused on two uncharacterized clp genes (clpS and clpA) that encode the adaptor (ClpS) and ATPase subunit (ClpA) of the ClpAP protease complex. Transcriptional analysis revealed that the expression of clpS and clpA was growth phase-dependent and affected by the growth temperature. The inactivation of clpA, but not of clpS, resulted in susceptibility to high temperature and attenuated virulence in the host plant. The altered phenotypes of the clpA mutant could be complemented in trans. Site-directed mutagenesis revealed that K223 and K504 were the amino acid residues critical for ClpA function in heat tolerance. The protein expression profile shown by the clpA mutant in response to heat stress was different from that exhibited by the wild type. In summary, we characterized two clp genes (clpS and clpA) by examining their expression profiles and functions in different processes, including stress tolerance and pathogenicity. We demonstrated that clpS and clpA were expressed in a temperature-dependent manner and that clpA was required for the survival at high temperature and full virulence of X. campestris pv. campestris. This work represents the first time that clpS and clpA were characterized in Xanthomonas.