ABSTRACT
BACKGROUND: Successful treatment of Acinetobacter (A.) baumannii-associated infection is complicated by the emergence of multidrug resistance (MDR), particularly in clinical settings. This urges searching for new alternatives to encounter such health problem. AIM: This study aimed to evaluate certain antibiotic combinations and CNPs either alone or in combination of some selected antibiotics for the purpose of combating MDR A. baumannii clinical isolates. METHODS: A total of 51 A. baumannii clinical isolates were recovered from discharged clinical specimens of the Clinical Microbiology Central Laboratory of AL Kasr Al Aini hospital, Cairo, Egypt. Conventional standard Lab tests were used for identification followed by recA gene testing for confirmation. Antimicrobial susceptibility tests were conducted out according to CLSI guidelines. Genotypic analysis using Enterobacterial Repetitive Intergenic Consensus-polymerase chain reaction (ERIC-PCR) of the respective isolates showed that they were clustered in nine clones. The prepared CNPs were characterized by dynamic light scattering and HR-transmission electron microscope imaging. Antibiotic combinations and co-effect of CNPs with some selected antibiotics (either each alone or in combination of two) were evaluated using the Checkerboard microdilution and minimum inhibitor concentration decrease factor (MDF) methods, respectively. RESULTS: The recovered 51 A. baumannii clinical isolates were MDR (100%) of these 92% (47/51) were extensively drug resistance (XDR). Combinations of colistin (CT)+meropenem (MEM) and MEM+tigecycline (TGC) showed synergism in 77.7% and 44.4% and additive effects in 22.3% and 55.6% of the tested MDR A. baumannii isolates (n=51), respectively. However, CT+TGC combination showed antagonism. CNPs exhibited good inhibitory activity (inhibition zones ranged from 24 to 31 mm) against selected nine MDR A. baumannii isolates (one isolate from each clone). The MIC of CNPs at concentrations (ranging from 1 to 5 mg/mL) were from 0.16 to 0.25 mg/mL, indicating good in vitro antimicrobial activities. CNPs (5 mg/mL) when combined with CT, TGC or MEM, CT+MEM and TGC+MEM significantly increased the susceptibilities of the MDR A. baumannii isolates to these antibiotics by 88.8%, 66.6%, 100%, 77.7%, and 44.4%, respectively. No significant effects were observed when CNPs (5 mg/mL) were combined with CT+TGC. CONCLUSION: The current study demonstrated the significant in-vitro activities of CNPs either alone or in combination with CT, TGC or MEM, CT+MEM and TGC+MEM and the successful combinations of MEM either with CT or with TGC against the MDR A. baumannii pathogens. However, further in vivo studies should be conducted to verify such activities and their potential use in human.
ABSTRACT
OBJECTIVE: The objective of this work was to isolate bacteria from Red Sea invertebrates, determine their antimicrobial activity, and screen for the biosynthetic gene clusters [polyketides (PKs) and nonribosomal peptides (NRPs)] which could be involved in the production of bioactive secondary metabolites. RESULT: Eleven different samples of marine invertebrates' were collected from Egypt's Red Sea (El-Tor-Sharm El-Sheikh and Hurghada) by scuba diving, and a total 80 isolates of the associated microorganisms were obtained from the cultivation on six different cultural medium. Seven isolates of them showed an antimicrobial activity against five pathogenic reference strains, while the most active antimicrobial agent was isolate number HFF-8 which was 99% identical to Bacillus amyloliquefaciens. HFF-8's extract showed positive results against Gram negative bacteria, Gram positive bacteria and yeast. Moreover, the isolates gave positive bands when screened for the presence of PK synthase (PKS) I and II and NRP synthetase (NRPS) I and II biosynthetic genes, those biosynthetic fragments when cloned and sequenced were primitively predicted as biosynthetic fragments for kirromycin and leinamycin production by NaPDoS program with 56 and 55%, respectively. CONCLUSION: The Red Sea can provide a sustainable solution to combat bacterial resistance. The contribution of this work is that B. amyloliquefaciens was isolated from Heteroxenia fuscescens, Red Sea, Egypt. Moreover, the bacterial extract showed a broad spectrum with a potent antimicrobial activity.
