Correlation between biofilm formation and antibiotic susceptibility pattern in Acinetobacter baumannii MDR isolates retrieved from burn patients

Prevalence of biofilm producing Acinetobacter baumannii clinical isolates: A systematic review and meta-analysis

BACKGROUND

Acinetobacter baumannii, the first human pathogen to be designated as a "red-alert" pathogen, is on the critical priority list of pathogens requiring new antibiotics. Biofilm-associated diseases are the most common infections caused by the antibiotic-resistant bacteria A. baumannii. Multidrug-resistant strains are more easily transmitted around the world due to A. baumannii's ability to produce biofilms, which allows it to develop antibiotic resistance mechanisms and thrive in healthcare environments. As a result, A. baumannii infections are becoming increasingly common in hospital settings allover the world. As a result, a comprehensive systematic review and meta-analysis were carried out to determine the global prevalence of biofilm-producing A. baumannii clinical isolates.

METHODS

Articles were extensively searched in bibliographic databases and grey literatures using entry terms or phrases. Studies meeting eligibility criteria were extracted in MS Excel and exported into STATA version 12 software for statistical analysis. A random-effects model was used to compute the pooled prevalence of biofilm-producing A. baumannii clinical isolates. The heterogeneity was quantified by using the I2 value. Publication bias was assessed using a funnel plot and Egger's test. Sensitivity analysis was done to assess the impact of a single study on pooled effect size.

RESULT

Of the 862 studies identified, 26 studies consisted of 2123 A.baumannii clinical isolates of which 1456 were biofilm-producing. The pooled prevalence of biofilm-producing A.baumannii clinical isolates was 65.63% (95% CI = 56.70%-74.56%). There was substantial heterogeneity with an I2 value of 98.1%. Moreover, 41.34%, 33.57%, and 27.63% of isolates of strong, mild, and weak producers of biofilm. Higher prevalence was found in studies published after 2014 (66.31%); Western Pacific region (76.17%); and Asia (66.22%) followed by the African continent (57.29%).

CONCLUSION

The pooled prevalence of biofilm-producing A. baumannii clinical isolates has risen alarmingly, posing a public health risk. This indicates the burden of biofilm-producing A. baumannii infections urges routine screening and appropriate treatment for better management of hospitalized patients, as well as effective controlling of the emergence of drug resistance. Furthermore, this finding is an alert call for the stakeholders to develop strong infection prevention and antibiotics stewardship programs for the prevention and control of biofilm-producing bacterial infections.

An Explorative Review on Advanced Approaches to Overcome Bacterial Resistance by Curbing Bacterial Biofilm Formation

The continuous emergence of multidrug-resistant pathogens evoked the development of innovative approaches targeting virulence factors unique to their pathogenic cascade. These approaches aimed to explore anti-virulence or anti-infective therapies. There are evident concerns regarding the bacterial ability to create a superstructure, the biofilm. Biofilm formation is a crucial virulence factor causing difficult-to-treat, localized, and systemic infections. The microenvironments of bacterial biofilm reduce the efficacy of antibiotics and evade the host's immunity. Producing a biofilm is not limited to a specific group of bacteria; however, Pseudomonas aeruginosa, Acinetobacter baumannii, and Staphylococcus aureus biofilms are exemplary models. This review discusses biofilm formation as a virulence factor and the link to antimicrobial resistance. In addition, it explores insights into innovative multi-targeted approaches and their physiological mechanisms to combat biofilms, including natural compounds, phages, antimicrobial photodynamic therapy (aPDT), CRISPR-Cas gene editing, and nano-mediated techniques.

In Silico Docking, Resistance Modulation and Biofilm Gene Expression in Multidrug-Resistant Acinetobacter baumannii via Cinnamic and Gallic Acids

Despite the mounting global burden of antimicrobial resistance (AMR), the generation of new classes of effective antimicrobials still lags far behind. The interplay between multidrug resistance and biofilm formation in Acinetobacter baumannii has drastically narrowed the available therapeutic choices. The use of natural compounds holds promise as an alternate option for restoring the activity of existing antibiotics and attenuating virulence traits through reduced biofilm formation. This study aimed to evaluate the modulatory effect of combining cinnamic and gallic acids at ½MIC with various antibiotics against multidrug-resistant (MDR) A. baumannii clinical isolates as well as study the effect on the expression of the biofilm-associated genes (bap, csuE, ompA) via quantitative, real-time PCR. Combining cinnamic or gallic acid with imipenem, amikacin or doxycycline resulted in significant reduction of resistance (p < 0.05). On the contrary, no effect was recorded when both acids were combined with levofloxacin, and only cinnamic acid had a synergistic effect with colistin. The transcriptomic changes of biofilm-related genes in the presence of gallic acid at ½MIC were compared with untreated control samples. The fold expression values proved that gallic acid substantially down-regulated the respective genes in all five strong biofilm formers. Molecular docking studies of gallic and cinnamic acids on target genes revealed good binding affinities and verified the proposed mechanism of action. To the best of our knowledge, this is the first report on the effect of gallic acid on the expression of bap, csuE and ompA genes in A. baumannii, which may permit its use as an adjunct anti-virulence therapeutic strategy.

GC/MS Analyses of the Essential Oils Obtained from Different Jatropha Species, Their Discrimination Using Chemometric Analysis and Assessment of Their Antibacterial and Anti-Biofilm Activities

The essential oils of Jatropha intigrimma, J. roseae and J. gossypifolia (Euphorbiaceae) were analyzed employing GC/MS (Gas Chromatography coupled with Mass Spectrometry) analyses. A total of 95 volatile constituents were identified from J. intigrimma, J. gossypifolia and J. roseae essential oils, accounting for 91.61, 90.12, and 86.24%, respectively. Chemometric analysis using principal component analysis (PCA) based on the obtained GC data revealed the formation of three discriminant clusters due to the placement of the three Jatropha species in three different quadrants, highlighting the dissimilarity between them. Heneicosane, phytol, nonacosane, silphiperfol-6-ene, copaborneol, hexatriacontane, octadecamethyl-cyclononasiloxane, 9,12,15-Octadecatrienoic acid, methyl ester and methyl linoleate constitute the key markers for their differentiation. In vitro antibacterial activities of the essential oils were investigated at doses of 10 mg/mL against the Gram-negative anaerobe Escherichia coli using the agar well diffusion method and broth microdilution test. J. gossypifolia essential oil showed the most potent antimicrobial activity, demonstrating the largest inhibition zone (11.90 mm) and the least minimum inhibitory concentration (2.50 mg/mL), followed by the essential oil of J. intigrimma. The essential oils were evaluated for their anti-adhesion properties against the Gram-negative E. coli biofilm using a modified method of biofilm inhibition spectrophotometric assay. J. intigrimma essential oil showed the most potent biofilm inhibitory activity, demonstrating the least minimum biofilm inhibitory concentration (MBIC) of 31.25 µg/mL. In silico molecular docking performed within the active center of E. coli adhesion protein FimH showed that heneicosane, followed by cubebol and methyl linoleate, displayed the best fitting score. Thus, it can be concluded that the essential oils of J. gossypifolia and J. intigrimma leaves represent promising sources for antibacterial drugs with antibiofilm potential.