Imipenem resistance and biofilm production in Acinetobacter

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.

Acinetobacter baumannii Biofilm Formation and Its Role in Disease Pathogenesis: A Review

Acinetobacter species, particularly Acinetobacter baumannii, is the first pathogen on the critical priority list of pathogens for novel antibiotics to become a "red-alert" human pathogen. Acinetobacter baumannii is an emerging global antibiotic-resistant gram-negative bacteria that most typically causes biofilm-associated infections such as ventilator-associated pneumonia and catheter-related infection, both of which are resistant to antibiotic therapy. A. baumannii's capacity to develop antibiotic resistance mechanisms allows the organism to thrive in hospital settings, facilitating the global spread of multidrug-resistant strains. Although Acinetobacter infections are quickly expanding throughout hospital environments around the world, the highest concentration of infections occurs in intensive care units (ICUs). Biofilms are populations of bacteria on biotic or abiotic surfaces that are encased in the extracellular matrix and play a crucial role in pathogenesis, making treatment options more difficult. Even though a variety of biological and environmental elements are involved in the production of A. baumannii biofilms, glucose is the most important component. Biofilm-mediated A. baumannii infections are the most common type of A. baumannii infection associated with medical equipment, and they are extremely difficult to treat. As a result, health care workers (HCWs) should focus on infection prevention and safety actions to avoid A. baumannii biofilm-related infections caused by medical devices, and they should be very selective when using treatments in combination with anti-biofilms. Therefore, this review discusses biofilm formation in A. baumannii, its role in disease pathogenesis, and its antimicrobial resistance mechanism.

Potential of Variovorax paradoxus isolate BFB1_13 for bioremediation of BTEX contaminated sites

Here, we report and discuss the applicability of Variovorax paradoxus strain BFB1_13 in the bioremediation of BTEX contaminated sites. Strain BFB1_13 was capable of degrading all the six BTEX-compounds under both aerobic (O₂ conc. 8 mg l⁻¹) and micro-aerobic/oxygen-limited (O₂ conc. 0.5 mg l⁻¹) conditions using either individual (8 mg‧l⁻¹) or a mixture of compounds (~ 1.3 mg‧l⁻¹ of each BTEX compound). The BTEX biodegradation capability of SBP-encapsulated cultures (SBP—Small Bioreactor Platform) was also assessed. The fastest degradation rate was observed in the case of aerobic benzene biodegradation (8 mg l⁻¹ per 90 h). Complete biodegradation of other BTEX occurred after at least 168 h of incubation, irrespective of the oxygenation and encapsulation. No statistically significant difference was observed between aerobic and microaerobic BTEX biodegradation. Genes involved in BTEX biodegradation were annotated and degradation pathways were predicted based on whole-genome shotgun sequencing and metabolic analysis. We conclude that V. paradoxus strain BFB1_13 could be used for the development of reactive biobarriers for the containment and in situ decontamination of BTEX contaminated groundwater plumes. Our results suggest that V. paradoxus strain BFB1_13—alone or in co-culture with other BTEX degrading bacterial isolates—can be a new and efficient commercial bioremediation agent for BTEX contaminated sites.

Methoxy-Substituted Hydroxychalcone Reduces Biofilm Production, Adhesion and Surface Motility of Acinetobacter baumannii by Inhibiting ompA Gene Expression

An increasing lack of available therapeutic options against Acinetobacter baumannii urged researchers to seek alternative ways to fight this extremely resistant nosocomial pathogen. Targeting its virulence appears to be a promising strategy, as it offers considerably reduced selection of resistant mutants. In this study, we tested antibiofilm potential of four synthetic chalcone derivatives against A. baumannii. Compound that showed the greatest activity was selected for further evaluation of its antivirulence properties. Real-time PCR was used to evaluate mRNA expression of biofilm-associated virulence factor genes (ompA, bap, abaI) in treated A. baumannii strains. Also, we examined virulence properties related to the expression of these genes, such as fibronectin- and collagen-mediated adhesion, surface motility, and quorum-sensing activity. The results revealed that the expression of all tested genes is downregulated together with the reduction of adhesion and motility. The conclusion is that 2'-hydroxy-2-methoxychalcone exhibits antivirulence activity against A. baumannii by inhibiting the expression of ompA and bap genes, which is reflected in reduced biofilm formation, adhesion, and surface motility.

Aerobic and oxygen-limited enrichment of BTEX-degrading biofilm bacteria: dominance of Malikia versus Acidovorax species

Due to their high resistance against environmental challenges, bacterial biofilms are ubiquitous and are frequently associated with undesired phenomena in environmental industry (e. g. biofouling). However, because of the high phylogenetic and functional diversity, bacterial biofilms are important sources of biotechnologically relevant microorganisms, e.g. those showing bioremediation potential. In our previous work, the high phylogenetic and metabolic diversity of a clogging biofilm, developed in a simple aromatic hydrocarbon (BTEX)-contaminated groundwater well was uncovered. The determination of relationships between different groups of biofilm bacteria and certain metabolic traits has been omitted so far. Therefore, by setting up new biofilm-based enrichment microcosms, the research goal of the present study was to identify the aerobic/hypoxic BTEX-degrading and/or prolific biofilm-forming bacteria. The initial bacterial community composition as well as temporal dynamics due to the selective enrichment has been determined. The obtained results indicated that the concentration of dissolved oxygen may be a strong selective force on the evolution and final structure of microbial communities, developed in hydrocarbon-contaminated environments. Accordingly, members of the genus Malikia proved to be the most dominant community members of the aerobic BTEX-degrading enrichments. Acidovorax spp. dominated the oxygen-limited/hypoxic setup. During the study, a strain collection of 23 different bacterial species was obtained. Non-pathogenic members of this strain collection, with outstanding biodegradation (e.g. Pseudomonas, Variovorax isolates) and biofilm-forming potential (e.g. Rhizobium), may potentially be applied in the development of biofilm-based semipermeable reactive biobarriers.

Acinetobacter baumannii isolated from hospital-acquired infection: biofilm production and drug susceptibility

Acinetobacter baumannii cause opportunistic nosocomial infections and is often multidrug resistant. It has ability to form biofilm. The possession of drug resistance mechanism and ability of biofilm formation seems to be the different way to enhancement of viability in stressful environment. In this study, we evaluate relation between these two factors. The biofilm formation was investigated in M63 medium with casein in microtiter plates, and the drug susceptibility was performed by disk diffusion methods. We found that 80-98% strains formed a biofilm. Strains showing sensitivity to amikacin and tobramycin from ICU produced more biofilm than strains showing resistance to these antibiotics. Ceftazidime-sensitive strains formed a smaller biofilm than resistant. The logistic regression shows association between drug resistance and strains originating from ICU. In case of ceftazidime, strong biofilm formation and descending from ICU reduced the likelihood of drug sensitivity. For other drugs such as aminoglycosides, fluoroquinolones, trimethoprim/sulfamethoxazole, and tetracycline, we found opposite relation (but it was not statistically significance). However, generally it seems that strong biofilm producers from ICUs are often more susceptible to antibiotics. This situation can be explained by the fact that bacteria protected in biofilm do not need mechanisms responsible for resistance of planktonic cells.

Recent updates of carbapenem antibiotics

Carbapenems are among the most commonly used and the most efficient antibiotics since they are relatively resistant to hydrolysis by most β-lactamases, they target penicillin-binding proteins, and generally have broad-spectrum antibacterial effect. In this review, we described the initial discovery and development of carbapenems, chemical characteristics, in vitro/in vivo activities, resistance studies, and clinical investigations for traditional carbapenem antibiotics in the market; imipenem-cilastatin, meropenem, ertapenem, doripenem, biapenem, panipenem/betamipron in addition to newer carbapenems such as razupenem, tebipenem, tomopenem, and sanfetrinem. We focused on the literature published from 2010 to 2016.