Fresh produce as a potential vehicle for transmission of Acinetobacter baumannii

Prevalence of antibiotic-resistant Acinetobacter spp. on soil and crops collected from agricultural fields in South Korea

The emergence of antibiotic resistance in Acinetobacter spp. is a rising public health concern worldwide. The objective of this study was to investigate the prevalence of antibiotic-resistance genes and the virulence of Acinetobacter spp. isolated from soil and crops obtained from agricultural fields in South Korea. Eight Acinetobacter spp. isolates carried various antibiotic resistance genes, such as emrAB (100%), cat/craA (100%), and aadA gene (87.5%). Minimum inhibitory concentration (MIC) analysis revealed that strains harboring antibiotic resistance genes exhibited high resistance to the respective antibiotics, such as colistin, chloramphenicol, and streptomycin. Interestingly, most of these isolates had high capability of biofilm formation and swarming motility, along with faster growth rates. Taken together, our study demonstrated that antibiotic-resistant Acinetobacter isolated from agricultural settings in South Korea not only frequently carries antibiotic resistance genes but also has virulence-related traits.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-023-01496-7.

Extensive Drug Resistance of Strong Biofilm-Producing Acinetobacter baumannii Strains Isolated from Infections and Colonization Hospitalized Patients in Southern Poland

Acinetobacter baumannii (AB) is a bacterium that causes infections, particularly in immunocompromised patients. Treatment is challenging due to biofilm formation by AB strains, which hinders antibiotic effectiveness and promotes drug resistance. The aim of our study was to analyze the biofilm-producing capacity of AB isolates from various forms of infections in relation to biofilm-related genes and their drug resistance. We tested one hundred isolates for biofilm formation using the crystal violet microplate method. Drug resistance analyses were performed based on EUCAST and CLSI guidelines, and biofilm genes were detected using PCR. All tested strains were found to form biofilms, with 50% being ICU strains and 72% classified as strong biofilm producers. Among these, 87% were extensively drug-resistant (XDR) and 2% were extra-extensively drug-resistant (E-XDR). The most common gene set was bap, bfmS, csuE, and ompA, found in 57% of all isolates. Our research shows that, regardless of the form of infection, biofilm-forming strains can be expected among AB isolates. The emergence of E-XDR and XDR strains among non-ICU infections highlights the necessity for the rational use of antibiotics to stop or limit the further acquisition of drug resistance by A. baumannii.

Acinetobacter baumannii Global Clone-Specific Resistomes Explored in Clinical Isolates Recovered from Egypt

Acinetobacter baumannii (A. baumannii) is a highly problematic pathogen with an enormous capacity to acquire or upregulate antibiotic drug resistance determinants. The genomic epidemiology and resistome structure of 46 A. baumannii clinical isolates were studied using whole-genome sequencing. The isolates were chosen based on reduced susceptibility to at least three classes of antimicrobial compounds and were initially identified using MALDI-TOF/MS, followed by polymerase chain reaction amplification of bla_OXA-51-like genes. The susceptibility profiles were determined using a broth microdilution assay. Multi-, extensive-, and pan-drug resistance was shown by 34.8%, 63.0%, and 2.2% of the isolates, respectively. These were most susceptible to colistin (95.7%), amikacin, and trimethoprim/sulfamethoxazole (32.6% each), while only 26.1% of isolates were susceptible to tigecycline. In silico multi-locus sequence typing revealed 8 Pasteur and 22 Oxford sequence types (STs) including four novel STs (ST^Oxf 2805, 2806, 2807, and 2808). The majority of the isolates belonged to Global Clone (GC) 2 (76.4%), GC5 (19.6%), GC4 (6.5%), GC9 (4.3%), and GC7 (2.2%) lineages. An extensive resistome potentially conferring resistance to the majority of the tested antimicrobials was identified in silico. Of all known carbapenem resistance genes, bla_OXA-23 was carried by most of the isolates (69.6%), followed by ISAba1-amplified bla_ADC (56.5%), bla_NDM-1 and bla_GES-11 (21.7% each), and bla_GES-35 (2.2%) genes. A significant correlation was found between carbapenem resistance and carO mutations, which were evident in 35 (76.0%) isolates. A lower proportion of carbapenem resistance was noted for strains possessing both bla_OXA-23- and bla_GES-11. Amikacin resistance was most probably mediated by armA, aac(6')-Ib9, and aph(3')-VI, most commonly coexisting in GC2 isolates. No mutations were found in pmrABC or lpxACD operons in the colistin-resistant isolates. Tigecycline resistance was associated with adeS (N268Y) and baeS (A436T) mutations. While the lineage-specific distribution of some genes (e.g., bla_ADC and bla_OXA-51-like alleles) was evident, some resistance genes, such as bla_OXA-23 and sul1, were found in all GCs. The data generated here highlight the contribution of five GCs in A. baumannii infections in Egypt and enable the comprehensive analysis of GC-specific resistomes, thus revealing the dissemination of the carbapenem resistance gene bla_OXA-23 in isolates encompassing all GCs.

Prevalence and Characterization of Beta-Lactam and Carbapenem-Resistant Bacteria Isolated from Organic Fresh Produce Retailed in Eastern Spain

Fresh fruits and vegetables are potential reservoirs for antimicrobial resistance determinants, but few studies have focused specifically on organic vegetables. The present study aimed to determine the presence of third-generation cephalosporin (3GC)- and carbapenem-resistant Gram-negative bacteria on fresh organic vegetables produced in the city of Valencia (Spain). Main expanded spectrum beta-lactamase (ESBL)- and carbapenemase-encoding genes were also detected in the isolates. One hundred and fifteen samples were analyzed using selective media supplemented with cefotaxime and meropenem. Resistance assays for twelve relevant antibiotics in medical use were performed using a disc diffusion test. A total of 161 isolates were tested. Overall, 33.5% presented multidrug resistance and 16.8% were resistant to all β-lactam antibiotics tested. Imipenem resistance was observed in 18% of isolates, and low resistance levels were found to ceftazidime and meropenem. Opportunistic pathogens such as Acinetobacter baumannii, Enterobacter spp., Raoultella sp., and Stenotrophomonas maltophilia were detected, all presenting high rates of resistance. PCR assays revealed bla_VIM to be the most frequently isolated ESBL-encoding gene, followed by bla_TEM and bla_OXA-48. These results confirm the potential of fresh vegetables to act as reservoirs for 3GC- and carbapenem-producing ARB. Further studies must be carried out to determine the impact of raw organic food on the spread of AMRs into the community.

Extensively drug-resistant Acinetobacter baumannii: role of conjugative plasmids in transferring resistance

Acinetobacter baumannii is one of the most successful pathogens that can cause difficult-to-treat nosocomial infections. Outbreaks and infections caused by multi-drug resistant A. baumannii are prevalent worldwide, with only a few antibiotics are currently available for treatments. Plasmids represent an ideal vehicle for acquiring and transferring resistance genes in A. baumannii. Five extensively drug-resistant A. baumannii clinical isolates from three major Jordanian hospitals were fully sequenced. Whole-Genome Sequences (WGS) were used to study the antimicrobial resistance and virulence genes, sequence types, and phylogenetic relationship of the isolates. Plasmids were characterized In-silico, followed by conjugation, and plasmid curing experiments. Eight plasmids were recovered; resistance plasmids carrying either aminoglycosides or sulfonamide genes were detected. Chromosomal resistance genes included bla_OXA-66, bla_OXA-91, and bla_OXA-23, and the detected virulence factors were involved in biofilm formation, adhesion, and many other mechanisms. Conjugation and plasmid curing experiments resulted in the transfer or loss of several resistance phenotypes. Plasmid profiling along with phylogenetic analyses revealed high similarities between two A. baumannii isolates recovered from two different intensive care units (ICU). The high similarities between the isolates of the study, especially the two ICU isolates, suggest that there is a common A. baumannii strain prevailing in different ICU wards in Jordanian hospitals. Three resistance genes were plasmid-borne, and the transfer of the resistance phenotype emphasizes the role and importance of conjugative plasmids in spreading resistance among A. baumannii clinical strains.

Virulence Characteristics and Emerging Therapies for Biofilm-Forming Acinetobacter baumannii: A Review

Simple Summary

Acinetobacter baumannii (A. baumannii) is one of the ESKAPE organisms and has the competency to build biofilms. These biofilms account for the most nosocomial infections all over the world. This review reflects on the various physicochemical and environmental factors such as adhesion, pili expression, growth surfaces, drug-resistant genes, and virulence factors that profoundly affect its resistant forte. Emerging drug-resistant issues and limitations to newer drugs are other factors affecting the hospital environment. Here, we discuss newer and alternative methods that can significantly enhance the susceptibility to Acinetobacter spp. Many new antibiotics are under trials, such as GSK-3342830, The Cefiderocol (S-649266), Fimsbactin, and similar. On the other hand, we can also see the impact of traditional medicine and the secondary metabolites of these natural products’ application in searching for new treatments. The field of nanoparticles has demonstrated effective antimicrobial actions and has exhibited encouraging results in the field of nanomedicine. The use of various phages such as vWUPSU and phage ISTD as an alternative treatment for its specificity and effectiveness is being investigated. Cathelicidins obtained synthetically or from natural sources can effectively produce antimicrobial activity in the micromolar range. Radioimmunotherapy and photodynamic therapy have boundless prospects if explored as a therapeutic antimicrobial strategy.

Abstract

Acinetobacter species is one of the most prevailing nosocomial pathogens with a potent ability to develop antimicrobial resistance. It commonly causes infections where there is a prolonged utilization of medical devices such as CSF shunts, catheters, endotracheal tubes, and similar. There are several strains of Acinetobacter (A) species (spp), among which the majority are pathogenic to humans, but A. baumannii are entirely resistant to several clinically available antibiotics. The crucial mechanism that renders them a multidrug-resistant strain is their potent ability to synthesize biofilms. Biofilms provide ample opportunity for the microorganisms to withstand the harsh environment and further cause chronic infections. Several studies have enumerated multiple physiological and virulence factors responsible for the production and maintenance of biofilms. To further enhance our understanding of this pathogen, in this review, we discuss its taxonomy, pathogenesis, current treatment options, global resistance rates, mechanisms of its resistance against various groups of antimicrobials, and future therapeutics.

Prevalence, genetic diversity, antibiotic resistance and biofilm formation of Acinetobacter baumannii isolated from urban environments

AIM

Acinetobacter baumannii is a well-known nosocomial pathogen that has been isolated from different clinical sources. This pathogen also causes community-acquired infections, with mortality rates as high as 64%. The exact natural habitat of this bacterium is still unknown. In this study, we investigated the prevalence of A. baumannii in diverse soil and high-touch surface samples collected from a university campus, malls, parks, hypermarkets and produce markets, roundabout playground slides, and bank ATMs.

METHODS AND RESULTS

All obtained isolates were characterized for their antibiotic susceptibility, biofilm formation capacities, and were typed by multi-locus sequence analysis. A total of 63 A. baumannii isolates were recovered, along with 46 A. pittii and 8 A. nosocomialis isolates. Sequence typing revealed that 25 A. baumannii isolates are novel strains. Toilets and sink washing basins were the most contaminated surfaces, accounting for almost 50% of the recovered isolates. A number of A. baumannii (n=10), A. pittii (n=19) and A. nosocomialis (n=5) isolates were recovered from handles of shopping carts and baskets. The majority of isolates were strong biofilm formers and 4 exhibited a multi-drug resistant (MDR) phenotype.

CONCLUSIONS

Our study is the first to highlight community restrooms and shopping carts as potential reservoirs for pathogenic Acinetobacter species. Further studies are required to identify the reasons associated with the occurrence of A. baumannii inside restrooms. Proper disinfection of community environmental surfaces and spreading awareness about the importance of hand hygiene may prevent the dissemination of pathogenic bacteria within the community.

SIGNIFICANCE AND IMPACT OF STUDY

Serious gaps remain in our knowledge of how A. baumannii spreads to cause disease. This study will advance our understanding of how this pathogen spreads between healthcare and community environments. In addition, our findings will help healthcare decision makers implement better measures to control and limit further transmission of A. baumannii.