High Proportions of Multidrug-Resistant Acinetobacter spp. Isolates in a District in Western India: A Four-Year Antibiotic Susceptibility Study of Clinical Isolates

Novel sequence type of carbapenem-resistant Acinetobacter pittii ST1451 with enhanced virulence isolated from septicaemic neonates in India

BACKGROUND

The clinical relevance of Acinetobacter pittii is increasing, but reports of this organism causing neonatal sepsis are rare.

OBJECTIVES

To understand the mechanisms of resistance and virulence of A. pittii isolated from neonatal blood belonging to a novel sequence type.

MATERIALS AND METHODS

Antibiotic susceptibility, MLST, WGS, phylogenomic comparison with a global collection of carbapenemase-harbouring A. pittii were done. To study the pathogenic potential of novel A. pittii, in vitro and in vivo assays were carried out.

RESULTS AND DISCUSSION

Two novel multidrug-resistant A. pittii from neonatal blood belonging to a novel sequence type 1451 (ST1451) were isolated. WGS revealed that the isolates were almost similar (147 SNP distant) and harbouring two carbapenem resistance genes blaNDM-1 with upstream ISAba125 and downstream bleMBL along with blaOXA-58 with upstream ISAba3. Other resistance genes included blaADC-25, blaOXA-533, aph(3″)-Ib, aph(3')-VIa, aph(6)-Id, aac(3)-IId, mph(E), msr(E), sul2 and tet(39), different efflux pump genes and amino acid substitutions within GyrA (Ser81Leu) and ParC (Ser84Leu; Glu88Ala) were detected among the isolates. The study genomes were closely related to four strains belonging to ST119. The isolates showed biofilm production, serum resistance, growth under iron limiting condition, surface-associated motility and adherence to host cell. Isolates induced cytokine production in the host cell and showed mice mortality.

DISCUSSION AND CONCLUSIONS

This study is the first report of the presence of blaNDM-1 in A. pittii from India along with another carbapenemase blaOXA-58. Emergence of highly virulent, multidrug-resistant A. pittii with attributes similar to A. baumannii calls for surveillance to identify the novel strains and their pathogenic and resistance potential.

The Roles of Plant-Growth-Promoting Rhizobacteria (PGPR)-Based Biostimulants for Agricultural Production Systems

The application of biostimulants has been proven to be an advantageous tool and an appropriate form of management towards the effective use of natural resources, food security, and the beneficial effects on plant growth and yield. Plant-growth-promoting rhizobacteria (PGPR) are microbes connected with plant roots that can increase plant growth by different methods such as producing plant hormones and molecules to improve plant growth or providing increased mineral nutrition. They can colonize all ecological niches of roots to all stages of crop development, and they can affect plant growth and development directly by modulating plant hormone levels and enhancing nutrient acquisition such as of potassium, phosphorus, nitrogen, and essential minerals, or indirectly via reducing the inhibitory impacts of different pathogens in the forms of biocontrol parameters. Many plant-associated species such as Pseudomonas, Acinetobacter, Streptomyces, Serratia, Arthrobacter, and Rhodococcus can increase plant growth by improving plant disease resistance, synthesizing growth-stimulating plant hormones, and suppressing pathogenic microorganisms. The application of biostimulants is both an environmentally friendly practice and a promising method that can enhance the sustainability of horticultural and agricultural production systems as well as promote the quantity and quality of foods. They can also reduce the global dependence on hazardous agricultural chemicals. Science Direct, Google Scholar, Springer Link, CAB Direct, Scopus, Springer Link, Taylor and Francis, Web of Science, and Wiley Online Library were checked, and the search was conducted on all manuscript sections in accordance with the terms Acinetobacter, Arthrobacter, Enterobacter, Ochrobactrum, Pseudomonas, Rhodococcus, Serratia, Streptomyces, Biostimulants, Plant growth promoting rhizobactera, and Stenotrophomonas. The aim of this manuscript is to survey the effects of plant-growth-promoting rhizobacteria by presenting case studies and successful paradigms in various agricultural and horticultural crops.

Differential Binding of Carbapenems with the AdeABC Efflux Pump and Modulation of the Expression of AdeB Linked to Novel Mutations within Two-Component System AdeRS in Carbapenem-Resistant Acinetobacter baumannii

Resistance-nodulation-division-type efflux system AdeABC plays an important role in carbapenem resistance among Acinetobacter baumannii. However, a knowledge gap is observed regarding the role of its regulator AdeRS in carbapenem-resistant A. baumannii (CRAB). This study effectively combines microbiological analysis with an in-silico structural approach to understand the contribution of AdeRS among CRAB (n = 38). Additionally, molecular docking was performed for the first time to study the interaction of FDA-approved carbapenems and pump inhibitor PAβN with the open and closed structure of AdeB at the three binding sites (periplasmic, proximal, distal). It was observed that open conformation of AdeB facilitates the binding of carbapenems and PAβN at entrance and proximal sites compared to the closed conformation. PAβN was found to block carbapenem interacting residues in AdeB, establishing its role as a competitive inhibitor of AdeB substrates. Overexpression of AdeABC was detected by q-RT-PCR among 29% of CRABs, and several mutations within AdeS (GLY186VAL, SER188PHE, GLU121LYS, VAL255ILE) and AdeR (VAL120ILE, ALA136VAL) were detected by sequencing. The sequence and structure-based study of AdeRS was performed to analyze the probable effect of these mutations on regulation of the two-component system (TCS), especially, utilizing its three-dimensional structure. AdeS mutations inhibited the transfer of a phosphate group to AdeR, preventing the binding of AdeR to the intercistronic region, leading to overexpression of AdeABC. The elucidation of the role of mutations in AdeRS improves our understanding of TCS-based regulation. Identification of the key residues of AdeB interacting with carbapenems and PAβN may help in future designing of novel inhibitors.

IMPORTANCE AdeABC is an important efflux pump in A. baumannii that plays a role in resistance toward different antibiotics including the “last resort” antibiotic, carbapenem. This pump is regulated by a two-component system, AdeRS. To understand the binding of carbapenems with AdeABC and pump inhibition by PAβN, we analyzed for the first time the possible atomic level interactions of carbapenems and PAβN with AdeB. In the current study, AdeRS-associated novel mutations in clinical A. baumannii are reported for the first time, and a sequence-structure based in-silico approach was used to interpret their role in AdeABC overexpression, leading to carbapenem resistance. None of the previous studies had undertaken both these aspects simultaneously. This study analyzes the open and closed conformation of AdeB, their binding with carbapenems, and key residues involved in it. This helps in visualizing the plausible atomic level causes of pump inhibition driving the discovery of novel inhibitors.

Vaccine development to control the rising scourge of antibiotic-resistant Acinetobacter baumannii: a systematic review

Acinetobacter baumannii has emerged as one of major nosocomial pathogen and global emergence of multidrug-resistant strains has become a challenge for developing effective treatment options. A. baumannii has developed resistance to almost all the antibiotics viz. beta-lactams, carbapenems, tigecycline and now colistin, a last resort of antibiotics. The world is on the cusp of post antibiotic era and the evolution of multi-, extreme- and pan–drug-resistant A. baumannii strains is its obvious harbinger. Various combinations of antibiotics have been investigated but no successful treatment option is available. All these failed efforts have led researchers to develop and implement prophylactic vaccination for the prevention of infections caused by this pathogen. In this review, the advantages and disadvantages of active and passive immunization, the types of sub-unit and multi-component vaccine candidates investigated against A. baumannii viz. whole cell organism, outer membrane vesicles, outer membrane complexes, conjugate vaccines and sub-unit vaccines have been discussed. In addition, the benefits of Reverse vaccinology are emphasized here in which the potential vaccine candidates are predicted using bioinformatic online tools prior to in vivo validations.

Antimicrobial resistance and the post antibiotic era: better late than never effort

Introduction: Antimicrobial resistance (AMR) is a multi-layered problem with a calamitous impact on humans, livestock, the environment, and the biosphere. Initiatives and action plan to preclude AMR remain poorly implemented in India.Area covered: This review highlights essential factors contributing to AMR, epidemiology of the resistant bacteria, current treatment options, economic impact, and regulatory efforts initiated by the Indian government to tackle AMR.Expert opinion: Health-care professionals, hospitals, and the general public must understand and cooperatively implement the 'One Health approach,' which entails judicious use of antibiotics in humans, animals, and the environment. Neglecting the AMR problem predicts the expansion of the 'Post-antibiotic era' characterized by drying antibiotic discovery pipelines, overuse of 'Watch' and 'Reserve' groups, coupled with underuse of 'Access' antibiotics, increased daily defined doses, increased healthcare cost, rise in morbidity, mortality, and environmental degradation. The Indian case study elucidates a looming international crisis that demands global attention and commitment for envisaging and implementing locally relevant solutions.

Multidrug-Resistant Acinetobacter baumannii - The Modern Menace: A Retrospective Study in a Tertiary Hospital in Mangalore

Background

Multidrug resistance in Acinetobacter baumannii is constantly on the rise. There has also been an increase in the morbidity and mortality of patients with infection by the same pathogen.

Aim

This study aimed to assess the patterns of antibiotic resistance exhibited by various clinical isolates of Acinetobacter baumannii, examine the risk factors associated, and investigate the prevalence of co-infecting pathogens and the clinical outcomes of the patients.

Study Design

Retrospective cross-sectional study.

Patients and Methods

Reports of 100 isolates of Acinetobacter baumannii obtained from patients admitted in two tertiary hospitals were used for the study. Identification and determination of antibiotic resistance patterns were done using Vitek2. The presence of probable risk factors was noted. The pattern of clinical outcomes of the patients and the prevalence of co-infecting pathogens were analyzed. Data analysis was done using descriptive statistics.

Results

More than 50% of isolates showed resistance independently to imipenem and meropenem. Higher rates of susceptibility were observed with tigecycline (55%). Isolates obtained from patients in the intensive care unit (ICU) showed resistance to a more number of antibiotics than those in the wards and operation theatre. Seventeen percent of the isolates were associated with a co-infecting pathogen such as Pseudomonas, Enterococcus, Klebsiella, 87% of the patients were discharged, 12% expired, and 1% were shifted. A positive correlation was found between the duration of hospital stay and number of antibiotics to which the isolate was resistant.

Conclusion

Multidrug resistance in Acinetobacter baumannii continues to be a menace. In this study, a large number of isolates exhibited resistance to carbapenems such as imipenem, meropenem, and ertapenem, thereby signifying the need for further research and the use of other antibiotics such as tigecycline, to which higher susceptibility was observed.

The Role of Zinc Efflux during Acinetobacter baumannii Infection

Acinetobacter baumannii is a ubiquitous Gram-negative bacterium, that is associated with significant disease in immunocompromised individuals. The success of A. baumannii is partly attributable to its high level of antibiotic resistance. Further, A. baumannii expresses a broad arsenal of putative zinc efflux systems that are likely to aid environmental persistence and host colonization, but detailed insights into how the bacterium deals with toxic concentrations of zinc are lacking. In this study we present the transcriptomic responses of A. baumannii to toxic zinc concentrations. Subsequent mutant analyses revealed a primary role for the resistance-nodulation-cell division heavy metal efflux system CzcCBA, and the cation diffusion facilitator transporter CzcD in zinc resistance. To examine the role of zinc at the host-pathogen interface we utilized a murine model of zinc deficiency and challenge with wild-type and czcA mutant strains, which identified highly site-specific roles for zinc during A. baumannii infection. Overall, we provide novel insight into the key zinc resistance mechanisms of A. baumannii and outline the role these systems play in enabling the bacterium to survive in diverse environments.

Considerations and Caveats in Combating ESKAPE Pathogens against Nosocomial Infections

ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) are among the most common opportunistic pathogens in nosocomial infections. ESKAPE pathogens distinguish themselves from normal ones by developing a high level of antibiotic resistance that involves multiple mechanisms. Contemporary therapeutic strategies which are potential options in combating ESKAPE bacteria need further investigation. Herein, a broad overview of the antimicrobial research on ESKAPE pathogens over the past five years is provided with prospective clinical applications.

Prevalence of Multi-drug Resistant Acinetobacter baumannii (MDRAB) in Amman Jordan During 2018

PURPOSE

Acinetobacter baumannii is an opportunistic pathogen, and is among the most problematic nosocomial infections as well as community-acquired infections. This retrospective study was conducted as an attempt to determine the prevalence of multidrug-resistant A. baumannii (MDRAB) isolates from the north and central Jordan area during 2018.

METHODS

Patients' records provided by an accredited central private laboratory located in Amman, were examined for A. baumannii isolates identified during this period. The isolates were identified to the species level using the API-10S system and the antimicrobial sensitivity testing was determined using the Kirby-Bauer disc diffusion method.

RESULTS

A total of 43 unduplicated isolates were obtained and classified according to clinical sampling source into: Group I (blood), Group II (urine) and Group III (wound, pus, sputum, bedsore and others). Total MDRAB isolates recorded were 29 (67.4 %). Resistance to imipenem was found to be 36% and 94% among groups II and III, respectively, and resistance to meropenem was 60% and 88% among the same groups, respectively.

CONCLUSION

Antimicrobial stewardship programs at a national scale are needed to calculate the actual proportion of MDRAB in the country and to combat its increasing emergence and decrease the magnitude of antibiotic resistance.

A 2-Year Single-Centre Audit on Antibiotic Resistance of Pseudomonas aeruginosa, Acinetobacter baumannii and Klebsiella pneumoniae Strains from an Intensive Care Unit and Other Wards in a General Public Hospital in Greece

Hospital-acquired infections, particularly in the critical care setting, are becoming increasingly common during the last decade, with Gram-negative bacterial infections presenting the highest incidence among them. Multi-drug-resistant (MDR) Gram-negative infections are associated with high morbidity and mortality, with significant direct and indirect costs resulting from long hospitalization due to antibiotic failure. As treatment options become limited, antimicrobial stewardship programs aim to optimize the appropriate use of currently available antimicrobial agents and decrease hospital costs. Pseudomonas aeruginosa, Acinetobacter baumannii and Klebsiella pneumoniae are the most common resistant bacteria encountered in intensive care units (ICUs) and other wards. To establish preventive measures, it is important to know the prevalence of Gram-negative isolated bacteria and antibiotic resistance profiles in each ward separately, compared with ICUs. In our single centre study, we compared the resistance levels per antibiotic of P. aeruginosa, A. baumannii and K.pneumoniae clinical strains between the ICU and other facilities during a 2-year period in one of the largest public tertiary hospitals in Greece. The analysis revealed a statistically significant higher antibiotic resistance of the three bacteria in the ICU isolates compared with those from other wards. ICU strains of P. aeruginosa presented the highest resistance rates to gentamycin (57.97%) and cefepime (56.67%), followed by fluoroquinolones (55.11%) and carbapenems (55.02%), while a sensitivity rate of 97.41% was reported to colistin. A high resistance rate of over 80% of A. baumannii isolates to most classes of antibiotics was identified in both the ICU environment and regular wards, with the lowest resistance rates reported to colistin (53.37% in ICU versus an average value of 31.40% in the wards). Statistically significant higher levels of resistance to most antibiotics were noted in ICU isolates of K. pneumoniae compared with non-ICU isolates, with the highest difference—up to 48.86%—reported to carbapenems. The maximum overall antibiotic resistance in our ICU was reported for Acinetobacter spp. (93.00%), followed by Klebsiella spp. (72.30%) and Pseudomonas spp. (49.03%).

High Prevalence and Endemicity of Multidrug Resistant Acinetobacter spp. in Intensive Care Unit of a Tertiary Care Hospital, Varanasi, India

The increasing emergence of Acinetobacter spp. with healthcare associated infections (HCAI) in intensive care units (ICU) is alarming. This study was a laboratory-based audit to determine the prevalence of Acinetobacter spp. associated with HCAI in the adult ICU of a tertiary care hospital in Varanasi, north India, with special reference to antimicrobial resistance and resistance determinants over a period of 5 years. A total of 993 cases of HCAI were analyzed. Isolates were characterized as multidrug resistance and extended drug resistance (MDR/XDR) based on antimicrobial susceptibility records. Few (100) randomly selected isolates of Acinetobacter baumannii (A. baumannii) were tested for imipenem, meropenem, and polymyxin B susceptibility by minimum inhibitory concentration (MIC) and for the presence of class A and B carbapenemases by multiplex PCR. Active surveillance of ICU environment was also performed. High prevalence of Acinetobacter related hospital acquired pneumonia (HAP) with significant resistance to imipenem (p<0.05) and 88.02% MDR and 61.97% XDR was detected along with persistence in the ICU environment. The isolates harbored bla_IMP (89%), bla_VIM (51%), bla_NDM-1 (34%), and bla_OXA-23-like (93%) genes. Specific interventional measures should be adopted to control these imipenem resistant Acinetobacter spp. which have attained the level of endemicity in our ICU setup.