Resistant Acinetobacter Research Articles

Prediction of tissue exposures of polymyxin-B, amikacin and sulbactam using physiologically-based pharmacokinetic modeling.

The combination antimicrobial therapy consisting of amikacin, polymyxin-B, and sulbactam demonstrated in vitro synergy against multi-drug resistant Acinetobacter baumannii. The objectives were to predict drug disposition and extrapolate their efficacy in the blood, lung, heart, muscle and skin tissues using a physiologically-based pharmacokinetic (PBPK) modeling approach and to evaluate achievement of target pharmacodynamic (PD) indices against A. baumannii. A PBPK model was initially developed for amikacin, polymyxin-B, and sulbactam in adult subjects, and then scaled to pediatrics, accounting for both renal and non-renal clearances. The simulated plasma and tissue drug exposures were compared to the observed data from humans and rats. Efficacy was inferred using joint probability of target attainment of target PD indices. The simulated plasma drug exposures in adults and pediatrics were within the 0.5 to 2 boundary of the mean fold error for the ratio between simulated and observed means. Simulated drug exposures in blood, skin, lung, and heart were consistent with reported penetration ratio between tissue and plasma drug exposure. In a virtual pediatric population from 2 to <18 years of age using pediatric dosing regimens, the interpretive breakpoints were achieved in 85-90% of the population. The utility of PBPK to predict and simulate the amount of antibacterial drug exposure in tissue is a practical approach to overcome the difficulty of obtaining tissue drug concentrations in pediatric population. As combination therapy, amikacin/polymyxin-B/sulbactam drug concentrations in the tissues exhibited sufficient penetration to combat extremely drug resistant A. baumannii clinical isolates.

Nosocomial carbapenem-drug resistant Acinetobacter baumannii, related factors and clinical outcomes in Northeast Iran

Background and objectivesNosocomial infections, including drug-resistant Acinetobacter baumannii infections, continue to impact the health of hospitalized patients. This study sought to determine the prevalence of these infections and assess the associated risk factors and clinical outcomes in Gorgan, Iran.MethodsA retrospective cross-sectional study was conducted on 143 infected patients with Acinetobacter baumannii in two educational hospitals in Gorgan city, Iran between 2016 and 2018. Patient information including age, gender, reason and duration of hospitalization, background of diseases, type of sample culture, symptoms, laboratory findings, prescribed antibiotics, and antibiogram were collected and analyzed. The Logistic regression and survival statistical methods were used by software of SPSS 26.ResultsA total of 37 patients (25.87%) died during hospitalization. The less than one year and 45–65 years age groups demonstrated more deaths (29.7%; p-value < 0.001). Being single (not being married) was found to be a risk factor in increasing the chance of death among patients (OR = 2.154, 95% CI: 1.02–4.53; p = 0.048). Hospitalization in intensive care units (ICUs) was a risk factor for the death of patients (OR = 4.655, 95% CI: 7.6–83.2). The resistance to carbapenems was reported to be an important risk factor for the death of patients.ConclusionsAcinetobacter baumannii infections, particularly those resistant to carbapenems, are a significant risk for patients in ICUs and can lead to higher mortality rates.

Emergence and spread of resistant and biofilm-forming Acinetobacter baumannii in critically ill COVID-19 patients

The COVID-19 pandemic has raised concerns beyond the viral infection itself. Bacterial co-infections, particularly those involving Acinetobacter baumannii, have become a significant worry in critically ill COVID-19 patients. A. baumannii is an opportunistic pathogen that can cause nosocomial infections, especially in patients with compromised immune systems. This study investigated 36 A. baumannii isolates obtained from COVID-19 patients during a concurrent outbreak. The isolates were collected over two years through routine medical requests sent to the Clinical Microbiology laboratory. Identification of the strains was confirmed through biochemical tests, the Phoenix BD® Automated Microbiology System, and MALDI-TOF Mass Spectrometry. The study assessed the antimicrobial sensitivity of the isolates, with a specific focus on resistance to the beta-lactam group as well as aminoglycosides. The presence of specific antibiotic resistance genes (blaOXA-23, -24, -51 and -58, blaKPC, blaSHV, blaIMP, blaVIM, aac(6')-Ib, ant(3'')-Ia, and aph(3')-Ia) was investigated using PCR and Sanger DNA sequencing. Biofilm-forming capabilities of the isolates were also evaluated. The findings revealed diverse resistance profiles, with a high prevalence of resistant strains, including resistance to carbapenems. Genetic analysis suggested potential clonal spread of certain strains within the hospital setting. Moreover, a significant proportion of the isolates demonstrated strong biofilm-forming abilities, which can enhance persistence and antibiotic resistance. In conclusion, this study highlights the need for vigilant monitoring and targeted interventions to address bacterial co-infections in COVID-19 patients. The diversity in resistance patterns, potential clonal spread, and robust biofilm-forming abilities among A. baumannii isolates underscore the importance of addressing this issue to better manage and treat critically ill COVID-19 patients.

Effect of colistin combined with sulbactam: 9 g versus 12 g per day on mortality in the treatment of carbapenems resistant Acinetobacter baumannii pneumonia: a randomized controlled trial.

The current treatment recommendation involves administering a high dose of sulbactam alongside at least one additional agent. However, there remains a lack of data regarding the optimal dosage of sulbactam. We investigated whether administering sulbactam at a dosage of 12 g/day decreases the mortality rate among patients with CRAB pneumonia compared to 9 g/day. The study was an open-label, superiority, randomized controlled trial conducted at Phramongkutklao Hospital between September 2019 and September 2023 in patients diagnosed with CRAB. Participants were randomly assigned to receive a combination of colistin with either 9 or 12 g/day of sulbactam. The primary endpoint was the all-cause mortality rate at 28 days post-randomization. Among the 138 participants, there was a trend toward a lower mortality rate in the 12 g/day group (59.4% vs. 47.8%; p = 0.158). After adjusting for factors associated with mortality, a lower mortality was observed in the 12 g/day group (adjusted HR 0.54 [95% CI 0.33-0.87]; p = 0.0110). The microbiological cure rate at day 7 was higher in the 12 g/day group (73.2% vs. 89.4%; p = 0.02). Colistin in combination with sulbactam at a dosage of 12 g/day may improve mortality compared to 9 g/day.

Environmental contamination with carbapenem resistant Acinetobacter baumannii in healthcare settings in Fiji: a potential source of infection.

There are multiple ongoing outbreaks of carbapenem resistant Acinetobacter baumannii (CRAb) infection in Fiji's hospitals. CRAb is able to colonize and persist on various hospital surfaces for extended periods. We conducted a study to understand the extent of hospital environmental contamination and phylogenetic links with clinical isolates. Swabs were collected from high-touch surfaces at Colonial War Memorial Hospital (CWMH) September 2021 and December 2022; Lautoka Hospital (LTKH) August 2022; and Labasa Hospital (LBSH) November 2022. All bacterial isolates were identified, and antimicrobial susceptibility testing (AST) performed; isolates resistant to carbapenems and producing a carbapenemase underwent whole genome sequencing. Comparison was made to clinical isolates obtained from CWMH in 2016-2017 and 2019-2021 and from LTKH and LBSH from 2020-2021. From the 180 environmental samples collected, ten (5.6%) CRAb were isolated; no other carbapenem-resistant gram-negative organisms were isolated. Seven (70%) of the CRAb were isolated from CWMH and three (30%) from LTKH; no CRAb were isolated from LBSH. Of the seven CWMH CRAb, two were sequence type 2 (ST2), three ST25, and two ST499. All LTKH isolates were ST499. The two environmental CRAb ST2 isolates were closely genetically linked to isolates obtained from patients in CWMH, LTKH, and LBSH 2020-2021. Similarly, the three environmental CRAb ST25 isolates were closely genetically linked to isolates obtained from patients admitted to CWMH in 2019-2021 and LBSH in 2020. The environmental CRAb ST499 isolates represented two distinct clones, with clone 1 comprising two genetically identical isolates from CWMH and clone 2 the three isolates from LTKH. Although no genetic linkages were observed when comparing environmental ST499 isolates to those from CWMH patients in 2020-2021, both clone 1 isolates were genetically identical to an isolate obtained from a patient admitted during the sampling period. Our study highlights the contamination of high-touch surfaces within Fiji hospitals with CRAb, suggesting that these may serve as important sources for CRAb. Phylogenetic linkages to CRAb isolated from patients since 2019 underscores the persistence of this resistant pathogen in hospital settings and the ongoing risk for hospital-acquired infections.

Exploiting human immune repertoire transgenic mice for protective monoclonal antibodies against antimicrobial resistant Acinetobacter baumannii

The use of monoclonal antibodies for the control of drug resistant nosocomial bacteria may alleviate a reliance on broad spectrum antimicrobials for treatment of infection. We identify monoclonal antibodies that may prevent infection caused by carbapenem resistant Acinetobacter baumannii. We use human immune repertoire mice (Kymouse platform mice) as a surrogate for human B cell interrogation to establish an unbiased strategy to probe the antibody-accessible target landscape of clinically relevant A. baumannii. After immunisation of the Kymouse platform mice with A. baumannii derived outer membrane vesicles (OMV) we identify 297 antibodies and analyse 26 of these for functional potential. These antibodies target lipooligosaccharide (OCL1), the Oxa-23 protein, and the KL49 capsular polysaccharide. We identify a single monoclonal antibody (mAb1416) recognising KL49 capsular polysaccharide to demonstrate prophylactic in vivo protection against a carbapenem resistant A. baumannii lineage associated with neonatal sepsis mortality in Asia. Our end-to-end approach identifies functional monoclonal antibodies with prophylactic potential against major lineages of drug resistant bacteria accounting for phylogenetic diversity and clinical relevance without existing knowledge of a specific target antigen. Such an approach might be scaled for a additional clinically important bacterial pathogens in the post-antimicrobial era.

A Five-Year Trend Analysis of Antibacterial Resistance Patterns Among Non-fermenting Gram-Negative Bacilli: A Retrospective Study From the ICU Settings of a Tertiary Care Hospital.

Non-fermenting gram-negative bacilli (NFGNB) infections have emerged as a serious health concern in ICUs. Multi-drug resistant (MDR) strains of NFGNB can evolve by acquiring resistance genes to at least one agent in three or more antibacterial categories. This study aimed to analyse the prevalence of NFGNB, the distribution of MDR strains, and antibiotic resistance trends of NFGNB in different ICUs of a tertiary care hospital over a period of five years. This retrospective study was conducted in a tertiary care teaching hospital in eastern India, including a total of 20,256 samples received from various ICUs over five years. Data retrieved from the Laboratory Information System (LIS) of the hospital, and repetitive isolates from the same patients, were excluded. All samples were processed according to standard microbiological protocols by automated systems. Data were entered into a Microsoft Excel spreadsheet (Microsoft® Corp., Redmond, WA, USA), analysed using Epi Info software, and presented using descriptive statistics. Chi-square and Fisher's exact tests (where appropriate) were used as tests of significance, with a p-value of <0.05 considered statistically significant. A total of 18,032 culture-positive samples out of 20,256 samples showed growth of 18,659 bacteria. Out of these, 952 isolates were NFGNB. The prevalence of NFGNB was found to be 5.10% among all isolated bacteria. The predominant sources were respiratory samples (37.3%). Acinetobacter spp. emerged as the most prevalent NFGNB (46.5%), followed by Pseudomonas spp. (31%) and Burkholderia spp. (14.3%). Among the NFGNB isolates, 61.76% exhibited MDR, with the highest prevalence of MDR strains seen in Elizabethkingia spp. (94.7%). Among the most prevalent NFGNB, Acinetobacter spp., 64.8% were MDR strains. Trend analysis of antibiotic resistance patterns of Acinetobacter spp. indicated a substantial increase for trimethoprim-sulfamethoxazole by 18.5%, minocycline (44.4%), amikacin (20.4%), and ceftazidime (7.4%), whereas there was a reduced trend in resistance to carbapenems (6.5%), ciprofloxacin (4.7%), and cefepime (3.7%) over five years. In Pseudomonas spp., resistance to meropenem increased by 17.4%, and for ceftazidime (11.8%), amikacin (10.6%), and piperacillin-tazobactam (7.9%), whereas resistance to aztreonam diminished by 13.9%. Burkholderia spp. exhibited a 23.5% escalation in resistance to meropenem and ceftazidime (5.9%), while resistance to levofloxacin experienced a decrease of 30.2%. The study showed the prevalence of various NFGNB as 5.10% in ICU settings, with Acinetobacter spp. (46.5%) being the most common isolated bacteria. Notably, 61.76% of the isolates were MDR. Antibiotic trend analysis over five years showed increasing resistance of Acinetobacter spp. to trimethoprim-sulfamethoxazole, minocycline, and ceftazidime, with improved susceptibility for carbapenems, ciprofloxacin, and cefepime. Pseudomonas spp. showed increased susceptibility to aztreonam and rising resistance for meropenem, piperacillin-tazobactam, ceftazidime, and amikacin. In Burkholderia spp., there was increased susceptibility to levofloxacin and rising resistance to meropenem and ceftazidime. These findings focus on the need for vigilant antibiotic stewardship, with the adoption of appropriate infection prevention and control practices to restrict the emergence and spread of MDR NFGNB infections in ICU settings of hospitals.

Comparison of Beta-Lactamase Profiles and Epidemiology of Multi-Drug Resistant Acinetobacter baumannii Isolates in Southwest Turkey: 2011 vs. 2019 Study

Background: The most significant problem encountered with hospital infections caused by multi-drug resistant Acinetobacter baumannii isolates is the difficulty in treatment. Defining resistance mechanisms is important for the development of treatment strategies. Objectives: The aim of this study was to investigate the beta-lactamase genes and clonal relationship in multi-drug resistant A. baumannii isolates in Mugla, Turkey, as no data are currently available for this province. Methods: Total 96 multi-drug resistant A. baumannii isolates obtained from hospitalized patients, between 2011 - 2012 period (n = 61) and in year 2019 (n = 35) were investigated and compared for antibiotic susceptibilities, beta-lactamase enzyme encoding genes by polymerase chain reaction (PCR) method. Repetitive extragenic palindromic (REP) PCR was made for dendrogram analysis to illustrate hierarchical relationship between isolates. Results: Overall, 74.0% of the isolates were obtained from patients in intensive care units. All multi-drug resistant isolates were found resistant to ciprofloxacin, piperacillin, piperacillin-tazobactam, meropenem, and imipenem by the disk diffusion method. The minimum inhibitory concentration values indicated that all isolates were resistant to imipenem, while colistin resistance was determined as 21.9%. The ISAba-I insertion element was present in all isolates. BlaOXA-23-like was present in 96.9%, and blaOXA-24-like was detected in three (3.1%) isolates. blaNDM positivity was shown in 5.2% of isolates. The indistinguishable or closely related isolates ratio was detected as 29.5% for the 2011 - 2012 period and 80% for 2019. Conclusions: Our findings showed that antibiotic resistance rates were high in A. baumannii, particularly isolated from intensive care unit patients in Mugla province. The prevalence of beta-lactamase and metallo-beta-lactamase genes has been increasing year by year, with the blaOXA-23-like gene region being the most prevalent. Additionally, the co-existence of these genes among strains is also on the rise. These findings from two different periods may provide useful reference data for future studies.

Intensifying inactivation strategies: Insights into the role of ultrasound on the inactivation of antibiotic resistant Acinetobacter baumannii via Photo-Fenton reaction

Improvisation of the contemporary water treatment technologies is critical not only to prevent water borne diseases but also to augment the available water sources. Here, a systematic study is effectuated to comprehend the upswing in the inactivation efficiency of Photo-Fenton (PF) chemistry induced by ultrasound (US) against antibiotic resistant (ABR) Acinetobacter baumannii (A. baumannii). Inactivation of A. baumannii (≈5×106 CFU/mL) was noticed within 75 and 105 min of US assisted PF (SPF) and PF processes respectively using 20 mg/L of H2O2 and 2 mg/L of Fe2+. It was interesting to notice that the PF reaction was effective under weak acidic condition (pH=3 and 5.5) whereas SPF process was realized over a wide pH range (3, 5.5, 7 and 9). No reactivation of the bacteria was found in both the processes till 96 h suggesting the impairment of not only the bacterial cell membrane but also the intracellular components. Experimental results although has suggested the generation of several reactive oxygen species (ROS), the inactivation mechanism was suggested to be dominated by the H2O2 and •OH. The damage caused to the bacterial cell membranes by the synergistic role of US and ROS was observed in the electron microscopy images. Comparative transcriptomic analysis has indicated the upregulation of genes regulating the LPS assembly proteins (Lpt A, B, C) and Pls B, Pgs A and Pal genes regulating the phospholipid synthesis which are known to regulate the stress induced response in bacteria. The SPF process was further validated with real water samples and the treated water was not found to have remarkable toxic effect on the in-vivo animal which endorse its candidature for future applications.

What is best choice for battle with multi drug resistant Acinetobacter? Newer antibiotics or prevention?

What is best choice for battle with multi drug resistant Acinetobacter? Newer antibiotics or prevention?

Exploring the Sequence analysis of the Two-Component System Response Regulator OmpR in Multi-Drug Resistant (MDR) Acinetobacter baumannii

Background: The study focuses on the clinical profiles, antibiotic susceptibility, and genetic characteristics of 25 A. baumannii isolates from patients with urinary tract infections (UTIs). Patient Cohort: Ages range from 18 to 70 years, with a male to female ratio of 1.375. Notable Finding: Some multidrug-resistant (MDR) isolates had commonalities with extensively drug-resistant (XDR) variations, showing the evolution of drug resistance.Methods: Antibiotic Efficacy Analysis: Evaluation of antibiotic efficacy when the variable moved from lower (Bin 1) to higher (Bin 2) levels. Correlation Matrix: An analysis of antibiotic correlations to better identify potential cross-resistance and shared characteristics. Genetic Diversity Analysis: An examination of variants in the OmpR gene, including mutations and polymorphisms. Sequence analysis is used to identify point mutations in OmpR, with an emphasis on transitions such as adenine (A) to guanine (G).Results: Significant improvement in antibiotic efficacy from Bin 1 to Bin 2. Correlation Findings: Antibiotics have complex interactions, which may indicate cross-resistance. Genetic diversity: Variations in the OmpR gene have implications for virulence and adaptability. Sequence Analysis: The majority of point mutations in OmpR were transitions, with A typically changing to G.Conclusion: In Iraq, researchers have discovered the first evidence that clinical resistance in A. baumannii may be caused by structural alterations in the OmpR gene. A. baumannii isolates' genetic diversity at certain locations suggests possible implications on virulence and adaptation.Keywords: Acinetobacter baumannii; OmpR; Polymorphism; MDR

Multidrug-resistant Acinetobacter baumannii: An underestimated pathogen in veterinary medicine in Italy

The increasing drug resistance of Acinetobacter (A.) baumannii is a growing concern globally. This bacterium, prevalent in hospitals, is responsible for multi-resistant infections and has been identified by the WHO as a priority pathogen for new antibiotic development. While there is extensive information on human isolates, data on animal isolates are scarce and fragmented based on limited clinical cases and genomic analyses. The impact of resistant strains on public and veterinary health is challenging to assess due to a lack of data. However, the potential impact on public health cannot be underestimated. Therefore, it is imperative to strengthen surveillance of A. baumannii in domestic animals, livestock, and wildlife. The growing presence of this pathogen in veterinary clinical samples is alarming, especially given the increasing interaction between animals and humans. Recognizing animals as potential reservoirs is crucial for understanding pathogen transmission dynamics, given their capacity for zoonotic transmission. With the rise in the number of animals testing positive for multi-resistant bacteria, monitoring A. baumannii in the animal population is vital to prevent the pathogen's spread and protect public health. A review of studies conducted in Italy on the topic underscores the role of pets, livestock, and foods of animal origin in the transmission of A. baumannii and Acinetobacter spp. Further animal research is urgently needed to gain a better understanding of the mechanisms of spread and resistance. This review underscores the need to explore this area, providing crucial insights for public health and infectious disease management within a One Health context.

Design of multi-epitope vaccine candidate based on OmpA, CarO and ZnuD proteins against multi-drug resistant Acinetobacter baumannii

Acinetobacter baumannii has been identified as a major cause of nosocomial infections. Acinetobacter infections are often difficult to treat with multidrug resistant phenotypes. One of the most effective ways to combat infectious diseases is through vaccination. In this study, an attempt was made to select the most protective and potent immunostimulatory epitopes based on the epitope-rich domains of the ZnuD, OmpA and CarO proteins of Acinetobacter baumannii to design a vaccine that can protect against this infection. After predicting the epitope of B- and T-cells, seven antigenic regions of three proteins CarO, ZnuD and OmpA, were selected. These regions were bound by a GGGS linker. The binding affinity and molecular interactions of the vaccine with the immune receptors TLR2 and TLR4 were studied using molecular docking analysis. This vaccine design was subjected to in silico immune simulations using C-ImmSim. The designed vaccine was highly antigenic, non-allergenic and stable. TLR2 and TLR4 were selected to analyze the ability of the modeled chimeric protein to interact with immune system receptors. The results showed strong interaction between the designed protein vaccine with TLR2 (−18.8 kcal mol-1) and TLR4 (−15.1 kcal mol-1). To verify the stability of the interactions and the structure of the designed protein, molecular dynamics (MD) simulations were performed for 200 ns. Various analyses using MD showed that the protein structure is stable alone and in interaction with TLR2 and TLR4. The ability of the vaccine candidate protein to stimulate the immune system to produce the necessary cytokines and antibodies against Acinetobacter baumannii was also demonstrated by the ability of the protein designed using the C-ImmSim web server to induce an immune response. Therefore, the designed protein vaccine may be a suitable candidate for in vivo as well as in vitro studies against Acinetobacter baumannii infections.

Multidrug resistant Acinetobacter species – Emergence of a potent pathogen from clinical isolates of tertiary care teaching centre of Central India

Multidrug resistant Acinetobacter species – Emergence of a potent pathogen from clinical isolates of tertiary care teaching centre of Central India

The Molecular Typing of Extensively Drug Resistant Acinetobacter baumannii Clinical Isolates Using Arbitrarily Primed PCR (AP-PCR)

The Molecular Typing of Extensively Drug Resistant Acinetobacter baumannii Clinical Isolates Using Arbitrarily Primed PCR (AP-PCR)

Prevalence and Antimicrobial Susceptibility Pattern of Acinetobacter baumannii Complex in Clinical Samples Among Patients at a Tertiary Care Hospital, Jaipur

Aims and objectives: Acinetobacter causes a wide spectrum of infections, including nosocomial pneumonia, secondary meningitis, surgical wound infections, skin and soft tissue infections, urinary tract infections, bacteraemia, and transmission via the hands of hospital personnel. The study aimed to determine the prevalence of Acinetobacter baumannii complex isolates and the antimicrobial susceptibility pattern of isolated A. baumannii complex. in clinical samples among patients at Mahatma Gandhi Medical College and Hospital. Introduction: In recent decades, Acinetobacter baumannii (A. baumannii) infections have also occurred outside the ICU or in trauma patients after natural disasters, and they have even affected patients after co-morbidities in the community. Materials and methods: All A. baumannii complex isolates (non-repetitive) from different clinical samples received in a clinical microbiology laboratory from inpatients and outpatients at Mahatma Gandhi Medical College and Hospital, Jaipur, Rajasthan, were included in the study. Routine microscopy of the samples was done. Gram‘s staining was done on all samples except urine. All clinical samples were inoculated on blood agar and MacConkey agar and incubated at 370 °C for 18–24 hours. Antimicrobial susceptibility testing of the isolated A. baumannii complex was done by the VITEK2-AST Compact system. Results: Among 6483 samples, 157 (2.42%) A. baumannii complex isolates were culture-positive, 68.37% were sterile, and 29.19% were other culture-positive. The maximum sensitivity of A. baumannii isolates was seen to be Tigecycline (70%), followed by Minocyclin (29.9%), while maximum resistance was observed for Piperacillin/Toazobactam (97%), followed by Imipenem, Meropenem (96.8%), Ceftazidime (96%), Cefepime (91.7%), Cipropfloxacin (88%), and Gentamycin (87%). Conclusion: Based on this study, it could be concluded that, as antibiotic resistance increases, hardships will be experienced in A. baumannii complex treatment unless the necessary precautions are taken and new antibiotics are discovered. In order to prevent the spreading of resistant Acinetobacter strains, infection control measures should be taken, clinicians and laboratory workers should cooperate during antibiotic use, and hospital hygienic rules should be observed.

An interstrand DNA crosslink glycosylase aids Acinetobacter baumannii pathogenesis

Maintenance of DNA integrity is essential to all forms of life. DNA damage generated by reaction with genotoxic chemicals results in deleterious mutations, genome instability, and cell death. Pathogenic bacteria encounter several genotoxic agents during infection. In keeping with this, the loss of DNA repair networks results in virulence attenuation in several bacterial species. Interstrand DNA crosslinks (ICLs) are a type of DNA lesion formed by covalent linkage of opposing DNA strands and are particularly toxic as they interfere with replication and transcription. Bacteria have evolved specialized DNA glycosylases that unhook ICLs, thereby initiating their repair. In this study, we describe AlkX, a DNA glycosylase encoded by the multidrug resistant pathogen Acinetobacter baumannii. AlkX exhibits ICL unhooking activity similar to that of its Escherichia coli homolog YcaQ. Interrogation of the in vivo role of AlkX revealed that its loss sensitizes cells to DNA crosslinking and impairs A. baumannii colonization of the lungs and dissemination to distal tissues during pneumonia. These results suggest that AlkX participates in A. baumannii pathogenesis and protects the bacterium from stress conditions encountered in vivo. Consistent with this, we found that acidic pH, an environment encountered during host colonization, results in A. baumannii DNA damage and that alkX is induced by, and contributes to, defense against acidic conditions. Collectively, these studies reveal functions for a recently described class of proteins encoded in a broad range of pathogenic bacterial species.

Four novel Acinetobacter lwoffii strains isolated from the milk of cows in China with subclinical mastitis

BackgroundAcinetobacter lwoffii (A. lwoffii) is a Gram-negative bacteria common in the environment, and it is the normal flora in human respiratory and digestive tracts. The bacteria is a zoonotic and opportunistic pathogen that causes various infections, including nosocomial infections. The aim of this study was to identify A. lwoffii strains isolated from bovine milk with subclinical mastitis in China and get a better understanding of its antimicrobial susceptibility and resistance profile. This is the first study to analyze the drug resistance spectrum and corresponding mechanisms of A. lwoffii isolated in raw milk.ResultsFour A. lwoffii strains were isolated by PCR method. Genetic evolution analysis using the neighbor-joining method showed that the four strains had a high homology with Acinetobacter lwoffii. The strains were resistant to several antibiotics and carried 17 drug-resistance genes across them. Specifically, among 23 antibiotics, the strains were completely susceptible to 6 antibiotics, including doxycycline, erythromycin, polymyxin, clindamycin, imipenem, and meropenem. In addition, the strains showed variable resistance patterns. A total of 17 resistance genes, including plasmid-mediated resistance genes, were detected across the four strains. These genes mediated resistance to 5 classes of antimicrobials, including beta-lactam, aminoglycosides, fluoroquinolones, tetracycline, sulfonamides, and chloramphenicol.ConclusionThese findings indicated that multi-drug resistant Acinetobacter lwoffii strains exist in raw milk of bovine with subclinical mastitis. Acinetobacter lwoffii are widespread in natural environmental samples, including water, soil, bathtub, soap box, skin, pharynx, conjunctiva, saliva, gastrointestinal tract, and vaginal secretions. The strains carry resistance genes in mobile genetic elements to enhance the spread of these genes. Therefore, more attention should be paid to epidemiological surveillance and drug resistant A. lwoffii.

In vivo efficacy of phage cocktails against carbapenem resistance Acinetobacter baumannii in the rat pneumonia model.

Acinetobacter baumannii, an opportunistic pathogen, poses a significant threat in intensive care units, leading to severe nosocomial infections. The rise of multi-drug-resistant strains, particularly carbapenem-resistant A. baumannii, has created formidable challenges for effective treatment. Given the prolonged development cycle and high costs associated with antibiotics, phages have garnered clinical attention as an alternative for combating infections caused by drug-resistant bacteria. However, the utilization of phage therapy encounters notable challenges, including the narrow host spectrum, where each phage targets a limited subset of bacteria, increasing the risk of phage resistance development. Additionally, uncertainties in immune system dynamics during treatment hinder tailoring symptomatic interventions based on patient-specific states. In this study, we isolated two A. baumannii phages from wastewater and conducted a comprehensive assessment of their potential applications. This evaluation included sequencing analysis, genome classification, pH and temperature stability assessments, and in vitro bacterial inhibition assays. Further investigations involved analyzing histological and cytokine alterations in rats undergoing phage cocktail treatment for pneumonia. The therapeutic efficacy of the phages was validated, and transcriptomic studies of rat lung tissue during phage treatment revealed crucial changes in the immune system. The findings from our study underscore the potential of phages for future development as a treatment strategy and offer compelling evidence regarding immune system dynamics throughout the treatment process.IMPORTANCEDue to the growing problem of multi-drug-resistant bacteria, the use of phages is being considered as an alternative to antibiotics, and the genetic safety and application stability of phages determine the potential of phage application. The absence of drug resistance genes and virulence genes in the phage genome can ensure the safety of phage application, and the fact that phage can remain active in a wide range of temperatures and pH is also necessary for application. In addition, the effect evaluation of preclinical studies is especially important for clinical application. By simulating the immune response situation during the treatment process through mammalian models, the changes in animal immunity can be observed, and the effect of phage therapy can be further evaluated. Our study provides compelling evidence that phages hold promise for further development as therapeutic agents for Acinetobacter baumannii infections.

Efficacy of Cefiderocol, a Novel Siderophore Cephalosporin, against Multidrug Resistant Acinetobacter baumannii Clinical Isolates in Japan.

Multidrug-resistant Acinetobacter baumannii (MDRAB) is an important pathogen that causes nosocomial infections and is resistant to almost all antibiotics, including carbapenems. Cefiderocol is a novel siderophore cephalosporin active against a broad spectrum of gram-negative bacteria. However, the susceptibility of MDRAB to cefiderocol has not yet been reported in Japan. In this study, we measured the minimum inhibitory concentrations (MICs) of antibiotics including cefiderocol against MDRAB clinical isolates collected during a nosocomial outbreak between 2009 and 2010 at the Teikyo University Hospital in Japan. We found that all 10 MDRAB clinical isolates tested were susceptible to cefiderocol, with an MIC range of 0.12 to 1 μg/mL. All the isolates also exhibited resistance to ampicillin-sulbactam and an intermediate resistance to colistin, whereas nine of them were susceptible to tigecycline. DNA sequencing revealed that all strains harbored an OXA-51-like carbapenemase, a major cause of carbapenem resistance in A. baumannii in Japan. In conclusion, this study showed that the cefiderocol susceptibility of MDRAB clinical isolates in Japan was equivalent to that to colistin or tigecycline, and thus cefiderocol is a potential treatment option for MDRAB infections.