Baumannii Complex Research Articles

Laboratory detection of carbapenemases among Gram-negative organisms.

SUMMARYThe carbapenems remain some of the most effective options available for treating patients with serious infections due to Gram-negative bacteria. Carbapenemases are enzymes that hydrolyze carbapenems and are the primary method driving carbapenem resistance globally. Detection of carbapenemases is required for patient management, the rapid implementation of infection prevention and control (IP&C) protocols, and for epidemiologic purposes. Therefore, clinical and public health microbiology laboratories must be able to detect and report carbapenemases among predominant Gram-negative organisms from both cultured isolates and direct from clinical specimens for treatment and surveillance purposes. There is not a "one size fits all" laboratory approach for the detection of bacteria with carbapenemases, and institutions need to determine what fits best with the goals of their antimicrobial stewardship and IP&C programs. Luckily, there are several options and approaches available for clinical laboratories to choose methods that best suits their individual needs. A laboratory approach to detect carbapenemases among bacterial isolates consists of two steps, namely a screening process (e.g., not susceptible to ertapenem, meropenem, and/or imipenem), followed by a confirmation test (i.e., phenotypic, genotypic or proteomic methods) for the presence of a carbapenemase. Direct from specimen testing for the most common carbapenemases generally involves detection via rapid, molecular approaches. The aim of this article is to provide brief overviews on Gram-negative bacteria carbapenem-resistant definitions, types of carbapenemases, global epidemiology, and then describe in detail the laboratory methods for the detection of carbapenemases among Gram-negative bacteria. We will specifically focus on the Enterobacterales, Pseudomonas aeruginosa, and Acinetobacter baumannii complex.

Multitarget Phytocomplex: Focus on Antibacterial Profiles of Grape Pomace and Sambucus ebulus L. Lyophilisates Against Extensively Drug-Resistant (XDR) Bacteria and In Vitro Antioxidative Power.

Objectives: This study was conceived with the aim of translating the experience and knowledge of the research group into the design and creation of multi-active phytocomplex cocktails from lyophilised winery by-products (Grape Pomace-GP) and weeds (Sambucus ebulus L., Dwarf Elder-DE). Methods: Quantification of bioactive molecules was performed by high-performance liquid chromatography (HPLC) method. Results: In the extract obtained from lyophilised GP, the most dominant component that was quantified was petunidin-3-glucoside. Prominent compounds that were quantified in DE extract were cyanidin derivatives. The total number of microorganisms in lyophilisates is low, but some of them still survive lyophilisation. Antibacterial activity was determined by microdilution, the minimum inhibitory concentration (MIC) of the tested bacteria ranged from 0.78 mg/mL to 25.00 mg/mL. Antibacterial susceptibility testing (AST) revealed that Klebsiella spp. and Acinetobacter baumannii complex are extensively drug-resistant (XDR). Conclusions: The GP + DE cocktail showed very strong AB power against both tested XDR bacteria. The total phenolic content and antioxidative effect (determined spectrophotometrically) indicate their linear correlation.

Distribution of the Pathogens Isolated from 6428 Tumor Patients in 2019-2023 and the Relevant Drug Resistance Surveillance Report

To investigate the characteristics of the pathogens isolated from the specimens of tumor patients and detection rates of multidrug-resistant bacteria in a hospital in the past five years, so as to provide references for infection prevention and control. The results of pathogenic culture and in vitro susceptibility of the strains isolated from the specimens collected between January 2019 and December 2023 from tumor patients were retrospectively collected, and the trends of the data were analyzed and summarized. A total of 16393 strains were isolated from 80386 specimens, producing a detection rate of 20.4%. After excluding the duplicate strains isolated from the same patients, Escherichia coli (14.5%), Klebsiella pneumoniae (13.2%), Staphylococcus aureus (9.4%), Acinetobacter baumannii complex (9.3%), and Pseudomonas aeruginosa (7.7%) predominated the 7951 (81.1%) bacterial strains. Among the 1857 (18.9%) fungal strains, Candida albicans (56.5%), Candida tropicalis (9.0%), and Candida parapsilosis (8.0%) were the most common ones. The specimen sources differed among the prevalent species, and the species distribution varied among specimens from different types of tumors (P<0.05). The detection rates of carbapenem-resistant Escherichia coli and Klebsiella pneumoniae were 2.5% (29/1152) and 12.3% (129/1050), respectively. The detection rate of methicillin-resistant Staphylococcus aureus was 22.0% (165/749), maintaining an upward trend in the last four years (P<0.01). The detection rates of carbapenem-resistant Acinetobacter baumannii and Pseudomonas aeruginosa were 40.3% (298/739) and 8.8% (54/612), respectively. Gram-negative bacteria were the prevalent pathogens of tumor patients. The detection rate of multidrug-resistant bacteria was relatively high, and the detection rate of methicillin-resistant Staphylococcus aureus showed an upward trend.

Pharmacokinetics and pharmacodynamics of bacteriophage therapy: a review with a focus on multidrug-resistant Gram-negative bacterial infections.

SUMMARYDespite the early recognition of their therapeutic potential and the current escalation of multidrug-resistant (MDR) pathogens, the adoption of bacteriophages into mainstream clinical practice is hindered by unfamiliarity with their basic pharmacokinetic (PK) and pharmacodynamic (PD) properties, among others. Given the self-replicative nature of bacteriophages in the presence of host bacteria, the adsorption rate, and the clearance by the host's immunity, their PK/PD characteristics cannot be estimated by conventional approaches, and thus, the introduction of new considerations is required. Furthermore, the multitude of different bacteriophage types, preparations, and treatment schedules impedes drawing general conclusions on their in vivo PK/PD features. Additionally, the drawback of acquired bacteriophage resistance of MDR pathogens with clinical and environmental implications should be taken into consideration. Here, we provide an overview of the current state of the field of PK and PD of bacteriophage therapy with a focus on its application against MDR Gram-negative infections, highlighting the potential knowledge gaps and the challenges in translation from the bench to the bedside. After reviewing the in vitro PKs and PDs of bacteriophages against the four major MDR Gram-negative pathogens, Klebsiella pneumoniae, Acinetobacter baumannii complex, Pseudomonas aeruginosa, and Escherichia coli, specific data on in vivo PKs (tissue distribution, route of administration, and basic PK parameters in animals and humans) and PDs (survival and reduction of bacterial burden in relation to the route of administration, timing of therapy, dosing regimens, and resistance) are summarized. Currently available data merit close scrutiny, and optimization of bacteriophage therapy in the context of a better understanding of the underlying PK/PD principles is urgent to improve its therapeutic effect and to minimize the occurrence of bacteriophage resistance.

In vitro resistance development gives insights into molecular resistance mechanisms against cefiderocol

Cefiderocol, a novel siderophore cephalosporin, demonstrates promising in vitro activity against multidrug-resistant Gram-negative bacteria, including carbapenemase-producing strains. Nonetheless, only a few reports are available regarding the acquisition of resistance in clinical settings, primarily due to its recent usage. This study aimed to investigate cefiderocol resistance using an in vitro resistance development model to gain insights into the underlying molecular resistance mechanisms. Cefiderocol susceptible reference strains (Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa) and a clinical Acinetobacter baumannii complex isolate were exposed to increasing cefiderocol concentrations using a high-throughput resistance development model. Cefiderocol susceptibility testing was performed using broth microdilution. Whole-genome sequencing was employed to identify newly acquired resistance mutations. Our in vitro resistance development model led to several clones of strains exhibiting cefiderocol resistance, with MIC values 8-fold to 512-fold higher than initial levels. In total, we found 42 different mutations in 26 genes, of which 35 could be described for the first time. Putative loss-of-function mutations were detected in the envZ, tonB, and cirA genes in 13 out of 17 isolates, leading to a decrease in cefiderocol influx. Other potential resistance mechanisms included multidrug efflux pumps (baeS, czcS, nalC), antibiotic-inactivating enzymes (ampR, dacB), and target mutations in penicillin-binding-protein genes (mrcB). This study reveals new insights into underlying molecular resistance mechanisms against cefiderocol. While mutations leading to reduced influx via iron transporters was the most frequent resistance mechanism, we also detected several other novel resistance mutations causing cefiderocol resistance.

Clinical and microbiological features of positive blood culture episodes caused by non-fermenting gram-negative bacilli other than Pseudomonas and Acinetobacter species (2020-2023).

Non-fermenting Gram-negative bacilli (NFGNB) other than Pseudomonas aeruginosa and Acinetobacter baumannii complex are pathogens of interest due to their ability to cause health-care associated infections and display complex drug resistance phenotypes. However, their clinical and microbiological landscape is still poorly characterized. Observational retrospective study including all hospitalized patients presenting with a positive positive blood culture (BC) episode caused by less common NFGNB over a four-year period (January 2020-December 2023). Clinical-microbiological features and factors associated with mortality were investigated. Sixty-six less common NFGNB isolates other than Pseudomonas and Acinetobacter species causing 63 positive BC episodes were recovered from 60 patients. Positive BC episodes were predominantly sustained by Stenotrophomonas maltophilia (49.2%) followed by Achromobacter species (15.9%) that exhibited the most complex resistance phenotype. Positive BC episodes had bloodstream infection criteria in 95.2% of cases (60 out 63), being intravascular device (30.2%) and respiratory tract (19.1%) the main sources of infection. Fourteen-day, 30-day, and in-hospital mortality rates were 6.4%, 9.5%, and 15.9%, respectively. The longer time from admission to the positive BC episode, older age, diabetes, admission due to sepsis, and higher Charlson Comorbidity Index were identified as the main predictors of in-hospital mortality. Positive BC episodes sustained by NFGNB other than Pseudomonas and Acinetobacter species were predominantly sustained by Stenotrophomonas maltophilia and Achromobacter species, having bloodstream infection criteria in the vast majority of cases. Factors that have emerged to be associated with mortality highlighted how these species may have more room in prolonged hospitalisation and at the end of life for patients with chronic organ diseases.

Detection of volatile organic compounds as new paradigm to accelerate antimicrobial susceptibility testing: performance evaluation of VITEK® REVEAL™.

The measurement of VOCs release in the headspace of a bacterial culture represents a new approach to rapidly assess antimicrobial susceptibility. Herein, we evaluated the diagnostic performance of the VITEK® REVEAL™ system directly from a collection of Gram-negative positive blood cultures. One hundred and twenty-eight positive blood cultures were included in the analysis (Enterobacterales, n = 95; Pseudomonas aeruginosa, n = 21; Acinetobacter baumannii complex, n = 12). Samples were processed using VITEK® REVEAL™ according to the manufacturer's recommendations, and MICs of 22 antimicrobials were compared with those obtained using reference methods. Categorical agreement (CA), essential agreement (EA) and categorical errors were calculated. Overall, 2220 strain/antibiotic pair combinations were analysed. Of these, most were classified as resistant by reference antimicrobial susceptibility testing (1091/2220; 48.7%). The overall CA and EA were 97.6% and 97.7%, respectively. CA ranged from 97.5% in Enterobacterales to 97.9% in both P. aeruginosa and A. baumannii complex. The overall number of categorical discrepancies were: 18 very major errors (1.6%), 13 major errors (1.2%) and 22 minor errors (2.4%). EA ranged from 95.2% in P. aeruginosa to 98.1% in Enterobacterales. Screening test for ESBL phenotype was positive, indeterminate and negative in 13.7%, 32.6% and 27.4% of Enterobacterales isolates tested by both VITEK® REVEAL™ and the reference method, showing 100% CA. VITEK® REVEAL™ represents a reliable tool to obtain antimicrobial susceptibility results of the main Gram-negative species directly from positive blood cultures with time to results of less than 8 h.

Carbapenem-resistant Acinetobacter baumannii and Carbapenem-resistant Enterobacterales in US Dialysis Populations, 2016-2021

Background: Infections lead to high mortality among patients on chronic dialysis; knowledge of multi-drug resistant infections is limited. The Centers for Disease Control and Prevention’s Emerging Infections Program (EIP) conducts laboratory- and population-based surveillance for carbapenem-resistant Enterobacterales (CRE) in 10 U.S. sites and carbapenem-resistant Acinetobacter baumannii (CRAB) in 9 U.S. sites. We investigated clinical characteristics, healthcare exposures, and outcomes of CRE and CRAB cases in persons on chronic dialysis from 2016-2021. Methods: Among EIP catchment-area residents on chronic dialysis, we defined a CRE case as the first isolation of Escherichia coli, Enterobacter cloacae complex, Klebsiella aerogenes (formerly Enterobacter aerogenes), Klebsiella oxytoca, Klebsiella pneumoniae, or Klebsiella variicola resistant to any carbapenem, from a normally sterile site or urine in a 30-day period. A CRAB case was defined as the first isolation of Acinetobacter baumannii complex resistant to any carbapenem (excluding ertapenem), from a normally sterile site or urine (or lower respiratory tract or wound since 2021) in a 30-day period. Medical records were reviewed. A case was considered colonized if the case culture had no associated infection type or colonization was documented in the medical record. Descriptive analyses, including analyses stratified by pathogen, were conducted. Results: Among 426 cases, 314 were CRE, and 112 were CRAB; most cases were male (235, 55.2%), Black (229, 53.8%), and 51-80 years old (320, 75.1%) (Table). An infection was associated with 363 (85.2%) case cultures; bloodstream infections (148; 40.8%), urinary tract infections (134; 36.9%), and pneumonia (17; 4.7%) were the most frequent. Overall, most cases had documented healthcare exposures (excluding outpatient dialysis) in the year before incident specimen collection, including: 366 (85.9%) hospitalizations, 235 (55.2%) surgeries, 209 (49.1%) long-term care facility stays, 54 (12.7%) long-term acute care facility stays. Additionally, 125 (29.3%) had an intensive care unit admission within the 7 days before incident specimen collection. Compared to CRE cases, a higher proportion of CRAB cases (a) had a long-term care facility stay (82/112 [73.2%] versus 127/314 [40.5%], P&lt;.0001) or hospitalization (103/112 [92%] versus 263/314 [83.8%], P = .03) within the preceding year and (b) died within 30 days of incident specimen collection (40/112 [35.7%] versus 64/314 [20.4%], P = .001). Discussion: Among CRE and CRAB cases in persons on chronic dialysis, healthcare exposures were common, and mortality was high. Additional efforts to better describe the burden of these organisms and associated risk factors in the dialysis population are needed for tailoring infection prevention strategies to this vulnerable.

An analysis of HRCT imaging characteristics and sputum culture results in hospitalized patients with community-acquired pneumonia - an institutional observational study

Background and Objectives. Community-acquired pneumonia (CAP) is a significant cause of morbidity and mortality worldwide. High-resolution computed tomography (HRCT) and sputum cultures are critical in diagnosing and managing CAP. This study aims to analyze HRCT imaging characteristics and sputum culture results in hospitalized patients with CAP, correlating imaging findings with specific pathogens to enhance diagnostic accuracy and treatment strategies. Materials and Methods. A retrospective analysis was conducted on 133 patients admitted with CAP at a tertiary care center in Chennai in last 12 months. HRCT scans were reviewed for specific imaging patterns, including ground-glass opacities, consolidation, interstitial patterns, and pleural effusion. Sputum samples were collected and cultured for bacterial pathogens. Data on patient demographics, HRCT findings, and sputum culture results were analyzed to identify correlations between imaging patterns and pathogens. Results. The study included 133 patients, with a mean age of 58 years, comprising 78 males (59%) and 55 females (41%). HRCT findings revealed ground-glass opacities in 68% of patients, consolidation in 54%, interstitial patterns in 32%, and pleural effusion in 21%. The most common organisms identified in sputum cultures were Klebsiella pneumoniae (20%), Pseudomonas aeruginosa (22%), Acinetobacter baumannii complex (9%), and E. coli (8%), with 25% of cultures yielding no growth. Ground-glass opacities were predominantly observed in cases with no bacterial growth, suggesting a viral etiology. Consolidation was the most common pattern associated with bacterial infections, particularly Klebsiella pneumoniae and Pseudomonas aeruginosa. Conclusions. This study highlights the importance of HRCT in diagnosing CAP and distinguishing between bacterial and viral infections. The correlation between specific HRCT patterns and pathogens can enhance diagnostic accuracy and guide treatment strategies. Future research should focus on integrating advanced diagnostic modalities and understanding the evolving patterns of CAP etiology to improve patient outcomes.

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.

The Effects of Changing Needles on Reducing Contamination of Postmortem Hemocultures

Background: Sepsis is a common cause of death and can be diagnosed through postmortem hemoculture. However, this method carries the risk of contamination. Some experts have argued that using a new needle before inoculation can help reduce the contamination rates. Objective: To evaluate the contamination rate from postmortem hemoculture in needle-changing and no-needle-changing groups. Methods: The present study analyzed postmortem hemoculture results from autopsy cases at Ramathibodi Hospital. Forty deceased individuals who had died within 24 hours and were not suspected of having an infection were included in the study. The blood samples were divided into 2 groups: one in which the needle was changed before inoculation and the other in which it was not. Differences in hemoculture results between the 2 methods were examined. Results: No statistically significant difference was detected in the positive culture rate between the needle-changing (57.5%) and non-needle-changing groups (57.5%) (P = 1.00). The Kappa coefficient was 0.795. Viridans group streptococci, Escherichia coli, Klebsiella pneumoniae complex, Enterobacter cloacae complex, and Acinetobacter baumannii complex were the most commonly cultured bacteria. Conclusions: Changing the needles did not reduce the contamination rate from postmortem hemocultures. Microorganisms commonly found in postmortem hemocultures are oral, gastrointestinal, and hospital-associated microorganisms.

Application of LAMP assay for detection of carbapenem-resistant Acinetobacter calcoaceticus-Acinetobacter baumannii complex in ICU admitted sepsis patients: A rapid and cost-effective diagnostic tool

Carbapenem-resistant significant members of Acinetobacter calcoaceticus–Acinetobacter baumannii (CR-SM-ACB) complex have emerged as an important cause of sepsis, especially in ICUs. This study demonstrates the application of loop-mediated-isothermal-amplification (LAMP) assay for detection of CR-SM-ACB-complex from patients with sepsis.Whole-blood and culture-broths(CB) collected from patients with culture-positive sepsis were subjected to LAMP and compared with PCR, and RealAmp. Vitek-2 system and conventional PCR results were used as confirmatory references.The sensitivity and specificity of LAMP(97 % & 100 %) and RealAmp(100 % & 100 %) for detection of CR-SM-ACB-complex from CB were better than PCR(87 % & 100 %). Diagnostic accuracy of LAMP, RealAmp, and PCR for detection of SM-ACB-complex from CB was 98.5 %, 100 %, and 88.5 % respectively. Turnaround time of Culture, LAMP, PCR, and RealAmp was 28-53, 6-20, 9-23, and 6-20hours, respectively.LAMP is a simple, inexpensive tool that can be applied directly to positive CB and may be customized to detect emerging pathogens and locally-prevalent resistance genes and to optimize antimicrobial use.

Optimizing Treatment for Carbapenem-Resistant Acinetobacter baumannii Complex Infections: A Review of Current Evidence.

Carbapenem-resistant Acinetobacter baumannii complex (CRAB) poses a significant global health challenge owing to its resistance to multiple antibiotics and limited treatment options. Polymyxin-based therapies have been widely used to treat CRAB infections; however, they are associated with high mortality rates and common adverse events such as nephrotoxicity. Recent developments include numerous observational studies and randomized clinical trials investigating antibiotic combinations, repurposing existing antibiotics, and the development of novel agents. Consequently, recommendations for treating CRAB are undergoing significant changes. The importance of colistin is decreasing, and the role of sulbactam, which exhibits direct antibacterial activity against A. baumannii complex, is being reassessed. High-dose ampicillin-sulbactam-based combination therapies, as well as combinations of sulbactam and durlobactam, which prevent the hydrolysis of sulbactam and binds to penicillin-binding protein 2, have shown promising results. This review introduces recent advancements in CRAB infection treatment based on clinical trial data, highlighting the need for optimized treatment protocols and comprehensive clinical trials to combat the evolving threat of CRAB effectively.

Assessing Clinician Utilization of Next-Generation Antibiotics Against Resistant Gram-Negative Infections in U.S. Hospitals : A Retrospective Cohort Study.

The U.S. antibiotic market failure has threatened future innovation and supply. Understanding when and why clinicians underutilize recently approved gram-negative antibiotics might help prioritize the patient in future antibiotic development and potential market entry rewards. To determine use patterns of recently U.S. Food and Drug Administration (FDA)-approved gram-negative antibiotics (ceftazidime-avibactam, ceftolozane-tazobactam, meropenem-vaborbactam, plazomicin, eravacycline, imipenem-relebactam-cilastatin, and cefiderocol) and identify factors associated with their preferential use (over traditional generic agents) in patients with gram-negative infections due to pathogens displaying difficult-to-treat resistance (DTR; that is, resistance to all first-line antibiotics). Retrospective cohort. 619 U.S. hospitals. Adult inpatients. Quarterly percentage change in antibiotic use was calculated using weighted linear regression. Machine learning selected candidate variables, and mixed models identified factors associated with new (vs. traditional) antibiotic use in DTR infections. Between quarter 1 of 2016 and quarter 2 of 2021, ceftolozane-tazobactam (approved 2014) and ceftazidime-avibactam (2015) predominated new antibiotic usage whereas subsequently approved gram-negative antibiotics saw relatively sluggish uptake. Among gram-negative infection hospitalizations, 0.7% (2551 [2631 episodes] of 362 142) displayed DTR pathogens. Patients were treated exclusively using traditional agents in 1091 of 2631 DTR episodes (41.5%), including "reserve" antibiotics such as polymyxins, aminoglycosides, and tigecycline in 865 of 1091 episodes (79.3%). Patients with bacteremia and chronic diseases had greater adjusted probabilities and those with do-not-resuscitate status, acute liver failure, and Acinetobacter baumannii complex and other nonpseudomonal nonfermenter pathogens had lower adjusted probabilities of receiving newer (vs. traditional) antibiotics for DTR infections, respectively. Availability of susceptibility testing for new antibiotics increased probability of usage. Residual confounding. Despite FDA approval of 7 next-generation gram-negative antibiotics between 2014 and 2019, clinicians still frequently treat resistant gram-negative infections with older, generic antibiotics with suboptimal safety-efficacy profiles. Future antibiotics with innovative mechanisms targeting untapped pathogen niches, widely available susceptibility testing, and evidence demonstrating improved outcomes in resistant infections might enhance utilization. U.S. Food and Drug Administration; NIH Intramural Research Program.

Evidence and antibiotic resistance profiles of clinical Acinetobacter calcoaceticus-Acinetobacter baumannii (ACB) and non-ACB complex members in companion animals: A 2020–2022 retrospective study

To evaluate the frequency of Acinetobacter spp., belonging to both Acinetobacter calcoaceticus-baumannii (ACB) and non-ACB complex, and their antibiotic resistance profiles in veterinary medicine, a three-year (2020–2022) retrospective study was carried out on sick companion animals. Epidemiological data from different clinical canine, feline, and equine samples, were acquired. For each strain, MALDI-TOF MS identification and susceptibility to a panel of 11 antibiotics, by Kirby-Bauer and E-test methods, were performed. Out of 628 bacteriological examinations, 2.5% resulted positive for strains belonging to Acinetobacter genus. Frequencies of 2.3%, 1.9%, and 3% were obtained from both in-visiting and hospitalized dogs, cats, and horses, respectively. Members of ACB-complex accounted for 50% of isolates. Since all strains resulted susceptible to aminoglycosides and polymyxins, no pandrug-resistant (PDR) species were recorded. While 12.5% A. baumannii resulted extensively-drug resistant (XDR), a higher percentage of multidrug-resistant strains was recorded among non-ACB strains (35.5%) than ACB strains (25%). Susceptibility was observed in the same percentage in both groups (62.5%). All ACB strains confirmed their intrinsic resistances. Non-ACB species showed lower resistances against antipseudomonal penicillins plus beta-lactamase inhibitors (P=0.1306), III generation cephalosporins (P=0.0547), and tetracyclines (P=0.0209) than ACB species. Carbapenem-resistance was observed for XDR A. baumannii (12.5%) and, in particular for MDR non-ACB complex members (25%). To our knowledge, A. lactucae represents the first description in two sick dogs in Italy. Furthermore, our results emphasize the role of non-ACB-complex species as important zoonotic pathogens, which could be reservoirs of clinically relevant resistance profiles.

Antibacterial activity of deer musk and Ziziphus spina-christi against carbapebem resis-tant gram negative bacteria isolated from patients with burns and wounds

Bacteria were isolated from 250 specimens obtained from patients attending the Plastic Reconstructive and Burn Surgery Hospital in the Sulaymaniyah (Kurdistan region) and the burn and wound care units of the Azadi Teaching Hospital (Kirkuk), Iraq. Gram-negative bacteria were isolated from 100 (40%) of the samples which identified by BD phoenix, 66 isolates (66%) were carbapenem-resistant species, Rapidec® Carba NP test and sensitivity tests revealed 17 different genera and species of carbapenem-resistant bacteria. The BD Phoenix system was used to evaluate the susceptibility test of the isolates to 18 different antibiotics. The number of isolates that exhibited resistance to the carbapenem antibiotics, ertapenem, imipenem and meropenem, was 40 (61%), 35 (54%) and 28 (42%) respectively. Meanwhile, the number of isolates resistant to the penicillin antibiotics, ampicillin, amoxicillin-clavulanic acid and piperacillin-tazobactam, was 61 (92%), 54 (82%) and 24 (36%) respectively. The isolates were also evaluated for their resistance to the cephalosporins, cefazolin, cefuroxime, ceftazidime, ceftriaxone, cefepime, and ceftolozane-tazobactam; the respective number of resistant isolates were 60 (91%), 60 (91%), 39 (59%), 48 (73%), 42 (64%) and 27(41%). In contrast, a fraction of Ziziphus spina-christi leaves that was extracted using ethyl acetate inhibited all of the carbapenem-resistant isolates studied. The zone of inhibition (ZoI) Ø was between 19 and 24 mm. The ZoI Ø of black deer musk was 11–19 mm. The minimum inhibitory concentration (MICs) of ethyl acetate extract of Ziziphus spina-christi leaves for Acinetobacter baumannii (PDR), CR-Citrobacter farmeri, CR-Escherichia coli, CR-Proteus mirabilis, CR-Pseudomonas fluorescens, CR-Escherichia vulneris, CR-Kluyvera ascorbata, CR-Pantoea agglomerans, CR-Pseudomonas putida and CR-Serratia marcescens, was 6.25 mg/mL. Meanwhile, the MIC for Acinetobacter calcoaceticus–baumannii complex, Citrobacter freundii, Enterobacter cloacae, Klebsiella pneumoniae, Morganella morganii, Pseudomonas aeruginosa and Stenotrophomonas maltophilia was 12.5 mg/mL. High-performance liquid chromatography (HPLC) was used to analyse the components of the ethyl acetate-extract of Ziziphus spina-christi leaves. The analysis found gallic acid (760.3 ppm/mL), caffeine (84.0 ppm/mL) and quercetin (2.2 ppm/mL); the total phenolic content was 846.5 ppm/mL. The evidence obtained from this study indicates that leaves of this plant (named sidr in the Middle East) have the potential to be used as a natural antibiotic against carbapenem-resistant Gram-negative bacteria. Thus, the leaves of this tree present an important opportunity in the development of novel therapeutic agents. The study found the MIC of deer musk for CR-Citrobacter farmeri, CR-Citrobacter freundii, CR-Enterobacter cloacae, CR-Escherichia vulneris, CR-Klebsiella pneumoniae, CR-Kluyvera ascorbata, CR-Morganella morganii, CR-Pantoea agglomerans, CR-Proteus mirabilis, CR-Pseudomonas fluorescens, CR-Pseudomonas putida and CR-Serratia marcescens to be 50 mg/mL. In contrast, the MIC of deer musk was 100 mg/mL for Acinetobacter baumannii (PDR), CR-Acinetobacter calcoaceticus–baumannii complex, CR-Escherichia coli, CR-Pseudomonas aeruginosa and CR-Stenotrophomonas maltophilia. The results of the gas chromatography–mass spectrometry (GC–MS) indicate that the primary constituents of musk were1,4,4-tetramethyltetralin, 7-acetyl-6-ethyl-1, diethyl phthalate and tonalid; their contribution to the whole ranged from 12.2% to 19.6%. Black musk exhibits considerable antibacterial activity, able to inhibit seventeen different species of carbapenem-resistant Gram-negative bacteria. The non-natural form of black musk can be used to scent detergent.

A bioinformatic approach to identify confirmed and probable CRISPR-Cas systems in the Acinetobacter calcoaceticus-Acinetobacter baumannii complex genomes.

The Acinetobacter calcoaceticus-Acinetobacter baumannii complex, or Acb complex, consists of six species: Acinetobacter baumannii, Acinetobacter calcoaceticus, Acinetobacter nosocomialis, Acinetobacter pittii, Acinetobacter seifertii, and Acinetobacter lactucae. A. baumannii is the most clinically significant of these species and is frequently related to healthcare-associated infections (HCAIs). Clustered regularly interspaced short palindromic repeat (CRISPR) arrays and associated genes (cas) constitute bacterial adaptive immune systems and function as variable genetic elements. This study aimed to conduct a genomic analysis of Acb complex genomes available in databases to describe and characterize CRISPR systems and cas genes. Acb complex genomes available in the NCBI and BV-BRC databases, the identification and characterization of CRISPR-Cas systems were performed using CRISPRCasFinder, CRISPRminer, and CRISPRDetect. Sequence types (STs) were determined using the Oxford scheme and ribosomal multilocus sequence typing (rMLST). Prophages were identified using PHASTER and Prophage Hunter. A total of 293 genomes representing six Acb species exhibited CRISPR-related sequences. These genomes originate from various sources, including clinical specimens, animals, medical devices, and environmental samples. Sequence typing identified 145 ribosomal multilocus sequence types (rSTs). CRISPR-Cas systems were confirmed in 26.3% of the genomes, classified as subtypes I-Fa, I-Fb and I-Fv. Probable CRISPR arrays and cas genes associated with CRISPR-Cas subtypes III-A, I-B, and III-B were also detected. Some of the CRISPR-Cas systems are associated with genomic regions related to Cap4 proteins, and toxin-antitoxin systems. Moreover, prophage sequences were prevalent in 68.9% of the genomes. Analysis revealed a connection between these prophages and CRISPR-Cas systems, indicating an ongoing arms race between the bacteria and their bacteriophages. Furthermore, proteins associated with anti-CRISPR systems, such as AcrF11 and AcrF7, were identified in the A. baumannii and A. pittii genomes. This study elucidates CRISPR-Cas systems and defense mechanisms within the Acb complex, highlighting their diverse distribution and interactions with prophages and other genetic elements. This study also provides valuable insights into the evolution and adaptation of these microorganisms in various environments and clinical settings.

Clinical characteristics and antimicrobial therapy of healthcare-associated carbapenem-non-susceptible gram-negative bacterial meningitis: a 16-year retrospective cohort study

ObjectiveHealthcare-associated Gram-negative bacterial meningitis is a substantial clinical issue with poor outcomes, especially for neurosurgical patients. Here, we aimed to study the characteristics and treatment options of patients with healthcare-associated carbapenem-non-susceptible (Carba-NS) Gram-negative bacterial meningitis.MethodsThis observational cohort study was conducted at a teaching hospital from 2004 to 2019. The clinical characteristics of patients with meningitis with Carba-NS and carbapenem-susceptible (Carba-S) bacilli were compared, and the antimicrobial chemotherapy regimens and outcomes for Carba-NS Gram-negative bacterial meningitis were analyzed.ResultsA total of 505 patients were included, of whom 83.8% were post-neurosurgical patients. The most common isolates were Acinetobacter spp. and Klebsiella spp., which had meropenem-resistance rates of 50.6% and 42.5%, respectively, and showed a markedly growing carbapenem-resistance trend. Kaplan–Meier curve analysis revealed that Carba-NS Gram-negative bacilli were associated with a significantly higher in-hospital mortality rate (18.8%, 35/186) compared to the Carba-S group (7.4%, 9/122; P = 0.001). For Carba-NS Enterobacterales meningitis, aminoglycoside-based and trimethoprim-sulfamethoxazole-based regimens yielded significantly higher clinical efficacy rates than non-aminoglycoside-based and non-trimethoprim-sulfamethoxazole-based regimens (69.0% vs. 38.7%, P = 0.019 and 81.8% vs. 46.9%, P = 0.036, respectively). For Carba-NS A. baumannii complex meningitis, tetracycline-based (including doxycycline, minocycline, or tigecycline) therapy achieved a significantly higher clinical efficacy rate (62.9%, 22/35) than the non-tetracycline-based therapy group (40.4%, 19/47; P = 0.044).ConclusionsOur findings revealed that Carba-NS Gram-negative bacilli are associated with higher in-hospital mortality in patients with healthcare-associated meningitis. The combination therapies involving particular old antibiotics may improve patients’ outcome.Trial registrationThis study was registered on the Chinese Clinical Trial Register under ChiCTR2000036572 (08/2020).

Carbapenem-resistant Acinetobacter baumannii complex in the United States—An epidemiological and molecular description of isolates collected through the Emerging Infections Program, 2019

BackgroundUnderstanding the epidemiology of carbapenem-resistant A. baumannii complex (CRAB) and the patients impacted is an important step towards informing better infection prevention and control practices and improving public health response. MethodsActive, population-based surveillance was conducted for CRAB in 9 U.S. sites from January 1-December 31, 2019. Medical records were reviewed, isolates were collected and characterized including antimicrobial susceptibility testing and whole genome sequencing. ResultsAmong 136 incident cases in 2019, 66 isolates were collected and characterized; 56.5% were from cases who were male, 54.5% were from persons of Black or African American race with non-Hispanic ethnicity, and the median age was 63.5 years. Most isolates, 77.2%, were isolated from urine, and 50.0% were collected in the outpatient setting; 72.7% of isolates harbored an acquired carbapenemase gene (aCP), predominantly blaOXA-23 or blaOXA-24/40; however, an isolate with blaNDM was identified. The antimicrobial agent with the most in vitro activity was cefiderocol (96.9% of isolates were susceptible). ConclusionsOur surveillance found that CRAB isolates in the U.S. commonly harbor an aCP, have an antimicrobial susceptibility profile that is defined as difficult-to-treat resistance, and epidemiologically are similar regardless of the presence of an aCP.

The causes of bacterial bloodstream infections and antimicrobial resistance patterns in children attending a secondary care hospital in Bhaktapur, Nepal, 2017-2022: a retrospective study.

Data on antimicrobial resistance (AMR) among children in Nepal are limited. Here we have characterized the causes of bacterial bloodstream infections (BSIs), antimicrobial resistance patterns and the mechanisms of β-lactamase production in Enterobacterales among children attending outpatient and inpatient departments of a secondary care paediatric hospital in Nepal. We retrospectively collected demographic and clinical data of culture-proven bacterial BSIs between January 2017 and December 2022 among children <18 years attending a 50-bedded paediatric hospital. Stored isolates were subcultured for antimicrobial susceptibility testing against commonly used antimicrobials. Enterobacterales displaying non-susceptibility to β-lactams were phenotypically and genotypically investigated for ESBLs, plasmid-mediated AmpC (pAmpC) β-lactamases and carbapenemases. A total of 377 significant bacteria were isolated from 27 366 blood cultures. Among 91 neonates with a BSI, Klebsiella pneumoniae (n = 39, 42.4%), Pseudomonas aeruginosa (n = 15, 16.3%) and Acinetobacter baumannii complex (n = 13, 14.1%) were most common. In the non-neonates, 275/285 (96.5%) infections were community-acquired including Staphylococcus aureus (n = 89, 32.4%), Salmonella Typhi (n = 54, 19.6%) and Streptococcus pneumoniae (n = 32, 11.6%). Among the 98 S. aureus, 29 (29.6%) were methicillin-resistant Staphylococcus aureus. K. pneumoniae and Escherichia coli demonstrated non-susceptibility to extended-spectrum cephalosporins and carbapenems in both community and hospital-acquired cases. For E. coli and K. pneumoniae, blaCTX-M (45/46), blaEBC (7/10) and blaOXA-48 (5/6) were common among their respective groups. We determined significant levels of AMR among children attending a secondary care paediatric hospital with BSI in Nepal. Nationwide surveillance and implementation of antimicrobial stewardship policies are needed to combat the challenge imposed by AMR.