Acinetobacter calcoaceticus-Acinetobacter Baumannii Complex Research Articles

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.

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.

Development of Modernized Acinetobacter baumannii Susceptibility Test Interpretive Criteria for Recommended Antimicrobial Agents Using Pharmacometric Approaches.

Acinetobacter baumannii-Acinetobacter calcoaceticus complex (referred to herein as A. baumannii) treatment guidelines contain numerous older antimicrobial agents with susceptibility test interpretive criteria (STIC, also known as susceptibility breakpoints) set using only epidemiological data. We utilized a combination of in vitro surveillance data, preclinical murine thigh and lung infection models, population pharmacokinetics, simulation, and pharmacokinetic/pharmacodynamic (PK/PD) target attainment analyses to evaluate A. baumannii STIC for four commonly recommended antimicrobials from different classes (amikacin, ceftazidime, ciprofloxacin, and minocycline). Antimicrobial in vitro surveillance data were based on 1,647 clinical A. baumannii isolates obtained from 109 centers in the United States and Europe. Among these isolates, 5 were selected for evaluation in murine infection models based on fitness and MIC variability. PK and dose-ranging studies were conducted using neutropenic murine thigh and lung infection models The MIC ranges for the 5 isolates evaluated were as follows: amikacin, 2 to 32 μg/mL; ceftazidime, 4 to 16 μg/mL; ciprofloxacin, 0.12 to 2 μg/mL; minocycline, 0.25 to 4 μg/mL. All organisms grew ≥1.5 log10 CFU in both models in untreated controls. Plasma and epithelial lining fluid (ELF) pharmacokinetics for all drugs were determined in mice using liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods. For each isolate, 5 dose levels of each drug were tested individually in the thigh and lung infection model. The inoculum ranged from 7.9 to 8.4 and 6.8 to 7.7 log10 CFU/mL for the lung and thigh models, respectively. PK/PD targets associated with net bacterial stasis and 1- and 2-log10 CFU reductions from baseline were identified for each organism/infection model using Hill-type models. Population pharmacokinetic models for each agent were identified from the literature. Using demographic variables for simulated patients with hospital-acquired or ventilator-associated bacterial pneumonia or urinary tract infections (including acute pyelonephritis) who were administered maximal dosing regimens of each agent, estimates of protein binding, and ELF penetration ratios based on data from the literature, free-drug plasma and total-drug concentration-time profiles were generated, and PK/PD indices by MIC were calculated. Percent probabilities of attaining median and randomly assigned PK/PD targets associated with the above-described endpoints were determined. Recommended susceptible breakpoints for each agent were those representing the highest MIC at which the percent probabilities of achieving PK/PD targets associated with a 1-log10 CFU reduction from baseline approached or were ≥90%. The following susceptible breakpoints for A. baumannii were identified: amikacin, ≤8 μg/mL for pneumonia; ceftazidime, ≤32 and ≤8 μg/mL for pneumonia; ciprofloxacin, ≤1 μg/mL; and minocycline, ≤0.5/≤1 μg/mL which correspond to the standard and high minocycline dosing regimens of 200 mg per day and 200 mg every 12 h, respectively. Implementation of appropriate STIC will help clinicians optimally use the above-described agents and improve the likelihood of successful patient outcomes.

Elucidating the Antibiotic Resistance of Acinetobacter calcoaceticus Strains

BackgroundAccording to the Center for Disease Control (CDC), antibiotic resistance is one of the largest public health challenges facing modern society. It has been estimated that 2.8 million people each year in the US are infected with an antibiotic‐resistant organism, resulting in >35,000 deaths. One of the multi‐drug resistant microbes listed on the CDC’s urgent threats list is Acinetobacter. The Acinetobacter calcoaceticus–Acinetobacter baumannii complex (ACB complex) is a group of clinically relevant Acinetobacter species that can cause pneumonia, urinary tract, skin and soft tissue infections. Although a lot of work has focused on antibiotic resistance in A. baumannii, the resistance of A. calcoaceticus is underexplored. To address this gap in knowledge, we obtained three commercially available A. calcoaceticus strains and four clinical isolates. We hypothesized that clinical isolates of A. calcoaceticus would be well adapted to withstand traditional antibiotics.Methods & ResultsTo test this hypothesis, we grew commercially available and clinical isolates of A. calcoaceticus in a fully defined bacterial media, termed ZMB1, which was then seeded into Biolog plates (12B) containing beta‐lactams (penicillin G, carbenicillin, oxacillin), tetracyclines (tetracycline, penimepicycline), aminoglycosides (polymyxin B, paromomycin, sisomicin, tobramycin, spectinomycin), glycopeptides (vancomycin), sulfonamides (sulfamethazine, sulfadiazine, sulfathiazole, sulfa‐methoxazole), aminocoumarins (novobiocin), pteridines (2,4‐diamino‐6,7‐ diisopropyl‐ pteridine), biocides (benzethonium chloride), macrolides (spiramycin), antimycobacterials (rifampicin), amphiphiles (dodecyltrimethyl ammonium bromide), and acids (D,L‐Serine hydroxamate, 5‐fluoroorotic acid, L‐aspartic‐β‐ hydroxamate). All A. calcoaceticusstrains were resistant to penicillin G, tetracycline, carbenicillin, and sisomicin. Interestingly, although our commercially available strains were sensitive to sulfamethazine, we observed that all of our clinical isolates were resistant to this antibiotic. We also identified that 2 of our isolates were resistant to polymyxin B and one isolate was highly resistant to dodecyltrimethyl ammonium bromide. These data suggest significant differences in antibiotic resistance between strains.ConclusionsCollectively, these data demonstrate reveal a profile of resistance for A. calcoaceticus. This data also indicates that clinical isolates of A. calcoaceticus are much more resistant to antibiotics than lab adapted strains and should be incorporated into experimental study design.

Complexo Acinetobacter calcoaceticus-Acinetobacter baumannii em animais: identificação e perfil de resistência antimicrobiana

ABSTRACT: Acinetobacter spp. is emerging as an important human and veterinary pathogen, mostly due to intrinsic and acquired resistance to antimicrobials. Despite its public health relevance, little is known about the prevalence, role of different Acinetobacter species and antimicrobial resistance profile of animal-origin isolates. Traditional phenotypic tests may fail to discriminate Acinetobacter species, therefore molecular analyses are often required as a complementary approach. The objectives of this study were to evaluate the occurrence of strains of the Acinetobacter calcoaceticus-Acinetobacter baumannii (Acb) complex isolated from animal infections including urinary tract infections, otitis, piodermitis and pododermatitis, and its resistance profile against different antimicrobial classes, including carbapenems. All Gram-negative coccobacilli isolates were characterized by MALDI-TOF and multiplex PCR, and the disk diffusion test was used to investigate multi-drug resistance (MDR) and carbapenem resistance genes by PCR as preconized by the standard guidelines. MALDI-TOF technique identified 21 strains belonging to the Acb complex (10 A. pittii, 8 A. baumannii, 3 A. nosocomialis, 1 A. ursingii, and 1 A. venetianus). Multiplex PCR confirmed the results of MALDI-TOF for 20 strains. Eight strains (34.78%) were classified as MDR, being 50% (4/8) A. baumannii, 37.5% (3/8) A. pittii, and 12.5% (1/8) A. nosocomialis. None of the isolates presented phenotypic carbapenemase production. Considering the carbapenem resistance genes, 26.09% (6/23) of the isolates presented one or more carbapenemase genes. From these, 50% (3/6) presented only bla VIM, 33.33% (2/6) presented only blaIMP, and 16.67% (1/6) presented blaIMP e blaVIM, simultaneously. These genes were detected among A. pittii isolates mostly (66.67%, 4/6). This study provides further insights into the occurrence and resistance profile of Acinetobacter of animal origin.

Distribution of clinical isolates obtained from sterile body fluids: a four-year retrospective data

Aim: Infections of sterile body fluids (SBFs) require rapid and accurate diagnosis and treatment, since their morbidities and mortalities are high. To achieve this goal, definite epidemiologic data is absolutely required, since empiric and preemptive treatments are mainly based on this. The aim of this study was to evaluate infectious agents isolated from SBFs, susceptibility results and molecular analysis (PCR) data, retrospectively.
 Material and Method: Clinical samples of SBFs (Cerebrospinal, pleural, peritoneal, pericardial and synovial fluids) obtained from January 2017 to December 2020 in Atatürk City Hospital (tertiary center) were included. Identification of bacterial and fungal agents and antibiotic susceptibility were done by conventional and automated system (BD Phoenix™, Becton Dickinson Co., Sparks, MD, USA). Löwenstein-Jensen media and BACTEC Mycobacteria Growth Indicator Tube 960 (Becton Dickinson Co., Sparks, MD, USA) were used for mycobacterial analysis. Bosphore Viral Meningitis Panel Multiplex PCR Kit (Anatolia Geneworks, İstanbul, Turkey) were applied to detect HSV-1, HSV-2, VZV, Enterovirus and/or Parechovirus.
 Results: A total of 221 (9.74%) organisms were detected among 2269 samples. Particularly common gram negative bacterial agents covered the top of the list (Escherichia coli, Pseudomonas spp., Klebsiella spp. and Acinetobacter baumannii-Acinetobacter calcoaceticus complex). Staphylococcus aureus was the most frequent gram positive strain, followed by enteroccocci. Most of the A. baumannii isolates were multidrug resistant, Pseudomonas spp. showed over than 20% resistance rate to ceftazidime, cefepime and piperacillin-tazobactam. All enterococci were vancomycin-susceptible, one S. aureus strain was methicillin-resistant. All Mycobacterium tuberculosis complex isolates were found to be susceptible to first-line anti-tuberculosis drugs.
 Conclusions: Continuous laboratory surveillance even in local phase is important to guide clinicians. Even though our data did not show significant changes, improvements on laboratory capabilities and clinical awareness must be done. Isolation rates might be underestimated due to requirement of improvements in our laboratory, especially about sampling, anaerobe transportation and usage of blood culture vials.

Ability of phages to infect Acinetobacter calcoaceticus-Acinetobacter baumannii complex species through acquisition of different pectate lyase depolymerase domains.

Environmental MicrobiologyVolume 23, Issue 6 p. 3334-3334 Corrigendum Ability of phages to infect Acinetobacter calcoaceticus-Acinetobacter baumannii complex species through acquisition of different pectate lyase depolymerase domains Hugo Oliveira, Hugo OliveiraSearch for more papers by this authorAna R. Costa, Ana R. CostaSearch for more papers by this authorNico Konstantinides, Nico KonstantinidesSearch for more papers by this authorAlice Ferreira, Alice FerreiraSearch for more papers by this authorErgun Akturk, Ergun AkturkSearch for more papers by this authorSanna Sillankorva, Sanna SillankorvaSearch for more papers by this authorAlexandr Nemec, Alexandr NemecSearch for more papers by this authorMikhail Shneider, Mikhail ShneiderSearch for more papers by this authorAndreas Dötsch, Andreas DötschSearch for more papers by this authorJoana Azeredo, Joana AzeredoSearch for more papers by this author Hugo Oliveira, Hugo OliveiraSearch for more papers by this authorAna R. Costa, Ana R. CostaSearch for more papers by this authorNico Konstantinides, Nico KonstantinidesSearch for more papers by this authorAlice Ferreira, Alice FerreiraSearch for more papers by this authorErgun Akturk, Ergun AkturkSearch for more papers by this authorSanna Sillankorva, Sanna SillankorvaSearch for more papers by this authorAlexandr Nemec, Alexandr NemecSearch for more papers by this authorMikhail Shneider, Mikhail ShneiderSearch for more papers by this authorAndreas Dötsch, Andreas DötschSearch for more papers by this authorJoana Azeredo, Joana AzeredoSearch for more papers by this author First published: 29 June 2021 https://doi.org/10.1111/1462-2920.15620Citations: 1Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL No abstract is available for this article.Citing Literature Volume23, Issue6Special Issue on Oxygen Minimum Zone MicrobiologyJune 2021Pages 3334-3334 RelatedInformation

Identification of carbapenem - resistant Acinetobacter calcoaceticus - Acinetobacter baumannii complex in ready-to-eat vegetables and meats in Hanoi

Acinetobacter spp. are common pathogenic bacteria. The Acinetobacter genus includes 65 species, of which the Acinetobacter calcoaceticus-Acinetobacter baumannii complex group has been identified as the cause of more than 80% of hospital infections in immunocompromised patients. Existing phenotypic techniques are not sufficient to accurately identify and distinguish clinically important Acinetobacter spp. 288 (60%, n = 480) of ready-to-eat vegetable and meat samples collected from ready-to-eat shops contaminated with Acinetobacter spp in 6 districts in Hanoi, including Dong Da, Hoang Mai, Hai Ba Trung, Long Bien, Ha Dong, and Cau Giay. The results of identification by MALDI-TOF MS technique recorded 208 (43%, n = 480) of samples contaminated with Acinetobacter calcoaceticus-Acinetobacter baumannii complex, of which 156 (65%, n = 240) of vegetable and 52 (22%, n = 240) of meat samples. Antibiotic susceptibility tests using antibiotic paper strips showed that 82% of Acinetobacter calcoaceticus-Acinetobacter baumannii complex strains were resistant to imipenem and 30% of the complex was resistant to meropenem.

The Identification of Acinetobacter baumannii Blood Isolates by MALDI-TOF MS, ARDRA and blaOXA-51-like Gene-Specific Real-Time PCR

The Acinetobacter calcoaceticus-Acinetobacter baumannii (Acb) complex consists of phenotypically very similar nosocomial species; A.baumannii, Acinetobacter nosocomialis, Acinetobacter pittii, Acinetobacter seifertii and Acinetobacter djikshoorniae and one environmental species A.calcoaceticus. The rapid and accurate identification of the members of Acb complex is critical as these nosocomial pathogens can show differences in antimicrobial susceptibility and clinical outcomes. The conventional phenotypic methods are slow, unreliable and less efficient for the differentiation of Acb complex species, including the A.baumannii species within the Acb complex. Although various molecular methods are available, such as amplified ribosomal DNA restriction analysis (ARDRA) and blaOXA-51-like gene specific PCR, they are usually inconvenient for the routine diagnostic laboratories. Recently, matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) offers an opportunity for rapid, cost-effective and convenient bacterial identification in routine diagnostic procedures conducted in clinical laboratory. In this study, we aimed to evaluate the diagnosis performance of MALDI-TOF MS system to identify blood isolates of A.baumannii. A total of 180 nonduplicate carbapenem resistant Acb complex (strain numbers; TR1-TR60) and A.baumannii (TR61-TR180) blood isolates were collected from the intensive care units of the three university hospitals in Turkey from January 2016 to December 2016. All isolates were evaluated by using blaOXA-51-like gene specific real time (Rt-PCR) analysis, ARDRA (restriction enzymes-AluI, CfoI, MboI, MspI, RsaI) method and MALDI-TOF MS (VITEK® MS, bioMérieux, France) system. All the strains except TR10, TR31, TR35 and TR52 were identified as A.baumannii by ARDRA method. Out of 177 of all the isolates, presence of blaOXA-51-like gene was found except for TR10, TR31 and TR52 isolates. However, TR31 without the presence of blaOXA-51-like gene was identified as A.pittii using the ARDRA. Totally 176 isolates which were identified as A.baumannii by both of the methods, ARDRA and Rt-PCR- blaOXA-51-like, were accepted as a reference for the evaluation of the diagnosis performance capacity of the MALDI-TOF MS. Overall, for all 176 isolates tested, the sensitivity obtained with the MALDI-TOF MS were 99.4% with 75% specificity. The accuracy value of the method was determined as 98.9% for the identification of A.baumannii to the species level. MALDI-TOF MS is increasingly used in diagnostic microbiology for the routine identification of bacteria to the genus, species or subspecies level with high rates of sensitivity and specificity. In future, by expanding the database, MALDI-TOF MS system would possibly become the ideal method for routine diagnostic laboratories that could potentially identify more species and even determine some characteristics of antimicrobial resistance and virulence determinants.

Molecular Characterization of Carbapenem-Resistant Acinetobacter baumannii Associated with Nosocomial Infection in the Pelotas, RS, Brazil

Acinetobacter calcoaceticus-Acinetobacter baumannii complex (ACB) comprises some opportunistic pathogens associated with infectious outbreaks in hospital settings. A. baumannii is the most relevant species owing to its capacity to develop resistance to the different classes of antimicrobials. The aim of this study was to identify the species, establish the genetic patterns, resistance and biofilm profiles in ACB isolates associated with nosocomial infection in a hospital of Pelotas, Rio Grande do Sul, Brazil. Twenty-two clinical isolates were characterized at the species level through multiplex polymerase chain reaction (PCR) for the gyrB and blaOXA51-like genes, and the genetic relationship was determined through pulsed-field gel electrophoresis (PFGE). Their antibiotic resistance profiles and carbapenemases synthesis were evaluated following CLSI guidelines. PCR was carried out to evaluate the presence of carbapenemases genes and the isolates were classified for their biofilm-forming ability. All isolates obtained in the study were identified as A. baumannii and 72.7% of the isolates were classified as strong biofilm formers. In the class carbapenems, 95.4% and 77.3% of the isolates were resistant to meropenem and imipenem, respectively. The blaVIM gene was identified in 90.9% of isolates and carbapenemases synthesis were confirmed in 95.4% of the isolates. Fourteen genetic patterns were confirmed through PFGE analyses. The isolates collected within a time gap of 2 years demonstrated a genetic relationship, and the same clone was identified in different departments in the hospital. To the best of our knowledge, this is the first report of identification and characterization of A. baumannii nosocomial isolates in Pelotas, RS, Brazil.

Long-Term Surveillance of Antibiotic Prescriptions and the Prevalence of Antimicrobial Resistance in Non-Fermenting Gram-Negative Bacilli.

The increasing emergence of multidrug-resistant (MDR) bacteria has been recognized as a public health threat worldwide. Hospitalized patients and outpatients are commonly infected by non-fermenting Gram-negative bacilli (NFGNB), particularly the Acinetobacter calcoaceticus-Acinetobacter baumannii complex (ACB) and Pseudomonas aeruginosa. Antimicrobial agents are critical for treating the nosocomial infections caused by NFGNB. The aim of this study was to assess antimicrobial resistance and the use of antimicrobial agents. The bacterial isolates of 638,152 specimens from both inpatients and outpatients, retrieved from 2001 to 2008 at a medical center in central Taiwan, were examined for their susceptibility to various antimicrobial agents, including cefepime, imipenem, ciprofloxacin, gentamicin, amikacin, meropenem, and levofloxacin. Administrated prescriptions of the monitored antibiotics were analyzed using the Taiwan National Health Insurance Research Database (NHIRD). Our results show that the defined daily doses (DDDs) for cefepime, imipenem, and ciprofloxacin increased with time, and a trend toward reduced antimicrobial sensitivities of both ACB and P. aeruginosa was noticeable. In conclusion, the antimicrobial sensitivities of ACB and P. aeruginosa were reduced with the increased use of antibiotics. Continuous surveillance of antibiotic prescriptions and the prevalence of emerging resistance in nosocomial infections is warranted.

Antimicrobial Susceptibility Pattern of Acinetobacter calcoaceticus-Acinetobacter baumannii Complex Isolated from Sputum in a Tertiary Care Hospital

Introduction: Acinetobacter calcoaceticus-Acinetobacter baumanni (ACB) complex is one of the commonest cause of hospital acquired and ventilator associated pneumonia. Multidrug resistant Acinetobacter species have become a matter of huge concern. This study was done to find out the antibiotic susceptibility pattern of Acinetobacter calcoaceticus-Acinetobacter baumanii complex from sputum samples. Methods: This descriptive cross-sectional study was carried out in Clinical Microbiology laboratory from July 2018 to Jan 2019 after ethical approval. Acinetobacter calcoaceticus-Acinetobacter baumannii complex was identified on the basis of its microscopy and morphological characteristics followed by biochemical tests. Antibiotic sensitivity test of isolated pathogens was done using Muller Hinton Agar by Kirby-Bauer method. Results: Of the 384 culture positive sputum specimen, 76 (19.80%) were Acinetobacter calcoaceticus-Acinetobacter baumannii complex. Most of the isolates were resistant to commonly used antibiotics, 72.36% of the isolates were multidrug resistance and 3.95% isolates were resistant to tigecycline. Conclusion: This study provides valuable information regarding prevalence of Acinetobacter calcoaceticus-Acinetobacter baumannii complex from sputum specimen. The alarming number of multidrug resistance isolates is worrisome finding. Antibiotics like Tigecycline and Colistin which is still sensitive to isolates should be cautiously used only in MDR cases.

Antimicrobial Susceptibility Pattern of Acinetobacter calcoaceticus-Acinetobacter baumannii Complex Isolated from Sputum in a Tertiary Care Hospital

Introduction Acinetobacter calcoaceticus-Acinetobacter baumanni (ACB) complex is one of the commonest cause of hospital acquired and ventilator associated pneumonia. Multidrug resistant Acinetobacter species have become a matter of huge concern. This study was done to find out the antibiotic susceptibility pattern of Acinetobacter calcoaceticus-Acinetobacter baumanii complex from sputum samples.
 MethodsThis descriptive cross-sectional study was carried out in Clinical Microbiology laboratory from July 2018 to Jan 2019 after ethical approval. Acinetobacter calcoaceticus-Acinetobacter baumannii complex was identified on the basis of its microscopy and morphological characteristics followed by biochemical tests. Antibiotic sensitivity test of isolated pathogens was done using Muller Hinton Agar by Kirby-Bauer method.
 ResultsOf the 384 culture positive sputum specimen, 76 (19.80%) were Acinetobacter calcoaceticus-Acinetobacter baumannii complex. Most of the isolates were resistant to commonly used antibiotics, 72.36% of the isolates were multidrug resistance and 3.95% isolates were resistant to tigecycline.
 ConclusionThis study provides valuable information regarding prevalence of Acinetobacter calcoaceticus-Acinetobacter baumannii complex from sputum specimen. The alarming number of Multidrug resistance isolates is worrisome finding. Antibiotics like Tigecycline and Colistin which is still sensitive to isolates should be cautiously used only in MDR cases.

Emergence of colistin and carbapenem-resistant Acinetobacter calcoaceticus-Acinetobacter baumannii (CCR-Acb) complex in a neurological intensive care unit followed by successful control of the outbreak

BackgroundColistin and carbapenem-resistant Acinetobacter calcoaceticus- Acinetobacter baumannii complex (CCR-Acb complex) was isolated from two consecutive patients in the neurological intensive care unit (NICU). An urgent reaction to this desperate situation was required. Patients and methodsScreening cultures were taken from the other patients sharing the NICU with index patients and repeated periodically. NICU was closed for new admissions. Infection control precautions (ICP) such as hand hygiene, cohorting patients colonized with CCR-Acb complex, cohorting the staff caring for these patients, daily bathing with chlorhexidine gluconate impregnated clothes, using gowns when contacting with patients and patient care area, and sodium hypochlorite tablets for environmental cleaning were enforced. ResultsScreening cultures revealed carbapenem-resistant Acb complex in 12 out of 32 patients and 8 of them were colonized with CCR-Acb complex. NICU was opened for new admissions one month later. No further new cases with CCR-Acb complex were detected by screening cultures after 6 weeks with enforcement of ICP. Moreover, the rate of nosocomial infections caused by other multi-drug resistant Gram-negative bacilli (MDR-GNB) decreased significantly when rates before and after closing the NICU were compared. ConclusionICP were effective not only to limit the spread of CCR-Acb complex but also decreased the incidence of other MDR-GNB infections when applied adequately.

Colistin for pneumonia involving multidrug-resistant Acinetobacter calcoaceticus-Acinetobacter baumannii complex.

To investigate clinical and microbiological response, and 30-day mortality of pneumonia involving multidrug-resistant (MDR) Acinetobacter calcoaceticus-Acinetobacter baumannii (Acb) complex treated with colistin, and identify associated factors of these outcomes. A retrospective study of 183 adult patients with colistin treatment for at least 7 days between January 2014 and October 2017. The mean age was 76.8 years, and mean Acute Physiology and Chronic Health Evaluation II score was 17.7. Eighteen (9.8%) and 128 (69.9%) patients had intravenous (IV) colistin alone and inhaled (IH) colistin alone, respectively. Thirty-seven patients had both IV and IH colistin, including 5 (2.7%) with concurrent, and 32 (17.5%) with non-concurrent use of IV and IH colistin. The 30-day mortality rate was 19.1% and 131 (71.6%) patients had clinical response. In the 175 patients with available data, 126 (72%) had microbiological eradication. The multivariate analyses revealed that IH colistin alone was an independent predictor for 30-day survival, clinical response, and microbiological eradication, and IV colistin alone was an independent predictor for clinical failure. Patients with IV colistin alone had a significantly higher nephrotoxicity rate than IH colistin alone (37.5% vs 6.1%, P=0.001). Sub-group analysis of 52 patients with IV colistin for ≧ 4 days revealed that 14 (26.9%) patients had inappropriate dose, and inappropriate dose was an independent predictor for 30-day mortality. IH colistin provided good outcomes with few side effects, and appropriate dosing of IV colistin was important to avoid excess mortality.

Characterization of an Environmental Multidrug-Resistant Acinetobacter seifertii and Comparative Genomic Analysis Reveals Co-occurrence of Antimicrobial Resistance and Metal Tolerance Determinants.

Acinetobacter calcoaceticus-Acinetobacter baumannii complex is considered one of the main causes of hospital-acquired infections. Acinetobacter seifertii was recently characterized within this complex and it has been described as an emergent pathogen associated with bacteremia. The emergence of multidrug-resistant (MDR) bacteria, including Acinetobacter sp., is considered a global public health threat and an environmental problem because MDR bacteria have been spreading from several sources. Therefore, this study aimed to characterize an environmental MDR A. seifertii isolate (SAb133) using whole genome sequencing and a comparative genomic analysis was performed with A. seifertii strains recovered from various sources. The SAb133 isolate was obtained from soil of a corn crop field and presented high MICs for antimicrobials and metals. The comparative genomic analyses revealed ANI values higher than 95% of relatedness with other A. seifertii strains than A. calcoaceticus-A. baumannii complex. Resistome and virulome analyses were also performed and showed different antimicrobial resistance determinants and metal tolerance genes as well as virulence genes related to A. baumannii known virulence genes. In addition, genomic islands, IS elements, plasmids and prophage-related sequences were detected. Comparative genomic analysis showed that MDR A. seifertii SAb133 had a high amount of determinants related to antimicrobial resistance and tolerance to metals, besides the presence of virulence genes. To the best of our knowledge, this is the first report of a whole genome sequence of a MDR A. seifertii isolated from soil. Therefore, this study contributed to a better understanding of the genetic relationship among the few known A. seifertii strains worldwide distributed.

Pathogenic Acinetobacter species including the novel Acinetobacter dijkshoorniae recovered from market meat in Peru

Species of the Acinetobacter calcoaceticus-Acinetobacter baumannii complex are important human pathogens which can be recovered from animals and food, potential sources for their dissemination. The aim of the present study was to characterise the Acinetobacter isolates recovered from market meat samples in Peru. From July through August 2012, 138 meat samples from six traditional markets in Lima were cultured in Lysogeny and Selenite broths followed by screening of Gram-negative bacteria in selective media. Bacterial isolates were identified by MALDI-TOF MS and DNA-based methods and assessed for their clonal relatedness and antimicrobial susceptibility.Twelve Acinetobacter isolates were recovered from calf samples. All but one strain were identified as members of the clinically-relevant Acinetobacter calcoaceticus-Acinetobacter baumannii complex: 9 strains as Acinetobacter pittii, 1 strain as A. baumannii, and 1 strain as the recently described novel species A. dijkshoorniae.The remaining strain could not be identified at the species level unambiguously but all studies suggested close relatedness to A. bereziniae. All isolates were well susceptible to antibiotics. Based on macrorestriction analysis, six isolates were further selected and some of them were associated with novel MLST profiles.The presence of pathogenic Acinetobacter species in human consumption meat might pose a risk to public health as potential reservoirs for their further spread into the human population. Nevertheless, the Acinetobacter isolates from meat found in this study were not multidrug resistant and their prevalence was low. To our knowledge, this is also the first time that the A. dijkshoorniae species is reported in Peru.

Phenotypic and Genotypic Characterization of Clinical Isolates Belonging to the Acinetobacter calcoaceticus-Acinetobacter baumannii (ACB) Complex Isolated From Animals Treated at a Veterinary Hospital in Switzerland.

Objectives: We investigated a collection of strains belonging to the Acinetobacter calcoaceticus-Acinetobacter baumannii (ACB) complex obtained from a veterinary clinic with regard to their genetic relatedness, presence of antibiotic resistance genes and antimicrobial susceptibility profiles.Methods: Fifty-eight ACB-complex strains from animals treated at a veterinary clinic between 2006 and 2017, and seven strains collected from the hospital environment during 2012 were analyzed. Assignment to sequence types (ST) and international complexes (IC) was done by multilocus sequence typing (MLST) according to the Pasteur scheme. Genes encoding carbapenemases, aminoglycoside-modifying enzymes, macrolide-, quinolone- and co-trimoxazole resistance genes, the ISAba1 element, virulence associated intI1 genes and plasmid associated toxin-antitoxin markers were identified by microarray. Genes encoding blaOXA−51-like carbapenemases were amplified by PCR and sequenced. Susceptibility profiles were determined by disc diffusion or by broth microdilution.Results: Among 50 A. baumannii isolates from animals, two predominant clones were observed linked to CC1 (n = 27/54% of the isolates) and CC25 (n = 14/28%), respectively. Strains of IC I harbored blaOXA−69, aac(3′)-la, aadA1, sul1, intI1, and splA/T genes. Isolates belonging to CC25 possessed blaOXA−64. Six (12%) isolates belonging to CC2 and carrying blaOXA−66 were also noted. One isolate belonged to CC10 (blaOXA−68), one to CC149 (blaOXA−104), the remaining isolate was assigned to ST1220 and possessed blaOXA−116. Of six environmental A. baumannii, four (66.7%) belonged to CC25 (blaOXA−64), one (16.7%) to CC2 (blaOXA−66) and one to CC3 (blaOXA−71). Nine isolates (eight from animals and one environmental strain) were non-baumannii strains and did not harbor blaOXA−51-like genes. None of the isolates carried blaOXA−23, blaOXA−48, or blaOXA−58, and none were resistant to carbapenems.Conclusions: Clonal lineages of the veterinary A. baumannii isolates in our collection are identical to those globally emerging in humans but do not harbor blaOXA−23. A. baumannii CC25 may be specific for this particular veterinary clinic environment.

Differentiation of Taxonomically Closely Related Species of the Genus Acinetobacter Using Raman Spectroscopy and Chemometrics.

In recent years, several efforts have been made to develop quick and low cost bacterial identification methods. Genotypic methods, despite their accuracy, are laborious and time consuming, leaving spectroscopic methods as a potential alternative. Mass and infrared spectroscopy are among the most reconnoitered techniques for this purpose, with Raman having been practically unexplored. Some species of the bacterial genus Acinetobacter are recognized as etiological agents of nosocomial infections associated with high rates of mortality and morbidity, which makes their accurate identification important. The goal of this study was to assess the ability of Raman spectroscopy to discriminate between 16 Acinetobacter species belonging to two phylogroups containing taxonomically closely related species, that is, the Acinetobacter baumannii-Acinetobacter calcoaceticus complex (six species) and haemolytic clade (10 species). Bacterial spectra were acquired without the need for any sample pre-treatment and were further analyzed with multivariate data analysis, namely partial least squares discriminant analysis (PLSDA). Species discrimination was achieved through a series of sequential PLSDA models, with the percentage of correct species assignments ranging from 72.1% to 98.7%. The obtained results suggest that Raman spectroscopy is a promising alternative for identification of Acinetobacter species.

Treatment outcomes of patients with non-bacteremic pneumonia caused by extensively drug-resistant Acinetobacter calcoaceticus-Acinetobacter baumannii complex isolates

Few therapeutic options exist for various infections caused by extensively drug-resistant Acinetobacter calcoaceticus-Acinetobacter baumannii (XDR-Acb) complex isolates, including pneumonia. This study investigated the clinical efficacy between aerosolized colistimethate sodium (AS-CMS, 2 million units thrice a day) treatment alone or in combination with standard-dose tigecycline (TGC) in patients with non-bacteremic pneumonia due to XDR-Acb, and explored the factors influencing patients’ 30-day mortality.A 1:1 case (n = 106; receiving TGC plus AS-CMS) control (receiving AS-CMS alone with matching scores) observational study was conducted among adult patients with non-bacteremic XDR-Acb complex pneumonia in a Taiwanese medical center from January 2014 through December 2016. The clinically relevant data were retrospectively recorded. The primary endpoint was 30-day case fatality. Secondary endpoints investigated that if the co-morbidities, XDR-A. baumannii as a pneumonic pathogen, therapy-related factors, or airway colonization with colistin-resistant Acb negatively influenced the 14-day clinical condition of enrolled patients.A higher 30-day mortality rate was noted among the group receiving combination therapy (34.0% vs 22.6%; P = .17). The ≥7-day AS-CMS therapy successfully eradicated > 90% of airway XDR-Acb isolates. Nevertheless, follow-up sputum specimens from 10 (6.4% [10/156]) patients were colonized with colistin-resistant Acb isolates. After the conditional factors were adjusted by multivariate logistic analysis, the only factor independently predicting the 30-day case-fatality was the failure of treating XDR-Acb pneumonia at 14 days (adjusted odds ratio [aOR] = 38.2; 95% confidence interval [CI] = 9.96–142.29; P < .001). Cox proportional regression analysis found that chronic obstructive pulmonary disease (COPD) (adjusted hazard ratio [aHR] = 2.08; 95% CI = 1.05–4.10; P = .035), chronic renal failure (aHR = 3.00; 95% CI = 1.52–5.90; P = .002), non-invasive ventilation use (aHR = 2.68; 95% CI = 1.37–5.25; P = .004), and lack of TGC therapy (aHR = 0.52; 95% CI = 0.27–1.00; P = .049) adversely influenced the 14-day clinical outcomes. Conversely, the emergence of colistin-resistant Acb isolates in the follow-up sputum samples was not statistically significantly associated with curing or improving XDR-Acb pneumonia.In conclusion, aggressive pulmonary hygiene care, the addition of TGC, and corticosteroid dose tapering were beneficial in improving the 14-day patients’ outcomes.