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Metabolism of bile acids by strains of Acinetobacter anitratum and Acinetobacter lwoffii.

The activity of two species of bacteria: Acinetobacter anitratum and Acinetobacter lwoffii, isolated from jejunum of patients with achlorhydria and Reichel-Polya resection towards bile salts was investigated. These species were not previously tested from this view point. All strains tested hydrolyzed bile salts; conjugates of deoxycholic acid were hydrolyzed more readily than those of cholic acid. This feature may be used as a bacteriological taxonomic criterion.

Acinetobacter

Protocatechuate 3, 4-dioxygenase from Acinetobacter calcoaceticus.

Protocatechuate 3,4-dioxygenase (PCD) from p-hydroxybenzoate-induced cells of Acinetobacter calcoaceticus was purified by heat and protamine sulfate treatment, ammonium sulfate fractionation, DEAE-cellulose, and Sephadex G-200 column chromatography. The enzyme appears to be homogeneous by ultracentrifugation and acrylamide gel electrophoresis. This is the first report of PCD purified from Acinetobacter. For comparison, crystalline Pseudomonas PCD was also obtained. The enzymes from Acinetobacter and Pseudomonas are quite similar in their molecular weight, molecular size, and iron content. The specific enzyme activity of PCD from Acinetobacter is about one-third of that from Pseudomonas, despite their similar iron content. Visible and circular dichroism spectra indicate some conformational differences between these two enzymes. Protocatechualdehyde, a competitive deadend inhibitor, binds Pseudomonas PCD more effectively than Acinetobacter PCD. p-Hydroxymercuribenzoate, specific for free-SH groups, inhibits only Acinetobacter PCD and shows no effect on Pseudomonas PCD. Amino acid analyses reveal very low proline and methionine content with higher lysine, glutamic acid, and isoleucine compositions for Acinetobacter PCD. Other properties, including active center conformation, were studied and discussed.

Acinetobacter

Gas chromatography of bacterial whole cell methanolysates. VII. Fatty acid composition of Acinetobacter in relation to the taxonomy of Neisseriaceae.

The cellular fatty acids of seventeen Acinetobacter strains were determined. Most acids identified were previously found in neisseriae and moraxellae. Specific for Acinetobacter was 2-hydroxydodecanoid acid and a few minor unidentified components. The fatty acid data were analysed by numerical methods and compared with previous results obtained for neisseriae and moraxellae. The findings were consistent with genetic evidence for some affinities of genus Acinetobacter to genus Moraxella and "false neisseriae". Occasionally, a high resemblance in fatty acid pattern was demonstrated between a Moraxella strain and certain strains of Acinetobacter, and also between an Acinetobacter strain and certain "true neisseriae". Still, the acinetobacters constituted one single cluster separated from the other genera of Neisseriaceae.

Acinetobacter

Growth inhibition of Acinetobacter by 5-chloro-indole-3-acetic acid.

The Acinetobacter calcoaceticus-baumannii complex includes high-priority, multidrug-resistant pathogens for which novel antibiotics are urgently needed. Many bacterial strains from this complex harbor a so-called iac gene cluster that codes for the catabolism of indole-3-acetic acid (IAA). Here, we demonstrate that possession and expression of iac genes represent an Achilles' heel for Acinetobacter species, which can be exploited to suppress bacterial growth by treatment with IAA and its analog 5-chloro-IAA.IMPORTANCEAcinetobacter baumannii is a deadly bacterial pathogen and one of the leading causes of hospital-acquired infections worldwide. It is also known for its resistance to many antibiotics currently available. In this study, we show that Acinetobacter bacteria choke on a mixture of IAA and 5-chloro-IAA, offering a path to the discovery and development of a novel drug treatment.

Indoleacetic Acids

The metabolism of trans-cyclohexan-1,2-diol by an Acinetobacter species.

1. Acinetobacter TD63 was one of some thirty organisms isolated by elective culture with trans-cyclohexan-1,2-diol as sole source of carbon. The great majority of these isolates displayed the same growth spectrum as Nocardia globerula CL1 and Acinetobacter NCIB 9871 being capable of utilizing trans-cyclohexan-1,2-diol, 2-hydroxycyclohexan-1-one, cyclohexanol, cyclohexanone,1-oxa-2oxocycloheptane and adipate and were assumed to use well described metabolic pathways. 2. Acinetobacter TD63 was distinctive in being incapable of growth with cyclohexanol, cyclohexanone or 1-oxa-2-oxocycloheptane and because of this it was hoped that it would display an alternative pathway for the oxidation of trans-cyclohexan-1,2-diol. 3. Studies with cell extracts have shown the presence of inducible dehydrogenase for the conversion of trans-cyclohexan-1,2-diol to 2-hydroxycyclohexan-1-one and cyclohexan-1,2-dione and of 6-oxohexanoate to adipate. These enzymes are linked into a metabolic sequence by the action of a monooxygenase of broad specificity but efficiently capable of converting 2-hydroxy-cyclohexan-1-one into the lactone 1-oxa-2-oxo-7-hydroxycycloheptane that spontaneously rearranges to yield 6-oxohexanoate. 4. An enzyme capable of attacking cyclohexan-1,2-dione (mono-enol) in the absence of an electron donor or oxygen has also been detected. Evidence has been presented indicating that this enzyme catalyses a keto-enol tautomerization between cyclohexan-1,2-dione (mono-enol) and cyclohexan-1,2-dione (mono-hydrate) and is not involved in the pathway of ring cleavage. 5. The failure of Acinetobacter TD63 to grow with cyclohexanol, cyclohexanone or 1-oxa-2-oxocycloheptane is due not to this organism possessing a distinctive metabolic sequence but to a narrow inducer specificity coupled with an inability to form a lactone hydrolase enabling it to cleave the stable 1-oxa-2-oxocycloheptane which is an intermediate in the established pathway of cyclohexanol and cyclohexanone oxidation.

Acinetobacter

Partial purification and characterization of the lipase of a facultatively psychrophilic bacterium (Acinetobacter O16).

The extracellular lipase(s) of the psychrophile Acinetobacter O16 was studied. When the enzyme was precipitated by (NH4)2SO4 and passed through a Sephadex G200 column, two peaks of lipase activity appeared. The larger peak, which behaved like a substance of high molecular weight, being eluted in the void volume, was purified 250-fold over the crude enzyme (culture supernatant) by passage through a DEAE-Sephadex column. When the enzyme was applied to a DEAE-cellulose column it could not be eluted unless it had first been treated with the detergent Titon X 100. It is suggested that lipids or phospholipids make up an important part of the molecule. The activity of the crude and partly purified enzymes was studied in relation to pH and temperature optima. Lipases from the psychrophilic Acinetobacter O16 and from the mesophilic Acinetobacter O4 reacted in the same way to temperature. The crude enzyme from Acinetobacter O16 was more temperature-stable than the purified enzyme.

Acinetobacter

Occurrence of blaOXA-72 in a clinical isolate of carbapenem-resistant Acinetobacter pittii ST206 in Japan.

The development of carbapenem resistance in Acinetobacter spp., which are recognized as significant opportunistic pathogens, is of critical importance as it poses challenges to therapy and the control of healthcare-associated infections in clinical settings. This study investigated the genetic characteristics of a carbapenem-resistant A. pittii clinical isolate from a university hospital using whole-genome sequencing. The A. pittii strain SU8507, which was detected in the abdominal drainage fluid of a patient, exhibited resistance to imipenem (MIC: 128 μg/mL) and meropenem (MIC: 64 μg/mL) and produced positive results by the CIMTris method. A. pittii SU8507, belonging to ST206, harbored the blaOXA-72 and new variants of intrinsic blaOXA-213-like gene blaOXA-1222, which lacks an upstream insertion sequence element, and blaADC-1-like gene blaADC-343. The blaOXA-72 gene, flanked by XerC/XerD-like recombination sites, was located on a plasmid pSU8507, sized at 10,913 bp, carrying 13 predicted protein-coding genes. Complete pSU8507 containing mobA, repB, and the yoeB-yefM toxin-antitoxin genes, showed 98.9% nucleotide sequence identity and 75% coverage with plasmid pA2702 of the A. baylyi strain A2702, but a low BLAST MAX score. SU8507 harbored virulence genes involved in biofilm formation, types II and VI secretion systems, type IV pilus system, and serum resistance. This study describes the first isolation of an OXA-72-producing, carbapenem-resistant A. pittii clinical isolate in Japan. Given that the isolation rate of carbapenem-resistant Acinetobacter spp. Remains low in Japan, it is crucial to expand the scope of rapid, accurate carbapenemase detection to include not only A. baumannii, but also non-baumannii Acinetobacter spp.

Humans

A regulator of amino acid catabolism controls Acinetobacter baumannii gut colonization.

Asymptomatic gut colonization increases the risk of clinical infection and transmission by the multidrug-resistant pathogen Acinetobacter baumannii. Ornithine utilization was shown to be critical for A. baumannii competition with the resident microbiota to persist in gut colonization, but the regulatory mechanisms and cues are unknown. Here, we identify a transcriptional regulator, AstR, that specifically activates the expression of the A. baumannii ornithine utilization operon astNOP. Phylogenetic analysis suggests that AstR was co-opted from the Acinetobacter arginine utilization ast(G)CADBE locus and is specialized to regulate ornithine utilization in A. baumannii. Reporter assays showed that astN promoter expression was activated by ornithine but inhibited by glutamate and other preferred amino acids. astN promoter expression was similarly activated by incubation with fecal samples from conventional mice but not germ-free mice, suggesting AstR-dependent activation of the astN promoter responds to intermicrobial competition for amino acids. Finally, AstR was required for A. baumannii to colonize the gut in a mouse model. Together, these results suggest that pathogenic Acinetobacter species evolved AstR to regulate ornithine catabolism, which is required to compete with the microbiota during gut colonization.

Animals

Infections with Acinetobacter calcoaceticus (Herellea vaginicola): clinical and laboratory studies.

In a retrospective review of 53 patients, 58 episodes of infection due to Acinetobacter calcoaceticus var. anitratus (Herellea vaginicola) were studied. Although the organism is widely distributed in nature, it is of relatively low virulence since colonization is more frequently noted than infection and since most infections occur in patients subjected to the epidemiologic pressures common to nosocomial, gram-negative bacillary infection: prior antibiotic therapy; instrumentation and manipulation (e.g., endotracheal intubation, urinary bladder catheterization, arterial and venous cannulation); surgery; hospitalization, especially with residence in an intensive care unit; severe underlying disease, either systemic (e.g., chronic obstructive pulmonary disease, malignancy) or localized to the infected area (e.g., prior bacterial or aspirational pneumonia, trauma). Pneumonia was the most common infection due to A. calcoaceticus, and occurred only in patients with a tracheostomy or endotracheal tube in place. In over half the 25 patients, more than one lobe was involved and bronchopneumonia was the usual roentgenographic appearance. Cavitation (2 patients) and empyema formation (3 patients) were uncommon. The severity of acinetobacter pneumonia is reflected in the high mortality rate (44% overall, with a 36% mortality rate due primarily to infection). Tracheobronchitis due to A. calcoaceticus was less severe than pneumonia since no patients died primarily as a result of the infection. Urinary tract infections occurred in five patients, none of whom were ill and none of whom died. Urinary bladder catheterization was thought to be responsible for infection in three patients, and in at least four of the five patients infection was restricted to the lower tract. Wound infections were noted in six patients who had undergone surgery and were related to the presence of foreign bodies in the operative site in five of the patients. Surgical debridement and/or drainage of the infected area was the primary therapeutic measure employed in most cases. Only one patient died and this was a result of noninfectious causes. Skin infection due to A. calcoaceticus was seen in two patients, one of whom exhibited fulminant, fatal cellulitis and septicemia in the setting of pancytopenia. All nine patients with acinetobacter septicemia had received antecedent antibiotic therapy, and in all cases intravenous catheters were in place at the time bacteremia occurred. Clinically, seven of the nine patients were in shock. The mortality rate was 44% overall, with a 22% mortality rate due to infection. Although septicemia was thought to be "line-related" in five of the nine patients, serious post-bacteremic complications developed in three patients: prosthetic valve endocarditis, suppurative thrombophlebitis and subhepatic abscess.

Acinetobacter

Acinetobacter and similar organisms in ear infections.

Fifty-seven strains of acinetobacter-like organisms were isolated over a period of 26 months from the ears of 55 patients with acute or chronic otitis media, or otitis externa, and one strain was isolated in a survey of 50 normal ears. After comparison with eight reference strains, 32 of the isolates were identified as Acinetobacter anitratus, 22 as Acinetobacter Iwoffii, three as Moraxella spp. and one as Achromobacter sp. Analysis of the clinical findings suggests that although most of these organisms played little part in the disease process, a few strains were probably pathogenic in this situation.

Acinetobacter

Serological cross-reactions between Acinetobacter calcoaceticus and chlamydiae.

A cross-reaction between Acinetobacter calcoaceticus and chlamydiae is described. A water-soluble, heat stable, non-dialyzable antigen was extracted from Acinetobacter species by boiling. This antigen fixed complement in the presence of homologous hyperimmune sera from rabbits or guinea pigs and in the presence of heterologous human or hyperimmunized animal sera containing chlamydial antibodies. Hyperimmune antisera to the extracted antigen, or to suspensions of live acinetobacters, also reacted in complement fixation with a group-specific antigen.

Acinetobacter

Acinetobacter and E. coli lipopolysaccharide preparations comparative mitogenicity and induction in vitro of immunoglobulin synthesis in adult and neonatal pig lymphocytes.

Lipopolysaccharide (LPS) was prepared by phenol/water extraction of bacterial membranes prepared from Acinetobacter and Escherichia coli. The mitogenicity of laboratory-prepared LPS was significantly greater than that of commercial E. coli LPS for pig, sheep, calf and rat lymphocytes, assayed as [3H]-thymidine incorporation. Mouse lymphocytes responded well to commercial LPS and no greater response was obtained with other LPS preparations. A small proportion (14%) of the Acinetobacter LPS preparations was soluble in aqueous medium, the remainder comprising membraneous fragments of variable form and size. It is suggested that the insoluble presentation of LPS to cells may contribute to the improved mitogenicity compared with wholly soluble LPS. Acinetobacter LPS preparations were used to induce synthesis and secretion in vitro of immunoglobulin by adult blood lymphocytes and pre-suckled, neonatal spleen cells of the pig. IgM was the dominant class of immunoglobulin secreted. This work thus demonstrated that virgin, unprimed B cells could be induced into immunoglobulin secretion by mitogen stimulation.

Acinetobacter

[Cytochrome composition of Acinetobacter calcoaceticus].

The qualitative and quantitative composition of cytochromes in intact cells of Acinetobacter calcoaceticus and in particle fractions obtained from cells following ultrasonic treatment by differential centrifugation were studied using spectrophotometric methods. Acinetobacter calcoaceticus contains cytochrome b, cytochrome o and low amounts of cytochrome d. Both the absolute content of cytochrome b and o and the relative composition do not essentially vary with the carbon source used (hexadecane, acetate, succinate, malate, yeast extract). Only bacterial cultivated on yeast extract show, under simultaneous decrease of the content of cytochrome o, an increased formation of cytochrome d. In Acinetobacter, cytochromes appear not to be immediately involved in n-alkane hydroxylation.

Acinetobacter

Characterization of blaOXA-542-mediated carbapenem resistance in Acinetobacter baumannii.

BACKGROUND: Carbapenem-resistant Acinetobacter baumannii (CRAB) causes multiple anatomical site infections, representing a significant public health threat. AIM: This study reports the isolation and characterization of a carbapenem-resistant A. baumannii harbouring blaOXA-542, followed by a comprehensive investigation of its antimicrobial resistance mechanisms and genomic characteristics. METHODS: Firstly, antimicrobial susceptibility testing was performed using the broth microdilution method. Subsequently, whole-genome sequencing was employed to identify and characterize the resistance and virulence determinants. The functional validation of resistance mechanisms was performed by gene knockdown and construction of expression vectors. The fitness cost of β-lactamase expression was identified by a bacterial growth kinetic test. Molecular docking was utilized to predict potential binding sites of β-lactamase and carbapenems. Finally, the genetic characteristics of the isolates were analysed through comparative genomics analyses and phylogenetic tree construction. RESULTS AND CONCLUSIONS: The results demonstrated that blaOXA-542 confers resistance to carbapenem and penicillin in A. baumannii and Escherichia coli while exhibiting no significant impact on cephalosporins. The ability of blaOXA-542 to hydrolyze meropenem was further confirmed by modified carbapenem inactivation assay (mCIM). Expression of blaOXA-542 in E. coli BL21 showed no significant growth rate alteration. Comparative analysis of the blaOXA-542 genetic environment revealed a close association with Acinetobacter pitti. This study reports the emergence of blaOXA-542-mediated carbapenem and penicillin resistance in a novel A. baumannii lineage (ST2795Pas/ST3464Oxf), highlighting the urgent need for rational antibiotic use against specific pathogens.

Acinetobacter baumannii

Acinetobacter anitratus infections in man.

During a period of 17 months, 142 strains of Acinetobacter anitratus were isolated from 140 patients. They were examined for biochemical characteristics, antibiotic susceptibilities to 15 chemotherapeutic drugs and clinical and epidemiologic features. Biochemical studies were necessary for positive identification of this gram negative rod. Many isolates were susceptible to kanamycin, gentamicin, polymixin B, cotrimoxazole and nalidixic acid. Most isolates were hospital acquired and had been cultured from a number of anatomic sites in the presence of a variety of clinical situations. Acinetobacter anitratus was the primary infecting organism in two cases of septicaemia (one fatal), two pneumonias, two wound infections and six urinary tract infections. Because of its potential pathogenicity this organism should not be dismissed as a harmless commensal by laboratory staff and clinicians.

Acinetobacter

Acinetobacter septicaemia following prolonged intravenous therapy.

A 76-year-old man developed septicaemia during the infusion of stable plasma protein solution (SPPS) which was subsequently shown to be contaminated with Acinetobacter anitratus. Septicaemia persisted for four days despite change of the intravenous cannula and administration of an appropriate antibiotic. Clinical improvement occurred only when the entire intravenous line, (infusion bottle, airway needle, giving set and intravenous cannula), all of which grew Acinetobacter, was replaced. Contamination of the SPPS probably occurred in the ward via a contaminated giving set and airway needle, which had been in use for one week. This case illustrates the importance of following accepted guidelines for infection control in intravenous therapy.

Acinetobacter

Outbreak of a multiply resistant Acinetobacter in a surgical intensive care unit: epidemiology and control.

During January, 1976 seven patients in an SICU became colonized or infected with Acinetobacter calcoaceticus (variation, anitratum) at an attack rate of 12.5 per cent. The organism showed a marked reduction in antimicrobial sensitivity from previous experience. Comparison with 34 uninfected control patients indicated that intubation and continuous ventilatory assistance were significantly associated with acquiring the organism (p = 0.0154). Acinetobacter was cultured from nurses' hands, AMBU adaptors, respirator apparatus, respirometers, and unlabeled bottles of saline used for tracheal irrigation. Control measures were designed to interrupt transmission. The investigation identified the nursing techniques and reservoirs that allowed this outbreak to occur, and we emphasize the need for close surveillance of patient care procedures in an intensive care unit.

Acinetobacter

Community-acquired Acinetobacter calcoaceticus var anitratus pneumonia.

Two patients had community-acquired Acinetobacter calcoaceticus var anitratus pneumonia. Both patients were alcoholic and one was cirrhotic. One patient died and the other received two weeks of gentamicin therapy and survived. Misinterpretation of the sputum Gram stain delayed diagnosis and institution of proper therapy in both cases. In addition to organisms sensitive to penicillins such as Neisseria or Haemophilus, Acinetobacter must be considered in the differential diagnosis of community-acquired Gram-negative coccobacillary pneumonia.

Acinetobacter