BackgroundAcinetobacter baumannii is emerging as an important nosocomial pathogen. Multidrug resistance, as well as ability to withstand environmental stresses, makes eradication of A. baumannii difficult, particularly from hospital settings.ResultsOver a six-year period, 73 isolates of A. baumannii were collected from infected patients in two hospitals in Italy. While 69 out of the 73 isolates displayed identical multidrug antibiotic resistance pattern, they were susceptible to carbapenems. Genetic profiles of these 69 isolates, determined by Pulsed Field Gel Electrophoresis (PFGE), indicated that they were genetically related and could be clustered in a specific clone, called SMAL. We tested the ability of the SMAL clone to form biofilm, an important determinant for bacterial colonization of the human host and for persistence in the hospital environment. Biofilm formation by A. baumannii SMAL, measured as surface adhesion to polystyrene, is strongly affected by growth conditions, being impaired in rich growth media such as LB, while being favoured in glucose-based medium. Surface adhesion in glucose-based media is inhibited by treatment with cellulase, suggesting that it depends on production of cellulose or of a chemically related extracellular polysaccharide. Exposure of A. baumannii SMAL to subinhibitory concentrations of imipenem resulted in biofilm stimulation and increased production of iron uptake proteins. Growth in iron-supplemented medium also stimulated surface adhesion, thus suggesting that increased intracellular iron concentrations might act as an environmental signal for biofilm formation in A. baumannii SMAL.ConclusionsOur results indicate that exposure to subinhibitory concentrations of imipenem can stimulate biofilm formation and induce iron uptake in a pathogenic strain of A. baumannii, with potential implications on antibiotic susceptibility and ability to persist in the human host.

New Delhi metallo-␤-lactamase (NDM-1) was initially identified in various Enterobacteriaceae and recently in Acinetobacter baumannii. This study described the clonal dissemination of an NDM-2-producing A. baumannii isolate in an Israeli rehabilitation ward and the genetic surroundings of the gene. The bla NDM-2 gene was surrounded by the ble and trpF genes downstream and two copies of the ISAba125 on both sides. These are the first NDM-producing A. baumannii strains in Israel from patients with no previous travel or hospitalization on the Indian subcontinent.Carbapenem resistance in Gram-negative bacteria is an important worldwide problem, particularly because of the production of class A, D, and B metallo-␤-lactamase enzymes (MBLs) as a resistance mechanism and the facility to spread by mobile genetic elements (12). The new MBL, New Delhi metallo-␤-lactamase 1 (NDM-1), initially reported in Klebsiella pneumoniae and Escherichia coli recovered from a Swedish patient who was previously hospitalized in India (23), has disseminated to several countries and other Enterobacteriaceae (4,9,13,(15)(16)(17)(18)22). Recently, cases of NDM-producing Acinetobacter baumannii have been described in India, Egypt, and China (1, 6, 8).Five carbapenem-resistant A. baumannii isolates were recovered from female patients at the TA-Sourasky-MA Rehabilitation hospital in Tel Aviv, Israel (Table 1). The five elderly patients (mean age, 81) were hospitalized in the same geriatric rehabilitation ward. The cultures were taken as a point prevalence study from 70 patients hospitalized in two wards in the rehabilitation center. Surveillance skin cultures were taken from six body sites (armpit, thigh, and groin, bilaterally). Four of the five patients were admitted to rehabilitation after orthopedic surgery in two different orthopedic wards located in the same hospital, adjacent to the rehabilitation center. Three of the patients shared a room with each other at a point during their hospital stay, and others shared with them common facilities. None of the patients had any clinical culture that grew Acinetobacter spp., and no signs of infection due to Acinetobacter were evident. There was no specific history taken regarding travel (Table 1). Isolates were initially identified using the Vitek-2 automatic system (bioMérieux, Marcy, France) and confirmed by amplified rRNA gene restriction analysis (ARDRA) (20). The epidemiological relationship was corroborated by pulsed-field gel electrophoresis (PFGE) under conditions described elsewhere (10). PFGE results showed an identical pattern for all the strains. Multiplex PCR to identify clonal lineages (19) showed that the strains did not belong to pan-European clone I, II, or III. Multilocus sequence typing (MLST) indicated that the strain corresponded to sequence type (ST) 103 according to the Pasteur system (http://www.pasteur.fr /recherche/genopole/PF8/mlst/Abaumannii.html), which is in agreement with the ST found in the NDM-2-producing A. baumannii isolate reported from Egypt (6).Antibiotic suscep...

This study was aimed at tracing the molecular characteristics of carbapenem-resistant Acinetobacter baumannii (CRAB) clinical isolates in Italy with both pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Two hundred and two CRAB isolates were collected during 2004-2009, in two different surveillance periods, from 22 Italian hospitals that were representative for both distribution and infection. PFGE was performed, and the MLST scheme used was based on the gene sequence as published on the MLST Pasteur website http://www.pasteur.fr/mlst. Representatives of the major European clones I (RUH 875) and II (RUH 134) were used as controls. The two groups of isolates were characterized for their carbapenem resistance genes: 154 of 202 carried bla(OXA-58) alone, 21 of 202 also carried bla(OXA-23) , and 27 of 202 carried bla(OXA-23) alone. No isolates were positive for bla(OXA-24) . Genotype analysis of all isolates identified four distinct patterns by PFGE, which correlated with four distinct sequence types (STs) by MLST. The distribution of these four clusters in Italy confirmed the propensity of A. baumannii for nosocomial cross-transmission in a vast geographical area. We observed that clones A and B had similarities with European clone II and I respectively. By MLST, clone A was ST2, like European clone II, and clone B was ST1, like European clone I. PFGE and MLST showed the same discriminatory power and reproducibility. In addition, the two methods were concordant in defining CRAB Italian clones and in correlating them with the two pan-European clones.

No abstract

Acinetobacter baumannii is a pathogenic organism that posesses a serious health threat because of the occurrence of the large number of (multi)drug‐resistant strains. It can persist for prolonged periods in the hospital environment, infecting debilitated or immune‐compromised patients. In this context, the endotoxin portion of the lipopolysaccharide, the lipid A, plays an important role in the pathogenesis of this bacterium, because it triggers the innate immune response and contributes to the inflammation state of the patient. In this study, the complete structure of the lipooligosaccharide has been determined. The saccharide backbone of the molecule was disclosed through chemical and spectroscopic analysis, whereas the lipid A moiety required detailed MS spectrometry and chemical investigations. The oligosaccharide backbone was found to be similar to that of A. baumannii ATCC 19606, although the LOS from the SMAL strain presented an enhanced zwitterionic character. The lipid A moiety comprises a heterogeneous and complex mixture of molecules: it possesses a conserved diphosphorylated disaccharide backbone substituted by three to seven fatty acids. The hexaacylated species appeared as the most abundant, and its chemical features, namely the number and the types of fatty acids, indicates its potential endotoxic activity.

A patient who developed a unilateral opercular syndrome following a cerebrovascular accident is described. Computed tomography showed that the lesion did not affect the opercular cortex, but involved deep white matter and the head of the caudate nucleus of the left hemisphere. Persistent hypophonia and transient aphasia were associated. Comparison with previous cases is discussed.

No abstract

No abstract