Characterization of N-acylhomoserine lactone-degrading bacteria associated with the Zingiber officinale (ginger) rhizosphere: Co-existence of quorum quenching and quorum sensing in Acinetobacter and Burkholderia

Background Cell-to-cell communication (quorum sensing (QS)) co-ordinates bacterial behaviour at a population level. Consequently the behaviour of a natural multi-species community is likely to depend at least in part on co-existing QS and quorum quenching (QQ) activities. Here we sought to discover novelN-acylhomoserine lactone (AHL)-dependent QS and QQ strains by investigating a bacterial community associated with the rhizosphere of ginger (Zingiber officinale) growing in the Malaysian rainforest. Results By using a basal growth medium containing N-(3-oxohexanoyl)homoserine lactone (3-oxo-C6-HSL) as the sole source of carbon and nitrogen, the ginger rhizosphere associated bacteria were enriched for strains with AHL-degrading capabilities. Three isolates belonging to the generaAcinetobacter (GG2), Burkholderia (GG4) and Klebsiella (Se14) were identified and selected for further study. Strains GG2 and Se14 exhibited the broadest spectrum of AHL-degrading activities via lactonolysis while GG4 reduced 3-oxo-AHLs to the corresponding 3-hydroxy compounds. In GG2 and GG4, QQ was found to co-exist with AHL-dependent QS and GG2 was shown to inactivate both self-generated and exogenously supplied AHLs. GG2, GG4 and Se14 were each able to attenuate virulence factor production in both human and plant pathogens. Conclusions Collectively our data show that ginger rhizosphere bacteria which make and degrade a wide range of AHLs are likely to play a collective role in determining the QS-dependent phenotype of a polymicrobial community.

Comparative genomic analysis of novel Acinetobacter symbionts : A combined systems biology and genomics approach

Acknowledgements This work was supported by University of Delhi, Department of Science and Technology- Promotion of University Research and Scientific Excellence (DST-PURSE). V.G., S.H. and U.S. gratefully acknowledge the Council for Scientific and Industrial Research (CSIR), University Grant Commission (UGC) and Department of Biotechnology (DBT) for providing research fellowship.

Demonstration of the interactions between aromatic compound-loaded lipid nanocapsules and Acinetobacter baumannii bacterial membrane

International audience

Complete genome of the multidrug-resistant Acinetobacter baumannii strain KBN10P02143 isolated from Korea

Acinetobacter baumannii , a strictly aerobic, non-fermentative, Gram-negative coccobacillary rod-shaped bacterium, is an opportunistic pathogen in humans. We recently isolated a multidrug-resistant A. baumannii strain KBN10P02143 from the pus sample drawn from a surgical patient in South Korea. We report the complete genome of this strain, which consists of 4,139,396 bp (G + C content, 39.08%) with 3,868 protein-coding genes, 73 tRNAs and six rRNA operons. Identification of the genes related to multidrug resistance from this genome and the discovery of a novel conjugative plasmid will increase our understanding of the pathogenicity associated with this species.

Estrategias de supervivencia de Acinetobacter baumannii en el ámbito hospitalario.

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Anti-biofilm and antimicrobial activity of Mentha pulegium L essential oil against multidrug-resistant Acinetobacter baumannii

Purpose: To investigate the antimicrobial and anti-biofilm activities of essential oil from Mentha pulegium L. (EOMP) on multi-drug resistant (MDR) isolates of A. baumannii , as well as its phytochemical composition, antioxidant properties and cytotoxic activity. Methods: The phytochemical composition of EOMP was analyzed by gas chromatography, while its antimicrobial activities were determined by disc diffusion and broth micro-dilution methods. Minimal biofilm inhibition concentration (MBIC) and minimal biofilm eradication concentration (MBEC) tests were used for assessment of its anti-biofilm properties. Viability in the biofilm was studied using 2,3-bis (2- methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) assay, while colorimetric assay was used to assess its cytotoxicity on L929 cells. Results: D-isomenthone, pulegone, isopulegone, menthol and piperitenone were the major components of the plant extract. EOMP produced > 22 mm inhibition zone for the isolates, with minimum inhibitory concentration (MIC) and MBIC of 0.6 - 2.5 and 0.6 - 1.25 μL/mL, respectively, while MBEC was ≥ 10 μL/msL. EOMP damaged biofilm structures formed by A. baumannii strains at MIC by 26 – 91 %. Conclusion: These results suggest that EOMP contains agents that may be useful in the development of new drugs against A. baumannii infections.

Aspectos técnicos da monitorização da pressão intracraniana pelo método subaracnóideo no traumatismo craniencefálico grave

Two hundred and six patients with severe head injury (Glasgow Coma Scale of 8 points or less after nonsurgical resuscitation on admission), managed at Intensive Care Unit-Hospital das Clínicas - Universidade Estadual de Campinas were prospectively analysed. All patients were assessed by CT scan and 72 required neurosurgical intervention. All patients were continuously monitored to evaluate intracranial pressure (ICP) levels by a subarachnoid device (11 with subarachnoid metallic bolts and 195 with subarachnoid polyvinyl catheters). The ICP levels were continuously observed in the bedside pressure monitor display and their end-hour values were recorded in a standard chart. The patients were managed according to a standard protocol guided by the ICP levels. There were no intracranial haemorrhagic complications or hematomas due the monitoring method. Sixty six patients were punctured by lateral C1-C2 technique to assess infectious complications and 2 had positive cerebrospinal fluid samples for Acinetobacter sp. The final results measured at hospital discharge showed 75 deaths (36,40%) and 131 (63,60%) survivors. ICP levels had significantly influenced the final results (p<0,001). The subarachnoid method to continuously assess the ICP levels was considered aplicable, safe, simple, low cost and useful to advise the management of the patients. The ICP record methodology was practical and useful. Despite the current technical advances the subarachnoid method was considered viable to assess the ICP levels in severe head injury.

Carbapenem stewardship: positive impact on hospital ecology

INTRODUCTION: Excessive group 2 carbapenem use may result in decreased bacterial susceptibility. OBJECTIVE: We evaluated the impact of a carbapenem stewardship program, restricting imipenem and meropenem use. METHODS: Ertapenem was mandated for ESBL-producing Enterobacteriaceae infections in the absence of non-fermenting Gram-negative bacilli (GNB) from April 2006 to March 2008. Group 2 carbapenems were restricted for use against GNB infections susceptible only to carbapenems and suspected GNB infections in unstable patients. Cumulative susceptibility tests were done for nosocomial pathogens before and after restriction using Clinical and Laboratory Standards Institute (CLSI) guide-lines.Vitek System or conventional identification methods were performed and susceptibility testing done by disk diffusion according to CLSI.Antibiotic consumption (t-test) and susceptibilities (McNemar's test) were determined. RESULTS: The defined daily doses (DDD) of group 2 carbapenems declined from 61.1 to 48.7 DDD/1,000 patient-days two years after ertapenem introduction (p = 0.027). Mean ertapenem consumption after restriction was 31.5 DDD/1,000 patient-days. Following ertapenem introduction no significant susceptibility changes were noticed among Gram-positive cocci. The most prevalent GNB were P. aeruginosa, Klebsiella pneumoniae, and Acinetobacter spp. There was no change in P. aeruginosa susceptibility to carbapenems. Significantly improved P. aeruginosa and K. pneumoniae ciprofloxacin susceptibilities were observed, perhaps due to decreased group 2 carbapenem use. K. pneumoniae susceptibility to trimethoprim-sulfamethoxazole improved. CONCLUSION: Preferential use of ertapenem resulted in reduced group 2 carbapenem use, with a positive impact on P. aeruginosa and K. pneumoniae susceptibility.

Rates of antimicrobial resistance in latin america (2004-2007) and in vitro activity of the glycylcycline tigecycline and of other antibiotics

As a part of the Tigecycline Evaluation and Surveillance Trial (T.E.S.T.), Gram-positive and Gram-negative bacterial isolates were collected from 33 centers in Latin America (centers in Argentina, Brazil, Chile, Colombia, Guatemala, Honduras, Jamaica, Mexico, Panama, Puerto Rico, and Venezuela) from January 2004 to September 2007. Argentina and Mexico were the greatest contributors of isolates to this study. Susceptibilities were determined according to Clinical Laboratory Standards Institute guidelines. Resistance levels were high for most key organisms across Latin America: 48.3% of Staphylococcus aureus isolates were methicillin-resistant while 21.4% of Acinetobacter spp. isolates were imipenem-resistant. Extended-spectrum β-lactamase were reported in 36.7% of Klebsiella pneumoniae and 20.8% of E. coli isolates. Tigecycline was the most active agent against Gram-positive isolates. Tigecycline was also highly active against all Gram-negative organisms, with the exception of Pseuodomonas aeruginosa, against which piperacillin-tazobactam was the most active agent tested (79.3% of isolates susceptible). The in vitro activity of tigecycline against both Gram-positive and Gram-negative isolates indicates that it may be an useful tool for the treatment of nosocomial infections, even those caused by organisms that are resistant to other antibacterial agents.

Biotransformations of Substituted Phenylethanols and Acetophenones by Environmental Bacteria

Whole cells of hydrocarbon-degrading bacteria, isolated from polluted sediments in the Santos Estuary (Baixada Santista, Sao Paulo, Brazil), were able to catalyse oxidoreduction reactions with various substituted phenylethanols and acetophenones as substrates. A number of substituted phenylethanols were formed with high (>99 %) enantiomeric excess. The results of microbial oxidation of phenylethanols 2, 3, 5-7 by Acinetobacter sp. 6.4T and the reduction of acetophenones 1a-6a by Serratia marcescens 5.4T showed that the bacteria used as biocatalysts in this study present significant potential for exploitation in biotechnological processes. The reduction of prochiral acetophenones by Serratia marcescens 3.5T yielded optically active alcohols with 90-99 % enantiomeric excess, and Acinetobacter sp. 6.4T is a potential biocatalyst for the oxidation of alcohols.

Bacterial stimulation of copper phytoaccumulation by bioaugmentation with rhizosphere bacteria

Copper contaminated areas pose environmental health risk to living organisms. Remediation processes are thus required for both crop production and industrial activities. This study employed bioaugmentation with copper resistant bacteria to improve phytoremediation of vineyard soils and copper mining waste contaminated with high copper concentrations. Oatmeal plant (Avena sativa L) was used for copper phytoextraction. Three copper resistant bacterial isolates from oatmeal rhizosphere (Pseudomonas putida A1 Stenotrophomonas maltophilia A2 and Acinetobacter calcoaceticus A6) were used for the stimulation of copper phytoextraction. Two long-term copper contaminated vineyard soils (Mollisol and Inceptisol) and copper mining waste from Southern Brazil were evaluated. Oatmeal plants substantially extracted copper from vineyard soils and copper mining waste. As much as 1549 mg of Cu kg(-1) dry mass was extracted from plants grown in Inceptisol soil. The vineyard Mollisol copper uptake (55 mg Cu kg(-1) of dry mass) in the shoots was significantly improved upon inoculation of oatmeal plants with isolate A2 (128 mg of Cu kg(-1) of shoot dry mass). Overall oatmeal plant biomass displayed higher potential of copper phytoextraction with inoculation of rhizosphere bacteria in vineyard soil to the extent that 404 and 327 g ha(-1) of copper removal were respectively observed in vineyard Mollisol bioaugmented with isolate A2 (S. maltophilia) and isolate A6 (A. calcoaceticus). Results suggest potential application of bacterial stimulation of phytoaccumulation of copper for biological removal of copper from contaminated areas. (C) 2010 Elsevier Ltd. All rights reserved.

Polymyxin B and colistimethate are comparable as to efficacy and renal toxicity

We compared 41 patients who received colistimethate with 41 who received polymyxin B for the treatment of serious infections caused by carbapenem-resistant Acinetobacter spp. and found both polymyxins have similar efficacy and toxicity. (C) 2009 Elsevier Inc. All rights reserved.

The challenge of multidrug resistance: The treatment of gram-negative rod infections

Infections caused by multidrug-resistant gram-negative bacteria are an increasing problem worldwide. Treatment of these microorganisms is a challenge because resistance limits dramatically therapeutic options. In this review, we discuss data of in vitro susceptibility and clinical studies of possible agents for the management of these infections. Currently, published data are limited, and there are no randomized clinical trials involving the treatment of infections caused by multidrug-resistant gram-negative rods. For imipenem-resistant Acinetobacter spp., most studied options are polymyxins and sulbactam. No newer antimicrobials active against Pseudomonas aeruginosa are available or under investigation. Tigecycline presents a broad spectrum of activity in vitro but has been studied mainly as treatment of community-acquired infections, as has ertapenem. They are potential options against extended-spectrum P-lactamase-producing Enterobacteriaceae, and tigecycline may be useful in treating Acinetobacter infections.

A survey of bacterial diversity in ticks, lice and fleas from Australia

We isolated bacteria from ticks, lice and fleas. Partial small subunit rRNA sequences were obtained for each isolate and the closest matches in the FastA database were determined. These bacteria were mostly Gram-positive (Firmicutes), although representatives from the Proteobacteria (alpha, beta, gamma subdivisions) and CFB group were also isolated. Most of the isolates we found were from genera that were present in most of the ectoparasites studied, but a few genera were restricted to one species of ectoparasite. The most commonly isolated genera were Stenotrophomonas, Staphylococcus, Pseudomonas, Acinetobacter and Bacillus. Species of Bacillus and Proteus, which have biopesticide potential, were found in some of these ectoparasites. Overall, the communities of bacteria were similar to those found in other studies of parasitic arthropods.

Weather parameters and nosocomial bloodstream infection: a case-referent study

OBJECTIVE To evaluate if temperature and humidity influenced the etiology of bloodstream infections in a hospital from 2005 to 2010.METHODS The study had a case-referent design. Individual cases of bloodstream infections caused by specific groups or pathogens were compared with several references. In the first analysis, average temperature and humidity values for the seven days preceding collection of blood cultures were compared with an overall “seven-days moving average” for the study period. The second analysis included only patients with bloodstream infections. Several logistic regression models were used to compare different pathogens and groups with respect to the immediate weather parameters, adjusting for demographics, time, and unit of admission.RESULTS Higher temperatures and humidity were related to the recovery of bacteria as a whole (versus fungi) and of gram-negative bacilli. In the multivariable models, temperature was positively associated with the recovery of gram-negative bacilli (OR = 1.14; 95%CI 1.10;1.19) or Acinetobacter baumannii (OR = 1.26; 95%CI 1.16;1.37), even after adjustment for demographic and admission data. An inverse association was identified for humidity.CONCLUSIONS The study documented the impact of temperature and humidity on the incidence and etiology of bloodstream infections. The results correspond with those from ecological studies, indicating a higher incidence of gram-negative bacilli during warm seasons. These findings should guide policies directed at preventing and controlling healthcare-associated infections.