What treatment for periprosthetic shoulder infection? Results from a multicentre retrospective series.

PURPOSE: Controversy still exists as to the best surgical treatment for periprosthetic shoulder infections. The aim of this multi-institutional study was to review a continuous retrospective series of patients treated in four European centres and to assess the respective eradication rate of various treatment approaches. METHODS: Forty-four patients were available for this retrospective follow-up evaluation. Functional and clinical evaluation of treatment for infection was performed using the Constant-Murley score, visual analogue scale and patient satisfaction Neer score. Erythrocyte sedimentation rate, serum leucocyte count and C-reactive protein were measured and shoulder X-ray examination performed prior to surgery and at the latest follow-up. RESULTS: At a mean follow-up of 41 months (range 24-98), 42 of 44 patients (95.5%) showed no signs of infection recurrence/persistence. Comparable eradication rates were observed after resection arthroplasty (100%; 6/6), two-stage revision (17/17) or permanent antibiotic-loaded spacer implant (93.3%; 14/15). No patient was treated by one-stage revision. On average, both functional and pain scores improved significantly; the worst joint function was observed after resection arthroplasty. CONCLUSIONS: This retrospective analysis conducted on the largest published series of patients to date shows comparable infection eradication rates after two-stage revision, resection arthroplasty or permanent spacer implant for the treatment of septic shoulder prosthesis.

Salmonella epidural abscess in sickle cell disease: failure of the nonsurgical treatment.

In patients suffering from sickle cell disease (SCD), bone is a preferred site of infection. We report the case of a five-year-and-eight-month-old black African boy with homozygous-SS disease who developed a cranial epidural abscess. This intracranial infectious complication originated from a Salmonella enteritidis osteitis of the frontal bone. Antibiotic treatment alone did not control the disease, so surgery was necessary to remove the necrotic bone and to evacuate the epidural pus. The numerous factors interfering with normal healing of a septic focus in sickle cell anemia, particularly in this previously undescribed intracranial complication, emphasize the need for a primary and early surgical treatment in similar situations.

Immune responses to Helicobacter pylori infection.

Helicobacter pylori (H. pylori) infection is one of the most common infections in human beings worldwide. H. pylori express lipopolysaccharides and flagellin that do not activate efficiently Toll-like receptors and express dedicated effectors, such as γ-glutamyl transpeptidase, vacuolating cytotoxin (vacA), arginase, that actively induce tolerogenic signals. In this perspective, H. pylori can be considered as a commensal bacteria belonging to the stomach microbiota. However, when present in the stomach, H. pylori reduce the overall diversity of the gastric microbiota and promote gastric inflammation by inducing Nod1-dependent pro-inflammatory program and by activating neutrophils through the production of a neutrophil activating protein. The maintenance of a chronic inflammation in the gastric mucosa and the direct action of virulence factors (vacA and cytotoxin-associated gene A) confer pro-carcinogenic activities to H. pylori. Hence, H. pylori cannot be considered as symbiotic bacteria but rather as part of the pathobiont. The development of a H. pylori vaccine will bring health benefits for individuals infected with antibiotic resistant H. pylori strains and population of underdeveloped countries.

Regulation of mucoidy in the biological control agent Pseudomonas fluorescens CHA0 and construction of an exopolysaccharide-overproducing variant

Pseudomonas fluorescens CHA0, an effective biological control agent of soilborne plant diseases, is naturally non-mucoid. We have isolated a highly mucoid Tn5 insertion mutant of strain CHA0. The mucoid phenotype was found to be due to the overproduction of exopolysaccharide (EPS), as a result of a mutation in the mucA gene. The wild-type mucA gene was cloned by a two-step, Tn5-dependent cloning procedure previously described and the deduced amino acid sequence showed 71% identity with MucA of P. aeruginosa, a negative regulator of the alternative sigma factor AlgU (=s22, sE). As in P. aeruginosa, mucA is preceded by the algU gene encoding s22 (91% identity at the amino acid sequence level). A mucA in-frame deletion mutant of CHA0 overproduced EPS and formed mucoid colonies, whereas an algU in-frame deletion mutant showed a non-mucoid phenotype. Pyoluteorin, an antibiotic produced by P. fluorescens, was found to be entrapped in EPS of a mucoid mutant. In natural soil, mucoidy negatively affected survival of the bacteria, suggesting that under these conditions the potential to produce abundant EPS does not confer a selective advantage on the bacteria.

Respiratory viruses in bronchoalveolar lavage: a hospital-based cohort study in adults.

BACKGROUND: The epidemiology of respiratory viruses and their potential clinical impact when recovered in lower respiratory specimens has not been established in the hospital setting. A study was performed to investigate the association between positive viral detection and respiratory infection in an at-risk population. METHODS: 299 adult patients who underwent bronchoalveolar lavage (BAL) procedures were enrolled in a hospital-based prospective cohort study. Descriptive epidemiology is presented of 17 different respiratory viruses detected by reverse transcription-polymerase chain reaction assays in BAL fluid specimens. Multivariate analysis was conducted to identify the clinical characteristics independently associated with the presence of virus. RESULTS: Of 522 BAL fluid specimens analysed, 81% were collected in adult transplant recipients or other immunocompromised patients. Overall, PCR assays identified viral nucleic acid in 91 BAL fluid samples (17.4%). Similar rates of virus-positive BAL fluid were found in the different subpopulations studied (p = 0.113). Coronaviruses were the most frequent (32.3%), followed by rhinovirus (22.6%), parainfluenza (19.5%), influenza (9.7%), respiratory synctial virus (8.6%), human metapneumovirus (4.2%) and bocavirus (3.1%). Multivariate analysis using mixed models showed that respiratory viral infections were associated with a lack of antibiotic treatment response (OR 2.2, 95% CI 1.2 to 4.1) and the absence of radiological infiltrate (OR 0.3, 95% CI 0.2 to 0.8). In lung transplant recipients in whom a respiratory infection was suspected, the respiratory viral detection rate was 24.4% compared with 13.8% overall in other patients (p = 0.02). CONCLUSIONS: In this cohort of hospitalised adults, respiratory viruses detected in BAL fluid specimens were associated with respiratory symptoms, absence of radiological infiltrates and a poor response to antibiotic therapy.

RpoN (sigma54) controls production of antifungal compounds and biocontrol activity in Pseudomonas fluorescens CHA0.

Pseudomonas fluorescens CHA0 is an effective biocontrol agent of root diseases caused by fungal pathogens. The strain produces the antibiotics 2,4-diacetylphloroglucinol (DAPG) and pyoluteorin (PLT) that make essential contributions to pathogen suppression. This study focused on the role of the sigma factor RpoN (sigma54) in regulation of antibiotic production and biocontrol activity in P. fluorescens. An rpoN in-frame-deletion mutant of CHAO had a delayed growth, was impaired in the utilization of several carbon and nitrogen sources, and was more sensitive to salt stress. The rpoN mutant was defective for flagella and displayed drastically reduced swimming and swarming motilities. Interestingly, the rpoN mutant showed a severalfold enhanced production of DAPG and expression of the biosynthetic gene phlA compared with the wild type and the mutant complemented with monocopy rpoN+. By contrast, loss of RpoN function resulted in markedly lowered PLT production and plt gene expression, suggesting that RpoN controls the balance of the two antibiotics in strain CHA0. In natural soil microcosms, the rpoN mutant was less effective in protecting cucumber from a root rot caused by Pythium ultimum. Remarkably, the mutant was not significantly impaired in its root colonization capacity, even at early stages of root infection by Pythium spp. Taken together, our results establish RpoN for the first time as a major regulator of biocontrol activity in Pseudomonas fluorescens.

Virulent infections due to alpha-haemolytic streptococci in cancer patients and their management

Streptococci of the viridans group have long been considered to be minor pathogens, except in bacterial endocarditis. For some years, however, these microorganisms have been the cause of serious bacteraemia in neutropenic patients receiving intensive chemotherapy. These infections can lead to severe complications such as endocarditis, respiratory distress syndromes or shock, and are associated with a mortality rate ranging from 6-30%. The principal risk factors for these infections are profound neutropenia, antibiotic prophylaxis with quinolones or cotrimoxazole, large doses of cytosine arabinoside, a recent history of chemotherapy, oropharyngeal mucositis and viridans streptococcal colonization. Protective factors are the early administration of parenteral antibiotics during periods of neutropenia, or the prophylactic administration of penicillin. Although the introduction of penicillin to prophylactic antibiotic regimens has led to a decrease in the incidence of these infections, the emergence of strains resistant to beta-lactams is a worrying problem which could compromise this type of treatment.

Quorum-sensing systems in staphylococci as therapeutic targets.

The staphylococci are an ever-present threat in our world, capable of causing a wide range of infections, and are a persistent presence in the clinical environment. As the number of antimicrobial compounds effective against staphylococci decreases, because of the acquisition and spread of antibiotic resistance, there is a growing need for novel therapeutic molecules. Intra and inter-species communication (quorum sensing) is a biologically significant phenomenon that has been associated with virulence, intracellular survival, and biofilm formation. Quorum sensing molecules of staphylococci and other species (e.g. Pseudomonas aeruginosa) can inhibit virulence factor production and/or growth of staphylococci, leading to the possibility that interference with staphylococcal quorum-sensing systems could be a way of controlling the diverse infections caused by the staphylococci. In this article, we discuss the potential of quorum-sensing systems of staphylococci as therapeutic targets.

Bloc atrioventriculaire complet sur borréliose de Lyme: aspects etectrocardiographiques, diagnostiques et microbiologiques [Atrioventricular heart block in Lyme disease]

Lyme disease is the most common tick-borne disease in Europe and in the United States. In comparison to dermatological, neurological and rheumatological manifestations, heart disease is quite rare. Atrioventricular heart block is nevertheless the most frequent cardiological manifestation. We hereby report the case of a patient with high degree heart block due to Lyme disease. We focus on the electrocardiographical evolution during antibiotic therapy, as well as on microbiological and diagnostic aspects. Lyme disease is a rare cause of conduction disturbances but it is treatable and potentially reversible.

Genomic islands: tools of bacterial horizontal gene transfer and evolution.

Abstract Bacterial genomes evolve through mutations, rearrangements or horizontal gene transfer. Besides the core genes encoding essential metabolic functions, bacterial genomes also harbour a number of accessory genes acquired by horizontal gene transfer that might be beneficial under certain environmental conditions. The horizontal gene transfer contributes to the diversification and adaptation of microorganisms, thus having an impact on the genome plasticity. A significant part of the horizontal gene transfer is or has been facilitated by genomic islands (GEIs). GEIs are discrete DNA segments, some of which are mobile and others which are not, or are no longer mobile, which differ among closely related strains. A number of GEIs are capable of integration into the chromosome of the host, excision, and transfer to a new host by transformation, conjugation or transduction. GEIs play a crucial role in the evolution of a broad spectrum of bacteria as they are involved in the dissemination of variable genes, including antibiotic resistance and virulence genes leading to generation of hospital 'superbugs', as well as catabolic genes leading to formation of new metabolic pathways. Depending on the composition of gene modules, the same type of GEIs can promote survival of pathogenic as well as environmental bacteria.

Loss of penicillin tolerance by inactivating the carbon catabolite repression determinant CcpA in Streptococcus gordonii.

OBJECTIVES: Antibiotic tolerance is a phenomenon allowing bacteria to withstand drug-induced killing. Here, we studied a penicillin-tolerant mutant of Streptococcus gordonii (Tol1), which was shown to be deregulated in the expression of the arginine deiminase operon (arc). arc was not directly responsible for tolerance, but is controlled by the global regulator CcpA. Therefore, we sought whether CcpA might be implicated in tolerance. METHODS: The ccpA gene was characterized and subsequently inactivated by PCR ligation mutagenesis in both the susceptible wild-type (WT) and Tol1. The minimal inhibitory concentration and time-kill curves for the strains were determined and the outcome of penicillin treatment in experimental endocarditis assessed. RESULTS: ccpA sequence and expression were similar between the WT and Tol1 strains. In killing assays, the WT lost 3.5 +/- 0.6 and 5.3 +/- 0.6 log(10) cfu/mL and Tol1 lost 0.4 +/- 0.2 and 1.4 +/- 0.9 log(10) cfu/mL after 24 and 48 h of penicillin exposure, respectively. Deletion of ccpA almost totally restored Tol1 kill susceptibility (loss of 2.5 +/- 0.7 and 4.9 +/- 0.7 log(10) cfu/mL at the same endpoints). In experimental endocarditis, penicillin treatment induced a significant reduction in vegetation bacterial densities between Tol1 (4.1 log(10) cfu/g) and Tol1DeltaccpA (2.4 log(10) cfu/g). Restitution of ccpA re-established the tolerant phenotype both in vitro and in vivo. CONCLUSIONS: CcpA, a global regulator of the carbon catabolite repression system, is implicated in penicillin tolerance both in vitro and in vivo. This links antibiotic survival to bacterial sugar metabolism. However, since ccpA sequence and expression were similar between the WT and Tol1 strains, other factors are probably involved in tolerance.

In vitro activities of tigecycline combined with other antimicrobials against multiresistant gram-positive and gram-negative pathogens.

OBJECTIVES: To test the activity of tigecycline combined with 16 antimicrobials in vitro against 22 gram-positive and 55 gram-negative clinical isolates. METHODS: Antibiotic interactions were determined by chequerboard and time-kill methods. RESULTS: By chequerboard, of 891 organism-drug interactions tested, 97 (11%) were synergistic, 793 (89%) were indifferent and 1 (0.1%) was antagonistic. Among gram-positive pathogens, most synergisms occurred against Enterococcus spp. (7/11 isolates) with the tigecycline/rifampicin combination. No antagonism was detected. Among gram-negative organisms, synergism was observed mainly with trimethoprim/sulfamethoxazole against Serratia marcescens (5/5 isolates), Proteus spp. (2/5) and Stenotrophomonas maltophilia (2/5), with aztreonam against S. maltophilia (3/5), with cefepime and imipenem against Enterobacter cloacae (3/5), with ceftazidime against Morganella morganii (3/5), and with ceftriaxone against Klebsiella pneumoniae (3/5). The only case of antagonism occurred against one S. marcescens with the tigecycline/imipenem combination. Selected time-kill assays confirmed the bacteriostatic interactions observed by the chequerboard method. Moreover, they revealed a bactericidal synergism of tigecycline with piperacillin/tazobactam against one penicillin-resistant Streptococcus pneumoniae and with amikacin against Proteus vulgaris. CONCLUSIONS: Combinations of tigecycline with other antimicrobials produce primarily an indifferent response. Specific synergisms, especially against enterococci and problematic gram-negative isolates, might be worth investigating in in vitro models and/or in animal models simulating the human environment.

Two novel MvaT-like global regulators control exoproduct formation and biocontrol activity in root-associated Pseudomonas fluorescens CHA0.

Pseudomonas fluorescens CHA0 protects various crop plants against root diseases caused by pathogenic fungi. Among a range of exoproducts excreted by strain CHA0, the antifungal compounds 2,4-diacetylphloroglucinol (DAPG) and pyoluteorin (PLT) are particularly relevant to the strain's biocontrol potential. Here, we report on the characterization of MvaT and MvaV as novel regulators of biocontrol activity in strain CHA0. We establish the two proteins as further members of an emerging family of MvaT-like regulators in pseudomonads that are structurally and functionally related to the DNA-binding protein H-NS. In mvaT and mvaV in frame-deletion mutants of strain CHA0, PLT production was enhanced about four- and 1.5-fold, respectively, whereas DAPG production remained at wild-type levels. Remarkably, PLT production was increased up to 20-fold in an mvaT mvaV double mutant. DAPG biosynthesis was almost completely repressed in this mutant. The effects on antibiotic production could be confirmed by following expression of gfp-based reporter fusions to the corresponding biosynthetic genes. MvaT and MvaV also influenced levels of other exoproducts, motility, and physicochemical cell-surface properties to various extents. Compared with the wild type, mvaT and mvaV mutants had an about 20% reduced capacity (in terms of plant fresh weight) to protect cucumber from a root rot caused by Pythium ultimum. Biocontrol activity was nearly completely abolished in the double mutant Our findings indicate that MvaT and MvaV act together as further global regulatory elements in the complex network controlling expression of biocontrol traits in plant-beneficial pseudomonads.

Fastidious intracellular bacteria as causal agents of community-acquired pneumonia.

Intracellular bacteria are common causes of community-acquired pneumonia that grow poorly or not at all on standard culture media and do not respond to beta-lactam antibiotic therapy. Apart from well-established agents of pneumonia such as Legionella pneumophila, Mycoplasma pneumoniae, Chlamydia pneumoniae, Chlamydia psittaci and Coxiella burnetii, some new emerging pathogens have recently been recognized, mainly Parachlamydia acanthamoebae and Simkania negevensis, two Chlamydia-related bacteria. Most of them are causes of benign and self-limited infections. However, they may cause severe pneumonia in some cases (i.e., Legionnaires' disease) and they may cause outbreaks representing a public health problem deserving prompt recognition and appropriate therapy. Although extrapulmonary manifestations are often present, no clinical features allow them to be distinguished from classical bacterial agents of pneumonia such as Streptococcus pneumoniae. Thus, specific molecular diagnostic tools are very helpful for early recognition of the offending bacteria, whereas serology often only allows retrospective or late diagnosis. Macrolides remain the best empirical treatment of intracellular respiratory pathogens, although some observational studies suggest that quinolones may be superior for the treatment of legionellosis.

Biosynthesis of pyochelin and dihydroaeruginoic acid requires the iron-regulated pchDCBA operon in Pseudomonas aeruginosa.

The high-affinity siderophore salicylate is an intermediate in the biosynthetic pathway of pyochelin, another siderophore and chelator of transition metal ions, in Pseudomonas aeruginosa. The 2.5-kb region upstream of the salicylate biosynthetic genes pchBA was sequenced and found to contain two additional, contiguous genes, pchD and pchC, having the same orientation. The deduced amino acid sequence of the 60-kDa PchD protein was similar to those of the EntE protein (2,3-dihydroxybenzoate-AMP ligase) of Escherichia coli and other adenylate-forming enzymes, suggesting that salicylate might be adenylated at the carboxyl group by PchD. The 28-kDa PchC protein showed similarities to thioesterases of prokaryotic and eukaryotic origin and might participate in the release of the product(s) formed from activated salicylate. One potential product, dihydroaeruginoate (Dha), was identified in culture supernatants of iron-limited P. aeruginosa cells. The antifungal antibiotic Dha is thought to arise from the reaction of salicylate with cysteine, followed by cyclization of cysteine. Inactivation of the chromosomal pchD gene by insertion of the transcription and translation stop element omega Sm/Sp abolished the production of Dha and pyochelin, implying that PchD-mediated activation of salicylate may be a common first step in the synthesis of both metabolites. Furthermore, the pchD::omega Sm/Sp mutation had a strong polar effect on the expression of the pchBA genes, i.e., on salicylate synthesis, indicating that the pchDCBA genes constitute a transcriptional unit. A full-length pchDCBA transcript of ca. 4.4 kb could be detected in iron-deprived, growing cells of P. aeruginosa. Transcription of pchD started at tandemly arranged promoters, which overlapped with two Fur boxes (binding sites for the ferric uptake regulator) and the promoter of the divergently transcribed pchR gene encoding an activator of pyochelin biosynthesis. This promoter arrangement allows tight iron-mediated repression of the pchDCBA operon.