Development of a DGGE method to explore Legionella communities

Legionella risk assessment is nowadays based on the presence and concentration of either Legionella pneumophila or Legionella spp. Many species of Legionella can cause Legionnaires' disease, indeed about half of the known species have been associated with infection. The aim of this work was to develop a method to assess the composition of the Legionella species community in an environmental sample in order to have a better understanding of the contamination of the ecosystem by pathogenic strains. The method is based on the comparison of PCR-DGGE profile of DNA sample with a database consisting in DGGE profiles of Legionella species. Such a database includes all pathogenic Legionella strains. In order to homogenize and normalize the different DGGE fingerprint, a reference marker has been built and added during DGGE gel analysis. This study gives a valuable advance in the methods available for the understanding of Legionella contamination of water environments.

A real-time PCR for specific detection of the Legionella pneumophila serogroup 1 ST1 complex

OBJECTIVE

Legionella pneumophila serogroup 1 (Lp1) sequence type (ST) 1 is globally widespread in the environment and accounts for a significant proportion of Legionella infections, including nosocomial Legionnaires' disease (LD). This study aimed to design a sensitive and specific detection method for Lp ST1 that will underpin epidemiological investigations and risk assessment.

METHODS

A total of 628 Lp genomes (126 ST1s) were analyzed by comparative genomics. Interrogation of more than 900 accessory genes revealed seven candidate targets for specific ST1 detection and specific primers and hydrolysis probes were designed and evaluated. The analytical sensitivity and specificity of the seven primer and probe sets were evaluated on serially diluted DNA extracted from the reference strain CIP107629 and via qPCR applied on 200 characterized isolates. The diagnostic performance of the assay was evaluated on 142 culture-proven clinical samples from LD cases and a real-life investigation of a case cluster.

RESULTS

Of seven qPCR assays that underwent analytical validation, one PCR target (lpp1868) showed higher sensitivity and specificity for ST1 and ST1-like strains. The diagnostic performance of the assay using respiratory samples corresponded to a sensitivity of 95% (19/20) (95% CI (75.1-99.9)) and specificity of 100% (122/122) (95% CI (97-100)). The ST1 PCR assay could link two out of three culture-negative hospitalized LD cases to ST1 during a real-time investigation.

CONCLUSION

Using whole genome sequencing (WGS) data, we developed and validated a sensitive and specific qPCR assay for the detection of Lp1 belonging to the ST1 clonal complex by amplification of the lpp1868 gene. The ST1 qPCR is expected to deliver an added value for Lp control and prevention, in conjunction with other recently developed molecular assays.

Molecular epidemiology, phylogeny and evolution of Legionella

Legionella are opportunistic pathogens that develop in aquatic environments where they multiply in protozoa. When infected aerosols reach the human respiratory tract they may accidentally infect the alveolar macrophages leading to a severe pneumonia called Legionnaires' disease (LD). The ability of Legionella to survive within host-cells is strictly dependent on the Dot/Icm Type 4 Secretion System that translocates a large repertoire of effectors into the host cell cytosol. Although Legionella is a large genus comprising nearly 60 species that are worldwide distributed, only about half of them have been involved in LD cases. Strikingly, the species Legionella pneumophila alone is responsible for 90% of all LD cases. The present review summarizes the molecular approaches that are used for L. pneumophila genotyping with a major focus on the contribution of whole genome sequencing (WGS) to the investigation of local L. pneumophila outbreaks and global epidemiology studies. We report the newest knowledge regarding the phylogeny and the evolution of Legionella and then focus on virulence evolution of those Legionella species that are known to have the capacity to infect humans. Finally, we discuss the evolutionary forces and adaptation mechanisms acting on the Dot/Icm system itself as well as the role of mobile genetic elements (MGE) encoding T4ASSs and of gene duplications in the evolution of Legionella and its adaptation to different hosts and lifestyles.

Chronic endocarditis due to Legionella anisa: a first case difficult to diagnose

Endocarditis due to Legionella spp. is uncommon but presumably underestimated given the prevalence of Legionellae in the environment. We report a first and unusual case of chronic native valve endocarditis due to L. anisa and advocate that the diagnosis of endocarditis be made collaboratively between the cardiologist, surgeon, microbiologist and pathologist.

Community-acquired Legionnaires' disease in a renal transplant recipient with unclear incubation period: the importance of molecular typing

Transplant recipients are at risk of developing Legionnaires' disease (LD) because of impaired cellular immunity. Here, we describe a renal transplant recipient who developed LD at least 10 days after hospital admission and transplantation. The hospital water network was initially suspected, but further testing determined that the probable source was the patient's domestic water supply. Our report also suggests that the patient's immunosuppressed state may have switched potential colonization to pneumonia.

Comparison of Sofia Legionella FIA and BinaxNOW® Legionella urinary antigen card in two national reference centers

The Sofia Legionella Fluorescence Immunoassay (FIA; Quidel) is a recently introduced rapid immunochromatographic diagnostic test for Legionnaires’ disease using immunofluorescence technology designed to enhance its sensitivity. The aim of this study was to evaluate its performance for the detection of urinary antigens for Legionella pneumophila serogroup 1 in two National Reference Centers for Legionella. The sensitivity and specificity of the Sofia Legionella FIA test were determined in concentrated and nonconcentrated urine samples, before and after boiling, in comparison with the BinaxNOW® Legionella Urinary Antigen Card (UAC; Alere). Compared with BinaxNOW® Legionella UAC, the sensitivity of the Sofia Legionella test was slightly higher in nonconcentrated urine samples and was identical in concentrated urine samples. The specificity of the Sofia Legionella FIA test was highly reduced by the concentration of urine samples. In nonconcentrated samples, a lack of specificity was observed in 2.3 % of samples, all of them resolved by heat treatment. The Sofia Legionella FIA is a sensitive test for detecting Legionella urinary antigens with no previous urine concentration. However, all positive samples have to be re-tested after boiling to reach a high specificity. The reading is automatized on the Sofia analyzer, which can be connected to laboratory information systems, facilitating accurate and rapid reporting of results.

Epidemiologic characteristics associated with ST23 clones compared to ST1 and ST47 clones of Legionnaires disease cases in France

In France, approximately 1200 cases of Legionnaires disease (LD) are reported annually, and isolates are available for approximately 20% of cases identified since 2000. All Legionella pneumophila serogroup 1 (sg1) isolates are characterized by sequence-based typing at the National Reference Centre. LD cases caused by L. pneumophila sg1 reported from 2008 through 2012 were considered for the study. Our study objective was to describe cases according to their sequence type (ST). We also constructed multivariable modified Poisson regression models to estimate the incidence rate ratio (IRR) and to identify characteristics potentially associated with ST23 clones compared to ST1 and ST47 clones. We studied 1192 patients infected by ST1 (n = 109), ST23 (n = 236), ST47 (n = 123) or other STs (n = 724). The geographic distribution of the ST23 cases across the country was significantly different compared to other ST groups. This genotype was significantly associated with the absence of corticosteroid therapy compared to ST1 (IRR = 0.56; p 0.016). Concerning exposure, the ST23 genotype was significantly less associated with hospital-acquired infections compared to ST1 (IRR = 0.32; p 0.001), but it was more associated with infections acquired in hospitals and elderly settings compared with ST47. Finally, the ST23 genotype was less frequently associated with travel than other STs. Despite the large number of cases of ST23 infection, we did not identify any characteristics specific to this ST. However, we identified independent associations between ST1 and nosocomial transmission and steroid therapy. These findings should encourage further exploration, especially in terms of environmental diffusion, strain virulence and host factors.

Hospital washbasin water: risk of Legionella-contaminated aerosol inhalation

The contamination of aerosols by washbasin water colonized by Legionella in a hospital was evaluated. Aerosol samples were collected by two impingement technologies. Legionella was never detected by culture in all the (aerosol) samples. However, 45% (18/40) of aerosol samples were positive for Legionella spp. by polymerase chain reaction, with measurable concentrations in 10% of samples (4/40). Moreover, immunoassay detected Legionella pneumophila serogroup 1 and L. anisa, and potentially viable bacteria were seen on viability testing. These data suggest that colonized hospital washbasins could represent risks of exposure to Legionella aerosol inhalation, especially by immunocompromised patients.

molecular typing of Legionella pneumophila strains isolated from environment in Morocco

Legionella pneumophila is a common cause of hospital and community-acquired pneumonia, being transmitted by inhalation of aqueous aerosols. Most legionellosis outbreaks are linked to contaminated hot water systems or cooling towers. The aim of this study was to determine the genetic diversity of (n= 55) environmental strains of L. pneumophila recovered from the hot water distribution systems of 16 establishments in seven Moroccan towns during the period 2009-2011. Thirteen chromosomal restriction patterns determined by Pulsed field gel electrophoresis were detected. The strains of L. pneumophila serogroup1 exhibited in 6/13 different PFGE patterns, while the strains of L. pneumophila serogroups 2-14 showed 7/13 PFGE patterns. The PFGE showed the existence of various patterns in Morocco, The pattern -XI- have tree similar profiles with the endemic L. pneumophila Paris's strain. This technique also allowed to conclude that the same pulsotype was found for many strains isolated from different establishments. Moreover, different pulsolypes were found for strains isolated from the same establishment. These results showed that PFGE analysis is a powerful tool to reveal the clonal nature and genetic differences among L. pneumophila strains.

Impact of the virulence-associated MAb3/1 epitope on the physicochemical surface properties of Legionella pneumophila sg1: An issue to explain infection potential?

The relationship between the presence/absence of the virulence-associated MAb3/1 epitope of sixteen Legionella pneumophila serogroup 1 strains and their respective surface physicochemical properties is evidenced from electrokinetic measurements (microelectrophoresis) performed as a function of KNO(3) electrolyte concentration (range 1-100mM, pH∼6.5). Among the bacteria selected, nine original strains constitute the Dresden reference panel and differ according to the presence/absence of the virulence-associated monoclonal antibody MAb3/1 of the O-specific chain of the lipopolysaccharides (LPS). Five isogenic Lens strains, also investigated in the current study, present the epitope MAb3/1 of their LPS and were involved to some extent in the outbreak that stroke the Nord Pas-de-Calais region (France) in 2004. All bacteria exhibit the typical electrokinetic features of soft (permeable) particles. On the basis of Ohshima's model, analysis of the electrophoretic mobility data allows evaluating the intraparticular flow penetration length 1/λ(0) and the (negative) volume charge density ρ(0) that both reflect the structure and chemical composition of the soft bacterial component. Our results show that the virulent MAb3/1 positive strains are characterized on average by 1/λ(0) and ǀρ(0)ǀ values that are about 1.5 times larger and 5 times lower, respectively, than those derived for lesser virulent (MAb3/1 negative) strains. In other words, on average the soft surface layer of MAb3/1 positive strains is significantly less charged and more permeable than those of MAb3/1 negative strains. The intimate correlation between virulence-associated MAb3/1 epitope and charge density carried by the bacterial envelop was further confirmed by lower 1/λ(0) and greater ǀρ(0)ǀ values for lag-1 mutant CS332 strain, lacking the MAb3/1 epitope, compared to the parental strain AM511. A closer inspection of the dispersion in 1/λ(0) and ǀρ(0)ǀ data over the ensemble of analysed bacteria together with the reported number of Legionnaires' disease cases they are responsible for, points out the charge density ǀρ(0)ǀ as the parameter that is most suitable for discriminating highly virulent (MAb3/1 positive) from less virulent (MAb3/1 negative) strains. Although short-range interaction determines infection process, our results suggest that the infection potential of Legionella pneumophila serogroup 1 may be also controlled significantly by non-specific long-range electrostatic repulsion the bacteria undergo when approaching negatively charged host cells to be infected.

Cluster of Legionnaires' disease associated with a public whirlpool spa, France, April-May 2010

In May 2010, a cluster of three cases of Legionnaires' disease was identified in France. The results of the epidemiological, environmental and microbiological investigations allowed the rapid identification of a public whirlpool spa as the most probable source of contamination and the implementation of appropriate control measures. This investigation has stressed the need for good cooperation between partners and the importance of the molecular analysis of Legionella strains.

Cluster of Legionnaires´ disease associated with a public whirlpool spa, France, April – May 2010

Binary file ES_Abstracts_Final_ECDC.txt matches

[Molecular comparison of Legionella pneumophila serogroup 1 isolated in Tunisia]

Legionella pneumophila is a common cause of hospital and community-acquired pneumonia, being transmitted by inhalation of aqueous aerosols. Most outbreaks are linked to contaminated hot water systems and cooling towers. Our study was about the molecular typing of 35 strains of L. pneumophila including four clinical isolates and 31 environmental strains isolated from the distribution systems of 14 hotels. Among the clinical strains, two have the same pattern, however, all were different from the studied environmental strains. For the 31 environmental strains, ten patterns were obtained. Among which, a same pulsotype was found for four strains isolated from four different establishments. In addition, two different pulsotypes were found for strains isolated from the same establishment. The pulsed-field gel electrophoresis showed the existence of various patterns. Although cases of legionellosis were declared in these hotels, there are no epidemiological links between the clinical and environmental strains.

[Legionnaire's disease: surveillance in France in 2005]

Legionnaire's disease is a recently described infection and surveillance in France was implemented in 1987. In 2005, 1,527 cases were notified corresponding to a population incidence rate of 2.5 per 100,000. The median age of cases was 61 years [5-100] and the male to female sex ratio was 3.0. The case fatality rate was 11%. One or more risk factors were identified for 1,084 (71%) cases. The majority of cases (91%) was diagnosed by urinary antigen detection and a strain was identified in 276 cases (18%). Legionella pneumophila serogroup 1 infection was confirmed in 95% of cases. A specific exposure during the incubation period was reported for 39% of cases. Travel exposure was reported for 17% and hospital exposure for 7%. Multiple clusters and outbreaks were investigated. The largest one reported was identified in the north Lyon with 34 cases. Since 1997 the incidence of LD has steadily increased. This probably suggests a better detection of cases and an improvement in the surveillance system. In recent years, several new measures concerning prevention and control were implemented. However these efforts must continue particularly in the research domain to improve knowledge of the disease, in order to limit its impact on exposed populations.

Légionellose à Legionella gormanii de découverte fortuite et leucémie lymphoïde chronique : à propos d'un cas et revue de la littérature

Legionellosis due to other species than Legionella pneumophila is rarely described in human cases. It has been reported in immunocompromised patients with respiratory symptoms of pneumonia. We report a case of legionellosis in an immunocompromised 54-year-old man hospitalized for a blood transfusion. A routine pulmonary X- Ray was made and then a bronchoalveolar lavage was collected in which Legionella gormanii was identified. The diagnostic of legionellosis must be considered in all immunocompromised patients presenting with any pulmonary symptoms.

Clusters of travel associated legionnaires' disease in France, September 2001- August 2003

Clusters of travel associated legionnaires' disease warrant urgent attention, and are detected by the French national surveillance system and the European network EWGLINET. Between September 2001 and August 2003, 37 clusters were identified in French tourist accommodation: 27 hotels and 10 campsites. The number of clinical cases per cluster was as follows: 30 clusters of 2 cases (81%), 6 clusters of 3 cases (16%) and one cluster of 4 cases (3%), a total of 82 cases. The local health authorities performed environmental investigations for 36 of the 37 clusters. Among the 36 clusters investigated, water samples were collected for 35. At 16 (46%) sites, Legionella pneumophila was found at a level of more than 103 cfu/litre. In all of the accommodation where risk assessment was found to be inadequate- control measures were implemented immediately. Six hotels were closed immediately following cluster alerts. Comparison of clinical and environmental isolates by pulsed field gel electrophoresis (PFGE) was possible in 3 clusters and identical genomic profiles of the isolates were found in all. During this two year period of surveillance, we found that on many sites there has been a risk of exposure to Legionella. This reinforces the importance of the European surveillance network and the timely notifications of all the cases to EWGLINET.

Repeat capture-recapture studies as part of the evaluation of the surveillance of Legionnaires' disease in France

We evaluated improvements made to the mandatory notification surveillance system for Legionnaires' disease in France by estimating its sensitivity in 1995 and 1998 using a repeat capture-recapture method. A case of Legionnaires' disease was defined as a person treated for pneumonia in whom legionella had been detected. Patient details were collected from (1) mandatory notifications; (2) the National Reference Centre for Legionella; (3) a postal survey of all hospital laboratories. The three sources were cross-matched and 715 individual cases were identified. A log-linear model, which included an interaction term between mandatory notifications and both the National Reference Centre and Laboratory sources, provided an estimated total of 1124 cases (95% CI 973-1275) in 1998, a twofold increase compared with 1995. The sensitivity of the surveillance system improved from 10% in 1995 to 33% (95% CI 29-38%) in 1998. Capture-recapture methods are important tools in the evaluation of surveillance systems.

[The epidemiology of toxemic infections caused by Staphylococcus aureus in an intensive care setting]

The mission of the National Reference Centre for Staphylococcal Toxemia (CNRTS) is to participate in the epidemiological surveillance of staphylococcal toxemia in France. As these syndromes do not have to be declared, the data collected remain incomplete. Comparison of the clinical data with the results of molecular analysis of the causal strains has nonetheless enabled advances in our understanding of the present-day epidemiology of these syndromes, a clearer knowledge of their pathophysiology and isolation of a hitherto unknown entity, staphylococcal necrotizing pneumonia.

Isolation and characterization of a protein-tyrosine kinase and a phosphotyrosine-protein phosphatase from Klebsiella pneumoniae

Two proteins of Klebsiella pneumoniae, termed Yor5 and Yco6, were analyzed for their capacity to participate in the reversible phosphorylation of proteins on tyrosine. First, protein Yco6 was overproduced from its specific gene and purified to homogeneity by affinity chromatography. Upon incubation in the presence of radioactive adenosine triphosphate, it was found to effectively autophosphorylate. Two-dimensional analysis of its phosphoamino acid content revealed that it was modified exclusively at tyrosine. Second, protein Yor5 was also overproduced from the corresponding gene and purified to homogeneity by affinity chromatography. It was shown to contain a phosphatase activity capable of cleaving the synthetic substrate p-nitrophenyl phosphate into p-nitrophenol and free phosphate. In addition, it was assayed on individual phosphorylated amino acids and appeared to dephosphorylate specifically phosphotyrosine, with no effect on phosphoserine or phosphothreonine. Such specificity for phosphotyrosine was confirmed by the observation that Yor5 was able to dephosphorylate protein Yco6 previously autophosphorylated. Together, these data demonstrate that similarly to other bacterial species including Acinetobacter johnsonii and Escherichia coli, the cells of K. pneumoniae contain both a protein-tyrosine kinase and a phosphotyrosine-protein phosphatase. They also provide evidence that this phosphatase can utilize the kinase as an endogenous substrate, which suggests the occurrence of a regulatory mechanism connected with reversible protein phosphorylation on tyrosine. Since Yco6 and Yor5 are both involved in the synthesis of capsular polysaccharide and since capsules are essential to the virulence of K. pneumoniae, we suggest that reversible protein phosphorylation on tyrosine may be part of the cascade of reactions that determine the pathogenicity of bacteria.

Different growth rates in amoeba of genotypically related environmental and clinical Legionella pneumophila strains isolated from a thermal spa

Two cases of legionellosis occurring 3 years apart were acquired in the same French thermal spa and were apparently due to the same strain of Legionella pneumophila serogroup 1, as shown by genomic macrorestriction analysis. Minor differences between the two isolates were found by random amplification PCR profiling which showed an additional band with one of the isolates. Analysis of 107 L. pneumophila strains isolated from the spa waters by genome macrorestriction failed to identify the infective strain, but a closely related L. pneumophila serogroup 3 strain differing from the clinical isolates by only one band was found. To determine if the clinical L. pneumophila serogroup 1 isolates was better adapted for intracellular multiplication than related serogroup 3 environmental isolates, the growth kinetics of six isolates were determined in co-culture with Acanthamoeba lenticulata. One clinical isolate failed to grow within amoeba, while the other clinical isolate yielded the highest increase in bacterial cell count per amoeba (1,200%) and the environmental isolates gave intermediate values. Genetic analysis of L. pneumophila isolates by DNA macrorestriction does not therefore appear to reflect their growth kinetics within amoeba, and is not sufficiently discriminatory to identify potentially virulent strains.

Phage conversion of Panton-Valentine leukocidin in Staphylococcus aureus : molecular analysis of a PVL-converting phage, φSLT

Staphylococcal Panton-Valentine leukocidin (PVL) is an important virulence factor, which causes leukocytolysis and tissue necrosis. Our previous report on the existence of the PVL genes (lukS-PV and lukF-PV) on the genome of prophage phiPVL in the Staphylococcus aureus strain V8 suggested the horizontal transmission of PVL genes by temperate bacteriophage among S. aureus (Kaneko, et al., 1998. Gene 215, 57-67). Here, we demonstrated the phage conversion of S. aureus leading to the production of PVL by discovery of a novel PVL-carrying phage, phiSLT (Staphylococcal Leukocytolytic Toxin) from a clinical isolate of S. aureus. phiSLT was able to lysogenize several clinical isolates of PVL-negative S. aureus strains as well as strain RN4220 at the conserved 29-bp sequence (attB) and all the lysogenized S. aureus strains had the ability to produce PVL. phiSLT had an elongated head of about 100x50 nm and a flexible tail of 400 nm long, that was quite different from phiPVL which had an isometric hexagonal head of about 60 nm diameter. The linear double-stranded phiSLT genome comprised 42,942 bp with 29-bp attachment core sequences and contained 62 open reading frames. Only 6.4 kbp region containing lysis cassette, PVL genes, attP, integrase, and orf204 of phiSLT was identical to that of phiPVL, while other regions were different from those of phiPVL. Thus, it can be concluded that PVL genes are carried by different temperate phages, which have the same attachment site.

Incidence of Staphylococcus aureus with reduced susceptibility to glycopeptides in two French hospitals

OBJECTIVES

To determine the incidence of Staphylococcus aureus isolates with reduced susceptibility to glycopeptides among all clinical isolates collected consecutively in two French hospitals between November 1998 and April 1999.

METHODS

Methicillin-resistant and -susceptible S. aureus isolates were screened on vancomycin- or teicoplanin-supplemented agar plates. Glycopeptide MICs were determined by the E test procedure with a high inoculum and by an agar dilution technique. Glycopeptide-intermediate S. aureus isolates were identified as homogeneously or heterogeneously resistant to vancomycin by performing population analysis.

RESULTS

Of the 640 isolates recovered from 518 patients, three from the same patient and two from two different patients showed homogeneous or heterogeneous intermediate resistance to vancomycin.

CONCLUSION

The incidence of glycopeptide-intermediate S. aureus (homogeneously or heterogeneously resistant) in a non-selected patient population, i.e. regardless of predisposing factors and glycopeptide therapeutics, remains low in the two French hospitals involved in the study, representing 0.6% of isolates.

egc, a highly prevalent operon of enterotoxin gene, forms a putative nursery of superantigens in Staphylococcus aureus

The recently described staphylococcal enterotoxins (SE) G and I were originally identified in two separate strains of Staphylococcus aureus. We have previously shown that the corresponding genes seg and sei are present in S. aureus in tandem orientation, on a 3.2-kb DNA fragment (Jarraud, J. et al. 1999. J. Clin. Microbiol. 37:2446-2449). Sequence analysis of seg-sei intergenic DNA and flanking regions revealed three enterotoxin-like open reading frames related to seg and sei, designated sek, sel, and sem, and two pseudogenes, psi ent1 and psi ent2. RT-PCR analysis showed that all these genes, including seg and sei, belong to an operon, designated the enterotoxin gene cluster (egc). Recombinant SEG, SEI, SEK, SEL, and SEM showed superantigen activity, each with a specific V beta pattern. Distribution studies of genes encoding superantigens in clinical S. aureus isolates showed that most strains harbored such genes and in particular the enterotoxin gene cluster, whatever the disease they caused. Phylogenetic analysis of enterotoxin genes indicated that they all potentially derived from this cluster, identifying egc as a putative nursery of enterotoxin genes.

Exfoliatin-producing strains define a fourth agr specificity group in Staphylococcus aureus

The staphylococcal virulon is activated by the density-sensing agr system, which is autoinduced by a short peptide (autoinducing peptide [AIP]) processed from a propeptide encoded by agrD. A central segment of the agr locus, consisting of the C-terminal two-thirds of AgrB (the putative processing enzyme), AgrD, and the N-terminal half of AgrC (the receptor), shows striking interstrain variation. This finding has led to the division of Staphylococcus aureus isolates into three different agr specificity groups and to the division of non-aureus staphylococci into a number of others. The AIPs cross-inhibit the agr responses between groups. We have previously shown that most menstrual toxic shock strains belong to agr specificity group III but that no strong clinical identity has been associated with strains of the other two groups. In the present report, we demonstrate a fourth agr specificity group among S. aureus strains and show that most exfoliatin-producing strains belong to this group. A striking common feature of group IV strains is activation of the agr response early in exponential phase, at least 2 h earlier than in strains of the other groups. This finding raises the question of the biological significance of the agr autoinduction threshold.

Isolation of Legionella oakridgensis from two patients with pleural effusion living in the same geographical area

Two cases of Legionnaire's disease caused by Legionella oakridgensis were diagnosed at the university hospital in Nantes, France. The two patients' isolates were identified by means of phenotyping and genotyping methods. Epidemiological investigations concluded that the first case was hospital acquired while the second case was considered community acquired.

Epidemic cluster of legionnaires disease in Paris, June 1998

From 29 June to July 1998, four cases of legionnaires disease in British citizens were reported to the Reseau National de Sante Publique (RNSP) by the statutory notification system (declaration obligatoire (DO)) and by theEuropean Surveillance Scheme for

Involvement of enterotoxins G and I in staphylococcal toxic shock syndrome and staphylococcal scarlet fever

We investigated the involvement of the recently described staphylococcal enterotoxins G and I in toxic shock syndrome. We reexamined Staphylococcus aureus strains isolated from patients with menstrual and nonmenstrual toxic shock syndrome (nine cases) or staphylococcal scarlet fever (three cases). These strains were selected because they produced none of the toxins known to be involved in these syndromes (toxic shock syndrome toxin 1 and enterotoxins A, B, C, and D), enterotoxin E or H, or exfoliative toxin A or B, despite the fact that superantigenic toxins were detected in a CD69-specific flow cytometry assay measuring T-cell activation. Sets of primers specific to the enterotoxin G and I genes (seg and sei, respectively) were designed and used for PCR amplification. All of the strains were positive for seg and sei. Sequence analysis confirmed that the PCR products, corresponded to the target genes. We suggest that staphylococcal enterotoxins G and I may be capable of causing human staphylococcal toxic shock syndrome and staphylococcal scarlet fever.

[Legionnaires' disease in travellers]

The outbreak of pneumonia involving delegates to the 1976 American Legion convention at a Philadelphia hotel was the first example of travel-associated legionnaires' disease. Travel is now well known as a common risk factor for legionnaires' disease. This travel-associated disease is a preoccupation among European countries because of morbidity among citizens of the European Union. The definition of the case of legionellosis is a patient who presents an acute lower respiratory tract infection with focal signs of pneumonia and/or radiological features, and microbiological evidence of Legionella infection. A case is considered to be travel associated if the patient has spent one or more nights away from home during the ten days before becoming ill. An European Surveillance Scheme for Travel-Associated Legionnaires' Disease was established in 1987 to identify clusters and outbreaks of cases of the disease. This group centralizes the case reports of twenty-nine collaborating centres in twenty-five countries. Outbreaks of legionnaires' disease were described in hotels, camps or cruise ships. In 1996, the number of travel-associated cases of legionnaires' disease represented 16% of the total number cases. The increase of the number of reported cases may reflect improved surveillance and increased ascertainment. In Europe in 1996, the diagnosis of legionellosis was confirmed by detection of Legionella pneumophila sero-group 1 antigen in urine (36%), seroconversion (fourfold rise in antibody titre, 33%) and culture of the organism (16%). Fifteen per cent of legionellosis was diagnosed by the identification of a single high antibody titre. In France a coordination between Public Health Institutions (Réseau National de Santé Public and DDASS), clinicians, laboratories and National Reference Center was established to improve prevention and control of legionnaires' disease outbreaks. Legislation obliges to report each case. When more two cases in the same area are notified an epidemiological investigation must be done. The knowing of the source of the contamination and its eradication allows to prevent new cases and outbreaks. Outbreaks of Legionnaires' disease are even now mediatic and this fact leads to maintain attention for the quality of diagnosis and epidemiology investigation due to touristic and economic consequences for the implicated countries.

Comparison of sample preparation methods for detection of Legionella pneumophila in culture-positive bronchoalveolar lavage fluids by PCR

A prospective study was conducted on 25 Legionella pneumophila culture-positive and 98 culture-negative bronchoalveolar lavage fluid samples to compare two DNA preparation methods: a rapid modified Chelex-based protocol and a proteinase K method. PCR was found to be more sensitive with the Chelex-based method (P = 0.03). N difference was found concerning the inhibition rate.

Transmembrane topology and histidine protein kinase activity of AgrC, the agr signal receptor in Staphylococcus aureus

The agr P2 operon in Staphylococcus aureus codes for the elements of a density-sensing cassette made up of a typical two-component signalling system and its corresponding inducer. It is postulated that the autoinducer, a post-translationally modified octapeptide generated from the AgrD peptide, interacts with a receptor protein, coded by agrC, to transmit a signal via AgrA regulating expression of staphylococcal virulence genes through expression of agr RNA III. We show by analysis of PhoA fusions that AgrC is a transmembrane protein, and confirm using Western blotting that a 46 kDa protein corresponding to AgrC is present in the bacterial membrane. This protein is autophosphorylated on a histidine residue only in response to supernatants from an agr+ strain, and can also respond to the purified native octapeptide. A recombinant fusion protein where most of the N-terminal region of AgrC is replaced by the Escherichia coli maltose-binding protein is also autophosphorylated in response to stimulation by agr+ supernatants or purified octapeptide. We conclude that AgrC is the sensor molecule of a typical two-component signal system in S. aureus, and that the ligand-binding site of AgrC is probably located in the third extracellular loop of the protein.