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Volume 65,
Issue 4,
2016
Volume 65, Issue 4, 2016
- Clinical Microbiology
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- Pathogenicity and Virulence/Host Response
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Multiple antibiotic resistance index, fitness and virulence potential in respiratory Pseudomonas aeruginosa from Jamaica
More LessRespiratory infections are common causes of morbidity and mortality worldwide. We sought to assess the multiple antibiotic resistance (MAR) index, fitness and virulence potential in Pseudomonas aeruginosa from patients with lower respiratory tract infections. Isolates were assessed for antimicrobial susceptibility, in vitro competitive fitness, and pigment, elastase and rhamnolipid production. Oxidative stress tolerance was determined on both planktonic and biofilm cells, and virulence potential was tested in a plant model. Mean MAR index for isolates was 0.34 (range 0.17–0.50). Whilst isolates exhibited good biofilm formation in the presence of ciprofloxacin, there was no significant difference in biofilm production over the concentration range assessed. Several drug-resistant strains were out-competed by a susceptible strain even in the presence of antibiotic. H2O2 exerted a greater oxidative stress than tert-butyl-hydroperoxide and, as expected, biofilms were more resistant than planktonic cells. Whilst most (81 %) isolates were pigmented there was no significant difference between pigmented and non-pigmented isolates when elastolytic activity was compared (P>0.05). More than half of the isolates produced the quorum sensing mediator rhamnolipid and infection of the plant model by bacteria occurred whether elastase or rhamnolipid was present or absent. These data suggest that non-pigmented strains of P. aeruginosa might pose an equally significant microbiological threat as pigmented strains even though pigment production appeared to be strongly associated with elastase expression. Whilst dual expression of elastase and rhamnolipid by these bacteria would cause severe tissue damage (as seen in the plant model), non-production of either does not prevent bacteria from causing serious infection.
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- Clinical Microbiology
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In vitro biofilm production of Candida bloodstream isolates: any association with clinical characteristics?
More LessCandida spp. are a leading cause of bloodstream infection (BSI) and are associated with high mortality rates. Biofilm production is a virulence factor of Candida spp., and has been linked with poor clinical outcome. The aim of our study was to assess biofilm production of Candida bloodstream isolates at our institute, and to determine whether in vitro biofilm production is associated with any clinical characteristics of infection. During the four-year study period, 93 cases of Candida BSI were analysed. The most frequently isolated species was C. albicans (66.7 %), followed by C. glabrata (9.7 %), C. parapsilosis (9.7 %), C. tropicalis (9.7 %) and C. krusei (4.3 %). Biofilm production was more prevalent among non-albicans Candida spp. (77.4 %) than C. albicans (30.6 %) (P = 0.02). Abdominal surgery was identified as a risk factor of BSI caused by biofilm producing non-albicans Candida isolates. No risk factors predisposing to bloodstream infection caused by a biofilm producing C. albicans isolate were identified. Biofilm production was not verified as a risk factor of mortality.
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Molecular characterization and drug susceptibility profile of a Mycobacterium avium subspecies avium isolate from a dog with disseminated infection
Mycobacterium avium–intracellulare complex (MAC) infections have been described in many mammalian species, including humans and pets. We isolated and molecularly typed the causative agent of a rare case of disseminated mycobacteriosis in a dog. We identified the pathogen as M. avium subspecies avium by sequencing the partial genes gyrB and rpsA. Considering the zoonotic potential of this infection, and in an attempt to ensure the most effective treatment for the animal, we also determined the drug susceptibility profile of the isolate to the most common drugs used to treat MAC disease in humans. The pathogen was tested in vitro against the macrolide clarithromycin, as well as against amikacin, ciprofloxacin, rifampicin, ethambutol and linezolid, by the resazurin microdilution assay. It was found to be sensitive to all tested drugs apart from ethambutol. Despite the fact that the pathogen was sensitive to the therapies administered, the dog's overall clinical status worsened and the animal died shortly after antimicrobial susceptibility results became available. Nucleotide sequencing of the embB gene, the target gene most commonly associated with ethambutol resistance, showed new missense mutations when compared to sequences available in public databases. In conclusion, we molecularly identified the MAC pathogen and determined its drug susceptibility profile in a relatively short period of time (7 days). We also characterized new genetic mutations likely to have been involved in the observed ethambutol resistance. Our results confirmed the usefulness of both the gyrB and the rpsA genes as biomarkers for an accurate identification and differentiation of MAC pathogens.
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Biofilm formation of Brazilian meticillin-resistant Staphylococcus aureus strains: prevalence of biofilm determinants and clonal profiles
Deivid William da Fonseca Batistão, Paola Amaral de Campos, Nayara Caroline Camilo, Sabrina Royer, Bruna Fuga Araújo, Karinne Spirandelli Carvalho Naves, Margarida Martins, Maria Olívia Pereira, Mariana Henriques, Paulo Pinto Gontijo-Filho, Cláudia Botelho, Rosário Oliveira and Rosineide Marques RibasBiofilms plays an important role in medical-device-related infections. This study aimed to determine the factors that influence adherence and biofilm production, as well as the relationship between strong biofilm production and genetic determinants in clinical isolates of meticillin-resistant Staphylococcus aureus (MRSA). Fifteen strains carrying different chromosomal cassettes recovered from hospitalized patients were selected; five SCCmecII, five SCCmecIII and five SCCmecIV. The SCCmec type, agr group and the presence of the virulence genes (bbp, clfA, icaA, icaD, fnbB, bap, sasC and IS256) were assessed by PCR. PFGE and multilocus sequence typing (MLST) techniques were also performed. The initial adhesion and biofilm formation were examined by quantitative assays. The surface tension and hydrophobicity of the strains were measured by the contact angle technique to evaluate the association between these parameters and adhesion ability. SCCmecIII and IV strains were less hydrophilic, with a high value for the electron acceptor parameter and higher adhesion in comparison with SCCmecII strains. Only SCCmecIII strains could be characterized as strong biofilm producers. The PFGE showed five major pulsotypes (A–E); however, biofilm production was related to the dissemination of one specific PFGE clone (C) belonging to MLST ST239 (Brazilian epidemic clonal complex). The genes agrI, fnbB and IS256 in SCCmecIII strains were considered as genetic determinants associated with strong biofilm-formation by an ica-independent biofilm pathway. This study contributes to the understanding of biofilm production as an aggravating factor potentially involved in the persistence and severity of infections caused by multidrug-resistant MRSA belonging to this genotype.
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- Microbial Epidemiology
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Population structure of colonizing and invasive Staphylococcus aureus strains in northern Vietnam
Staphylococcus aureus is an important global health problem worldwide. There is still scarce information on the population structure of S. aureus strains in Asia, where the majority of the world population lives. This study characterized the diversity of S. aureus strains in northern Vietnam through multilocus sequence typing (MLST). Eighty-five carriage isolates from the community and 77 invasive isolates from the clinical setting were selected and tested for meticillin resistance and the presence of Panton–Valentine leukocidin (PVL). MLST was performed on these isolates, of which CC59 (25.4 %), CC188 (17.3 %) and CC45 (16.7 %) were the predominant clonal complexes (CCs). CC59 carriage isolates had significantly lower rates of meticillin-resistant S. aureus (MRSA) than their corresponding clinical group isolates (32 vs 83 %). There were no significant differences in rates of MRSA between carriage isolates and clinical isolates of CC45 and CC188. CC59 carriage isolates were significantly lower in rates of PVL+ than CC59 clinical isolates (32 vs 83 %), but the converse was shown in CC45 isolates (14 vs 0 %, respectively). This study revealed vast differences in the molecular epidemiology and population structure of S. aureus in community and clinical settings in Vietnam. Nevertheless, the data underline the spread of virulent and/or resistant strains (MRSA and/or PVL+) in the community, suggesting the necessity for further surveillance to determine the mechanism of transmission of these strains (i.e. MRSA/PVL+) outside clinical settings.
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Molecular epidemiology of bloodstream-associated Escherichia coli ST131 H30-Rx subclone infection in a region with high quinolone resistance
More LessBloodstream infections caused by Escherichia coli ST131 and ST131 H30-Rx subclones have emerged worldwide. This study was carried out to evaluate the prevalence of the ST131-Rx subclone and characterize the virulence properties of the Rx isolates among the bloodstream E. coli isolates. A total of 297 non-duplicated E. coli bloodstream isolates were studied. Antibiotic susceptibilities were tested using the disc diffusion method. PCR amplification and sequencing was used to identify ST131 and H30-Rx, the virulence gene, the β-lactamase and virotype. Quinolone resistance among bacteraemic E. coli strains was 51 %, and it was 98 % among E. coli ST131 isolates. The ST131 isolates accounted for 16 % (49) of all isolates and all ST131 isolates belonged to the extraintestinal pathogenic E. coli. The proportion of H30 subclone among the ST131 isolates was 98 %, and 75 % of H30 isolates belonged to the H30-Rx subclone. The prevalence of ST131 increased from 13 to 23 % in 4 years; however, there was a decrease in the ratio of H30-Rx infections. CTX-M-15 was detected in 85 % of ST131 and all of the H30-Rx isolates. The virulence genes associated with adhesion, cell protection, iron uptake and toxins (papA, iha, kpsMTII, iut and sat) were more common in ST131 than in non-ST131 isolates. Most of the ST131 and H30-Rx isolates were of the C virotype. All papA-positive isolates were in virotype C. The E. coli ST131 clone has increased rapidly among bloodstream isolates. However, a decrease in the proportion of the H30-Rx subclone in the quinolone-resistant population suggests the possibility of dissemination of other virulent and quinolone-resistant subclones in hospital settings.
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Characterization of carbapenem resistance mechanisms and integrons in Pseudomonas aeruginosa strains from blood samples in a French hospital
More LessMetallo-β-lactamases (MBLs), porin OprD, integrons, virulence factors and the clonal relationships were characterized in imipenem-resistant Pseudomonas aeruginosa (IRPA) isolates. Fifty-six IRPA strains were recovered from blood samples of different patients at a Toulouse teaching hospital from 2011 to 2013. Susceptibility testing of 14 antibiotics was performed by the disc diffusion method. Detection and characterization of MBLs, the oprD gene and integrons were studied by PCR and sequencing. Thirteen genes involved in the virulence of P. aeruginosa were analysed. Molecular typing of IRPA strains was performed by PFGE and multilocus sequence typing. In this study, 61 % of the IRPA isolates showed a multi-resistance phenotype. The MBL phenotype, detected in three isolates (5.4 %), was linked to the bla VIM-2 gene. The oprD gene was amplified in 55 (98.2 %) IRPA strains, and variations were observed in 54 of them. Insertion sequences (IS) truncating oprD were detected in eight IRPA strains, with the novel ISPa56 identified in two strains. Class 1 integrons were detected in 24 (42.9 %) IRPA strains. The bla VIM-2 gene was found inside the class 1 integron arrangements. The new integrons In1054 (intI1-aacA56-qacEΔ1-sul1) and In1160 (intI1-aacA4-aacC1d-ISKpn4-gcuE-qacEΔ1-sul1) have been described for the first time, to the best of our knowledge, in this study. A high clonal diversity was found in our strains. Among the variety of sequence types (STs) found, ST175, ST233, ST235, ST244 and ST654 were noteworthy as epidemic clones. In conclusion, 5.4 % of IRPA strains showed an MBL phenotype linked to the bla VIM-2 gene. The identified oprD high polymorphism could be implicated in the variable resistance to carbapenems in IRPA strains. The dissemination of high-risk clones is a cause of concern.
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A comparison of Clostridium difficile diagnostic methods for identification of local strains in a South African centre
Accurate diagnosis of Clostridium difficile infection is essential for disease management. A clinical and molecular analysis of C. difficile isolated from symptomatic patients at Groote Schuur Hospital, South Africa, was conducted to establish the most suitable clinical test for the diagnosis and characterization of locally prevalent strains. C. difficile was detected in stool samples using enzyme-based immunoassays (EIA) and nucleic acid amplification methods, and their performance was compared with that of C. difficile isolation using direct selective culture combined with specific PCR to detect the C. difficile tpi gene, toxin A and B genes and binary toxin genes. Toxigenic isolates were characterized further by ribotyping. Selective culture isolated 32 C. difficile strains from 145 patients (22 %). Of these, the most prevalent (50 %) were of ribotype 017 (toxin A− B+) while 15.6 % were ribotype 001 (toxin A+B+). No ribotype 027 strains or binary toxin genes (cdtA and cdtB) were detected. The test sensitivities and specificities, respectively, of four commercial clinical diagnostic methods were as follows: ImmunoCard Toxins A & B (40 % and 99.1 %), VIDAS C. difficile Toxin A & B (50 % and 99.1 %), GenoType CDiff (86.7 % and 88.3 %) and Xpert C. difficile (90 % and 97.3 %). Ribotype 001 and 017 strains had a 100 % detection rate by Xpert C. difficile, 100 % and 93.3 % by GenoType CDiff, 75 % and 53.3 % by ImmunoCard and 75 % and 60 % by VIDAS, respectively. The overall poor performance of EIA suggests that a change to PCR-based testing would assist diagnosis and ensure reliable detection of locally prevalent C. difficile 017 strains.
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- Prevention and Therapy
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Inhibition of Candida albicans biofilm formation and modulation of gene expression by probiotic cells and supernatant
More LessOral candidiasis is a disease caused by opportunistic species of Candida that normally reside on human mucosal surfaces. The transition of Candida from budding yeast to filamentous hyphae allows for covalent attachment to oral epithelial cells, followed by biofilm formation, invasion and tissue damage. In this study, combinations of Lactobacillus plantarum SD5870, Lactobacillus helveticus CBS N116411 and Streptococcus salivarius DSM 14685 were assessed for their ability to inhibit the formation of and disrupt Candida albicans biofilms. Co-incubation with probiotic supernatants under hyphae-inducing conditions reduced C. albicans biofilm formation by >75 % in all treatment groups. Likewise, combinations of live probiotics reduced biofilm formation of C. albicans by >67 %. When live probiotics or their supernatants were overlaid on preformed C. albicans biofilms, biofilm size was reduced by >63 and >65 % respectively. Quantitative real-time PCR results indicated that the combined supernatants of SD5870 and CBS N116411 significantly reduced the expression of several C. albicans genes involved in the yeast–hyphae transition: ALS3 (adhesin/invasin) by 70 % (P < 0.0001), EFG1 (hyphae-specific gene activator) by 47 % (P = 0.0061), SAP5 (secreted protease) by 49 % (P < 0.0001) and HWP1 (hyphal wall protein critical to biofilm formation) by >99 % (P < 0.0001). These findings suggest the combination of L. plantarum SD5870, L. helveticus CBS N116411 and S. salivarius DSM 14685 is effective at both preventing the formation of and removing preformed C. albicans biofilms. Our novel results point to the downregulation of several Candida genes critical to the yeast–hyphae transition, biofilm formation, tissue invasion and cellular damage.
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Antibiofilm efficacy of honey and bee-derived defensin-1 on multispecies wound biofilm
More LessMany clinically relevant biofilms are polymicrobial. Examining the effect of antimicrobials in a multispecies biofilm consortium is of great clinical importance. The goal of this study was to investigate the effect of different honey types against bacterial wound pathogens grown in multispecies biofilm and to test the antibiofilm activity of honey defensin-1 (Def-1) in its recombinant form. A modified Lubbock chronic wound biofilm formed by four bacterial species (Staphylococcus aureus, Streptococcus agalactiae, Pseudomonas aeruginosa and Enterococcus faecalis) was used for evaluation of honey and recombinant bee-derived Def-1 antibiofilm efficacy. Recombinant Def-1 was prepared by heterologous expression in Escherichia coli. We showed that different types of honey (manuka and honeydew) were able to significantly reduce the cell viability of wound pathogens (Staphylococcus aureus, Streptococcus agalactiae and Pseudomonas aeruginosa) in mature polymicrobial biofilm. None of the tested honeys showed the ability to eradicate Enterococcus faecalis in biofilm. In addition, recombinant Def-1 successfully reduced the viability of Staphylococcus aureus and Pseudomonas aeruginosa cells within established polymicrobial biofilm after 24 and 48 h of treatment. Interestingly, recombinant Def-1 did not affect the viability of Streptococcus agalactiae cells within the biofilm, whereas both natural honeys significantly reduced the viable bacteria. Although Enterococcus faecalis was highly resistant to Def-1, Def-1 significantly affected the biofilm formation of Enterococcus faecalis and Streptococcus agalactiae after 24 h of treatment, most likely by inhibiting its extracellular polymeric substances production. In conclusion, our study revealed that honey and Def-1 are effective against established multispecies biofilm; however, Enterococcus faecalis grown in multispecies biofilm was resistant to both antimicrobials.
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Volumes and issues
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Volume 72 (2022 - 2023)
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Volume 71 (2022)
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Volume 70 (2021)
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Volume 69 (2020)
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Volume 68 (2019)
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Volume 67 (2018)
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Volume 66 (2017)
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Volume 65 (2016)
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Volume 64 (2015)
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Volume 63 (2014)
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Volume 62 (2013)
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Volume 61 (2012)
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Volume 60 (2011)
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Volume 59 (2010)
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Volume 58 (2009)
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Volume 57 (2008)
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Volume 56 (2007)
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Volume 55 (2006)
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Volume 54 (2005)
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Volume 53 (2004)
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Volume 52 (2003)
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Volume 51 (2002)
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Volume 50 (2001)
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Volume 49 (2000)
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Volume 48 (1999)
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Volume 47 (1998)
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Volume 46 (1997)
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Volume 45 (1996)
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Volume 44 (1996)
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Volume 43 (1995)
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Volume 42 (1995)
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Volume 41 (1994)
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Volume 40 (1994)
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Volume 39 (1993)
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Volume 38 (1993)
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Volume 37 (1992)
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Volume 36 (1992)
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Volume 35 (1991)
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Volume 34 (1991)
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Volume 33 (1990)
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Volume 32 (1990)
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Volume 31 (1990)
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Volume 30 (1989)
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Volume 29 (1989)
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Volume 28 (1989)
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Volume 27 (1988)
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Volume 26 (1988)
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Volume 25 (1988)
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Volume 24 (1987)
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Volume 23 (1987)
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Volume 22 (1986)
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Volume 21 (1986)
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Volume 20 (1985)
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Volume 19 (1985)
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Volume 18 (1984)
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Volume 17 (1984)
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Volume 16 (1983)
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Volume 15 (1982)
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Volume 14 (1981)
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Volume 13 (1980)
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Volume 12 (1979)
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Volume 11 (1978)
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Volume 10 (1977)
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Volume 9 (1976)
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Volume 8 (1975)
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Volume 7 (1974)
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Volume 6 (1973)
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Volume 5 (1972)
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Volume 4 (1971)
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Volume 3 (1970)
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Volume 2 (1969)
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Volume 1 (1968)
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