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Britton KJ, Pickering JL, Pomat WS, de Gier C, Nation ML, Pell CL, Granland CM, Solomon V, Ford RL, Greenhill A, Hinds J, Moore HC, Richmond PC, Blyth CC, Lehmann D, Satzke C, Kirkham LAS. Lack of effectiveness of 13-valent pneumococcal conjugate vaccination against pneumococcal carriage density in Papua New Guinean infants. Vaccine 2021; 39:5401-5409. [PMID: 34384633 DOI: 10.1016/j.vaccine.2021.07.085] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2021] [Revised: 07/22/2021] [Accepted: 07/26/2021] [Indexed: 11/17/2022]
Abstract
BACKGROUND Papua New Guinea (PNG) introduced the 13-valent pneumococcal conjugate vaccine (PCV13) in 2014, with administration at 1, 2, and 3 months of age. PCV13 has reduced or eliminated carriage of vaccine types in populations with low pneumococcal carriage prevalence, carriage density and serotype diversity. This study investigated PCV13 impact on serotype-specific pneumococcal carriage prevalence, density, and serotype diversity in PNG infants, who have some of the highest reported rates of pneumococcal carriage and disease in the world. METHODS Nasopharyngeal swabs were collected at 1, 4 and 9 months of age from PCV13-vaccinated infants (n = 57) and age-/season-matched, unvaccinated infants (at approximately 1 month, n = 53; 4 months, n = 57; 9 months, n = 52). Serotype-specific pneumococcal carriage density and antimicrobial resistance genes were identified by qPCR and microarray. RESULTS Pneumococci were present in 89% of swabs, with 60 different serotypes and four non-encapsulated variants detected. Multiple serotype carriage was common (47% of swabs). Vaccine type carriage prevalence was similar between PCV13-vaccinated and unvaccinated infants at 4 and 9 months of age. The prevalence of non-vaccine type carriage was also similar between cohorts, with non-vaccine types present in three-quarters of samples (from both vaccinated and unvaccinated infants) by 4 months of age. The median pneumococcal carriage density was high and similar at each age group (~7.0 log10genome equivalents/mL). PCV13 had no effect on overall pneumococcal carriage density, vaccine type density, non-vaccine type density, or the prevalence of antimicrobial resistance genes. CONCLUSION PNG infants experience dense and diverse pneumococcal colonisation with concurrent serotypes from 1 month of age. PCV13 had no impact on pneumococcal carriage density, even for vaccine serotypes. The low prevalence of vaccine serotypes, high pneumococcal carriage density and abundance of non-vaccine serotypes likely contribute to the lack of PCV13 impact on carriage in PNG infants. Indirect effects of the infant PCV programs are likely to be limited in PNG. Alternative vaccines with broader coverage should be considered.
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Affiliation(s)
- Kathryn J Britton
- Wesfarmers Centre of Vaccines and Infectious Diseases, Telethon Kids Institute, The University of Western Australia, Perth, Australia; Division of Paediatrics, School of Medicine, The University of Western Australia, Perth, Australia.
| | - Janessa L Pickering
- Wesfarmers Centre of Vaccines and Infectious Diseases, Telethon Kids Institute, The University of Western Australia, Perth, Australia.
| | - William S Pomat
- Wesfarmers Centre of Vaccines and Infectious Diseases, Telethon Kids Institute, The University of Western Australia, Perth, Australia; Papua New Guinea Institute of Medical Research, Goroka, Papua New Guinea.
| | - Camilla de Gier
- Wesfarmers Centre of Vaccines and Infectious Diseases, Telethon Kids Institute, The University of Western Australia, Perth, Australia; Division of Paediatrics, School of Medicine, The University of Western Australia, Perth, Australia.
| | - Monica L Nation
- Translational Microbiology Group, Murdoch Children's Research Institute, Melbourne, Australia.
| | - Casey L Pell
- Translational Microbiology Group, Murdoch Children's Research Institute, Melbourne, Australia.
| | - Caitlyn M Granland
- Wesfarmers Centre of Vaccines and Infectious Diseases, Telethon Kids Institute, The University of Western Australia, Perth, Australia.
| | - Vela Solomon
- Papua New Guinea Institute of Medical Research, Goroka, Papua New Guinea.
| | - Rebecca L Ford
- Papua New Guinea Institute of Medical Research, Goroka, Papua New Guinea.
| | - Andrew Greenhill
- School of Health and Life Sciences, Federation University, Victoria, Australia.
| | - Jason Hinds
- Institute for Infection and Immunity, St. George's University of London, London, United Kingdom.
| | - Hannah C Moore
- Wesfarmers Centre of Vaccines and Infectious Diseases, Telethon Kids Institute, The University of Western Australia, Perth, Australia.
| | - Peter C Richmond
- Wesfarmers Centre of Vaccines and Infectious Diseases, Telethon Kids Institute, The University of Western Australia, Perth, Australia; Division of Paediatrics, School of Medicine, The University of Western Australia, Perth, Australia.
| | - Christopher C Blyth
- Wesfarmers Centre of Vaccines and Infectious Diseases, Telethon Kids Institute, The University of Western Australia, Perth, Australia; Division of Paediatrics, School of Medicine, The University of Western Australia, Perth, Australia; Department of Paediatric Infectious Diseases, Perth Children's Hospital, Perth, Australia; Department of Microbiology, PathWest Laboratory Medicine WA, QEII Medical Centre, Perth, Australia.
| | - Deborah Lehmann
- Wesfarmers Centre of Vaccines and Infectious Diseases, Telethon Kids Institute, The University of Western Australia, Perth, Australia.
| | - Catherine Satzke
- Translational Microbiology Group, Murdoch Children's Research Institute, Melbourne, Australia; Department of Paediatrics, The University of Melbourne, Melbourne, Australia; Department of Microbiology and Immunology, The University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, Australia.
| | - Lea-Ann S Kirkham
- Wesfarmers Centre of Vaccines and Infectious Diseases, Telethon Kids Institute, The University of Western Australia, Perth, Australia; Centre for Child Health Research, The University of Western Australia, Perth, Australia.
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Pickering JL, Barth DD, Bowen AC. Performance and Practicality of a Rapid Molecular Test for the Diagnosis of Strep A Pharyngitis in a Remote Australian Setting. Am J Trop Med Hyg 2020; 103:2530-2532. [PMID: 32901604 DOI: 10.4269/ajtmh.20-0341] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Over 5 days, 120 schoolchildren from two schools in the remote Kimberley region of Australia were screened for Strep A pharyngitis. Molecular point-of-care testing identified Strep A pharyngitis in 13/18 (72.2%) symptomatic children. The portability and feasibility of molecular point-of-care testing was highly practical for remote settings.
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Affiliation(s)
- Janessa L Pickering
- Wesfarmer's Centre for Vaccines and Infectious Diseases, Telethon Kids Institute, Nedlands, Australia.,Centre for Child Health Research, University of Western Australia, Nedlands, Australia
| | - Dylan D Barth
- Centre for Child Health Research, University of Western Australia, Nedlands, Australia.,Wesfarmer's Centre for Vaccines and Infectious Diseases, Telethon Kids Institute, Nedlands, Australia
| | - Asha C Bowen
- Menzies School of Health Research, Charles Darwin University, Darwin, Australia.,Wesfarmer's Centre for Vaccines and Infectious Diseases, Telethon Kids Institute, Nedlands, Australia.,Department of Infectious Diseases, Perth Children's Hospital, Nedlands, Australia.,Centre for Child Health Research, University of Western Australia, Nedlands, Australia
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de Gier C, Granland CM, Pickering JL, Walls T, Bhuiyan M, Mills N, Richmond PC, Best EJ, Thornton RB, Kirkham LAS. PCV7- and PCV10-Vaccinated Otitis-Prone Children in New Zealand Have Similar Pneumococcal and Haemophilus influenzae Densities in Their Nasopharynx and Middle Ear. Vaccines (Basel) 2019; 7:vaccines7010014. [PMID: 30708945 PMCID: PMC6466140 DOI: 10.3390/vaccines7010014] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Revised: 01/17/2019] [Accepted: 01/29/2019] [Indexed: 12/30/2022] Open
Abstract
Otitis media (OM) is a major reason for antibiotic consumption and surgery in children. Nasopharyngeal carriage of otopathogens, Streptococcus pneumoniae and nontypeable Haemophilus influenzae (NTHi), is a prerequisite for development of OM, and increased nasopharyngeal otopathogen density correlates with disease onset. Vaccines can reduce or eliminate otopathogen carriage, as demonstrated for pneumococcal serotypes included in pneumococcal conjugate vaccines (PCV). The 10-valent PCV (PCV10) includes an NTHi carrier protein, and in 2011 superseded 7-valent PCV on the New Zealand Immunisation Program. Data are conflicting on whether PCV10 provides protection against NTHi carriage or disease. Assessing this in otitis-prone cohorts is important for OM prevention. We compared otopathogen density in the nasopharynx and middle ear of New Zealand PCV7-vaccinated and PCV10-vaccinated otitis-prone and non-otitis-prone children to determine PCV10 impact on NTHi and S. pneumoniae carriage. We applied qPCR to specimens collected from 217 PCV7-vaccinated children (147 otitis-prone and 70 non-otitis-prone) and 240 PCV10-vaccinated children (178 otitis-prone and 62 non-otitis-prone). After correcting for age and day-care attendance, no difference was observed between NTHi density in the nasopharynx of PCV7-vaccinated versus PCV10-vaccinated otitis-prone (p = 0.563) or non-otitis-prone (p = 0.513) children. In contrast, pneumococcal nasopharyngeal density was higher in PCV10-vaccinated otitis-prone children than PCV7-vaccinated otitis-prone children (p = 0.003). There was no difference in otopathogen density in middle ear effusion from PCV7-vaccinated versus PCV10-vaccinated otitis-prone children (NTHi p = 0.918; S. pneumoniae p = 0.415). When pneumococcal carriage was assessed by vaccine serotypes (VT) and non-vaccine serotypes (NVT), there was no difference in VT density (p = 0.546) or NVT density (p = 0.315) between all PCV7-vaccinated versus all PCV10-vaccinated children. In summary, PCV10 did not reduce NTHi density in the nasopharynx or middle ear, and was associated with increased pneumococcal nasopharyngeal density in otitis-prone children in New Zealand. Development of therapies that prevent or reduce otopathogen colonisation density in the nasopharynx are warranted to reduce the burden of OM.
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Affiliation(s)
- Camilla de Gier
- School of Medicine, University of Western Australia, Perth 6009, Australia.
- Wesfarmers Centre of Vaccines and Infectious Disease, Telethon Kids Institute, Perth 6009, Australia.
| | - Caitlyn M Granland
- Wesfarmers Centre of Vaccines and Infectious Disease, Telethon Kids Institute, Perth 6009, Australia.
| | - Janessa L Pickering
- Wesfarmers Centre of Vaccines and Infectious Disease, Telethon Kids Institute, Perth 6009, Australia.
| | - Tony Walls
- Department of Paediatrics, University of Otago, Christchurch 8011, New Zealand.
| | - Mejbah Bhuiyan
- School of Medicine, University of Western Australia, Perth 6009, Australia.
- Wesfarmers Centre of Vaccines and Infectious Disease, Telethon Kids Institute, Perth 6009, Australia.
| | - Nikki Mills
- Starship Hospital, Auckland 1023, New Zealand.
- School of Medicine, University of Auckland, Auckland 1023, New Zealand.
| | - Peter C Richmond
- School of Medicine, University of Western Australia, Perth 6009, Australia.
- Wesfarmers Centre of Vaccines and Infectious Disease, Telethon Kids Institute, Perth 6009, Australia.
- Department of General Paediatrics, Perth Children's Hospital, Perth 6009, Australia.
| | - Emma J Best
- Starship Hospital, Auckland 1023, New Zealand.
- School of Medicine, University of Auckland, Auckland 1023, New Zealand.
| | - Ruth B Thornton
- School of Medicine, University of Western Australia, Perth 6009, Australia.
- Wesfarmers Centre of Vaccines and Infectious Disease, Telethon Kids Institute, Perth 6009, Australia.
| | - Lea-Ann S Kirkham
- Wesfarmers Centre of Vaccines and Infectious Disease, Telethon Kids Institute, Perth 6009, Australia.
- Centre for Child Health Research, University of Western Australia, Perth 6009, Australia.
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Blakeway LV, Tan A, Lappan R, Ariff A, Pickering JL, Peacock CS, Blyth CC, Kahler CM, Chang BJ, Lehmann D, Kirkham LAS, Murphy TF, Jennings MP, Bakaletz LO, Atack JM, Peak IR, Seib KL. Moraxella catarrhalis Restriction-Modification Systems Are Associated with Phylogenetic Lineage and Disease. Genome Biol Evol 2018; 10:2932-2946. [PMID: 30335144 PMCID: PMC6241649 DOI: 10.1093/gbe/evy226] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/16/2018] [Indexed: 01/25/2023] Open
Abstract
Moraxella catarrhalis is a human-adapted pathogen, and a major cause of otitis media (OM) and exacerbations of chronic obstructive pulmonary disease. The species is comprised of two main phylogenetic lineages, RB1 and RB2/3. Restriction–modification (R-M) systems are among the few lineage-associated genes identified in other bacterial genera and have multiple functions including defense against foreign invading DNA, maintenance of speciation, and epigenetic regulation of gene expression. Here, we define the repertoire of R-M systems in 51 publicly available M. catarrhalis genomes and report their distribution among M. catarrhalis phylogenetic lineages. An association with phylogenetic lineage (RB1 or RB2/3) was observed for six R-M systems, which may contribute to the evolution of the lineages by restricting DNA transformation. In addition, we observed a relationship between a mutually exclusive Type I R-M system and a Type III R-M system at a single locus conserved throughout a geographically and clinically diverse set of M. catarrhalis isolates. The Type III R-M system at this locus contains the phase-variable Type III DNA methyltransferase, modM, which controls a phasevarion (phase-variable regulon). We observed an association between modM presence and OM-associated middle ear isolates, indicating a potential role for ModM-mediated epigenetic regulation in OM pathobiology.
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Affiliation(s)
- Luke V Blakeway
- Institute for Glycomics, Griffith University, Gold Coast, Queensland, Australia
| | - Aimee Tan
- Institute for Glycomics, Griffith University, Gold Coast, Queensland, Australia
| | - Rachael Lappan
- The Marshall Centre for Infectious Diseases Research and Training, School of Biomedical Sciences, The University of Western Australia, Perth, Western Australia, Australia.,Wesfarmers Centre of Vaccines and Infectious Diseases, Telethon Kids Institute, The University of Western Australia, Perth, Western Australia, Australia
| | - Amir Ariff
- The Marshall Centre for Infectious Diseases Research and Training, School of Biomedical Sciences, The University of Western Australia, Perth, Western Australia, Australia
| | - Janessa L Pickering
- Wesfarmers Centre of Vaccines and Infectious Diseases, Telethon Kids Institute, The University of Western Australia, Perth, Western Australia, Australia.,School of Biomedical Sciences, The University of Western Australia, Perth, Western Australia, Australia
| | - Christopher S Peacock
- The Marshall Centre for Infectious Diseases Research and Training, School of Biomedical Sciences, The University of Western Australia, Perth, Western Australia, Australia.,Wesfarmers Centre of Vaccines and Infectious Diseases, Telethon Kids Institute, The University of Western Australia, Perth, Western Australia, Australia
| | - Christopher C Blyth
- Wesfarmers Centre of Vaccines and Infectious Diseases, Telethon Kids Institute, The University of Western Australia, Perth, Western Australia, Australia.,School of Medicine, The University of Western Australia, Perth, Western Australia, Australia.,Department of Infectious Diseases, Perth Chilren's Hospital, Perth, Western Australia, Australia.,Department of Microbiology, PathWest Laboratory Medicine, QEII Medical Centre, Perth, Western Australia, Australia
| | - Charlene M Kahler
- The Marshall Centre for Infectious Diseases Research and Training, School of Biomedical Sciences, The University of Western Australia, Perth, Western Australia, Australia.,Wesfarmers Centre of Vaccines and Infectious Diseases, Telethon Kids Institute, The University of Western Australia, Perth, Western Australia, Australia
| | - Barbara J Chang
- The Marshall Centre for Infectious Diseases Research and Training, School of Biomedical Sciences, The University of Western Australia, Perth, Western Australia, Australia
| | - Deborah Lehmann
- Wesfarmers Centre of Vaccines and Infectious Diseases, Telethon Kids Institute, The University of Western Australia, Perth, Western Australia, Australia
| | - Lea-Ann S Kirkham
- Wesfarmers Centre of Vaccines and Infectious Diseases, Telethon Kids Institute, The University of Western Australia, Perth, Western Australia, Australia.,School of Biomedical Sciences, The University of Western Australia, Perth, Western Australia, Australia
| | - Timothy F Murphy
- Clinical and Translational Research Center, University at Buffalo, the State University of New York, Buffalo, New York, USA
| | - Michael P Jennings
- Institute for Glycomics, Griffith University, Gold Coast, Queensland, Australia
| | - Lauren O Bakaletz
- Center for Microbial Pathogenesis, The Research Institute at Nationwide Children's Hospital, Columbus, Ohio, USA.,Department of Pediatrics, The Ohio State University College of Medicine, Columbus, Ohio, USA
| | - John M Atack
- Institute for Glycomics, Griffith University, Gold Coast, Queensland, Australia
| | - Ian R Peak
- Institute for Glycomics, Griffith University, Gold Coast, Queensland, Australia.,School of Medical Science, Griffith University, Gold Coast, Queensland, Australia
| | - Kate L Seib
- Institute for Glycomics, Griffith University, Gold Coast, Queensland, Australia
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Pickering JL, Prosser A, Corscadden KJ, de Gier C, Richmond PC, Zhang G, Thornton RB, Kirkham LAS. Haemophilus haemolyticus Interaction with Host Cells Is Different to Nontypeable Haemophilus influenzae and Prevents NTHi Association with Epithelial Cells. Front Cell Infect Microbiol 2016; 6:50. [PMID: 27242968 PMCID: PMC4860508 DOI: 10.3389/fcimb.2016.00050] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2016] [Accepted: 04/18/2016] [Indexed: 02/02/2023] Open
Abstract
Nontypeable Haemophilus influenzae (NTHi) is an opportunistic pathogen that resides in the upper respiratory tract and contributes to a significant burden of respiratory related diseases in children and adults. Haemophilus haemolyticus is a respiratory tract commensal that can be misidentified as NTHi due to high levels of genetic relatedness. There are reports of invasive disease from H. haemolyticus, which further blurs the species boundary with NTHi. To investigate differences in pathogenicity between these species, we optimized an in vitro epithelial cell model to compare the interaction of 10 H. haemolyticus strains with 4 NTHi and 4 H. influenzae-like haemophili. There was inter- and intra-species variability but overall, H. haemolyticus had reduced capacity to attach to and invade nasopharyngeal and bronchoalveolar epithelial cell lines (D562 and A549) within 3 h when compared with NTHi. H. haemolyticus was cytotoxic to both cell lines at 24 h, whereas NTHi was not. Nasopharyngeal epithelium challenged with some H. haemolyticus strains released high levels of inflammatory mediators IL-6 and IL-8, whereas NTHi did not elicit an inflammatory response despite higher levels of cell association and invasion. Furthermore, peripheral blood mononuclear cells stimulated with H. haemolyticus or NTHi released similar and high levels of IL-6, IL-8, IL-10, IL-1β, and TNFα when compared with unstimulated cells but only NTHi elicited an IFNγ response. Due to the relatedness of H. haemolyticus and NTHi, we hypothesized that H. haemolyticus may compete with NTHi for colonization of the respiratory tract. We observed that in vitro pre-treatment of epithelial cells with H. haemolyticus significantly reduced NTHi attachment, suggesting interference or competition between the two species is possible and warrants further investigation. In conclusion, H. haemolyticus interacts differently with host cells compared to NTHi, with different immunostimulatory and cytotoxic properties. This study provides an in vitro model for further investigation into the pathogenesis of Haemophilus species and the foundation for exploring whether H. haemolyticus can be used to prevent NTHi disease.
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Affiliation(s)
- Janessa L Pickering
- Wesfarmers Centre of Vaccines and Infectious Diseases, Telethon Kids Institute, The University of Western AustraliaPerth, WA, Australia; School of Paediatrics and Child Health, The University of Western AustraliaPerth, WA, Australia
| | - Amy Prosser
- School of Paediatrics and Child Health, The University of Western Australia Perth, WA, Australia
| | - Karli J Corscadden
- Wesfarmers Centre of Vaccines and Infectious Diseases, Telethon Kids Institute, The University of Western Australia Perth, WA, Australia
| | - Camilla de Gier
- School of Paediatrics and Child Health, The University of Western Australia Perth, WA, Australia
| | - Peter C Richmond
- Wesfarmers Centre of Vaccines and Infectious Diseases, Telethon Kids Institute, The University of Western AustraliaPerth, WA, Australia; School of Paediatrics and Child Health, The University of Western AustraliaPerth, WA, Australia; Department of Paediatrics, Princess Margaret Hospital for ChildrenPerth, WA, Australia
| | - Guicheng Zhang
- School of Public Health, Curtin University Perth, WA, Australia
| | - Ruth B Thornton
- Wesfarmers Centre of Vaccines and Infectious Diseases, Telethon Kids Institute, The University of Western AustraliaPerth, WA, Australia; School of Paediatrics and Child Health, The University of Western AustraliaPerth, WA, Australia
| | - Lea-Ann S Kirkham
- Wesfarmers Centre of Vaccines and Infectious Diseases, Telethon Kids Institute, The University of Western AustraliaPerth, WA, Australia; School of Paediatrics and Child Health, The University of Western AustraliaPerth, WA, Australia
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Loutfi A, Pickering JL. The spectrum of surgery in Ethiopia. Can J Surg 1993; 36:91-5. [PMID: 8443727] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Ethiopia's need for surgical services is assessed from on-site reviews of operating-room records in various hospitals and compared with data from other countries. Information on surgical manpower and total operations for the country were obtained from the Ministry of Health of Ethiopia. In Ethiopia the ratio of surgeons to population is very low (0.32 surgeons per 100,000 population) and inadequate numbers of essential operations (e.g., cesarean section and inguinal-hernia repair) are performed. The average age of the surgical patient is young (37 years), and men are operated on twice as frequently as women. Of the 9422 operations performed during 6 months in the central, regional and rural hospitals surveyed, 7037 (75%) could be performed by a general practitioner or a paramedic specially trained for the procedure and would not require a fully trained general surgeon. The implications for surgical manpower training are discussed.
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Affiliation(s)
- A Loutfi
- Department of Surgery, McGill University, Montreal, Que
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Lo EK, Coukell MB, Tsang AS, Pickering JL. Physiological and biochemical characterization of aggregation-deficient mutants of Dictyostelium discoideum: detection and response to exogenous cyclic AMP. Can J Microbiol 1978; 24:455-65. [PMID: 205330 DOI: 10.1139/m78-075] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Forty independently isolated aggregation-deficient (Agg−) mutants of Dictyostelium discoideum, which have been partially characterized genetically, were examined for the ability to respond chemotactically to exogenous cAMP and for certain cellular and extracellular activities thought to be involved in this process. Only five of the mutants failed to produce a statistically significant chemotactic response to cAMP. When shaken in buffer, most of the Agg− mutants produced reduced levels of the cAMP-binding sites and the cell-bound cAMP phosphodiesterase reported to be components of a cell-surface cAMP receptor involved in the chemotactic response. In addition, most of the mutants failed to form contact sites A and were unable to develop on water agar plates. When the mutants were pulsed with 100 nM cAMP, 36 of 40 mutants produced detectable contact sites A and three-quarters of these strains underwent further development when placed on a solid substratum. Treatment with cAMP pulses also stimulated certain mutants to form higher levels of cAMP receptors. These observations suggest that the impaired differentiation of the plasma membrane of many Agg− mutants is due, at least in part, to the abnormal synthesis and (or) secretion of cAMP by these strains. When grown in bacterial suspension, all 40 of the mutants produced extracellular phosphodiesterase (ePD) activity, and all but 8 of the mutants secreted detectable amounts of the ePD inhibitor. In general, Agg− strains carrying mutations at the same aggregation locus (aggF–J) exhibited very similar physiological and biochemical properties.
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