"SLE334 Medical Microbiology and Immunology, T2, 2017Topic 1: The Enemy – MicrobesThe Bacteria(Mims’ Chapters 1 & 2)Lecture 3Friday 14 July 2017LT13 (HC2.005), 11am-12 pm(date, time and venue different for Geelong students)Dr Sharon La [email protected] Medical Microbiology and Immunology, T2, 2017This lecture will cover……•? Basic biology of bacteria- the generalised bacterial cell- cell wall structure and the Gram stain•? Bacterial division and growth•? Formation of endospores •? Exchange of genetic material•? Identification and classification of bacteria•? Brief overview of bacteria and disease•? Introduction to antibiotics SLE334 Medical Microbiology and Immunology, T2, 2017Top 6 killers (2004)Infections responsible for the greatestnumbers of deaths in the world (datafrom 2004). 2008http://www.bcm.edu/molvir/idSLE334 Medical Microbiology and Immunology, T2, 2017Top killers (2012)Deaths due to infectious diseases are highlightedSource: World Health Organizationhttps://www.bcm.edu/departments/molecular-virology-and-microbiology/emerging-infections-and-biodefense/introduction-to-infectious-diseases SLE334 Medical Microbiology and Immunology, T2, 2017Top killers (2015)•? Lower respiratory infections were among the leading causes of death across all income groups•? Non-communicable diseases (NCDs) caused 70% of deaths globally" •? All but 1 of the 10 leading causes of death in high-income countries were NCDs•? HIV/AIDS is no longer among the world’s top 10 causes of death.Source: World Health Organization: http://www.who.int/mediacentre/factsheets/fs310/en/index1.htmlSLE334 Medical Microbiology and Immunology, T2, 2017Challenges in Infectious Disease Research•? Despite significant advances in infectious disease research and treatment, thecontrol and eradication of these diseases faces major challenges. •? A WHO report released in 2007 warns that:- infectious diseases are spreading more rapidly than ever before - new infectious diseases are being discovered at a higher rate than at anytime in history- in the past five years, the WHO has identified over 1000 epidemics ofinfectious diseases including avian flu, swine flu, polio, and cholera. •? With greatly increased human mobility, infectious diseases have the potentialto swiftly become global epidemics and pandemics.•? Some of the reasons for difficulty in combating infectious diseases are:v? New infectious diseases continue to emergev? Old infectious diseases increase in incidence or geographical distributionv? Old infectious diseases previously under control begin to re-emergev? Potential for intentional introduction of infectious agents by bioterroristsv? Increasing resistance of pathogens to current antimicrobial drugsv? Breakdowns in public health systems and communication between nationsSource: World Health Organizationhttps://www.bcm.edu/departments/molecular-virology-and-microbiology/emerging-infections-and-biodefense/introduction-to-infectious-diseases SLE334 Medical Microbiology and Immunology, T2, 2017Name the different types of microbes /parasites?SLE334 Medical Microbiology and Immunology, T2, 2017Parasite andpathogens•? Parasite –? an organism that livesin or on the livingtissue of a hostorganism at theexpense of that host. •? Pathogen –? a specific biologicalcausative agent ofdiseaseSLE334 Medical Microbiology and Immunology, T2, 2017Prokaryotes andEukaryotes Bacteria areprokaryotes and sharemany commonbiochemical pathways(e.g. glycolysis) witheukaryotic cells, butalso have uniquepathways that aretargets for antibiotics.Major features of cellular organisation SLE334 Medical Microbiology and Immunology, T2, 2017Basic biology ofbacteria•? Bacteria are single cell organisms that existeither as free living cells or colonies.•? Bacteria have acell membrane and a cell wall that protectsthem from their environment. SLE334 Medical Microbiology and Immunology, T2, 2017Basic biology of bacteriaSLE334 Medical Microbiology and Immunology, T2, 2017Generalised BacteriumSLE334 Medical Microbiology and Immunology, T2, 2017The bacterial cell wall comes in two forms thatare distinguished by the “Gram stain” •? Gram positive bacteriahave a simpler wallstructure with a relativelylarge amount ofpeptidoglycan (murein).•? Peptidoglycan = polymerof disaccharides cross- linked by short chains ofamino acids•? Gram negative bacteriahave a more complex cellwall structure. SLE334 Medical Microbiology and Immunology, T2, 2017Bacterial cell walls are distinguished by the“Gram stain” The Gram stain uses two dyes: one purple, the other red. The purple dye binds strongly to the cell wall of Gram positive bacteria, butis easily washed out of the wall of Gram negative bacteria, leaving these apink/red colour. SLE334 Medical Microbiology and Immunology, T2, 2017QuestionDo you think it is important to understand thedifferences in bacterial cell wall structures?Why?SLE334 Medical Microbiology and Immunology, T2, 2017Why is it important to understand thedifferences in bacterial cell wall structures?•? Fundamental differences in cell wall structure allowbacteria to be divided into two broad groups basedon a simple staining procedure – the Gram stain - Gram positive and Gram negative•? Important for diagnosis of infectious disease - direct Gram staining of clinical specimens - guides choice of further diagnostic tests - guides physician on initial choice of antibiotic,pending further tests SLE334 Medical Microbiology and Immunology, T2, 2017Why is it important to understand thedifferences in bacterial cell wall structures?•? Helps us to understand why some bacteriaare susceptible or resistant to certainantibiotics – eg penicillin•? Can determine the type of host response tobacterial infection•? For the bacteria, the cell wall structureinfluences their habitat•? Protects them from osmotic lysisSLE334 Medical Microbiology and Immunology, T2, 2017The Gram stain Heat-fix cells to slide SLE334 Medical Microbiology and Immunology, T2, 2017Gram-negative E. coliSLE334 Medical Microbiology and Immunology, T2, 2017Gram-positive cocci in tissue cellculture "