What is Medical Microbiology? Medical Microbiology is the study of microbes that infect humans, the diseases they cause, their diagnosis, prevention & treatment. It also deals with the response of the human host to microbial and other antigens. Microbes, or microorganisms are minute living things that are usually unable to be viewed with the naked eye.

Medical Microbiology Why is it Important? Infection is one of the most important causes of mortality and morbidity in the population. Approximately 30% of hospital patients are on antibiotics at any one time 1 in 10 patients acquires an infection whilst in hospital.

How to Study Medical Microbiology? Fundamentals of Microbiology Bacteriology Virology Mycology Dr.T.V.Rao MD

Pathogenic Prokaryotes Bacteria Mycoplasma Spirochetes Chlamydiae Rickettsia Actinomyces Dr.T.V.Rao MD

Pathogens Subcellular Infectious Entities: Prions (proteinaceous infectious particles). The evidence indicates that prions are protein molecules that cause degenerative central nervous system (CNS) diseases such as Creutzfeldt-Jakob disease, kuru, scrapie in sheep, and bovine spongiform encephalopathy (BSE) (general term: transmissible spongiformencephalopathies [TSE]). Viruses. Ultramicroscopic, obligate intracellular parasites that: — contain only one type of nucleic acid, either DNA or RNA, — possess no enzymatic energy-producing system and no protein-synthesizing apparatus, and — force infected host cells to synthesize virus particles.

Prion A kind of infectious protein that can resist the digestion of proteinase The cellular form of the prion protein (PrPc) is encoded by the host’s chromosomal DNA An abnormal isoform of this protein (PrPres) is the only known component of the prion and is associated with transmissibility. Kuru, Creutzfeldt-Jakob disease (CJD), Gerstmann- Sträussler-Scheinker disease, fatal familial insomnia , and Bovine spongiform encephalopathy (BSE) Dr.T.V.Rao MD

Viroid Small, single-stranded, covalently closed circular RNA molecules existing as highly base-paired rod-like structures; they do not possess capsids They range in size from 246 to 375 nucleotides in length. The extracellular form of the viroid is naked RNA—there is no capsid of any kind The RNA molecule contains no protein-encoding genes, and the viroid is therefore totally dependent on host functions for its replication The RNAs of viroids have been shown to contain inverted repeated base sequences at their 3' and 5' ends, a characteristic of transposable elements and retroviruses. Thus, it is likely that they have evolved from transposable elements or retroviruses by the deletion of internal sequences

How to Study Medical Microbiology? Fundamentals of Microbiology Biological Properties Morphology, identification, Antigenic structure Pathogenesis and Pathology Clinical findings Diagnostic Laboratory Tests Immunity Treatment & Prevention Epidemiology & Control Bacteriology Virology Mycology Dr.T.V.Rao MD

Successful infectious microorganisms must take certain obligatory steps: Obligatory steps for infectious microorganisms Step Requirement Phenomenon Attachment ± entry into body Evade natural protective and cleansing mechanisms Entry (infection Local or generalspread in the body Evade immediate local defences Spread Multiplication Increase numbers (many will die in the host, or in route to new hosts) Evasion of host defences Evade immune and other defences long enough for the full cycle in the host to be completed Microbial answer to host defences Shedding from body (exit) Leave body at a site and on a scale that ensures spread to fresh hosts Transmission Cause damage in host Not strictly necessary but often occurs Pathology, disease

a The last step, causing damage in the host, is not strictly necessary, but a certain amount of damage may be essential for shedding. The outpouring of infectious fluids in the common cold or diarrhea, for instance, or the trickle from vesicular or pustular lesions, is required for transmission to fresh hosts.

Major Bacterial Pathogens is divided into organisms that are readily Gram stained and those that are not. The readily stained organisms fall into four categories: gram-positive cocci, gram-negative cocci, gram-positive rods, gram-negative rods. Because there are so many kinds of gram-negative rods, they have been divided into three groups: (1) Organisms associated with the enteric tract (2) Organisms associated with the respiratory tract (3) Organisms from animal sources (zoonotic bacteria)