Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Epidemiology wikipedia , lookup
Eradication of infectious diseases wikipedia , lookup
Diseases of poverty wikipedia , lookup
Marburg virus disease wikipedia , lookup
Public health genomics wikipedia , lookup
Focal infection theory wikipedia , lookup
Compartmental models in epidemiology wikipedia , lookup
Hygiene hypothesis wikipedia , lookup
Principles of Infection Control Dr J Mooney, PhD Categories of Disease Contagious disease /infection transmissible diseases (i.e.: transmit from person to person) by physical contact with the person suffering the disease casual contact with their Non-contagious disease / infection requires a special mode of transmission between persons or host bodily secretions including exhaled particles objects they have touched vector species (e.g.: anopheles [malarial] mosquito) non-casual transfer of bodily fluid (e.g.;\ transfusions; needle sharing; sexual contact) genetic inheritance (autosomal dominant; autosomnal recessive) environmental factors (e.g.: goitre formation and low iodine intake) behavioural (e.g.: cigarette smoking) usually more harmful and painful than contagious diseases. The boundary between categories is not perfectly drawn E.g.: TB is contagious and also subject to environmental factors Infection Invasion of body tissues by disease-inducing microorganisms and The reaction of those tissues to the microorganisms and/or their toxins NB: The mere presence of microorganisms without tissue reaction is not evidence of infection Concept of MO load >106 MOs / mm3 affected tissue NNB: >103 MOs / mm3 affected tissue in DM Eukaryocytes * ** 50% Biomass Eukaryocyte organisms nucleated cells ** Single celled animals and plants All multi-celled animals All multi-celled plants NB: Biomass = Total mass of living matter within a given unit of environmental area Prokaryocytes ** Prokaryocytes = non-nucleated MOs * * e.g.: bacteria Found everywhere - sea water, soil, air, gastrointestinal tracts, hot springs, and in rocks Cover all non-sterilized surfaces Prokaryocyte organsism are estimated to make up remaining 50% of earth’s biomass Microorganisms (MOs) MOs are a very diverse group of unicellular eukaryotic and prokaryotic organisms essential to all ecosystems MOs live in all parts of the biosphere where there is liquid water Include bacteria, fungi, archaea, and protists; microscopic plants (green algae); and animals such as plankton and the planarian. Some microbiologists also include viruses, (others do not, classing viruses to be non-living organic material) Soil, hot springs, on the ocean floor, high in the atmosphere and deep inside rocks MOs are critical to ecosystems Nutrient recycling where they act as decomposers Nitrogen fixation: vital part of the nitrogen cycle Airborne MOs may play a role in precipitation and weather Bacteria Prokaryocytic MOs, ~1-5 X10-6mm long surrounded by a cell wall, Also harbor small pieces of DNA called plasmids Plasmids can transfer via bacterial conjugation. Reproduce by binary fission Do not undergo sexual reproduction. Some species form extraordinarily resilient spores Often aggregate into multicellular colonies Non-nucleated - Have a single loop of DNA lack membrane-bound intra-cellular organelles Can function and reproduce as individual cells provides strength and rigidity Mechanism for survival, not reproduction. Under optimal conditions bacterial colony can double every 10 minutes Bacteria (contd) Vast majority of bacteria are harmless or beneficial Some are pathogenic and cause infectious diseases, e.g.: Pathogenic bacteria also cause infections such as TB caused by Mycobacterium tuberculosis Pneumonia, caused by bacteria such as Streptococcus and Pseudomonas Foodborne illnesses, caused by Shigella, Campylobacter and Salmonella *. tetanus, typhoid fever, diphtheria, syphilis and Hansen's disease. Bacteria can often be killed by antibiotics ABs destroy their cell wall and then their D.N.A. Typical bacterial skin, bone and soft tissue infecting agents Staphylococcus aureus Streptococcus pyogenes Cause localised infections, and abscess formation Causes rapidly spreading infections, such as erysipelas Eschericha (E) coli Can cause deep infections, e.g.: osteomyelitis Gram Classification of Bacteria Gram positive (G+ve) Bacteria Thin cell wall Take up gram stain (crystal violet granules) More easily overcome by antibiotics (unless bacteria develop ABx resistance) E.g.: Staph aureus Gram negative (G-ve) Bacteria More complex cell wall Tend not to take up gram stain Less easily overcome by antibiotics Eg.: Pseudomonas Fungi Fungi are eukaryotic (have nuclei) Several unicellular species Some fungi, e.g.: pathogenic yeast Candida albicans *, can undergo phenotypic switching E.g.: baker's yeast (Saccharomyces cerevisiae) grow as single cells in some environments or form filamentous hyphae (mats) in others Reproduce both asexually, by budding or binary fission, and by producing spores (1-40 10-6mm long) conidia when produced asexually basidiospores when produced sexually. Fungi (contd) Fungi are usually saprophytes Some can cause diseases in humans, animals and plants Fungal infections are more common in the immuno-incompetent population (e.g.: DM, stressed), affecting skin and nails * Fungi are non-susceptible to antibiotics most common cause of diseases in crops and other plants Life threatening fungal infections in humans most often occur in immunocompromised patients or vulnerable people with a weakened immune system MO that feeds on dead or decaying matter both fungi and their hosts both have eukaryotic cells. Most clinical fungicides are azole drugs Common dermatophytes of skin and nail Trichophyton rubrum Epidermophyton ‘Pencils’ ‘Clubs’ Microsprorum ‘Spindles’ Viruses Sub-microscopic MOs 20-300 nanometers in length (1nm = 1 x 10-9mm) DNA enclosed within a capsule Not susceptible to antibiotics Pathogenic viruses include Adenoviridae, Picornaviridae, Herpesviridae, Hepadnaviridae, Flaviviridae, Retroviridae, Orthomyxoviridae, Paramyxovirida, Papovaviridae, Polyomavirus, Rhabdoviridae, Togaviridae. Cause diseases including Smallpox, influenza, mumps, measles, chicken pox, ebola, rubella, warts (VPs), shingles, polio, hepatitis B, HIV, etc etc. Prions Infectious pathogens that do not contain nucleic acids. Abnormal proteins whose presence causes e.g.: scrapie, bovine spongiform encephalopathy (BSE; ‘mad cow’ disease) and Creutzfeldt–Jakob disease (CJD) Prions are very difficult to destroy by normal sterilization processes It requires up to 18 autoclave cycles to denature prion protein Control of Infection Control of Infection Infection Control Policies and procedures used in hospitals and health care facilities to minimize the risk of spreading infections Procedures and protocols designed to prevent or limit cross-contamination in the health care delivery environment Purpose of infection control To reduce the occurrence of infectious diseases To prevent iatrogenic infection Causes of Infectious Disease Spread of Microorganisms bacteria, viruses, fungi or Infected material via a Vector, i.e.: Human to human contact Animal to human contact (Zoonoses) Human contact with An infected surface Airborne transmission of microscopic airborne droplets of infectious agents / desiccated MOs / spore forms Contaminated food or water Infection control in hospitals and other health care settings Infection control is a formal hospital discipline Hospital Acquired Infections = nosocomial infections, e.g.: MRSA CDiff Affect ~ 5% of all hospital patients Copied into all health care settings Forms part of formal clinical governance procedures Especially elderly, frail and immunocompromised patients Medical procedures may introduce infection to patient Infections also introduced by carriers (visitors / workers) are transmitted to vulnerable cases Increase morbidity duration of hospital stay Increase mortality Increased focus on hospital hygiene is not reducing incidence of CDiff (up 28% in 2011) Examples of Infectious Diseases Hepatitis B Legionnaire’s Disease Legionella (bacteria) contamination of air conditioning systems Inhalation of infected water droplets Treated with antibiosis Ringworm (Tinea) Viral infection causing liver dysfunction Spread by sexual contact with infected person, or by contact with infected blood No treatment Fungal infection of skin Contact with infected shed squames from human or animal Treated with antifungals Tetanus Soil-borne bacterium causing severe muscle tetany and respiratory failure Via break in skin Antibiosis; muscle relaxants (Poor prognosis) New threats and infections Any control of infection protocol must prevent transmission of all known, and also all as yet unknown, infectious agents New diseases emerge constantly: Many common infectious diseases have become resistant to known treatments HIV / AIDs SARS (severe acute respiratory syndrome) Most staphylococci now show a degree of antibiotic resistance TB Increased international and air travel exposes a naïve population to unfamiliar MOs Bioterrorism Anthrax Goals of infection control programs Definition of formal precautions and protocols that prevent / reduce exposure to infectious agents Introduction of immunization programmes against preventable diseases Restriction of exposure of health care workers to infectious agents Precautions that avoid and control the spread of infections Vaccinate against diseases for which a vaccine is available. Wash hands often. Cook food thoroughly. Use antibiotics only as directed. See a doctor for infections that do not heal. Avoid areas with a lot of insects. Do not purchase exotic animals as pets. Do not engage in unprotected sex or intravenous drug use. Find out about infectious diseases prior to travelling: take appropriate vaccinations / preventative drugs. Do not drink water that might be contaminated Ebola Some hope Infection Control? No hope And…. Wear disposable gloves with all patients, since it is difficult to know whether a transmittable disease is present or not. Isolate patients who have a known infectious disease to decrease the risk of transmitting the infectious agent to another person. Hospital workers who come in contact with infected patients must wear gloves and gowns to decrease the risk of carrying the infectious agent to other patients. Use air filtration mechanisms to remove MOs and spore forms Dispose of all items of equipment used in an isolation rooms, or decontaminate before re-use House vulnerable patients (immunocompromised) in protective isolation to decrease the risk of infection Restrict all hospital workers with infections, including colds, from entry to isolation rooms. Handle infected materials so that numbers of infectious agents that may become airborne are minimized Hospital ventilation systems must be maintained to prevent recirculation of contaminated air. Historical Perspectives Surgery was very chancy before there was an understanding of infection control A surgeon operated in a blood- and often pus-stained coat Infection was expected within 3-4 days (laudable pus) Instruments were only rinsed to remove obvious contamination Wounds were packed with moist lint or raw cotton, or plugged with cotton wool soaked in collodion Bandages were kept damp Thought to be the essential sloughing off of the lining of the wound It allowed ‘clean tissue’ to form prior to healing Healing without pus formation was an unexplained mystery In contrast, damnable pus was feared (death sentence) = infected gangrene From the ancients up to 1800s Diseases caused by imbalance of 4 bodily ‘humours’ 4 elements Blood, phlegm, black bile, yellow bile Air, fire, earth and water In relation to the 4 seasons Treatments focused on reestablishing their balance Purging, emesis, blistering, bloodletting Understanding without knowledge Marcus Terentius Varro (in 36 BC) ‘...and because therein are bred certain minute creatures (in swamps) which cannot be seen by the eyes, which float in the air and enter the body through the mouth and nose and there cause serious diseases’ Ibn al-Khatib, (in 1300s, re: Bubonic Plague [Yesinia infection]) ‘The fact of infection becomes clear to the investigator who notices how he who establishes contact with the afflicted gets the disease, whereas he who is not in contact remains safe, and how transmission is affected through garments, vessels and earrings.’ Girolamo Fracastoro (1546) ‘… that epidemic diseases are caused by transferable seed-like entities that can transmit infection by direct or indirect contact or even without contact over long distances. ’ Knowledge emerges Anton van Leeuwenhoek (1642 – 1723) First direct observation of MOs using a microscope Agostino Bassi first stated the germ theory of disease in 1835 He linked fatal muscardine disease in silkworms to a visible fungus JANSSEN Edward Jenner (1749-1823) Common empirical observation that Benjamin Jesty (farmer) inoculated his wife and two sons with the exudate from cowpox pustules, Milkmaids had good complexions They seemed to be immune to smallpox Conferred on them immunity to smallpox during the epidemic of 1774 Edward Jenner promoted smallpox vaccination in 1790s Got all the credit, including a knighthood! He had no knowledge of why vaccination was effective Oliver Wendell-Holmes, Snr US Poet, physician, and medical reformist 1843: published a landmark essay on the germ theory of disease 4 years before Semmelweis Insisted that any physician with even 1 case of puerperal fever, should: Puerperal fever = often fatal infection contracted during or shortly after childbirth Transmitted from patient to patient via examining physician (iatrogenic infection) Cited doctors who had become ill and died after performing autopsies on patients who had died of puerperal fever ‘Purify’ his instruments Burn all clothing worn while assisting in the fatal delivery Cease obstetric practice for a period of at least six months He was vilified by the medical establishment who did not believe in ‘contagion’ He re-published his paper in 1855, to great acclaim Ignaz Semmelweis Worked in Vienna in 1847 Noted exceptionally high maternal mortality rate due to puerperal fever Women were examined by medical students studying obstetrics Students had often had prior contact with autopsy specimens Puerperal fever was a contagious disease transmitted by cadaver material Noted far lower morality rate for women attended by midwives Who had not been examined by medical students Introduced hand-washing prior to patient examination Reduced mortality from childbirth to < 2% at his hospital Was vilified by most of the Viennese medical establishment (1818-1865) His theories on the effectiveness of handwashing as effective C of I were not accepted until Pasteur’s ‘germ theory’ was accepted Ironically, he died of septicaemia ‘Spontaneous generation’ It was thought that corruption and rotting of organic material was ‘self generating’, until….. Francesco Redi (1626 – 1697) demonstrated that maggots only grew on material that could be accessed by flies It had been thought that maggots emerged from meat as it rotted He showed that maggots did not appear on meat in sealed jars Louis Pasteur demonstrated conclusively that MO growth did not occur by spontaneous generation. He exposed freshly boiled broth to air in vessels that was filtered to prevent all particles passing into the growth medium As nothing grew in the vessels, it demonstrated that MOs that corrupted organic materials must be sourced from the exterior. Louis Pasteur (1822 – 1895) Formulated the ‘Germ Theory’ of disease Formulated and proved the rabies vaccine Named 3 methods to eliminate MOs causing wet gangrene: Repeated heating of food products to reduce their MO load Quality and taste remained unaffected by process 3 of his 5 children died of typhoid Filtration, Exposure to heat, or Exposure to chemical solutions Invented Pasteurization (food preservation method) Determined that MOs (‘germs’) were the cause of many diseases Noted that MOs can grow under both aerobic and anaerobic conditions Clean, potable water was not readily available Would not shake hands for fear of cross infection John Snow (1813-1858) He used microscopy and statistics to establish the source of an outbreak of cholera in Soho The Broad Street pump water was contaminated by sewage, in 1854 (via local broken drain) Local cases who did not contract cholera sourced their water from another pump But distant residents who used the Broad Street pump, did He removed the pump handle and the epidemic reduced He scotched the ‘miasma’ theory (‘bad air’) and helped establish the ‘germ’ theory as the cause of contagion He also pioneered anaesthesia, and administered chloroform to Queen Victoria during the birth of 2 of her children He was TT, vegetarian, drank only boiled water, and died of a stroke aged 45! Florence Nightingale (1820 – 1910) She is best known for her work in the Crimean War (1853-56) 6/12 later a UK Sanitary Commission was sent out to Crimea They made the sewers function, and then death rates began to fall Nightingale still believed that the improvement was due to better food and supplies! After the war she worked for the Royal Commission for the Health of the Army But death rates rose in the 1st year she was in charge of nursing at Scutari hospital Her methods focused on a good diet and adequate supplies, but ignored hygiene! 10x more soldiers died from typhus, typhus and cholera than from battle wounds She was a keen statistician, and showed by statistics that: Hygiene was paramount in the control of infection Poor hygiene had been the cause of the majority Crimea deaths She became a great advocate of hospital hygiene designed the ‘X’ hospital format (clean at the centre, dirty at the periphery) Sir Joseph Lister (1827-1912) Prior to Lister it was generally accepted that wound infections were desirable and arose due to ‘miasma’ (bad air) Lister confirmed Pasteur's conclusions by his own experiments He developed chemical antiseptics to avoid wound infections Carbolic acid (phenol) was used to deodorize sewage, so Lister Sprayed instruments, incisions and dressings with carbolic acid solution Instructed surgeons to wear clean gloves and wash hands in 5% phenol solution Forbade porous handles on surgical instruments Remarkable reduction in the incidence of gangrene Heat and filtration not appropriate to human tissue Published results in BMJ (Vol 90; 2299) 21.09.1867 Lister’s guidelines were followed to the letter during appendectomy on Edward VII, 2 days before his planned coronation date, in June 1902 Appendectomies were notorious for post-operative infections and patient death The King survived and was crowned in August, 1902 Lister got his gong Joseph Bazalgette (1819–91) ~ 1845 Metropolitan Commission of Sewers ordered Cholera epidemics of 1848-9 and 1853 killed 25,000 Londoners 1856 Bazalgette (railway builder) appointed CE of MBW 1858: the ‘great stink’: Thames was biologically dead, and putrid all residences used cess pits all cesspits should be closed all residences to be connected to a system of drains and sewers all sewers to empty into the Thames Parliament was suspended due to the smell Enabling Act passed to allow ‘enclosed handling’ of London sewage 1100 miles of brick-lined sewer tunnels were constructed + Pumping stations at Deptford, Erith, Chelsea and Abbey Wood Still just about coping with 2012 level of demands Cholera was eradicated and there are now fish in the Thames Unless Thames Water pumps sewage into the Oggin Abbey Wood Pumping Station The flush toilet Invented by John Harrington (courtier of Elizabeth 1) in 1596 Joseph Brahma (Locksmith) improved the water closet in 1778, so that it did not freeze up in winter (still working on I of W) Thomas Crapper, did not invent the flush toilet, but he invented the ballcock in 1882 Roman communal lavatory with flushing gutter Harrington model: there was a flap that opened by a lever to let content drain into a cess pit Victorian Flush Toilet Koch’s 4 Postulates of Infectious Disease (1890) 1. 2. 3. 4. Formulated by Robert Koch and Friedrich Loeffler (1884) Causative MO must be found in abundance in all suffering from the disease, but should not be found in the healthy. NB: does not recognize the carrier state or sub-clinical disease state NB: does not apply to the prion of CJD NB: does not apply to those with a natural immunity or to diseases that Causative MO can be isolated from a diseased subject and grown in pure culture Cultured MO should cause disease when introduced into a healthy subject. do not affect all equally, e.g. polio Cultured MO will be identified as identical to the original causative MO when re-isolated from diseased experimental host Science backs Empirical Observation 1 Pre-1850s: Sanitation/sterilization measures and methods were known to limit the outbreak and spread of disease. The actual mechanism of specific infective MOs, their vectors and mechanisms of their transmission & biological attack, how MOs progressed in the body at the cellular level, and the bio-chemical mechanism of their natural course in the bodies of living organisms were wholly unknown. Science backs Empirical Observation 2 By the late 1800s: Rigorous investigative scientific methods and practices in all the physical sciences, allowed anecdotal information to be subject to rigorous examination. Led to the knowledge of how living organisms receive infection, how living organisms manage infections once established, and (most important, in penicillin’s case) how natural and man-made agents could alter the progress of infection within the living organism Summary Early voices on disease prevention / infection control were largely ignored Pus and infection was considered an essential and desirable part of post-surgical healing Pasteur established the role of MOs in infection Public health measures played the major part of infection control in populations Lister is credited with the introduction of aseptic techniques during surgery Nightingale is credited with formalization of nursing principles and clean / dirty hospital design