Gram Positive Bacteria PDF

Gram Positive Bacteria 1 Asst. Prof. Dr. Ayhan Mehmetoğlu [email protected]  Classification of Medically Important Bacteria  The current classification of bacteria is based primarily on...

Gram Positive Bacteria 1 Asst. Prof. Dr. Ayhan Mehmetoğlu [email protected]  Classification of Medically Important Bacteria  The current classification of bacteria is based primarily on morphologic and biochemical characteristics. Classification Only organisms that medically important bacteria are included. 3  Italicize family, genus, species, and variety or subspecies. Begin family and genus with a capital letter. Kingdom, phylum, class, order, and suborder begin with a capital letter Scientific but are Nomenclature Binary genus-species of Bacteria Salmonella enterica Escherichia coli Staphylococcus aureus 4 https://wwwnc.cdc.gov/eid/page/scientific-nomenclature  Bacteria Gram positive Gram negative Cocci Rods Spore forming Non-Spore forming Staphylococci Streptococcii Enterococci Bacillus Clostridium Corynebacterium Listeria  Dr. Ayham Abulaila 6 Review of Medical Microbiology and Immunology, Fourteenth Editi, Copyright © 2016 by McGraw  Free-living (extracellular bacteria) 1. Gram-positive Cocci Spore-forming rods (bacilli) Non-spore-forming rods (bacilli) 7 a. Gram-positive Cocci; Streptococcus 8 9  α-Hemolytic streptococci cause a chemical change in the hemoglobin of red cells in blood agar, resulting in the appearance of a green pigment that A. Hemolytic forms a ring around the colony. properties on β-Hemolytic streptococci cause gross lysis of red blood cells, resulting in a blood agar clear ring around the colony. γ-Hemolytic a term applied to streptococci that cause no color change or lysis of red blood cells. 10 11  Many species of streptococci have a polysaccharide in their cell walls which is antigenic. B. Serologic The Lancefield scheme classifies (Lancefield) primarily β-hemolytic streptococci into Groups A-U. groupings The clinically most important groups of β -hemolytic streptococci are types A and B. 12 13  Group A β-Hemolytic Streptococci S. pyogenes S. pyogenes, the most clinically important member of this group of gram- positive cocci, is one of the most frequently encountered bacterial pathogens of humans worldwide. It can invade apparently intact skin or mucous membranes, causing some of the most rapidly progressive infections known. A low inoculum suffices for infection. Some strains of S. pyogenes cause postinfectious sequelae, including rheumatic fever and acute glomerulonephritis. 14 15 16  S. agalactiae Group B streptococci, represented by the pathogen S. agalactiae, are gram-positive. S. agalactiae is found in the vaginocervical tract of female carriers, and the urethral mucous membranes of male carriers, as well as in the GI tract. Transmission occurs from an infected mother to her infant at birth, and venereally (propagated by sexual contact) among adults. 17  S. pneumoniae S. pneumoniae are gram-positive, nonmotile, encapsulated cocci. They are lancet-shaped, and their tendency to occur in pairs accounts for their earlier designation as Diplococcus pneumoniae. S. pneumoniae is the most common cause of pneumonia and otitis media and an important cause of meningitis and bacteremia/sepsis. 18  Enterococci The clinically most important species are E. faecalis and E. faecium. Enterococci can be γ, β, or nonhemolytic. 19  Viridans Streptococci The viridans group of streptococci includes many species that constitute the main facultative oral flora. Streptococcus mutans and other members of the viridans group cause dental caries. In patients with abnormal or damaged heart valves, they can also infect these valves during a bacteremia, causing subacute bacterial endocarditis Therefore, at-risk patients with rheumatic, congenital, or arteriosclerotic valvular disease should receive prophylactic penicillin before undergoing dental procedures. 20  Streptococcal endocarditis showing vegetation of the mitral valve leaflet. [Note: Vegetation is a tissue outgrowth composed of fibrin, bacteria, and aggregated blood platelets adherent to a diseased heart valve. Lippincotts_Illustrated_Reviews_Microbiology_ 3rd_Edition_by_Richard_A._Harvey_Cynthia_N au_Cornelissen_Ph.D 21 Lippincotts_Illustrated_Reviews_Microbiology_ 3rd_Edition_by_Richard_A._Harvey_Cynthia_N au_Cornelissen_Ph.D 22 Lippincotts_Illustrated_Reviews_Microbiology_ 23 3rd_Edition_by_Richard_A._Harvey_Cynthia_N au_Cornelissen_Ph.D Gram-positive Cocci Staphylococcus 24  The most virulent of the genus, Staphylococcus aureus, is one of the most common causes of bacterial infections and is also an important cause of food poisoning and toxic shock syndrome. Staphylococcus Among less virulent staphylococcal species, Staphylococcus epidermidis is an important cause of prosthetic implant infections, whereas Staphylococcus saprophyticus causes urinary tract infections, especially cystitis in women. 25  Diseases caused by Staphylococcus aureus. Lippincotts_Illustrated_Rev iews_Microbiology_3rd_Ed ition_by_Richard_A._Harve y_Cynthia_Nau_Cornelisse n_Ph.D 26  Coagulase-Negative Staphylococci S. epidermidis and S. saprophyticus are the most common CNS which has a special medical importance. Coagulase-negative staphylococcal species are important agents of hospital-acquired infections associated with the use of implanted prosthetic devices and catheters. 27 28 Gram-positive Rods  Corynebacterium diphtheriae Diphtheria, caused by C. diphtheriae, is an acute respiratory or cutaneous disease and may be a life-threatening illness. The development of effective vaccination protocols and widespread immunization beginning in early childhood has made the disease rare in developed countries. Diphtheria is a serious disease throughout the world, particularly in those countries where the population has not been immunized. 30 31  Listeria species Listeria species are slender, short, gram-positive rods. They do not form spores. L. monocytogenes is capable of growth at 4 °C Foodborne: dairy products (including ice cream and cheese) Septicemia and meningitis (listeriosis). 32 https://www.foodpoisonjournal.com/food-poisoning-information/what-to-know-during-a-listeria-outbreak/ Spore-forming rods (Aerobic Bacillus Anthrax) 33  Cutaneous anthrax About 95 percent of cases of anthrax are cutaneous. Upon introduction of organisms or spores that germinate, a papule develops. It rapidly evolves into a painless, black, severely swollen malignant pustule which eventually crusts over. The organisms may invade regional lymph nodes and then the general circulation, leading to fatal septicemia. Although some cases remain localized and heal, the overall mortality in untreated cutaneous anthrax is about twenty percent. 34  Pulmonary anthrax Pulmonary anthrax (woolsorter's disease) is caused by inhalation of spores. It is characterized by progressive hemorrhagic lymphadenitis (inflammation of the lymph nodes), Has a mortality rate approaching 100 percent if left untreated. 35 36  Clostridia Clostridia are the anaerobic gram-positive rods of greatest clinical importance. Clinically significant species of Clostridium include C. perfringens, which causes histotoxic (tissue destructive) infections (myonecrosis) and food poisoning; C. difficile, which causes pseudomembranous colitis associated with antibiotic use; C. tetani, which causes tetanus (lockjaw); and C. botulinum, which causes botulism. 37  Spore-forming rods Anaerobic Clostridium Clostridium causes theses diseases: Tetanus Gas gangrene Botulism Diarrhea 38  C. perfringens is a large, rod-shaped, nonmotile, gram-positive, encapsulated bacillus. It is ubiquitous in nature, with its vegetative form as part of the normal flora of the vagina and gastrointestinal (GI) tract. Its spores are found in soil. When introduced into tissue, however, C. 1. perfringens can cause anaerobic cellulitis, and myonecrosis (gas gangrene). Clostridium Some strains of C. perfringens also cause a perfringens common form of food poisoning. 39 40  C. botulinum causes botulism, which occurs in several clinical forms. Botulism is caused by the action of a neurotoxin that is one of the most potent poisons known. It causes a flaccid paralysis. 2. Contact with the organism itself is not Clostridium required; hence, the disease can be a pure intoxication. botulinum 41  Clostridium botulinum It produces an extremely lethal neurotoxin called botulinum toxin and causes botulism, a rare life-threatening neuroparalytic disease. Botulism is manifested as food poisoning, wound infection and infant botulism. Lethal dose of botulinum toxin for a human is 2μg or less, so C. botulinum has the potential to be used as a biological weapon. CDC has listed it as ‘Category A agents’, along with Bacillus anthracis, Yersinia pestis, etc. 42 43  The introduction of C. tetani spores into even small wounds via contaminated soil is probably a common occurrence. But a combination of the extreme O2 sensitivity of vegetative C. tetani and widespread immunization against its exotoxin, make the resulting disease, tetanus, 3. rare in developed countries. Clostridium Growth of C. tetani is completely local, but it produces a powerful neurotoxin that is tetani transported to the central nervous system, where it causes spastic paralysis. 44 45  Diarrhea, a common complication of antimicrobial drug treatment, can range from loose stools to life-threatening pseudomembranous colitis (PMC). C. difficile is estimated to be responsible for about one forth of antibiotic-associated diarrheas (AAD) in hospitalized patients and almost all cases of PMC. After its introduction to a site, the environment dust, bedding, toilets becomes persistently 4. contaminated with spores, and new residents are easily colonized. Clostridium They are then at higher risk for developing the difficile adverse intestinal effect of antibiotic treatments 46 Filamentous Actinomyces Nocardia 47  For any question [email protected] Dr. Ayham Abulaila 48