Bacterial Infections Overview PDF

Overview of Infection Bacterial s 1- Staphylococcus aureus Gram positive cocci arranged in grape like clusters Catalase positive and coagulase positive. Facultative anaerobe Sources of infection: 1-healthy carrier harbouring the bacteria in: Nose , throat , skin and under t...

Overview of Infection Bacterial s 1- Staphylococcus aureus Gram positive cocci arranged in grape like clusters Catalase positive and coagulase positive. Facultative anaerobe Sources of infection: 1-healthy carrier harbouring the bacteria in: Nose , throat , skin and under the nail. 2-Case Mode of transmission - Contact with pus from an infected wound - Skin-to-skin contact with an infected person - Contact with objects used by an infected person such as towels, sheets, clothing, or athletic equipment. Diseases caused by aureus  Bacteremia Staphylococcus   Infective endocarditis  Pneumonia  Meningitis  Skin and soft tissue infections  Food poisoning as a result of toxin ingestion. Scalded skin syndrome   Major bone and joint infections: osteomyelitis and septic arthritis  Urinary tract infection  Scalded skin syndrome (Neonates and children under 4 years) Antibiotic resistance Antibioticresistance is widespread in S. aureus including Methicillin Resistant S. aureus (MRSA) (Type of staph bacteria that is resistant to certain antibiotics, including methicillin,  penicillin and amoxicillin) MRSA infections causing both hospital acquired and community acquired infections. First-line treatment for serious invasive infections due to MRSA is currently glycopeptide oxacillin , antibiotics (vancomycin and teicoplanin) 2- Streptococcus pyogenes:  Gram positive cocci arranged in chains. Catalase negative Mode of transmission - Inhalation of respiratory droplets - Skin contact with infectious lesions - Contact with objects, surface, or dust that is contaminated with bacteria Diseases caused by Streptococcus pyogenes  Streptococcal pharyngitis and tonsillitis  Scarlet fever (rash on upper chest spreading to extremities).  Mild skin infection (impetigo) or more with lymphatic invasive infection including Erysipelas (Acute superficial cellulitis of skin involvement) and cellulitis (Involvement of deeper subcutaneous tissues with systemic symptoms).  Streptococcal Toxic Shock Syndrome (TSS): Multisystem toxicity following soft Erysipelas tissue infection progressing to shock and organ failure.  S. pyogenes can also cause disease in the form of post- infectious autoimmune-mediated complications including rheumatic fever and acute post-infectious glomerulonephritis. N.B: This bacterium remains acutely sensitive to penicillin (Usually amoxicillin) 3- Other Gram positive cocci - Strept. pnemoniae Pneumonia, Otitis media, sinusitis and meningitis  - Strept. viridans Dental caries, bacteremia, Subacute bacterial endocarditis -The organism reaches the blood stream after tooth extraction, settles on deformed valve and causes the inflammatory process - Strept. Agalactiae Transmitted through birth canal and causes Neonatal septicaemia, Neonatal Meningitis and Neonatal pneumonia 4- Clostridium - Gram positive bacilli - Obligate anaerobe The main species responsible for disease in humans are:  Clostridium botulinum can produce botulinum toxin in food or wounds and can cause botulism.  Clostridium perfringens causes a wide range of symptoms, from food poisoning to cellulitis, fasciitis, necrotic enteritis and gas gangrene.  Clostridium tetani causes tetanus.  Clostridium difficile causes antibiotic-associated diarrhea. 1- Escherichia coli  Gram negative bacilli  Facultative anaerobic  Motile by peritrichate flagella  Ferment lactose.  Escherichia is commonly found in the lower intestine of humans.  Some enteropathogenic serotypes can cause serious forms of gastroenteritis.  Uropathogenic E. coli is one of the main causes of urinary tract infections.  It can also cause neonatal meningitis. 2- Klebsiella pneumoniae  Gram negative bacilli  Facultative anaerobic  Non motile Diseases caused by K. pneumonia: -Pneumonia -Urinary tract infections -Septicaemia -Wound infection -Meningitis 3- Salmonella  Gram negative bacilli  Facultative anaerobes  Do not ferment lactose.  Most infections aredue to ingestion contaminated by animal feces, or by human feces. of food  Typhoidal serotypes can only be transferred from humanto-human, and can cause typhoid fever 4- Neisseria  They are Gram negative diplococci.  Oxidase positive and aerobic Two important pathogens, N. meningitides and N. gonorrhoeae. -Neisseria gonorrhoeae causes the sexually transmitted genitourinary infection gonorrhoea. -Neisseria meningitides causes meningitis and other forms of meningococcal disease such as meningococcemia, a life-threatening sepsis.  It is the main cause of bacterial meningitis in children and young adults. 5- Helicobacter pylori  It is a Gram-negative spiral (helical) shaped bacilli usually found in the stomach.  Helicobacter pylori has four to six unipolar flagella that help it to penetrate stomach mucus lining.  H. pylori infection usually has no symptoms but sometimes causes gastritis (stomach inflammation) or ulcers of the stomach or first part of the small intestine (Duodenum).  The infection is also associated with the development of certain cancers of stomach.