Anaerobic bacteria and more. Stijn van der Veen

Transcription

1 Anaerobic bacteria and more Stijn van der Veen

2 Anaerobic bacteria Anaerobic bacteria do not require oxygen for growth. Some anaerobic bacteria die in the presence of oxygen, while others are able to tolerate oxygen. Obligate anaerobic bacteria are killed by normal atmospheric concentrations of oxygen (20.95% O 2 ).

3 Identification of oxygen tolerance 1. Obligate aerobes need oxygen because they cannot ferment or respire anaerobically. They gather at the top of the tube where the oxygen concentration is highest. 2. Obligate anaerobes are poisoned by oxygen, so they gather at the bottom of the tube where the oxygen concentration is lowest. 3. Facultative anaerobes can grow with or without oxygen because they can metabolise energy aerobically or anaerobically. They gather mostly at the top because aerobic respiration generates more ATP than either fermentation or anaerobic respiration. 4. Microaerophiles need oxygen because they cannot ferment or respire anaerobically. However, they are poisoned by high concentrations of oxygen. They gather in the upper part of the test tube but not the very top. 5. Aerotolerant organisms do not require oxygen and cannot utilise it even if present; they metabolise energy anaerobically. Unlike obligate anaerobes, however, they are not poisoned by oxygen. They can be found evenly spread throughout the test tube.

4 Obligate Anaerobes Molecular oxygen is readily reduced to superoxide and hydrogen peroxide Superoxide anions O 2- ) and hydrogen peroxide (H 2 O 2 ), are very reactive and damaging to cellular structures such as DNA, proteins, and lipids. Obligate anaerobic bacteria lack the detoxifying enzymes superoxide dismutase (SOD), catalase (Kat), and peroxidase.

5 Anaerobic infections Infections caused by anaerobes usually occurs at sites with low oxidation-reduction potential such as the periodontal pocket, intestinal tract and vagina. Anaerobes often co-infect with other facultative anaerobes that consume oxygen to establish a local anaerobic environment. Endogenous infections: caused by anaerobes of the normal flora which are generally non-spore formers. Exogenous infections: pathogens are usually anaerobic sporeformers and come from the environment (e.g., soil).

6 Clostridia Clostridium is a genus of Gram-positive anaerobic spore-formers consisting of over 100 species. Several Clostridium species are able to cause human disease Clostridium tetani => tetanus Clostridium botulinum => botulism Clostridium perfringens => gas gangrene, food poisoning Clostridium difficile => pseudomembranous colitis

7 Sporulation Endospores are very resistant to environmental insults and can survive in this states (almost) indefinitely

8 Overview of bacterial infections Gastroenteritis

9 Tetanus The causative agent Clostridium tetani Sign and symptoms Muscle stiffness in jaw and neck Toxin involved Neurotoxin Transmission Wounds contaminated with soil, dust and animal feces Treatment Tetanus antitoxin, penicillin Prevention and control DTaP vaccine

10 Transmission process Spore-contaminated soil or other foreign objects Narrow deep wounds with limited blood and oxygen supply Co-infection with facultative anaerobe can use up the local oxygen Spores germinate and then produce tetanus toxins. The organism still remains in the local wound.

11 Tetanus toxins Clostridium tetani produces two exotoxins Tetanospasmin => neurotoxin with strong toxicity and its most important virulence factor. Tetanolysin => hemolysin able to lyse red blood cells

12 Tetanospasmin This toxin causes excitation of the CNS leading to spasmodic contractions and death from respiratory failure. The disease it produces is also called lockjaw. Used as toxoid vaccine If not treated in time, aprox. 20% of the patients die of respiratory failure Besides humans, horses are most susceptible to tetanospasmin

13 Examples This the neonatal tetanus patient displays sardonic smile, lockjaw and dyspnea The infection is frequenty caused by exposure to Clostridium tetani when cutting umbilical cord. This patient shows opisthotonos

14 Botulism The causative agent Clostridium botulinum Sign and symptoms Difficulty swallowing, slurred speech, blurred vision, trouble breathing, flaccid paralysis Toxin involved Neurotoxin Transmission Contaminated canned foods, contaminated wounds Treatment Antitoxin, breathing assistance Prevention and control Practicing good canning and storing food properly

15 Treatment and prevention Botulism is food-borne intoxication => antibiotics do not work Instead large doses of antitoxins (antibodies) are required to neutralize toxin Often transmitted through home-canned foods Heating foods to 90 degrees for 10 min will destroy the toxin Wound botulism is caused by toxins produced in anaerobic tissues of a wound infected with C. botulinum, which can be treated with penicillin

16 Botulinum toxin This toxin is unique in that it is not released until the death of the microorganism. It acts at the neuromuscular junction to prevent the transmission of nerve impulses leading to flaccid paralysis and death from respiratory failure.

17 Botulinum toxin The toxin can be divided into 7 types (A-G) Types A, B and E are most common in human disease Type E causes most cases of food-borne transmission The toxin binds to other non-toxic proteins to form a complex, which is released when the bacteria die When the complex enters intestines, the alkaline condition releases the botulinum toxin

18 Clostridium perfringens Forms spores that are heat resistant and germinate after improper storage of food Shortest germination (doubling) time of any known organism: 6-8 min Most common agent in gas gangrene

19 Clostridial food poisoning The causative agent Clostridium perfringens Sign and symptoms Abdominal cramping, watery diarrhea Toxin involved Enterotoxin Transmission Foodborne, from protein-rich foods improperly handled or stored Treatment Illness usually resolves without treatment Prevention and control Practicing good hand hygiene and avoiding suspected foods

20 Gas gangrene The causative agent Clostridum perfringens Sign and symptoms Foul odor and intense pain and swelling at the wound site Toxin involved Enterotoxin Transmission Soil, endogenous transfer Treatment Surgery, cephalosporin, hyperbaric oxygen Prevention and control Cleaning wounds, debridement

21 Disease Wound contaminated by soil (main source) and mammalian feces Gas gangrene results in severe tissue swelling due to release of gas Gas presses against the blood vessels, thereby blocking the flow and forcing the cells away from their blood supply This finally results in tissue necrosis

22 Clostridial necrotizing enteritis An acute necrotizing process in the jejunum with symptoms of abdominal pain, bloody diarrhea and peritonitis. It is a fatal type of food poisoning caused by a β-toxin of Clostridium perfringens (Type C) The death rate of this disease is as high as approximately 50%.

23 Toxins Clostridium perfringens secretes at least 12 different exotoxins that include hemolytic, proteolytic and saccharolytic enzymatic activities Alpha-toxin is the most important, it lyses erythrocytes, platelets, leukocytes and endothelial cells According to antigenic differences of 4 major toxins, the bacterial strains can be divided into A~E toxic types. Type A is clinically the most important. Type A can also produce enterotoxin to cause food poisoning.

24 Pseudomembranous colitis The causative agent Clostridium difficile Sign and symptoms Watery diarrhea, fever, loss of appetite, nausea, dehydration, and abdominal pain Toxin involved Enterotoxin, cytotoxin Transmission Indirect from contaminated hands or materials Treatment Stopping antibiotic therapy, anticlostridial antibiotic therapy Prevention and control Practicing good hand hygiene, keeping bathrooms and kitchens disinfected

25 Healthcare associated infection

26 Toxins Clostridium difficile produces two toxins Enterotoxin => causes fluid loss Cytotoxin => causes mucosal injury

27 Non-spore-forming anaerobes Present in large numbers in the intestines and urogenital tract as normal flora Generally, they are opportunistic pathogens that co-infect with facultative anaerobic bacteria Medically relevant genera include Gram-negative rods: Bacteroides, Prevotella, Porphyromonas, Fusobacterium Gram-positive rods Propionibacterium, Actinomyces, Eubacterium, Bifidobacterium Gram-positive cocci: Peptostreptococcus, Peptococcus Gram-negative cocci: Veillonella

28 Obligate intracellular bacteria Chlamydia Chlamydia trachomatis Coxiella Coxiella burnetii Rickettsia Rickettsia rickettsii Rickettsia prowasekii Ehrlichia Ehrlichia chaffeensis

29 Chlamydia The causative agent Chlamydia trachomatis Sign and symptoms Pain on urination, watery discharge, salpingitis Transmission Sexual intercourse Treatment Doxycycline, erythromycin Prevention and control Practicing safe sex, limiting sex partners, screening for STDs

30 Chlamydia Chlamydia is the most frequently reported STD Chlamydia is in 85-90% asymptomatic, but may lead to complicated cases, including salpingitis, PID and ectopic pregnancies No cell wall Unique biphasic reproductive cycle

31 Chlamydia life cycle Elementary body (EB): µm in diameter, dense structure, infectious Reticulate body (RB): µm in diameter, loose structure, not infectious

32 Q fever The causative agent Coxiella burnetii Sign and symptoms Headache, fever, dry cough Transmission Dust particles, contact with infected animals Treatment Doxycycline Prevention and control Vaccination of high risk occupations

33 Rocky Mountain spotted fever The causative agent Rickettsia rickettsii Sign and symptoms High fever, severe headache, skin rash of red spots Transmission Bite of infected hard tick Treatment Doxycycline, tetracycline Prevention and control Avoiding and preventing tick bites

34 Epidemic typhus The causative agent Rickettsia prowazekii Sign and symptoms Fever and rash Transmission Scratching bites from body lice Treatment Doxycycline Prevention and control Avoiding and preventing lice infestation

35 Ehrlichiosis The causative agent Ehrlichia chaffeensis Sign and symptoms Headache malaise, fever Transmission Bite of infected lone star tick or blacklegged tick Treatment Doxycycline, tetracycline Prevention and control Avoiding and preventing tick bites

36 Bacteria lacking cell wall Mycoplasma Mycoplasma pneumoniae Ureaplasma Ureaplasma urealyticum

37 Culturing Mycoplasma Mycoplasma is the smallest microbe ( µm) that can grow on artificial cell-free media and it forms very small colonies on agar. Due to the slow growth, the colonies need 3 weeks to develop. The colonies are extremely small.

38 Cell envelope No cell wall Cell membrane contains sterols for stability

39 Pneumonias The causative agent Mycoplasma pneumoniae Sign and symptoms Headache, fever, fatigue, dry hacking cough Transmission Respiratory droplets via water systems, whirlpool spa, or air conditioning systems Treatment Antibiotics that do not target cell wall Prevention and control Extreme cleaning and disinfecting of water systems, pools and spa

40 Infectious bronchitis The causative agent Mycoplasma pneumoniae Sign and symptoms Runny nose, sore throat, chills, general malaise, slight fever, dry cough Transmission Respiratory droplets Treatment Antibiotics Prevention and control Annual flu vaccination, good hygiene

41 Ureaplasma urethritis The causative agent Mycoplasma urealyticum Sign and symptoms Pain on urination, variable discharge, salpingitis Transmission Sexual intercourse Treatment Doxycycline Prevention and control Practicing safe sex

42 Spirochetes Treponema Treponema pallidum Borrelia Borrelia burgdorferi Leptospira Leptospira interrogans

43 Syphilis The causative agent Treponema pallidum Sign and symptoms Chancre, skin lesions, gumma Transmission Sexual intercourse Treatment Azithromycin, erythromycin, ceftriaxone Prevention and control Practicing safe sex

44 Syphilis stages Syphilis develops in several different stages Primary syphilis manifests as a single sore (chancre) at the site of infection around days after exposure and last for 3-6 weeks. Secondary syphilis shows as a body rash with possible fever, swollen lymph glands, sore throat, hair loss, headaches, weight loss, muscle aches, and fatigue. Latent syphilis is without any symptoms Tertiary syphilis develops on 1/3 of infected people and can appear 3-20 y after infection. At this stage the disease is no longer contagious and it comes in many different forms such as paralysis, numbness, gradual blindness, and dementia.

45 Lyme disease The causative agent Borrelia burgdorferi Sign and symptoms Rash, flu-like symptoms, joint pain Transmission Bite of infected deer tick Treatment Amoxicillin Prevention and control Avoiding tick bites

46 B. burgdorferi life cycle

47 Leptospirosis The causative agent Leptospira interrogans Sign and symptoms Acute headache, muscle aches, vomiting and nausea, fever and chills Transmission Contaminated soil, food, water Treatment Antibiotics Prevention and control Avoiding contaminated water

48 Gram-positive rods Bacillus Bacillus anthracis Bacillus cereus Listeria Listeria monocytogenes

49 Anthrax The causative agent Bacillus anthracis Sign and symptoms Fever, chills, cough, chest pain, headache, malaise, severe breathing difficulty, shock Transmission Airborne endospores Treatment Penicillin, ciprofloxacin Prevention and control Avoiding contact with infected livestock and animal products

50 Anthrax Manifestation Pulmonary or respiratory Gastrointestinal by consumption of infected meat Cutaneous through skin lesions Common organism present in the soil. B. anthracis can form dormant endospores that are able to survive for centuries. Used for development of biological weapons. First vaccines developed by Pasteur.

51 Food poisoning The causative agent Bacillus cereus Sign and symptoms Diarrhea, vomiting Toxin involved Enterotoxin Transmission Foodborne, from meats, cream, sauces Treatment Recovery without treatment Prevention and control Avoiding suspected foods

52 Listeriosis The causative agent Listeria monocytogenes Sign and symptoms Headache, stiff neck, confusion, loss of balance, convulsions Toxin involved Not established Transmission Food contaminated with fecal matter, contaminated animal foods Treatment Ampicillin Prevention and control Practicing good hand hygiene, washing and preserving food properly

53 Gram-negative rods Campylobacter Campylobacter jejuni Bordetella Bordetella pertussis Hemophilus Hemophilus influenzae Pseudomonas Pseudomonas aeruginosa

54 Campylobacteriosis The causative agent Campylobacter jejuni Sign and symptoms Diarrhea, fever Toxin involved Enterotoxin Transmission Foodborne from contaminated food or water Treatment None, antibiotics for severe or prolonged illness Prevention and control Practicing good hand hygiene and food preparation

55 Pertussis (whooping cough) The causative agent Bordetella pertussis Sign and symptoms Malaise, low-grade fever, severe cough Transmission Respiratory droplets Treatment Erythromycin Prevention and control Vaccination with DTaP, Tdap

56 Pneumonia The causative agent Haemophilus influenzae, Pseudomonas aeruginosa Sign and symptoms Chills, high fever, sweating, shortness of breath, chest pain, cough with thick greenish or yellow sputum Transmission Respiratory droplets Treatment Antibiotics Prevention and control Practicing good hand hygiene

57 Online quiz Date: Monday 6 November Time: hour Format: MCQ 30x

58 In class quiz Matching pair questions: 10x True-false questions: 10x