GRAM-POSITIVE BACILLI I Spore-forming bacilliNon-spore-forming bacilli Bacillus anthracisCorynebacterium diptheriae Bacillus cereusListeria monocytogenes Actinomyces

BACILLUS ANTHRACIS

1915 German agents in the US believed to have injected horses, mules and cattle with anthrax on their way to Europe during World War I 1937 Japan starts biological warfare program in Manchuria 1942 UK experiments with anthrax at Gruinard Island off the coast of Scotland (only recently decontaminated) 1943 United States begins developing anthrax weapons 1945 Anthrax outbreak in Iran kills 1 million sheep 1969 US biological weapons program ends

1972 International convention outlaws development and stokpiling of biological weapons Human anthrax epidemic in Zimbabwe infects 6,000 and killing Aaerosolized anthrax spores are released accidentally at a Soviet Union military facility, killing 68 people 1991 US troops vaccinated for anthrax in preparation for Gulf War 1995 Iraq admits it produced 8,500 liters of concentrated anthrax 1998 Anthrax vaccination approved by for all military service members

BACILLUS ANTHRACIS Form spores aerobically Prominent polypeptide capsule composed of D-glutamate residues Capsule is antiphagocytic Antibodies against capsule are not protective

Micrographs of anthrax bacilli taken by Robert Koch, who confirmed the bacterial origin of anthrax in 1876

Spore formation in Bacillus

Mucoid type colonies of encapsulated Bacillus

Bacillus anthracis capsule visualized by India Ink negative stain

BACILLUS ANTHRACIS Pathogenesis Virulence factors: Capsule composed of poly-D-glutamic acid Anthrax toxin

“Anthrax toxin” consists of 3 proteins encoded by a large plasmid, pXO1 1. Protective antigen (PA) 2. Lethal factor (LF) 3. Edema factor (EF) Non-toxic individually

Protective antigen (PA) facilitates cell entry of the other toxins. Binds to 2 types of receptors on cell surfaces: Tumor endothelial marker 8 (TEM8) (anthrax toxin receptor) and Capillary morhpogenesis protein Present on cells in the heart, brain, intestine, lung, skeletal muscle, pancreas, macrophages

After receptor binding, PA is cleaved by cellular proteases, and forms a heptameric “prepore” LF or EF bind to the heptamer and are endocytosed In the acidified endosome, the prepore transforms into a pore, releasing the factors into the cell

Lethal factor A zinc metalloprotease Cleaves the phosphokinase that activates the mitogen-activated protein kinase (MAPK) signal transduction pathway Cleavage of phosphokinase inhibits cell growth 3. Edema factor: An adenylate cyclase dependent on protective antigen for binding and entry into the cell

Edema factor An adenylate cyclase Increases intracellular cAMP Related to the enzyme produced by Bortedella pertussis and Pseudomonas aeruginosa

BACILLUS ANTHRACIS Transmission Through exposed skin or mucous membranes, from contaminated soil or infected animal products or by contact with sick animals Inhalation: rare in humans, more common in herbivores

BACILLUS ANTHRACIS Clinical syndromes Cutaneous anthrax Spores entering abrasions in the skin Painless ulcer with a black eschar (scab) Local edema Called "malignant pustule" Can lead to death in 20% of patients if untreated

BACILLUS ANTHRACIS Clinical syndromes Inhalation anthrax (pulmonary anthrax, "Woolsorter's disease”) Initially appears like a viral respiratory illness Can progress to diffuse pulmonary disease with respiratory failure Mortality rate is high (>95% if untreated)

Treatment and control Early antibiotic treatment of anthrax is essential Ciprofloxacin is the drug of choice Penicillin, doxycycline, erythromycin, or chloramphenicol may be used if susceptible Vaccination of animal herds and people in endemic areas Burning or burial of animals that die of anthrax BACILLUS ANTHRACIS

BACILLUS CEREUS Causes: Food poisoning Gastroenteritis Ocular infections Intravenous catheter-mediated sepsis

BACILLUS CEREUS Pathogenesis Spores can survive in soil Heat stable enterotoxin: Acts as a superantigen Causes gastroenteritis with vomiting Heat labile enterotoxin: ADP-ribosylates a G protein > stimulates adenylate cyclase Causes the diarrhea and fluid loss

Transmission and clinical syndromes Ingestion (food poisoning) Emetic (vomiting) form caused by contaminated rice Heat-resistant spores survive and germinate Nausea, vomiting, and abdominal cramps Diarrheal form Transmitted via contaminated meat, vegetables or sauces BACILLUS CEREUS

Treatment & Prevention Symptomatic treatment Proper refrigeration of food Rice should not be kept warm for long periods BACILLUS CEREUS

BACILLUS Bacillus species used in sterilization monitoring B. stearothermophilus spores Monitoring proper sterilization in an autoclave o C for 15 min Then placed in medium at 37 o C to grow B. subtilis spores Monitoring sterilization by dry heat 171 o C for 1 h or 160 o C for 2 h

CORYNEBACTERIUM DIPHTHERIAE

Club-shaped (wider at one end) rods Form short chains or clump together Aerobic or facultatively anaerobic Causes respiratory and cutaneous diphtheria

CORYNEBACTERIUM DIPHTHERIAE Pathogenesis Exotoxin secreted by the bacterium The "tox" gene introduced into strains of C. diphtheriae by a lysogenic phage (beta phage)

CORYNEBACTERIUM DIPHTHERIAE Exotoxin B subunit receptor binding domain membrane translocation domain A subunit ADP-ribosylation of elongation factor 2 (EF-2)

CORYNEBACTERIUM DIPHTHERIAE

Transmission Inhalation of airborne droplets Skin contact at the site of a pre-existing lesion Humans are the only natural host

CORYNEBACTERIUM DIPHTHERIAE Clinical syndromes Respiratory diphtheria malaise, sore throat exudative pharyngitis low-grade fever thick "pseudomembrane” bacteria, lymphocytes, plasma cells, fibrin, dead cells may cause airway obstruction

CORYNEBACTERIUM DIPHTHERIAE

Clinical syndromes Cutaneous diphtheria entry into subcutaneous tissue through breaks in the skin papule which evolves into a non-healing ulcer sometimes covered with a grayish membrane

CORYNEBACTERIUM DIPHTHERIAE Treatment and control Early administration of diphtheria antitoxin Penicillin G or erythromycin to eliminate the organism and terminate toxin production Active immunization with diphtheria toxoid during childhood (as part of the DPT vaccine) and with booster shots every 10 years

LISTERIA MONOCYTOGENES Non-spore forming Facultatively anaerobic small coccobacilli Causes meningitis and bacteremia Found in water, soil and the GI tracts of humans and animals

LISTERIA MONOCYTOGENES

Human disease restricted to neonates and the elderly pregnant women immunocompromised patients defective cell-mediated immunity

LISTERIA MONOCYTOGENES Pathogenesis Can grow in macrophages and epithelial cells Virulent strains produce listeriolysin O, a hemolysin Phospholipase C Can replicate at 4-8 o C

Growth at 4˚C

LISTERIA MONOCYTOGENES Transmission Contaminated food milk, soft cheese, undercooked meat, unwashed raw vegetables, cabbage From bacteremic mother to fetus The incidence of disease in AIDS patients is 100- fold greater Mortality rate (20-30%) higher than most other food- borne diseases.

LISTERIA MONOCYTOGENES Clinical syndromes Neonatal disease Early onset disease (granulomatosis infantiseptica) acquired transplacentally in utero disseminated abscesses and granulomas in multiple tissues Late-onset disease acquired soon after birth meningitis or meningoencephalitis with septicemia

LISTERIA MONOCYTOGENES Clinical syndromes Disease in adults mild, influenza-like illness in healthy adults severe illness in immuno-compromised patients meningitis should be suspected in organ transplant patients, patients with cancer, or pregnant women developing meningitis bacteremia high-grade fever and hypotension in acute cases

LISTERIA MONOCYTOGENES Treatment and control Penicillin or Ampicillin, either alone or with gentamicin Trimethoprim-sulfamethoxazole Avoid raw or partially cooked foods of animal origin, soft cheese or unwashed raw vegetables

ACTINOMYCES

Delicate filamentous forms (hyphae) Actinomyces = "ray fungus" (Gr.) Gram-positive bacilli Facultative anaerobic or strict anaerobic Form long branching filaments (not acid-fast) Produce slowly-developing chronic infections Most human infections are caused by Actinomyces israelii Actinomyces

Gram stain of Actinomyces in pus

Sulfur granule (filamentous organisms bound by calcium phosphate) collected from the sinus tract of a patient with actinomycosis

Actinomyces Macroscopic colony Gram stain

“Molar tooth” appearance of a colony of Actinomyces israelii

Pathogenesis Cause opportunistic infections of upper respiratory tract gastrointestinal tract female genital tract when normal mucosal barriers are disrupted Actinomycosis is characterized by multiple abscesses connected by sinus tracts Actinomyces

Epidemiology Endogenous infection Cervicofacial actinomycosis may occur after dental procedures The dentist may be the first to diagnose the swelling due to this condition Thoracic actinomycosis is established via inhalation or via the bloodstream Actinomyces

Epidemiology Abdominal infections usually caused by surgery or trauma Pelvic infections may result from abdominal infections or intrauterine devices Central nervous system infections spread from other locations Actinomyces

Actinomyces has colonized the surface of an intrauterine device, leading to the development of pelvic actinomycosis

Cervicofacial actinomycosis

Treatment and control Surgical debridement and long-term administration of penicillin G (or tetracycline, erythromycin or clindamycin) An undrained focus must be suspected if If infections do not respond to prolonged therapy Good oral hygiene is necessary for prevention Antibiotic prophylaxis before oral operations Actinomyces