Gram Positive Rods Aerobic Gram positive rods Spore forming Non spore forming Anaerobic Aerobic Clostridium spp Bacillus spp Corynebacterium

SPORE FORMING GRAM POSITIVE

There are four Genera of gram positive rods: Bacillus Clostridium Corynebacterium Listeria Bacillus and Clostridium form spores while Corynebacterium and Listeria do not. Members of the genus bacillus are aerobic while members of Clostridium are anaerobic.

SPORES (ENDOSPORES) Central: Bacillus anthracis Subterminal: Present near the end Terminal: Present at the end

SPORES Bacillus anthracis Clostridium tetani

Two genera are of medical importance: Bacillus anthracis causes Anthrax disease and Bacillus cereuscauses food poisoning Bacillus anthracis: causes Anthracis Important disease in animals, but rare in humans ( potential biological weapon) Human disease occur in three main forms which are cutaneous, pulmonary and gastrointestinal

Important properties Large gram positive rod with square ends, Frequently found in chain. Its ant phagocytic capsule is composed of D- glutamate) the other bacterial capsule are polysaccharide Its non motile Anthrax toxin is encoded on one plasmid and the polyglutamate capsule is encoded on a different plasmid

Transmission Spores of the organism can persist in soil for years; therefore: Human contact with the spore hides in the environment such as from hides, bristles and wool. Inhalation of spores into the respiratory tract Pulmonary anthrax occurs when spore are inhaled into lungs Gastrointestinal anthrax occurs when contaminated meat are ingested Inhalation anthrax is not communicable from person to person despite the severity of the infection. After the organism being inhaled into lungs, it moves rapidly to the mediastinal lymph nodes , where it causes hemorrhagic mediastinitis. Because it leaves the lungs so rapidly, it is not transmitted by respiratory route to others.

Pathogenesis Consisted of two factors: edema factor and lethal factor each consisted of two proteins in an A-B sub unit configuration. The B, or binding subunit is the protective antigen. Edema factor is an adenylade cyclase causes outpouring of fluid from cell into the extracellular space which manifest as edema Lethal factor cleaves the phosphokinase that activates the mitogen-activated protein and inhibit cell growth. Protective antigen forms pores in the human cell membrane that allows edema factor and lethal factor to enter into cell.

Pathogenesis Infection Primarily a disease of animals ( sheep, cattle, horses) Humans affected rarely Infection is by entry of spore through injured skin or mucous membranes, rarely by inhalation into lungs In animals the portal entry is mouth and GIT

Spores in soil may be taken up with spiny or irritating vegetation In humans scratches in the skin or inhalation leads to infection (woolsorter disease) – rapidly fatal Germination of spores occurs in tissue at site of entry – leads to formation of gelatinous edema

Spread & multiplication – via lymphatics to the blood stream. Multiply in blood and tissue shortly before and after animal dies. Toxic anthrax factor has demonstrated to kill when studied on animal models Toxic anthrax factor can be neutralised with anthrax antiserum

anthrax toxin: Protective antigen –has antigenic properties Edema factor Lethal factor Toxin production is controlled by presence of a specific plasmid, its absence means absence of toxin

Woolsorter disease Spores from the dust of wool hair etc germinate in the lungs, or in the trachea, broncho lymph nodes Results in hemorrhagic mediastinitis, pneumonia, meningitis It is rapidly fatal

Pathology In susceptible organisms Bacteria proliferate at site of entry Bacterial capsule remain intact Bacteria surrounded by large amount of proteinaceous fluid containing few leukocytes Bacteria rapidly disseminate and reach the blood stream

In resistant organisms Bacteria proliferate for a few hours, then there is massive accumulation of leukocytes Bacteria remain localized

Clinical Findings Malignant pustule at site of infection on skin A papule develops 13 – 36 hrs Papule rapidly changes into vesicle, then a pustule and finally a necrotic ulcer, from which the bacteria may disseminate giving rise to septicemia

Inhalation anthrax Early manifestation may include mediastinitis, sepsis, meningitis, or haemorrhagic pulmonary edema Haemorrhagic pneumonia with shock is a terminal event

Laboratory investigation Specimen Fluid or pus from local lesion, blood, sputum - demonstration of large gram positive rods Immunofluorescence staining techniques can also be used Culture Blood agar – is useful

Resistance & Immunity Some animals (guinea pig) are highly susceptible, others (rats) are very resistant to anthrax infection. Resistance factors: Leukocyte activity Bactericidal action of blood Polypeptides – that kill anthrax ( synthetic polysine has similar effect)

Active immunity to anthrax Can be induced to susceptible animals by vaccination ( live attenuated bacilli, spore suspension or protective antigens from culture filtrates)

Treatment Ciprofloxacin/Penicillin is satisfactory except against inhalation anthrax ( inhalation anthrax remains to have high mortality rate) Some may produce beta lactamase and thus resist penicillin. Tetracycline, Erythromycin or Clindamycin may be effective. In prevention the disease to develop for those exposed Ciprofloxacin and Doxycycline can be used as prophylaxis.

Epidemiology, Prevention & Control Carcasses - dead animals ( source of spore) pH – 6.5 can allow spore germination in the soil. Grazing – animals are infected through injured mucous membranes Contact with infected animals or their hide, hair, bristles

Control measures Disposal of animal carcasses – burning or deep burial in lime pits Decontamination of animals products (autoclave) Protective clothing, gloves for handling potentially infected materials Active immunization of domestic animals People exposed occupationally should be vaccinated

B.cereus Is an ubiquitous soil organism found in grains, vegetables and dairy product Causes food poisoning Transmission: spores on grains such as rice survive steaming and rapid frying. The spore germinate when rice is kept warm for hours (eg reheated fried rice). The portal of entry is the gastrointestinal tract.

Emetic type food poisoning Is caused by preformed heated stable enterotoxin ingested in reheated foods eg rice beans Manifested by: Nausea Vomiting Abdominal cramps Occasionally diarrhea Is self limiting, recovery within 24 hrs Begins 1-5 hrs after ingestion of rice, or pasta dishes

Diarrheal type Has incubation period of 1 -24 hrs Profuce diarrhea Abdominal pain and cramps Fever & vomiting uncommon Toxin may be preformed in the food or produced in the intestine

B cereus & eye infections Organism introduced into eye by foreign bodies associated with trauma

B cereus & systemic infections Endocarditis Meningitis Osteomyelitis Pneumonia Obs! Presence of medical device - intravenous drug use predisposes to these infections

Prevention and treatment Refrigeration of food after cooking: spores survive initial cooking and will germinate into toxin producing vegetative cells if foods are not well s refrigerated properly;. Later reheating in activate heat labile toxin but does not affect vegetative cells or heat stable toxin. Supportive therapy eg replenish fluids and electrolytes.

2. CLOSTRIDIUM SPECIES C. tetani C.perfregent C.botulinum C.defficile

Important feature of pathogenesis by Clostridium species organism Disease Transmission/predisposing factor Action of toxin prevention 1 C. tetani Tetanus Spore in soil enter wound Blocks release of inhibitory transmitters eg glycine Toxoid vaccine 2 C. botulinun Botulism Exotoxin in food is ingested Blocks release of acetycholine Proper canning: cook food 3 C. perfringes 1.Gas gangrene 2.food poisoning Lecithinase superrantigen Debride wounds Cook food 4 C. difficile Pseudomembranous colitis Antibiotic suppress normal flora Cytotoxin damages colon Appropriate use of antibiotics.

Properties Large anaerobic gram (+ve) Many decompose proteins or produce toxins, some do both Their natural habitat is the soil or intestinal tract of humans and animals (saprophytic life) Pathogenic strains include those that cause botulism, tetanus, gas gangrene, pseudomembranous colitis

C. tetani a gram-positive rod commonly found in the soil, dust and animal feces, rusted iron materials

C. tetani………….. Commonly found in the soil, dust and animal feces Contamination of wounds, which provide anaerobic conditions, can lead to spore germination and tetanus frequently fatal disease. Tetanus is also know as lockjaw because of the patient's inability to open the mouth as a result of muscle paralysis. In developing countries, (about half) of tetanus cases are in neonates where the unhealed umbilical stump becomes infected, or circumsion often as a result of cutting the area with a contaminated knife

identification Small rods with tennis racquet shape due to presence of terminal spore Strict anaerobic that is very sensitive to oxygen

C. tetani

Pathogenesis Infection usually occurs when spores enter wounds and scratches where they germinate and produce tetanus toxin The exotoxin (tetanospasmin) binds to ganglioside receptors and bocks the release inhibitory mediators (eg. Glycine) at the spinal synapsesin central nervous system and this stops nerve impulse transmission to muscle leading to spastic paralysis.

The toxin can act at peripheral motor nerve end plates, the brain, spinal cord and also in the sympathetic nervous system. Because inhibitory neurons are involved, the result is unopposed  muscle contraction

Toxins Tetanolysin - heat and oxygen labile/lyse RBC/ Tetanospasmin - heat and oxygen stable/highly lethal (for mice 0.0000001 mg) dies within 1 - 2 days get easily neutralize with antitoxin

Tetanus symptoms include · Headache. · Jaw cramping. · Sudden, involuntary muscle tightening – often in the stomach (muscle spasms) · Painful muscle stiffness all over the body. · Trouble swallowing. · Jerking or staring (seizures) · Fever and sweating. · High blood pressure and fast heart rate

Tetanospasmin disseminates systemically binds to ganglioside receptors inhibitory neurones in CNS, signal stopped muscles keep on working spastic (rigid) paralysis glycine, neurotransmitter

Tetanospasmin GABA GLYCINE

A severe case of tetanus. muscles, back and legs are rigid muscle spasms can break bones can be fatal (e.g respiratory failure)

Clinical Findings In generalized tetanus, the most common form, the patient typically experiences lockjaw  Stiffness of the jaw muscles - inability to open the mouth or swallow leading to the appearance of a sardonic smile (risus sardonicus). Speech as a result of spasm of the vocal cords may be affected.  Continued severe muscle contractions, which can even cause broken bones The patient often experiences a fever (a rise of 2 to 4 degrees) with sweating, elevated heart rate blood pressure.  Aspiration pneumonia is often a late complication.

About eight days after infection symptoms of tetanus appear (though the incubation period can be a short as three days and as long as three weeks). Incubation period seems to depend on the distance of the infection site from the central nervous system. In neonates the average latent period is about a week

Cephalic tetanus a rare infection involving the middle ear Cephalic tetanus a rare infection involving the middle ear. It can affect cranial nerves. Local tetanus rare and manifests itself as localized muscle contractions in the area of infection Few cases are fatal

Treatment and prevention Vaccination with Tetanus toxoid (formaldehyde inactivated toxin) administered as a part of DPT vaccine. Booster shots required every ten years and recommended after probable exposure. Treatment for unvaccinated individuals Supportive care eg muscle relaxants, oxygen to reduce spasms and maintain breathing until circulating toxin is metabolized. Passive immunization with human antitoxin immunoglobulin to neutralize circulating tetanospasmin Debridement of the primary wound and penicillin therapy to eliminate clostridial cells If infants receive the complete vaccination regimen, virtually 100% protection is achieved Boosters should be given every ten years

DPT (diptheria, pertussis, tetanus) tetanus extremely uncommon in US infant DPT (diptheria, pertussis, tetanus) tetanus extremely uncommon in US tetanus toxoid antigenic no exotoxic activity

Clostridium perfringens Causes wound colonization – gas gangrene after soil, and food poisoning to a lesser extent intestinal tract after swallowing contaminated food

Gas gangrene Term gas gangrene refers to swelling of tissues due to release of gas, as fermentation products, of clostridia. Is caused by C perfringes . Can also be caused by other histotoxic clostridai such as Clostridium histolyticum, Clostroridium septicum and C. novyi.

Pathogenesis The organism produces several tissue degrading enzymes (including lecithinase [alpha toxin], proteolytic and saccharolytic enzymes). Necrosis and destruction of blood vessels and the surrounding tissue, especially muscle, result. This creates an anaerobic environment in adjacent tissue and the organism spreads systemically.

Clinical findings Pain, edema, and cellulitis occurs in the wound area. Crepitation indicate presence of a gas in tissue. Hemolysis and jaundice are common, are blood, -tinged exudates. Shock and death can ensue. Mortality rate are high.

Treatment Treatment (including anti- toxin, antibiotic therapy) is extremely effective and amputation and death is rare.

Laboratory Diagnosis production of lecithinase is important in laboratory identification of the organism.

C. Botulinum - Causes Botulism

Transmission Spores wide distributed in soil, contaminated vegetables, and meats. When these foods are canned or vacuum – packed without adequate sterilization, spores survive and germinate in the anaerobic environment. Toxin is produced within the canned food and ingested preformed. The highest risk food are: -a) alkaline vegetables such as green beans, peppers, and mushroom -b) smoked fish The toxin is relatively heat-labile, it is inactivated by boiling for several minutes. This disease can be prevented by sufficient cooking.

Pathogenesis Botulinum toxin is absorbed from the gut and carried via blood to peripheral nerve synapses where it blocks release of acetylcholine. It is a protease that cleaves the proteins involved in acetylcholine release. The toxin is a polypeptide encoded by a lysogenic phage. It is the most toxic known as tetanus. There are 8 immunological types of toxin. Type A, B, and E are most common in human illness. FIND THE OTHERS ( ASSIGNMENT)

Pathogenesis toxin binds to receptors on peripheral nerves, where acetylcholine is the neurotransmitter. toxin inhibits nerve impulses and flaccid paralysis and often death (from respiratory and/or cardiac failure) results. The organism does not grow in the gut, but pre-formed exotoxin from prior germination of spores may be present in inadequately autoclaved canned food (usually at home). 

Wound botulism can occur but is even rarer.  C. botulinum does not readily grow in the adult intestine due to competition with the normal flora and their requirement for an anaerobic, low acidity environment. In the neonate, where the flora is not established, colonization with C. botulinum can easily occur.

Clinical findings usually with a day or two but sometimes there may be a period of up to a week before they appear. Vision and swallowing are affected patient may become nauseated and constipated. Muscle paralysis ensues, usually starting at the head and, when the respiratory muscles are  affected, death can result. Eating honey contaminated by spores is one source.

LABORATORY DIGNOSIS The organism is usually NOT cultured . The Botulinum toxin is demonstrated in uneaten food and the patient serum by mouse protection test. Mice are inoculated with a sample of the clinical specimen and will die unless protected by antitoxin.

Treatment Adults includes an enema to clear the gastro-intestinal tract of the toxin and injection of It is important that the anti-toxin is given early to neutralize the toxin and protect nerve endings from damage. Trivalent antitoxin A, B and E is given with respiratory support. Antibiotics are not used to treat botulism, although they may be used in secondary infections, because of the possibility of more toxin being released as bacteria are lysed.

Supportive treatment of infants is based on helping them breath and on tube feeding. Adults may also require a respirator.  Complete recovery from botulism usually occurs over a period of months as the damaged nerve endings are replaced.

Prevention Proper sterilization and proper techniques in canning by adequate heating. Food must be adequately cooked to inactivate the toxin. Swollen can must be discarded.

C. difficile Is part of intestinal normal flora greatly decreased colonization occurs exotoxin A (enterotoxin) exotoxin B (cytoxin) pseudomembanous colitis

C. difficile……… When the normal flora of the intestine is altered by antibiotic therapy, this organism - which is present in the gastro-intestinal tract of many babies - can grow and colonize. C. difficile produces an enterotoxin and pseudomembranous colitis can result.  

EPIDEMIOLOGY

PATHOGENESIS

Clinical Findings abdominal cramps watery diarrhea, start some days (4 to 8) after initiation of antibiotic therapy. In mild cases, there is no blood in the diarrhea but, in severe cases, bloody diarrhea a distended tender abdomen fever can occur.

Treatment Discontinuation of the implicated antibiotic (e.g. ampicillin). Severe cases require specific antibiotic therapy (e.g. metronidazole and vancomycin).