CLOSTRIDIA Obligate anaerobes: Clostridia G+ spore-forming rods Soft tissue and skin infections Antibiotic-associated colitis & diarrhea Toxins: botulism tetanus gas gangrene pseudomomembranous colitis

C. perfringens histotoxics C. difficile pseudomembranous colitis C. tetani tetanus C. botulinum botulism

General features of Clostridia large, gram-positive, blunt-ended rods endospore-forming in vegetative cells

Physiology utilize pyruvate grow on enriched media of cysteine or thioglycollate (↓ redox) or O 2 -free gaseous atmosphere

Epidemiology environment intestinal tract soil, sewage or aquatic persistent survival in environment commensals & contaminants of clinical materials

Clostridium perfringens encapsulated vegetative form in GIT and vagina spores in soil anaerobic cellulitis, myonecrosis

Pathogenesis C. perfringens secretes exotoxins, enterotoxins and enzymes 12 exotoxins alpha toxin → lysis of endothelial cells, RBC’s WBC’s and platelets Types A → E

Enterotoxins: disrupts in transport = loss of fluid and proteins degradative enzymes – proteases (DNAses, hyaluronidase, collagenases

Diseases Myonecrosis gas-fermentation of tissue carbohydrates

Exudates → increased capillary permeability →exotoxins →circulation →other organs & intravascular hemolysis shock, renal failure →death Anaerobic cellulitis – clostridial infection of connective tissue rapid spread of the infection

Food poisoning, nausea, abdominal cramps and diarrhea Enteritis necrosticans Clostridial endometritis

Clostridium botulinum flaccid paralysis = toxin pure intoxication = disease

Epidemiology Soil and aquatic sediments Spores – vegetables, meat or fish toxin produced during vegetative growth

Pathogenesis Toxin: A-G ABE – human disease Serotypes = homologous types of proteins with tetanus toxin Toxin affects peripheral cholinergic Synapses = blocks neuromuscular junction = inhibit release of Ach = prevents contraction = Flaccidity

a. Classic botulism – food poisoning s/s difficulties in focusing vision, swallowing, in other CN functions progressive paralysis

b. Infant botulism toxin absorbed from the large bowel that is colonized s/s constipation, feeding problems, lethargy, poor muscle tone c. Wound contamination

Laboratory identification: Culture by anaerobic methods Treatment: antitoxin (Trivalent horse antiserum) mechanical ventilation

Clostridium tetani Epidemiology soils puncture wound foreign bodies, small areas of cell killing = divitalized material umbilical wound

Pathogenesis Tetanospasmin – transported by retrograde neuronal flow or by blood. Plasmid – coded exotoxin B fragment – binding to neurons - penetration of A A fragment – blocks neurotransmitter release at inhibitory synapses Result: prolonged muscle spasms

A fragment: a protease cleaves synaptobrevin Immunity: None Tetanus – Incubation period: days to weeks s/s trimus or lockjaw painful spasms, convulsions respiratory failure

Laboratory identification: clinical diagnosis characteristic morphology: “racquet shaped” bacillus swarming growth

Treatment: antitoxin – human horse antitoxin sedatives, muscles relaxants ventilation

Prevention: Active immunization with tetanus toxoid DPT – given at 2, 4, 6 & 18 mos.

Clostridium difficile

may be part of normal flora of the colon proliferates with antibiotic treatment 2 toxic polypeptides A & B Toxin A – enterotoxin Toxin B – cytotoxi

Drugs implicated: Ampicillin, Clindamycin, Cephalosporins s/s: diarrhea inflammation fulminant PMC (Pseudomembranous colitis)

Laboratory identification: Toxin production ELISA – Enzyme immunoassays Treatment: Oral metronidazole Oral vancomycin

B. anthracis enzootic worldwide domestic herbivores (sheep, goats and horses) humans – contact with infected animals products or contaminates dust.

Pathogenesis: capsule = D. glutamic acid 2 exotoxins = edema factor lethal toxin

Clinical forms: a.Cutaneous anthrax – 95% papule →black eschar → septicemia b. Pulmonary anthrax (“Woolsorter’s” disease) inhalation c. Gastrointestinal form

Laboratory identification: blunt-ended bacilli: singly, in pairs or frequently in long chains Spores are oval and centrally located Blood agar: colonies are large, grayish and non-hemolytic

Treatment: Penicillin, Doxycycline and Cipofloxacin

Listeria Slender, short, gram-positive rods Do not form spores Catalase-positive Tumbling motility in liquid media Can be confused morphologically with streptococci and corynebact.

L. monocytogenes widespread among animals in nature, infections usually food-borne capable of growth at 4 O C pregnant women, newborns, fetuses and immunocompromised

Pathogenesis L. monocytogenes – facultative, intracellular internalized → escapes the phagocytic vacuole: Listeriolysin O

Corynebacterium Bacillus anthracis Corynebacteria small, slender, pleiomorphic do not form spores non-motile and unencapsulated Toxin; A & B fragments

NAD & EF-2: ADP-ribosylation Blocks translocation of polypeptidyl-t-RNA from A site to P site The structural gene tox is encoded on the corynecbacterial phage; Β phage

Disease manifestations: 1.Upper respiratory tract – local formation of pseudomembrane Respiratory obstruction Cardiac condition defects Myocarditis CHF Neuritis of cranial nerves and parolysis of muscle groups

2. Cutaneous diphtheria Immunity: Antibodies

Laboratory identification clinical observation isolation of organism and tested for virulence Tinsdale agar – Methylene blue staining shows characteristic bands and polychromatic granules “Chinese characters”, picket fence

Treatment: Antitoxin Penicillin/Erythromycin Prevention: Toxoid