Module 9.11 Part A

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Nonsporeforming (largely Gram-negative) anaerobes and Mycoplasma :

Nonsporeforming (largely Gram-negative) anaerobes and Mycoplasma Module 9.11 Part A

Blazing Star:

Blazing Star

Blazing Star:

Blazing Star 5-year-old Thoroughbred gelding Shipped from Florida Went off feed 2 days after arrival, mild fever, mild cough Attributed to “stress of new place” Over next 2 days, increasingly dull, depressed, off feed; febrile, coughing increased, elevated respiratory rate; Dx pneumonia. Treated penicillin G.

Blazing Star:

Blazing Star Auscultation, crackly sounds, heart muffled Pleural tap: Purulent effusion, large numbers Gram-positive rods in chains, large numbers Gram-negative swollen rods, filaments; foul smell Dx: Septic pleuritis, mixed aerobic-anaerobic infection

Blazing Star:

Blazing Star Treatment: Penicillin G, metronidazole Response: Failed to respond, remained febrile, coughing, etc over next 5 days Ultrasound extensive pleural adhesions, septic pockets Decided to euthanize

Blazing Star:

Blazing Star Where did these bacteria come from?




Moggo Moggo was chased through a barb-wired fence by “the neighbourhood terror” Cut abdomen, perforated colon One gram of colonic content leaked into peritoneum: 10 8 E. coli /gram, 500 species anaerobes at 10 10 /gram


Moggo Moggo very ill in 24 hours, high fever (endotoxemia), E. coli sepsis controlled by fluoroquinolones E. coli facultative anaerobe, reduced environment Septic peritonitis continued because Bacteroides fragilis , Fusobacterium nucleatum , Peptostreptocccus species synergized, caused fibrinopurulent peritonitis, peritoneal adhesions….


Moggo Treated cefoxitin, amoxiclav 10 days Recovered Over next year 3-4 episodes febrile illness, vomiting Local peritoneal abscesses Treated amoxiclav

Nonsporeforming anaerobes:

Nonsporeforming anaerobes Important opportunist pathogens of animals Commonly found in “mixed” infections with aerobes Oxygen is toxic, so may be unrecognized in diagnostic labs Key genera: Bacteroides, Fusobacterium, Porphyromonas

Nonsporeforming anaerobes:

Nonsporeforming anaerobes Up to 25% unselected clinical specimens contain these bacteria Anaerobic transport systems Need anaerobic environment in lab Relatively slow growing (2-4 days) Mixed: eg 1-2 aerobic, 2-3 anaerobic species, need aerobes to remove oxygen

Nonsporeforming anaerobic infections: Key features:

Nonsporeforming anaerobic infections: Key features Endogenous organisms usually Typically chronic, associated necrosis and purulence Often breaks in mucosal surfaces where anaerobic microflora Sometimes foul smell (volatile fatty acids) About 10-15 opportunist anaerobic species per animal species

Virulence and Pathogenesis:

Virulence and Pathogenesis Virulence: Multifactorial, depending on agent Complex because mixed infections, sometimes synergistic interactions between agents Host factors important: Opportunists Host defenses: Innate rather than acquired immunity

Anaerobic bacterial infections in animals:

Anaerobic bacterial infections in animals Bacteroides 20-30% B. fragilis, B. ruminicola Porphyromonas , Prevotella 10-20% P. asaccharolytica, P. gingivalis Fusobacterium 6-20% F. necrophorum Peptostreptococcus 6-15% P. anaerobius Clostridium 4-30% C. perfringens Actinomyces 1-9% Eubacterium 2-3 Non-selected infections

Common infections involving anaerobes:

Common infections involving anaerobes Head and neck Periodontal disease, dental disease, chronic sinusitis Pleuro-pneumonia Aspiration pneumonia, pleuritis , pleural effusion Abdominal Peritonitis, intestinal perforation, navel infection

Common infections involving anaerobes:

Common infections involving anaerobes Female genital PP metritis, pyometra, mastitis Soft tissue Cellulitis , bite, wound Skeletal Arthritis, footrot , traumatic osteomyelitis Abscesses Anywhere

Periodontal disease:

Periodontal disease Accumulation subgingival “plaque” Mix of Porphyromonas gingivalis, Prevotella intermedia, Fusobacterium nucleatum, Actinomyces viscosus, Aggregatibacter actinomycetemcomitans , etc . Complex mixed aerobic-anaerobic infection P. gingivalis co-aggregates other bacteria, resists host defenses, produces collagenases, inflammation, synergistic interaction Agents change as disease progresses Progressive destruction periodontal membrane

“Keystone role” of Porpyromonas gingivalis in periodontal disease:

“Keystone role” of Porpyromonas gingivalis in periodontal disease

Nonsporeforming anaerobic infections: Treatment and control:

Nonsporeforming anaerobic infections: Treatment and control Remove necrotic and purulent material, flush

“4 quadrant approach to antimicrobial selection”:

“4 quadrant approach to antimicrobial selection” Gram-positive anaerobe Gram-negative anaerobe NOT Fluoroquinolones Aminoglycosides Polymyxins ; Trimethoprim-sulpamethoxazole Penicillin G, most cephalosporins ( cefoxitin ++), chloramphenicol , metronidazole , lincosamides , macrolides

Selected anaerobes:

Selected anaerobes

Bacteroides fragilis:

Bacteroides fragilis Major pathogenic Bacteroides Small part of intestinal microflora Virulence: +++ Disease: Typical nonsporeforming anaerobic infection, but often pure culture Disease: Typical anaerobic infections + diarrheal illness animals and humans, usually undiagnosed

Fusobacterium necrophorum:

Fusobacterium necrophorum Gram-negative filamentous rod Large bowel ruminants, swine Survives well-manured pasture 12 months Virulence: Leukotoxin, leucocidin Synergistic Trueperella pyogenes

Fusobacterium necrophorum:

Fusobacterium necrophorum “Necrobacillosis” Liver abscess cattle : High grain diet, acidosis, rumenitis, invades to liver, causes abscesses May rupture to cause sudden death Tylosin used in feedlot rations to prevent

Fusobacterium necrophorum:

Fusobacterium necrophorum Foot-rot in cattle , contagious necrotizing interdigital dermatitis (“foul in the foot”) Destructive, invasive cellulitis of foot Synergism with P. asaccharolytica Standing in wet, fecally contaminated conditions

Fusobacterium necrophorum:

Fusobacterium necrophorum Nonspecific infections cattle and swine, often synergistic with T. pyogenes Foot rot in sheep: Specific synergism with Dichelobacter nodosus

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