Lecture 4 Listeria, Streptomyces, Corynebacteria 2023 PDF

The Firmicutes- Actinobacteria – Low GC gram-positive bacteria the high GC gram positive bacteria Non Spore forming bacteria The lactic acid bacteria Streptomyces Streptococcus Lactobacillus ✔ Nocardia Stap...

The Firmicutes- Actinobacteria – Low GC gram-positive bacteria the high GC gram positive bacteria Non Spore forming bacteria The lactic acid bacteria Streptomyces Streptococcus Lactobacillus ✔ Nocardia Staphylococcus ✔ Corynebacteria Listeria Mycobacteria Mycoplasma ✔ The spore forming bacteria Clostridium ✔ Bacillus ✔ Listeria monocytogenes There are several species of listeria – L.monocytogenes is an important cause of Disease in man and animals. Short, Gram positive, non-spore forming rod. Tumbling motility at room temperature but not at 37C distinguishes it from others eg. Corynebacteria. Catalase positive facultative anaerobe.  Listeriosis Disease split in to two types Perinatal – Early onset- intrauterine infection, sepsis and death before birth – Late onset – infected at birth, meningitis and sepsis within 2-3 weeks. Significant mortality Adult – In immunocompetent individuals it causes”flu-like symptoms” and gastro upset- resolution in a couple of weeks – In immunocompromised it causes meningo-encephalitis and bacteraemia Treatment – penicillin and gentamicin (latter does not enter host cells)  Source of infection Main reservoir of infection is infected environment, animals, silage, infected humans Normal route of infection is gastrointestinal. Infection and outbreaks are associated with dairy products – especially soft unpasteurised cheeses, packaged meat like luncheon meat and fruit and vegetables. Avoidance of infection is by pasteurisation of dairy foodstuffs and cooking of food. Note bacterium is psychrotrophic (grows in the fridge!)  2011 epidemic 33 deaths and 147 total confirmed cases since the beginning of the first recorded case on July 31, 2011.  DENVER — Two Colorado farmers whose listeria-contaminated cantaloupes killed 33 people pleaded guilty on Tuesday to federal criminal charges stemming from one of the deadliest outbreaks of food-borne illness in the United States. Prosecutors last month charged the brothers, the former owners of Colorado-based Jensen Farms, with six counts each of introducing adulterated food into interstate commerce tied to shipping tainted melons to markets. In May 2011, prosecutors said, the Jensens began washing the farm’s cantaloupes with devices used to clean potatoes and failed to use a chlorine spray feature that kills deadly bacteria. Both men pleaded guilty in Federal District Court in Denver. They face sentences of up to six years in federal prison and fines of up to $1.5 million for their conviction on all six counts. The brothers initially pleaded not guilty to the charges, but later agreed to change their plea in a deal with prosecutors. “The defendants have now admitted that they failed to protect the public from deadly bacteria on their cantaloupe, in violation of the law and critical F.D.A. requirements,” the United States attorney for Denver, John F. Walsh, said in a statement. Forrest Lewis, a lawyer for Eric Jensen, said the brothers thought the cleaning operation they used “was safe and inspected and adequate.” In addition to the deaths, the listeria outbreak led to the hospitalization of 147 people across 28 states, the authorities said. One woman suffered a miscarriage. The Jensens filed for bankruptcy in 2012 and suspended farming after lawsuits were filed by people sickened or whose family members died from listeria infections. Last week, the Jensens sued a food safety audit firm, the Primus Group, which they said approved the cleaning operation. October 2013 Pathogenesis The Firmicutes- Actinobacteria – Low GC gram-positive bacteria the high GC gram positive bacteria Non Spore forming bacteria The lactic acid bacteria Streptomyces Streptococcus Lactobacillus Nocardia Staphylococcus Corynebacteria Listeria Mycobacteria Mycoplasma The spore forming bacteria Clostridium Actinomycetes Bacillus Streptomyces Abundant soil organisms Mycelial Generate spores at ends of terminal hyphae Strict aerobes Nutritionally versatile Produce many antibiotics Antibiotic production by Streptomyces Droplet of Antibiotic Secreted by Streptomyces coelicolor Some Streptomyces antibiotcs From Brock, Biology of Microorganisms  Corynebacteria Diverse group of Gram +, aerobic, non- motile club-shaped rods – Koryne (Greek) = club Animal pathogens, plant pathogens and saprophytes Corynebacterium diptheriae  Pathology of Diptheria CDC describes diptheria as: "an upper respiratory tract illness characterized by sore throat, low-grade fever, and an adherent membrane of the tonsil(s), pharynx, and/or nose" Occurs in respiratory tract or in wounds Spread by droplets or by contact Toxigenic strains produce a toxin Toxin absorbed onto the mucous membrane and causes destruction of epithelium And produces local inflammation The necrotic epithelium becomes embedded in the exuded fibrin and immune cells so that a greyish “pseudomembrane” is formed Pathology of Diptheria Severe symptoms are due to action of toxin which is transported to all parts of the body in blood. Lesions occur in kidney, heart, nervous system -> acute nephritis and serious weakness of the heart, paralysis. 5 – 10% mortality even with treatment 4000 children die from diphtheria each year Diphtheria toxin Encoded by lysogenic phage A (catalytic) and B (receptor-binding) domains ADP-ribosylation of elongation factor EF2, preventing protein synthesis The lethal dose for humans is about 0.1 μg/kg Inactivated toxoid used as vaccine Antitoxin used for treatment Toxin used for Elek test Action of Diptheria toxin From Brock, Biology of Microorganisms Diphtheria toxin Encoded by lysogenic phage A (catalytic) and B (receptor-binding) domains ADP-ribosylates elongation factor EF2, preventing protein synthesis The lethal dose for humans is about 0.1 μg/kg Inactivated toxoid used as vaccine Antitoxin used for treatment Toxin used for Elek test  Diagnosis and treatment Gram stain or methylene blue show beaded bugs from swab aerobic growth on most media – Loefflers serum media is semi selective Elek test for toxigenicity- Antitoxin soaked filter paper Perpendicular streaked samples Treated with antitoxin and antibiotic (eg erythromycin) Vaccine (Diptheria toxoid, DPT)