Lactobacilli and Corynebacteria PDF Lecture Notes

Lactobacilus Corynebacterium Propionibacteria 3rd stage/ Microbiology Assist prof dr. Zubaida Najat Mustafa  Lactobacilli are saprophytes in vegetable and animal material (e.g. milk). Some species are common animal and human commensals inhabiting the oral ca...

Lactobacilus Corynebacterium Propionibacteria 3rd stage/ Microbiology Assist prof dr. Zubaida Najat Mustafa  Lactobacilli are saprophytes in vegetable and animal material (e.g. milk). Some species are common animal and human commensals inhabiting the oral cavity and other parts of the body. They have the ability to tolerate acidic environments and hence are believed to be associated with the carious process. The taxonomy of lactobacilli is complex. They are characterized into two main groups: homofermenters, which produce mainly lactic acid (65%) fromglucose fermentation (e.g. Lactobacillus casei), and heterofermenters, which produce lactic acid as well as acetate, ethanol and carbon dioxide (e.g. Lactobacillus fermentum). L. casei and Lactobacillus rhamnosus, Lactobacillus acidophilus and the newly described species, Lactobacillus oris, are common in the oral cavity.  Habitat and transmission Lactobacilli are found in the oral cavity, gastrointestinal tract and female genital tract. I n the oral cavity, they constitute less than 1% of the total flora. Transmission routes are unknown Lactobacilli are also major constituents of the vaginal flora and help maintain its low pH equilibrium. Recently, the beneficial role of lactobacilli in maintaining the homoeostasis of the intestinal flora has been recognized  Characteristics Gram- positive coccobacillary forms (mostly bacillary), α- or non- haemolytic, facultative anaerobes. These organisms ferment carbohydrates to formacids (i.e. they are acidogenic) and can survive well in acidic milieu (they are aciduric); they may be homofermentative or heterofermentative. The question as to whether they are present in carious lesions because they prefer the acidic environment, or whether they generate an acidic milieu and destroy the tooth enamel, has been debated for years Dr.T.V.Rao MD 7  Pathogenicity Lactobacilli are frequently isolated fromdeep carious lesions where the pH tends to be acidic. I ndeed, early workers believed that lactobacilli were the main cariogenic agent , the number of lactobacilli in saliva (the lactobacillus count) was taken as an indication of an individual’s caries activity. Although this test is not very reliable, it is useful for monitoring the dietary profile of a patient because the level of lactobacilli correlates well with the intake of dietary carbohydrates  Definition Diphtheria is an acute, toxin- mediated disease caused by toxigenic Corynebacteriumdiphtheriae I t’s a very contagious and potentially life- threatening bacterial disease. I t’s a localized infectious disease, which usually attacks the throat and nose mucous membrane  Corynebacteria The genus Corynebacteriumcontains many species that are widely distributed in nature. These Gram- positive bacilli demonstrate pleomorphism (i.e. coccobacillary appearance) and are non- sporing, non- capsulate and non- motile. The sometimes fatal upper respiratory tract infection of childhood diphtheria is caused by Corynebacterium diphtheriae. I t is important to distinguish this, and other pathogens within the genus, fromcommensal corynebacteria.  Corynebacteriumdiphtheriae Habitat and transmission Human throat and nose, occasionally skin; patients carry toxigenic organisms up to 3 months after infection. Transmission Transmission is most often person- to- person spread fromthe respiratory tract (by small droplet when coughing or sneezing). Rarely, transmission may occur fromskin lesions or articles soiled with discharges fromlesions of infected persons  Characteristics Pleomorphic, Gram- positive, club- shaped (tapered at one end) bacilli, 2–5 µm in length, arranged in palisades. They divide by ‘snapping fission’ and hence are arranged at angles to each other, resembling Chinese characters. The rods have a beaded appearance, with intracellular store of polymerized phosphate. The granules stain metachromatically with special stains such as methylene blue stain (i.e. the cells are stained with blue and the granules in red). 13  Toxin production The exotoxin responsible for virulence can be demonstrated by the gel precipitation test, which uses the Elek plate in Vitro & Animale inoculation in Vivo I n Vitro Elek test I n this test, a flter paper soaked in diphtheria antitoxin is incorporated into serumagar before it has set; the test strain of C. diphtheriae under investigation is then streaked on to the agar at right angles to the filter- paper strip and incubated at 37°C. After 24 h, white lines of precipitation will be visible as a result of the combination of the antitoxin and the antigen (i.e. the toxin) if the strain is a toxigenic isolate. Although this is the traditional method for toxin detection, Enzyme- linked immunosorbent assays (ELI SAs) and immunochromographic strips are now available for quick detection of the exotoxin fromthe cultured isolates. - A rapid diagnostic test based on polymerase chain reaction for the toxin gene (tox) is another new direct assay of patient specimens.  Diphtheria toxin This exotoxin –produced by strains carrying bacteriophages with the tox gene –inhibits protein biosynthesis in all eukaryotic cells. The toxin has two components: Subunit A, Active site Enzyme Blocks protein synthesis – ADP- ribosyl transferase – elongation factor 2 (EF2).  Diphtheria Toxin: Part B Binding Site Binds to cell receptor Bound receptor internalized Endosome – Hydrolyzed by protease – Disulfide broken – Part A released Macroscopically, its action on the respiratory mucosa results in the production of a grey, adherent pseudo membrane comprising bacteria, fibrin and epithelial and phagocytic cells. This may obstruct the airway, and the patient may die of asphyxiation. When the toxin permeates into the blood stream, it acts systemically, affecting motor nerves of the myocardiumand the nervous system. The toxin can be converted to a toxoid (i.e. made nontoxic but still antigenic) by treatment with formaldehyde; the toxoid can then be used for prophylactic immunization –the first component of the diphtheria–tetanus–pertussis (DTP) vaccine Antitoxin, produced by injecting the toxin into horses, neutralizes the toxin Dr.T.V.Rao MD 20  Pathogenicity C. diphtheriae is the agent of diphtheria; it usually affects the mucosa of the upper respiratory(nasopharynx tract, or anterior nurse) skin, middle ear. Cutaneous infections are especially seen in the tropics and are usually mixed infections with Staphylococcus aureus and/or Streptococcus pyogenes. Serious systemic manifestations are the result of the absorption of the exotoxin. Dr.T.V.Rao MD 22  Treatment and prevention I n the acute phase, supportive therapy to maintain the airway is critical. Antitoxin is given to neutralize the toxin and penicillin to kill the organisms. I n epidemic outbreaks, carriers are given either penicillin or erythromycin. I mmunization is highly effective in preventing diphtheria. A special test (the Schick test) is used to demonstrate immunity. Here, the circulating level of antibody after immunization (or clinical/subclinical infection) is assessed by inoculating a standardized dose of the toxin.  Schick Test I njection of toxin I D Produces redness/ erythematic in 2- 4 days No reaction – Protective immunity present.  Other corynebacteria Corynebacteriumulcerans is responsible for diphtheria- like throat lesions, but it does not cause toxaemia. Corynebacterium(formerly Bacterionema) matruchotti is the only true coryneform organismin the oral cavity.  Diphtheroids Bacilli that morphologically resemble diphtheria bacilli are called diphtheroids (e.g. Corynebacteriumhofmannii, Corynebacterium xerosis). They are normal inhabitants of the skin and conjunctiva and are occasional opportunistic pathogens in compromised patients (e.g. endocarditis in prosthetic valves).  Propionibacteria Propionibacteria are obligate anaerobic, Gram- positive rods, sometimes called ‘diphtheroids’ Propionibacteriumacnes is part of the normal skin flora and may also be isolated fromdental plaque. Acne is follicle- associated lesions The pathogenesis of facial acne is closely related to the lipases produced by P. acnes, hence the name. A new member of this genus is Propionibacterium propionic morphologically similar to Actinomyces israelii (except for the production of propionic acid fromglucose by the former) 29 Actinomycetes, which were formerly thought to be fungi, are true bacteria with long, branching flaments analogous to fungal hyphae. The two important genera of this group are Actinomyces and Nocardia. Actinomyces spp. are microaerophilic or anaerobic; Nocardia spp. are aerobic organisms GRAM POSI TI VE CELL ENVELOPE Degradative enzyme Lipoteichoic acid Peptidoglycan- teichoic acid Cytoplasmic membrane Cytoplasm  Actinomyces spp Although most Actinomyces are soil organisms, the potentially pathogenic species are commensals of the mouth in humans and animals. They are a major component of dental plaque, particularly at a proximal sites of teeth, and are known to increase in numbers in gingivitis. An association between root surface caries of teeth and Actinomyces has been described. Other sites colonized are the female genital tract and the tonsillar crypts A number of Actinomyces species are isolated fromthe oral cavity. These include Actinomyces israelii, Actinomyces gerencseriae, Actinomyces odontolyticus, Actinomyces Viscosus Actinomyces Meyeri A close relationship between Actinomyces odontolyticus and the earliest stages of enamel demineralization, and the progression of small caries lesions have been reported. The most important human pathogen is A. israelii. Habitat and transmission This organismis a commensal of the mouth and possibly of the female genital tract. I t is a major agent of human actinomycosis.  Characteristics Gram- positive filamentous branching rods. Non- motile, non- sporing and non- acid- fast. Clumps of the organisms can be seen as yellowish ‘Sulphur granules’ in pus discharging fromsinus tracts, or the granules can be squeezed out of the lesions. (Strains belonging to A. israelii serotype I I are now in a separate species, A. gerencseriae, a common but minor component of healthy gingival flora.) G/S :Variable cellular morphology, ranging fromdiphtheroidal to coccoid filaments มักพบ sulfur granule จากการยอม gramได และยอมไมติด mAFB The colonies resemble breadcrumbs or the surface of ‘molar’ teeth Because of the exacting growth requirements and the relatively slow growth, isolating this organismfromclinical specimens is difficult, particularly because the other, faster- growing bacteria in pus specimens tend to obscure the slow- growing actinomycetes.  Actinomycosis Sulphur granules’in lesions are a clue to their presence. When possible, these granules should be crushed, Sulfur granules Gram- stained and observed for Gram- positive, branching flaments, and also cultured in preference to pus. G/S :sulfur granule  ACTI NOMYCOSI S Not highly virulent (Opportunist) Component of Oral Flora Periodontal pockets Dental plaque Tonsilar crypts Take advantage of injury to penetrate mucosal barriers Coincident infection Trauma Surgery  Pathogenicity Most (70–80%) actinomycotic infections are chronic, granulomatous, endogenous infections of the orofacial region. Typically, the lesions present as a chronic abscess,commonly at the angle of the lower jaw, with multiple external sinuses. There is usually a history of trauma such as a tooth extraction or a blow to the jaw. Although most infections are monomicrobial in nature (i.e. with Actinomyces alone causing the disease), a significant proportion of infections could be polymicrobial, with other bacteria such as Aggregatibacter actinomycetemcomitans, Haemophilus spp. and anaerobes acting as co- infecting agents  Dr.T.V.Rao MD 42 People at risk with actinomycosis Having a dental disease or recent dental surgery (for jaw abscess) Aspiration (liquids or solids are sucked into lungs) (for lung abscess) Having bowel surgery (for abdominal abscess) Swallowing fragments of chicken or other bones (for abdominal abscess) For women: having an intrauterine contraceptive device (I UD) in place for many years (for abscess affecting the reproductive organs)  I nfection Cervicofacial region 43 Dr.T.V.Rao MD  Dr.T.V.Rao MD 44 I ntestinal actinomycosis  Dr.T.V.Rao MD 45 Abdominal actinomycosis  Dr.T.V.Rao MD 46 Diagnosis:. Gramstain. Culture. (poor growth in culture only in less than 50% of cases.) Sulphur granules (yellowish myecelial masses) Specimens –open biopsy, aspiration material The discharge should mix with sterile saline in a universal bottle and allow to stand, particles will separate out. Place between 2 slides Crush and gramstain Observe for Grampositive branching filaments  Dr.T.V.Rao MD 47 Examination of discharges will help in diagnosis Examination of drained fluid under a microscope shows "sulphur granules" in the fluid. They are yellowish granules made of clumped organisms  48 Treatment of actinomycosis Treatment classically begins with I V penicillin for 2–6 weeks, followed by oral therapy with penicillin or amoxicillin for 6–12 months. For penicillin allergic patients, tetracycline, erythromycin, minocycline and clindamycin have been administered. amoxicillin are now popular. well to tetracycline because of its good bone penetration. Surgical intervention may be necessary in chronic jaw lesions. Prevention of these infections is difficult because of their endogenous nature