Legionella, Listeria and Corynebacteria Alsowww.amm.co.uk,

Legionella 52 genetically defined species and about half are pathogenic to humans. Thin Gram negative rods with unusual complex nutritional requirements : eg high Fe and cysteine. Not related to other respiratory pathogens.

Legionella Legionella pneumophila Others associated with infection in the compromised : L. micdadei L. bozemanii L. longbeachae L. dumoffii

Legionella Legionella pneumophila: First recognised as a pathogen in 1976 following a major outbreak amongst American Legionnaires in Philadelphia - >180 affected. Subsequently recognised as a cause of disease as far back as 1947 and an outbreak in 1957.

Legionella Ubiquitous in nature and can be isolated from terrestrial and aquatic habitats and from patients with LD. Isolated from lakes, streams and soil in small numbers. It is relatively resistant to heat and chlorine. (It appears to go into some form of suspended animation in adverse conditions.) It is normally spread through water distribution or air conditioning systems in which high numbers may be found.

Legionella Outbreaks seem to occur at the end of the summer but cases may occur all year round as it is found in hot water tanks, and whirlpool spas (where it multiplies readily at 35-45oC ). Spread by inhalation of aerosols from showers etc. NOT spread from person to person.

Legionella Annual prevalence in US is steady at about 0.5 per 100,000. It is likely that many cases are undiagnosed.

Legionella Prevention is by: Maintenance and cleaning of A/C systems. Improved design of water systems and elimination of dead legs, Hyperchlorination, Hyperchlorination, Heating water to 63oC.

Legionella Pathogenesis. L. pneumophila is an intracellular parasite that grows in alveolar macrophages and monocytes. Phagocytosed cells are protected from intracellular killing by lysosomal fusion and acidification. Virulent strains are difficult to distinguish from avirulent strains. Virulence seems to depend on proteolytic enzymes, lipases, phosphatases and nucleases.

Legionella Pontiac Fever : A mild self-limiting disease - mild cough, sore throat, mild headache and fever. No treatment necessary and it resolves in 2-5 days. Possibly due to inhalation of antigen rather than bacterial invasion. Sometimes shows high attack rates (95%)in outbreaks

Legionella Legionnaires Disease: In the elderly - often who are immunocompromised for some reason a more severe disease which is an atypical pneumonia. There are 18 serotypes– serogroup 1 is the most pathogenic and seems to cause 95% of such infections in these islands. Low attack rates in outbreaks ( %)

Legionella Predisposing factors: Smoking, malignancy, diabetes, Aids, end- stage renal disease, and alcohol abuse. Male : Female 2.5 : 1 Very rare in those under 20

Legionella Legionnaires Disease cont’d Prior to the onset of pneumonia intestinal disorders are common followed by high fevers and chills and muscle aches. Followed by dry cough, and chest and abdominal pains. Fatality at about 10% usually as a result of respiratory failure

Legionella Diagnosis Culture of bronchial washings, pleural fluid and possibly other body fluids. Culture using buffered charcoal yeast extract agar with iron and cysteine. Growth may take 5 (L. pneumophila)-10 days (other species).

Legionella Antigen detection in patient’s urine – ELISA for Serotype 1 only. Serology for retrospective diagnosis: FAT, Rapid microagglutination Test, RIA or ELISA. Antibody response in 8 days 4-fold rise in titre or a titre of 1:256 is usually diagnostic.

Legionella Treatment: Conventional sensitivity tests are unreliable but L. pneumophila is susceptible to rifampicin, erythromycin, quinolones and tetracyclines. All these have good intracellular penetration. Beta lactams and aminoglycosides are ineffective IV erythromycin is preferred.

Listeria Two species may be pathogenic – mostly Listeria monocytogenes and occasionally L. ivanovii. L. innocua, L. welshimeri and L. seeligeri are non pathogenic. Up to 5% of healthy adults carry Listeria.

Listeria Widespread in nature but infections are rare in the general population but may cause life threatening infections usually bacteraemia or meningo-encephalitis in susceptible groups which are: Post 20 weeks of pregnancy, neonates and the immunosuppressed. Mortality highest in infants of septic mothers or the severely immunocompromised.

Listeria Short intracellular Gram-positive rods, but in clinical specimens may appear Gram variable and look like diphtheroids or cocci. Motile with tumbling motility. Grow on blood agar – There are no identifiable toxins but virulent strains are haemolytic. Animal studies suggest the production of listeriolysin which protects the organism after phagocytosis and facilitates the extraction of iron

Listeria Grow best at 30 – 37oC but can grow at 4 -10oC. Some claim it may grow at 0oC. Definitive identification by biochemistry or serology

Listeria Neonatal disease: Early onset: acquired transplacentally. Disseminated abscesses and granulomas with high mortality if untreated. Late onset: 2-3 weeks after birth meningitis or meningoencephalitis and septicaemia

Listeria Treatment: Penicillin or ampicillin alone or with an aminoglycoside. No vaccine is available and because of the ubiquitous nature of the organism and the sporadic infections, prevention and control are difficult.

Listeria Reservoir: Domestic and wild animals, water and mud. Contaminated silage gives rise to listeriosis in animals. Faecal carriage in man in about 5%

Listeria Listeria is found in a wide range of foods including fish, meat and vegetables and consequently in food products such as soft cheeses and those not made with pasteurised milk. A relatively recent outbreak involved pork pate from Brussels.

Listeria Its ability to grow at 4oC and survive temperatures of 70oC has implications in the management of cook chill catering. Also in ready prepared meals bought in supermarkets.

Corynebacteria The genus includes the diphtheria bacillus as well as a number of commensals and pathogens of man and animals. These are usually referred to as coryneforms or diphtheroids. These are pleomorphic gram-positive rods arranged as pallisades. These are pleomorphic gram-positive rods arranged as pallisades.

Corynebacteria C. diphtheriae is the type strain It is aerobic and facultatively anaerobic non-sporing non-motile and non-capsulate. It is grown on media containing blood or serum and produces characteristic black colonies on blood tellurite medium.

Corynebacteria Three types of colonies may be observed : Large – gravis Medium – intermdius Small – mitis. Historically these reflected the severity of the infection. Gravis and intermedius are usually toxigenic due to the presence of a bacteriophage

Corynebacteria Diphtheria is an acute infection of the tonsils, pharynx, nose and other mucous membranes or even skin and on occasion the conjunctiva and genitals. Diphtheria is an acute infection of the tonsils, pharynx, nose and other mucous membranes or even skin and on occasion the conjunctiva and genitals. A greyish membrane covers much of the throat and is surrounded by inflammation. The throat is moderately sore and the patient will have enlarged cervical lymph nodes.

Corynebacteria Diphtheria should be differentiated from other causes of sore throat and premature use of antibiotics may delay diagnosis with fatal results. Specific treatment with antibiotics and antitoxin is indicated even if lab results are negative.

Corynebacteria Man is the reservoir of this bacterium. The disease is normally manifest in the colder months. Usually unvaccinated children of less than 15 y. This is a story of a very successful vaccination programme. It used to be very common but now diphtheria is very rare.

Corynebacteria Spread is by direct contact with patient or articles soiled with discharges. Raw milk has been a vehicle. Incubation is 2-5 days. Communicability depends on the success of the treatment which if good, will prevent carriage and spread. Rarely carriers may shed for 6 months or more.

Corynebacteria Non diphtheria coryneforms include : C.ulceransAcute pharyngitis C. haemolyticum C.minutissimumCutaneous infections C.jeikeium

Corynebacteria C.pseudotuberculosis causing Granulomatous lymphadenitis. C.jeikeiumInfective endocarditis C.xerosisC.pseudodiphtheriticumC.bovis

Corynebacteria C.jeikeiumLine shunt and cannula C.xerosisC.bovis C.equinecrotising pneumonia CDC group D-2 Complicated UTI (abnormality or stones)