GRAM POSITIVE BACILLI

BacillusCorynebacteria

Listeria, etc

Clinically important Gram positive bacilli

Spore forming• BacillusNon spore forming• Corynebacterium• ListeriaBacilli w/ branching filaments• Actinomyces • Nocardia

BACILLUS

• Bacillus anthracis• Bacillus cereus

Bacillus anthracis

• Large bacilli of 1-3 m• Single or paired in

clinical isolates• In vitro – prominent

capsule• Highly resistant spores

Anthrax

Virulence factors• Capsule (antiphagocytic)• Toxin (oedema & death)

Cutaneous anthraxAbout 20% mortality

Cutaneous anthraxAbout 20% mortality

Gastrointestinal anthraxHigh mortality

Gastrointestinal anthraxHigh mortality

Inhalation anthraxHigh mortality

Inhalation anthraxHigh mortality

Anthrax - Epidemiology

Anthrax - Diagnosis

• Specimen– Aspirate or swab from cutaneous lesion– Blood culture– Sputum

• Laboratory investigation– Gram stain– Culture– Identification of isolate

Anthrax – treatment and prevention

• Penicillin• Tetracycline /chloramphenicol

• Erythromycin,Clindamicin• Prevention

– Vaccination of animal herds– Proper disposal of carcasses

• Active immunisation with live attenuated bacilli

Bacillus cereus

• Large, motile, saprophytic bacillus• Heat resistant spores• Pre formed heat and acid stable toxin (Emetic

syndrome)• Heat labile enterotoxin (Diarrhoeal disease)• Lab diagnosis – Demonstation of large number

of bacilli in food

Gastroenteritis

Gastroenteritis

Bacillus cereus clinical presentation

Incubation period < 6 hoursSevere vomitingLasts 8-10 hours

Incubation period > 6 hoursDiarrhoea

Lasts 20-36 hours

EMETIC FORM DIARRHOEAL FORM

CORYNEBACTERIA

• Causes localized inflammation (pseudomembrane, greyish white exudate ) and generalized toxaemia

• Prevalent in baby’s after 3-6 months, very high in young children

Morphology

• Gram+ve/ palisade/Chinese letter arrangement

• Irregular swellings at one end -club shaped.• Corynebacteria tend to pleomorphism in

microscopic and colonial morphology.

Culture characteristics

• On blood agar Small granular & gray with irregular edges and may have small zones of hemolysis.

• Also grow on Loeffler's serum slope• On blood telurite agar (black colonies)

Important species

• Corynebacterium diphtheriae• Normal flora of nasopharynx in about 10%

– Some may cause Diphtheria• Diptheroids

– Normal flora of skin, contaminants of samples– Can cause disease in ‘compromised’ host

• C. ulcerans C. haemolyticum C. jeikeium

Epidemiology

• Rare in developed countries/ • Disease of third world countries• Still highly prevalent in the former Soviet

Union.• Spread through droplets.• Nasal carriers are very dangerous

Types of Diphtheria

• Faucial• Laryngeal• Nasal• Conjunctival• Vulvovaginal• Otitic• Cutaneous around the mouth and the nose

Pathology

• Toxin is absorbed in the mucus membrane and causes destruction of epithelium and causes a superficial inflammatory response.

• Necrotic epithelium becomes embedded in exuding fibrin and red and white cells, with bacteria.

• Grayish pseudomembrane is formed over the tonsils and pharynx and larynx.

Pathology

• Removal of pseudomembrane - capillary damage and bleeding..

• Regional lymphadenopathy with marked edema of the neck within the membrane bacilli produce toxin.

• This results in distant toxic damage - parenchymatous degeneration, fatty infiltration & necrosis in heart muscle liver kidney & adrenals.

Diagnosis• Direct smear - Albert's stain• Culture - Loffler's serum slope/blood agar/blood

telurite agar

Check the toxigenicity• Animal inoculation - Guinea pigs/rabbits - Death

within 96 hrs• Elek’s test

Elek's plate test

Filter paper with antitoxin

Precipitation

Strain

Management

1. Patients – Isolation of the patient– Bed rest– Antibiotic treatment

(Penicillin/erythromycin/teracycline/rifampicin/clindamycin )– Antitoxins (horse serum)

2. Contacts– Immunize (toxoid)– Prophylactic antibiotic – erythromycin– Swab nose and throats of contacts

3. Community – immunization

DIPHTHERIA

DIAGNOSIS

Clinical suspicionSwab for cultureToxin production

TREATMENT

PenicillinAnti-diphtheretic serum

Maintaining airwaySupportive

PREVENTION

Immunization(toxoid)

Listeria monocytogenes

Clinical Manifestations

• Listeriosis is a serious disease for humans, with a mortality greater than 25 percent.

• Two main clinical manifestations, sepsis and meningitis.

Characteristics

• Small, gram-positive rods, which are sometimes arranged in short chains.

• Flagella are produced at room temperature rather than at 37° C.

• A particular property of L monocytogenes is the ability to multiply at low temperatures. Bacteria therefore can accumulate in contaminated food stored in the refrigerator.

Pathogenesis

• Listeria monocytogenes is presumably ingested with raw, contaminated food.

• An invasion factor secreted by the pathogenic bacteria enables them to penetrate host cells of the epithelial lining.

• Normally, the immune system eliminates the infection before it spreads. If the immune system is compromised, however, systemic disease may develop.

Pathogenesis

• Listeria monocytogenes multiplies not only extracellularly but also intracellularly within macrophages after phagocytosis and even within parenchymal cells which are entered by induced phagocytosis.

• Survival within the phagosomes and eventual escape into the cytoplasm are mediated by a toxin, which also acts as a hemolysin.

Host immune response

• Because it multiplies intracellularly, L monocytogenes is largely protected against humoral immune factors such as antibodies,

• The effective host response is cell- mediated, involving both CD4+ (T-helper) cells and direct lysis of infected cells by CD8+ (cytotoxic) T lymphocytes.

Epidemiology

• Listeria species are found in living and nonliving matter. Various foodstuffs of vegetable and animal origin are sources of infection.

• Most human cases of listeriosis develop in immunocompromised hosts: newborns, old people, cancer patients, and transplant recipients.

• Outbreaks of listeriosis are due mainly to a common source of contaminated food.

• Listeriosis also may be transmitted congenitally across the placenta. The immunocompetent mother suffers at worst a brief, flu-like febrile illness, but the fetus, whose defense system is still immature, becomes seriously ill.

Diagnosis

• Listeria monocytogenes is implicated when monocytosis is observed in the peripheral blood as well as the cerebrospinal fluid.

• Early diagnosis may be obtained by finding pleocytosis with Gram-positive rods in a Gram stain of smears of the cerebrospinal fluid.

• Final proof is obtained by culture. • Serologic tests are highly unreliable.

Control

• Hygienic food processing and storage may reduce the risk of listeriosis.

• Individuals in high-risk groups (i.e., immuno-compromised individuals and pregnant women) should avoid uncooked food or should at least marinate salads for a long time in a vinegar-based dressing to kill adherent bacteria.

• Antimicrobial agents are the mainstay of treatment. Most of the common antibiotics, except cephalosporins, are active against L monocytogenes in vitro. High doses for prolonged periods are indicated.

Erysipelothrix Rhusiopathiae

• Clinical Manifestations• The most common human infection by E

rhusiopathiae is erysipeloid, a well-defined, violet or wine-colored inflammatory lesion of the skin of the fingers or hand .

• Itching is typical. Infrequently, septicemia develops, followed by various organ manifestations such as endocarditis or arthritis without fever.

Erysipelothrix Rhusiopathiae

• Structure and Classification• Erysipelothrix rhusiopathiae is a slender, Gram-

positive rod similar to L monocytogenes. • They grow on routine culture media under aerobic

conditions, but preferentially in a CO2 atmosphere. • In contrast to L monocytogenes, they are nonmotile,

nonhemolytic, and catalase negative. • The production of H2S is highly indicative.

Erysipelothrix Rhusiopathiae

• Pathogenesis• A minor skin injury may facilitate the penetration of E

rhusiopathiae after contact with infected material. After an incubation of 1 to 4 days the local lesion develops; spontaneous recovery occurs in 2 to 3 weeks. Septicemia has been observed without previous local lesions so that an oral infection is assumed. Endocarditis may develop in a few cases.

Erysipelothrix Rhusiopathiae

• Epidemiology• Erysipelothrix rhusiopathiae is found in mammals,

poultry, and fish. • Individuals who have occupational exposure to such

animals (i.e., farmers, veterinarians, slaughterhouse workers, and fish handlers) are at risk.

Erysipelothrix Rhusiopathiae

• Diagnosis• Since there is no wound, a swab is not useful.

Bacteria can be cultured from a biopsy of the progressing, inflamed edge of the lesion.

• Blood culture is indicated in the setting of sepsis and endocarditis.

• Control• Penicillin is the drug of choice to treat serious

infections. Since local skin infection is self-limited, therapy is not essential.

ACTINOMYCETES(FACULTATIVELY ANAEROBES)

• Fermentative gp: Actinomyces, Arcanobacterium and Rothia

• Oxidative gp : Actinomadura (actinomycetoma), Nocardia (nocardiosis), Streptomyces and related species.

Actinomycosis

• A. israelii – the commonest• A .meyeri• A.naeslundii• A.odontolyticus• A. viscosus

6. Actinomyces israelii

• Has branching filaments• Facultative anaerobes• Normal flora of oral cavity• Causes ‘Actinomycosis’ characterised by

multiple abscess and granuloma formation• Tissue destruction, fibrosis and sinus

formation

ACTINOMYCOSIS

• Mostly in cervico-facial region• Endogenous infection• Can get

– Thoracic actinomycosis (aspiration)– Pelvic actinomycosis (IUCD)– Rarely haematogenous spread

• Treatment– Surgical– Long term penicillin

Diagnosis

• Specimens – open biopsy, aspiration material

• Sulphur granules (yellowish myecelial masses)

• 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 gram stain

• Gram positive branching filaments

ACTINOMYCOSIS

7.Nocardia asteroides

• Branched, strictly aerobic bacillus• Environmental saprophytes (exogenous

infection)• Lightly acid-fast • Uncommon causes of opportunistic

pulmonary disease• Causes primary post-traumatic or post-

inoculation lung disease

Cutaneous nocardiasis