N. Gonorrhea N.Meningitidis

Morphology • Gram -ve , diplococci • Typically seen in pus cells (intracellularly) but also

extracellularly • non-motile, non-capsulated

• Gram -ve , diplococci • Typically seen in pus cells (intracellularly) but also

extracellularly • non-motile, Capsulated

Culture

Aerobe or facultative anaerobes, it is a fastidious organism, grows best in a moist carbon-dioxide enriched atmosphere, grows at 37°C on:

• MNYC (modified New York City) medium and Thayer Martin medium:

This is a selective media for N.gonorrhea, where it grows rapidly producing small, raised grey or translucent colonies after overnight CO2 incubation

• Chocolate Agar

Non-selective media. colorless raised colonies and by adding fresh oxidase reagent to the culture plate, the colonies turn deep purple in color

Aerobe or facultative anaerobes, grows best in a moist carbon-dioxide enriched atmosphere, grows at 37°C on:

• Chocolate Agar

transparent or grey colonies after overnight incubation

Biochemical tests

• Oxidase +ve • Ferments glucose only • DNAse -ve • Beta-galactosidase (ONPG) -ve • Glutamyl-aminopeptidase (GAP) -ve

• Oxidase +ve • Ferments glucose and maltose • DNAse -ve • Beta-galactosidase (ONPG) -ve • Glutamyl-aminopeptidase (GAP) +ve

Serology Slide coagglutination tests Direct latex agglutination and Slide coagglutination tests

Pathogenicity

1. Gonorrhea of the urogenital tract 2. Acute conjunctivitis in infants born of mothers with

urogenital gonorrhea. The eyes become infected at the time of delivery, and if untreated can lead to blindness.

3. Vulvovaginitis in pre-pubertal girls 4. Gonococcal arthritis, as complication of gonococcal

bacteraemia

1. Pyogenic meningitis: following bacteraemia, often has a sudden onset with intense headache, vomiting, and stiff neck.

2. Meningococcal septicaemia: A severe fatal condition with high fever, circulatory collapse, and hemorrhagic rash and petechiae.

3. Chronic meningococcal arthritis

Antimicrobial sensitivity Penicillin, tetracycline, and spectinomycin Penicillin, ampicillin, rifampicin, and chloramphenicol

Moraxella catarrhalis & Acinetobacter baumanii

Moraxella catarrhalis Acinetobacter baumanii

Morphology Gram -ve cocci, non motile, 

possessing many of the features of 

neisseriae. 

Gram-negative cocci occurring singly and 

in Neisseria-like pairs, non motile

Habitat It is a normal commensal of the 

upper respiratory tract

- Occasionally, it forms the normal flora in 

oropharynx.  

-Could be found in natural environments.  

-Present in moist surfaces in hospitals 

(e.g. respiratory therapy equipment)  

-Present on dry surface (e.g. human skin ) Pathogenicity As an opportunistic pathogen, it 

occasionally causes upper and lower 

respiratory tract infections, mostly in 

immunocompromised patients and 

those with chronic bronchitis.

Clinical syndromes: 

It can produce:  

Respiratory tract infection.  

Urinary tract infection. 

Wound infection 

Septicaemia

Culture Blood agar and chocolate agar 

grey-white dry colonies (with no need 

to CO2) 

-

Biochemical

tests

Oxidase +ve  

Catalase +ve  

Cytochrome oxidase +ve

Cytochrome oxidase negative

Antibiotic

sensitivity

most strains produce 

B-lactam and penicillin resistant

Common 

Treatment of acute infection: 

B-lactam aminoglycoside

CORYNEBACTERIUM DIPHTHERIAE It is the causative organism of diphtheria. Morphology -Corynebacteria are small gram +ve pleomorphic bacilli, non-capsulated, generally

non-motile. They are enlarged at one end (club-like end). -They appear in short chains (“V” or “Y” configurations) or in clumps resembling Chinese letters -They contain metachromatic granules which are energy-storing granules (visualized with methylene blue stain)

Cultural character

They are aerobe and grow best on Loffler's serum at 37°C. Opaque white colonies appear after 12-18 hrs.

- On blood tellurite, they give gray to black colonies It is possible to recognize three colony types; gravis, intermedius and mitis, on the latter medium. Gravis types are responsible for severe forms of diphtheria .

Habitat -Many species of Corynebacteria can be isolated from various places such as soil, water and human skin. - Humans are the only reservoir for the pathogenic strains of Corynebacteria. -The bacteria is usually found in temperate zones but also may be found in other parts of the world.

Pathogenesis Corynebacterium diphtheriae is the etiological agent for Diphtheria, which is of two types: 1- Nasal, nasopharyngeal and tonsillar diphtheria: - An upper respiratory tract disease mainly affecting the children. - Infection is by inhaling repiratory droplets. - The virulence factor is diphtheria toxin. 2- Cutaneous diphtheria: - It is infection for the open wounds - Infection is by skin contacts.

Diphtheria toxin: -Virulent strains of Corynebacterium diphtheriae produce a powerful exotoxin that is absorbed through the damaged mucous membrane into the blood circulation. - If not neutralized by antitoxin, the toxin cause toxaemia with fatal cardiac and neural complications. N.B.: These complications occur mainly in respiratory diphtheria and rarely in cutaneous diphtheria .

Inflammatory membrane:

-At the site of infection, there is an acute inflammatory response which leads to formation of a grey-yellow membrane which becomes necrotic at a later stage. - If this membrane extends downwards to the larynx, it can block the passage of air and cause death from asphyxia.

Clinical picture of respiratory diphtheria

an upper respiratory tract illness characterized by: -Sore throat -Low-grade fever -An adherent membrane of the tonsil(s), pharynx, and/or nose, which is known as pseudomembrane.

strains of Corynebacterium

gravis, intermedius and mitis. - They are listed here by the severity of the disease that they produce in humans. - All strains produce the same toxin and are capable of colonizing the throat. - The differences in virulence between the three strains depends on the rate of production of the toxin and quantity of this toxin.

Laboratory features:

Because of the powerful and rapidly fatal exotoxin produced by Corynebacterium diphtheriae, a patient suspected of having diphtheria is treated immediately with antitoxin. The role of the laboratory is to confirm the clinical diagnosis .

Specimens -Throat and nasopharyngeal swab for the respiratory diphtheria. -Skin swab for the cutaneous diphtheria

Culture - aerobe and facultative anaerobe , growing at optimum temperature of 37oc on: 1- Loeffler serum medium and dorset egg medium: C.diphtheria grows rapidly on these media within 4-6 hours giving the characteristic feature of diphtheria in the form of granules. These media are not selective for isolation of Corynebacterium diphtheriae because commensal diphtheroids grow over them. 2- Tellurite blood agar: Selective media for isolation of Corynebacterium diphtheriae. C.diphtheriae reduces tellurite and produces grey-black colonies after 24-48 hours of incubation. 3- Tellurite-cystine blood agar or Tinsdale medium: Selective media for isolation of Corynebacterium diphtheriae. After 24-48 hours of incubation, grey-black colonies appear, surrounded by a dark brown area. This brown colour in Tinsdale medium is due to the hydrogen sulphide produced from the cystine interacting with tellurine. It has to be known that the commensal diphtheroid could also grow over the Tinsdale medium. However, differentiation between the pathogenic and the commensal strains occurs by the brown colour that is formed around the colonies in the pathogenic strains only. This is because the commensal diphtheroids don’t produce hydrogen sulphide .

Testing for toxigenicity (virulence) of C. diphtheria:

To prove that an isolate can cause diphtheria, one must demonstrate toxin production. This is most often done on an Elek gel precipitation test: – The organism is streaked on a plate containing low iron. – A filter strip containing anti-toxin antibody is placed perpendicular to the streak of the organism . – Diffusion of the antibody into the medium and secretion of the toxin into the medium occur. – At the zone of equivalence, a precipitate will form.

Biochemical tests:

Catalase +ve , Nitrate +ve Oxidase –ve , Urease –ve

Antibiotic sensitivity

- Early use of diphtheria antitoxin to neutralize the diphtheria exotoxin. - Corynebacterium diphtheriae is sensitive to penicillin and erythromycin. - Antimicrobial prophylaxis for the patient’s contacts. - Active immunization with diphtheria toxoid (DPT) to the childhood, then give booster dose every 10 years

LISTERIA MONOCYTOGENES L. monocytogenes causes meningitis and septicaemia mainly in neonates, pregnant women, elderly and immunosuppressd persons. Listeriosis in pregnancy may lead to abortion and stillbirth. Common sources of infection are contaminated meat, chicken, soft cheese and vegetables

Morphology Gram-positive non-capsulated small rods or coccobacilli. ➢Tumbling and rotating motility at low temperature (18-22oC), and it is non motile or weakly motile at (35-37oC ). ➢CAMP Test positive (like Group B Streptococcus)

Habitat Intestinal tract of mammals & birds (especially chickens) ➢Persists in soil ➢Soft cheeses & unwashed raw vegetables ➢Raw or undercooked food of animal origin: · Luncheon meats · Hot dogs

Culture Listeria is an aerobe and facultative anaerobe. Multiply at refrigerator temperatures (4oC) the temperature range for growth is 3-45oC with an optimum of 30oC. Blood agar: Slightly Beta haemolytic colonies (Slight clear area around the colonies). Clear tryptose agar (Mueller Hinton agar): Pale blue-green colonies. The colonies may show iridescence: seen as different shades of red, green, blue and orange. They could be only seen when the plate is obliquely examined with illumination from below.

Test for motility of Listeria

Listeria is inoculated in soft agar (semisolid media), leave it at room temperature. It gives an umbrella like motility Explanation: The organism searches for the oxygen, so it ascends upward producing the umbrella-shape.

Biochemical tests

Catalase +ve Indole –ve Oxidase –ve Urease –ve Listeria is similar to group B streptococci in: 1- CAMP test is positive 2- 2- Both on blood agar produce beta haemolytic colonies.

To differentiate between both, I have to do catalase test, it is +ve in Listeria and it is –ve in group B streptococci

Pathogenesis • Mode of transmission: Ingestion of contaminated food Transplacental • Risk persons: Neonates, pregnant women, elderly & immunocompromised patients. • Clinical picture: meningitis and septicaemia

Antibiotic sensitivity

Listeria is sensitive to ampicillin, penicillin. • Listeria infections frequently respond to treatment with a combination of ampicillin and one of the aminoglcosides as gentamycin.

Erysipelothrix rhusopathiae In humans, it causes a rare skin disease called erysipeloid (cellulitis).

- It is an occupational disease of meat and fish handlers, hunters, veterinarians

- Preventable with protective gloves & clothing

-

Morphology Gram-positive non-motile bacillus; long, thin, forms filaments.

Mode of infection

Organisms enter through break in skin

Clinical picture Non-suppurative, self-limiting skin lesions with erythema and eruption

Peripheral spread may lead to generalized infection, septicemia and/or

endocarditis

Culture Organisms can be isolated from skin biopsy It grows best on blood agar in

a carbon dioxide enriched atmosphere at 30-35oc :

slight alpha-haemolytic colonies.

Antibiotic sensitivity

The organism is sensitive to penicillin, cephalosporins and erythromycin.

It is resistant to gentamycin and kanamycin.