Batterjee Medical College. Dr. Manal El Said Head of Medical Microbiology Department Brucella...

Batterjee Medical College


Dr. Manal El SaidDr. Manal El Said Head of Medical Microbiology Department

Brucella Species (B. abortus, B. suis, B. melitensis)



DiseasesBrucellosis (undulant fever).

•Incubation period of 1 to 3 weeks & onset acute or gradual•Nonspecific symptoms: fever, chills, fatigue, malaise, anorexia, & weight loss occur.

•Undulating (rising-and-falling) fever pattern.•Enlarged lymph nodes, liver & spleen are frequently found. •Pancytopenia occurs.•B. melitensis infections more severe & prolonged whereas B. abortus are more self-limited.

•Osteomyelitis is the most frequent complication. •Secondary spread from person to person is rare.




Characteristics

Small gram-negative rods.

Habitat and Transmission

• Reservoir is domestic livestock.

• Transmission is via:

- Unpasteurized milk & cheese

- Direct contact with infected

animal.







• Organisms localize in reticuloendothelial cells,

especially liver & spleen.

• Able to survive and replicate intracellularly.

• Predisposing factors include consuming

unpasteurized dairy products & working in abattoir.

Pathogenesis







Laboratory Diagnosis• Gram-stained smear plus culture on blood agar plate.• Identified by biochemical reactions & by agglutination with

known antiserum. • Serologically by detecting antibodies in patient's serum.



Treatment

Tetracycline plus rifampin.

•Pasteurize milk; vaccinate cattle.

• No human vaccine is available

Prevention




Francisella tularensis



Diseases

Tularemia.

•Presentation can vary from sudden onset of influenzalike syndrome to prolonged onset of low-grade fever & adenopathy.

•Approximately 75% of cases are "ulceroglandular" type, in which site of entry ulcerates & regional lymph nodes are swollen & painful.

•Less frequent forms of tularemia include glandular, oculoglandular, typhoidal, gastrointestinal, & pulmonary.

•Disease usually confers lifelong immunity.



Characteristics


• Reservoir is many species of wild animals,

especially rabbits, deer & rodents.

• Transmission is by ticks , aerosols, contact &

ingestion.



Pathogenesis


•Organisms localize in reticuloendothelial cells.Francisella tularensis enters respiratory tract & (2) lamina propria of respiratory bronchioles via M cells; (3) Digested antigen is taken up by dendritic cells; dendritic cells travel to regional lymph nodes &present F. tularensis antigens to T-helper 1 cells; (4) T-helper 1 cells proliferate; they may return to site of initial infection; (5) restimulation by local antigen presenting cells results in interferon-γ production & macrophage activation; (6) Failure to clear F. tularensis results in granuloma formation.


Laboratory Diagnosis• Culture is rarely done because special media are required & there is high risk of infection of laboratory personnel.

• Serologic tests detect antibodies in patient's serum.


Francisella tularensis in a liver cell.





Colonization of Francisella tularensis on various media, namely: (A) buffered charcoal yeast extract; (B) chocolate agar medium; (C) sheep’s blood agar; (D) cysteine heart agar.


Treatment


Streptomycin.

• Live, attenuated vaccine for persons in high-risk occupations.

• Protect against tick bites.

Prevention


Dr. Manal El SaidDr. Manal El Said Head of Microbiology Department

Pasteurella multocida



Diseases

• Rapidly spreading cellulitis at site of animal bite is indicative of P. multocida infection.

• Incubation period is brief, less than 24 hours.

• Osteomyelitis can complicate cat bites, because cats' sharp, pointed teeth can implant organism under periosteum.

Wound infection, e.g., cellulitis



Characteristics



• Reservoir is mouth of many animals, especially cats & dogs.

• Transmission is by animal bites.


Pathogenesis


• Spreads rapidly in skin & subcutaneous tissue.



Laboratory Diagnosis

Gram-stained smear and culture.


Treatment


Penicillin G..

Prevention• Ampicillin should be given to individuals with cat bites.

• There is no vaccine.


Capnocytophaga gingivalis •It is gram-negative fusiform rod that is associated with periodontal disease•It can be opportunistic pathogen, causing sepsis in immunocompromised patients.

Capnocytophaga


Capnocytophaga canimorsus •It is a member of the oral flora of dogs and causes infections following dog bites.• It cause sepsis in immunocompromised patients, especially those without spleen.

Capnocytophaga


This is group of small gram-negative rods that have in common the following: •Slow growth in culture,•Requirement for high CO2 levels to grow in culture•Ability to cause endocarditis. -They are members of the human oropharyngeal flora and can enter the bloodstream from that site. -The name "HACEK" is an acronym of the first letters of the genera of the following bacteria: Haemophilus aphrophilus and Haemophilus paraphrophilus, Actinobacillus actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, and Kingella kingae.

HACEK Group


Vibrio cholerae

Diseases

Cholera.

•Watery diarrhea (Rice-water stool) in large volumes.

•There are no red blood cells or white blood cells in stool.

•There is no abdominal pain & subsequent symptoms are

referable to marked dehydration.

• Loss of fluid & electrolytes leads to cardiac & renal failure.

• Acidosis & hypokalemia occur as result of loss of

bicarbonate & potassium in stool.


Vibrio cholerae

Diseases


Vibrio cholerae

• Comma-shaped gram-negative rods.

• Oxidase-positive

Characteristics


• Habitat is human colon.

•Transmission is by fecal–oral route.


Vibrio cholerae

Pathogenesis• Massive, watery diarrhea caused by

enterotoxin that activates adenylate

cyclase by adding ADP-ribose to

stimulatory G protein.

• Increase in cyclic AMP causes outflow

of chloride ions & water.

• Toxin has two components:

- Subunit A: ADP-ribosylating activity

- Subunit B: binds toxin to cell surface

receptors.


Vibrio cholerae

Pathogenesis

• Organism produces mucinase, which enhances attachment

to intestinal mucosa.

• Infectious dose is high (>107 organisms).

• Carrier state rare

string test


Vibrio cholerae

• Gram-stained smear and culture. (During epidemics,

cultures not necessary.)

• Agglutination of the isolate with known antisera confirms

the identification.


Vibrio cholerae on TCBS agar

string test


Treatment

Vibrio cholerae

• Treatment of choice is fluid and electrolyte replacement.

• Tetracycline is not necessary but shortens duration and

reduces carriage.

•Public health measures, e.g., sewage disposal, chlorination

of the water supply, stool cultures for food handlers, and

handwashing prior to food handling.

•Vaccine containing killed cells has limited effectiveness.

•Tetracycline used for close contacts.

Prevention


• Comma-shaped gram-negative rod found in warm sea water.

• Causes watery diarrhea• Acquired by eating contaminated raw seafood. • Outbreaks have occurred on cruise ships in Caribbean.• Diarrhea is mediated by enterotoxin similar to cholera

toxin..

Vibrio parahaemolyticus

Forms GREEN non-sucrose fermenting agars


• Comma-shaped gram-negative rod found in warm sea water.

• Causes cellulitis & life-threatening sepsis with hemorrhagic

bullae.

• Acquired either by trauma to skin, especially in shellfish

handlers, or by ingestion of raw shellfish, especially in

patients who are immunocompromised or have liver

damage.

Vibrio vulnificus


Dr. Manal El SaidDr. Manal El Said

Campylobacter jejuni

Head of Medical Microbiology Department


• Habitat is human & animal feces.•Transmission is by fecal–oral route.


DiseasesEnterocolitis.

Characteristics•Comma-shaped gram-negative rods.• Microaerophilic.• Grows well at 42°C




• Invades mucosa of colon but does not penetrate• Sepsis rarely occurs.

Pathogenesis

Laboratory Diagnosis•Gram-stained smear plus culture on special agar, e.g., Skirrow's agar, at 42°C in high-CO2, low-O2 atmosphere.


• Public health measures, e.g., sewage disposal, chlorination of the water supply, stool cultures for food handlers, and handwashing prior to food handling.

• No preventive vaccine or drug is available.

Usually symptomatic treatment only; erythromycin for severe disease.


Treatment

Prevention


Dr. Manal El SaidDr. Manal El Said

Helicobacter pylori

Head of Medical Microbiology Department


Helicobacter pylori

Diseases

Characteristics

•Gastritis & peptic ulcer.

•Risk factor for gastric carcinoma.

Curved gram-negative rod.

• Habitat is the human stomach.

• Transmission is by ingestion.



• Organisms synthesize urease, which produces

ammonia damages gastric mucosa.

• Ammonia neutralizes acid pH in stomach, which

allows the organism to live in gastric mucosa.

Helicobacter pylori

Pathogenesis


Laboratory Diagnosis• Gram stain and culture.• Urease-positive. • Serologic tests for antibody •"urea breath" test are useful.

Helicobacter pylori


Treatment

Amoxicillin, metronidazole & bismuth (Pepto-

Bismol).

Prevention

No vaccine or drug is available.

Helicobacter pylori



Bacteroides fragilis



Diseases

Characteristics


Sepsis, peritonitis, and abdominal abscess.

Anaerobic, gram-negative rods

• Habitat is the human colon, where it is the predominant anaerobe.

• Transmission occurs by spread from the colon to the blood or peritoneum.


Pathogenesis

• Lipopolysaccharide in cell wall is chemically

different from & less potent than typical

endotoxin.

• No exotoxins known.

• Capsule is antiphagocytic.

• Predisposing factors to infection include bowel

surgery and penetrating abdominal wounds.




• Gram-stained smear plus anaerobic culture

• Identification based on biochemical reactions and

gas chromatography.

• Serologic tests not useful.



Treatment

Prevention


• Metronidazole, clindamycin & cefoxitin are effective • Abscesses should be surgically drained.• Resistance to penicillin G, some cephalosporins, and

aminoglycosides is common.• Plasmid-encoded β -lactamase mediates resistance to

penicillin.

• In bowel surgery, perioperative cefoxitin can reduce the frequency of postoperative infections.

• No vaccine is available.

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Batterjee Medical College. Dr. Manal El Said Head of Medical Microbiology Department Brucella...

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