PsuedomonaceaePsuedomonaceae

Gram Negative rods

Nonfermentative (Strict aerobic)

Oxidation of sugars

Cytochrome C oxidase

Motile

Pseudomonas aeroginosa (Piocianic bacillus)Pseudomonas aeroginosa (Piocianic bacillus)

Growth in soil and water containing only traces of nutrients.

A remarkable ability to withstand disinfectants (found in soap solutions, in antiseptics and in detergents).

Persistent in the hospital environment

An important role in hospital-acquired infections

P.a. Producing 2 pigments:P.a. Producing 2 pigments:

Pyocyanin (colors the pus in a wound blue-green)

Pyoverdin /Fluorescein (a yellow-green pigment that fluoresces under ultraviolet light

In the lab, these pigments diffuse into the agar, imparting a blue-green color that is useful in identification of the species.

In cystic fibrosis patients, P. aeroginosa has a slime layer (glycocalyx):

very mucoidal colonies. The slime layer mediates adherence of the organism to mucous membranes of the respiratory tract and prevents antibody from binding to the organism.

PathogenesisPathogenesis

Virulance factors:

Endotoxin

Exotoxin A (inhibits eukaryotic protein synthesis by the same mechanism as diphteria exotoxin)

An opportunistic pathogen when An opportunistic pathogen when neutrophil counts is below 500/uLneutrophil counts is below 500/uL

In those with extensive burns (skin host defenses are destroyed)

In those with chronic respiratory disease (such as cystic fibrosis)

10-20% of hospital-acquired infections.

In immunosuppressed

In those with catheters

Clinical findingClinical finding

Can cause infections virtually anywhere in the body, but more frequent in:

Urinary tract infections (UTIs)PneumoniaExternal otitisWound infections (especially burns).Sepsis with mortality rate of over 50%.

10% of people carry it in the normal flora of the colon and on the skin in moist areas.

It can colonize the upper respiratory tract of hospitalized patients.

Its ability to grow in simple aqueous solutions has resulted in contamination of respiratory therapy and anesthesia equipments, and even distilled water.

EpidemiologyEpidemiology

Lab diagnosisLab diagnosis

Non-lactose-fermenting (colorless) colonies on MacConkey or EMB agar.

Blue-green pigment on nutrient agar

Catalaze and gelatinase positive

In TSI: Alkalin/Alkalin

Gram negative rods

Oxidase-positive

Fruity aroma

Oxidase TestOxidase TestDetecting cytochrome C oxidase enzyme

Indicator: 1% tetra methyl-para-phenylene diamine dihydrochloride

TreatmentTreatment

Resistant to many antibiotics

Antibiogram test is essential

Usually is chosen from penicillins or cephalosporins along with an aminoglycoside.

PreventionPrevention

Keeping neutrophil counts above 500/uL

Removing indwelling catheters promptly

Taking special care of burned skin

BrucellaBrucella

Microbiology characteristicsSmall bacilliGram negativeAerobic CapsuleNonmotileCo2 neededFastidious

Virulence factorsVirulence factors

Endotoxin

No exotoxin

The organism is an obligative intracellular parasite.

TransmissionTransmissionA zoonotic organism

From domestic animals:B. melitensis from goatB. abortus from cowB. suis from pigB. canis from dogEntering portals: Mouth, conjunctive, respiratory

tract, abraded skin.

PathogenesisPathogenesis

Entering the body through ingestion / skin / mucosa

Localization in mononuclear phagocytes to the reticuloendothelial system: lymph nodes, liver, spleen, and bone marrow

Small granulomas reveal a mononuclear response

Effective host defense depends primarily on cell-mediated immunity.

Some organisms survive within macrophages.

The host responses by granulomatous along with lymphocytes and epithelioid giant cells, which can progress to form focal abscesses and caseation.

Clinical findingsClinical findingsEnlarged lymph nodes, liver and spleen

The onset may be insidious or abrupt.

Undulant (rising and falling )fever

Subclinical infection is common

Sweating, weakness and fatigue

Incubation period: 2-4 weeks

Severe limb and back pains

Influenza like onset

B. melitensis infections tend to be more severe and prolonged, whereas those caused by B. abortus are more self-limited.

Osteomyelitis is the most frequent complication.

In untreated cases, symptoms may continue for 2-4 weeks.Most patients recover entirely within 3-12 months but some develop complications marked by involvement of various organs.

Laboratory diagnosisLaboratory diagnosis

Diagnosis can be made clinically if there is a history of exposure.

Recovery of the organism requires the use of enriched culture media and incubation in 10% co2.

Blood cultures are positive in early disease, but serology is the mainstay of diagnosis.

Interpretation is complicated by subclinical infections and persistent antibodies.

TreatmentTreatment

Doxycycline

Streptomycin

Rifampin

ControlControlPasteurizing milk

Eradicating infection from herds by immunization of animals and slaughtering of infected animals.

Using safety precautions (protective clothing and laboratory safety).

CampylobacterCampylobacter

Microbiology propertiesCurved (comma- or S-shaped)Gram-negative rodsMicroaerophilic (growing in 5% oxygen)NonfermentingMotile(darting motility) with single flagellumOxidase positive

Important speciesImportant species

Campylobacter jejunui : Gastroenteritis

Campylobacter fetus: An opportunistic organism

Bacteremia in compromised hosts and self-limited diarrhea in previously healthy individuals.

Campylobacter coli:Gastroenteritis

Campylobacter jejuniCampylobacter jejuni•

Virulence factorsVirulence factors

EndotoxinEndotoxin

Enterotoxin Enterotoxin that acts in the same manner as cholera toxin

Transmission and EpidemiologyTransmission and Epidemiology

Source of the organisms:

Domestic animals, such as cattle, chickens and dogs

Person-to-person transmission:

oral-fecal

The major cause of bacterial diarrhea in developed countries (4.6% of patients with diarrhea, compared with 2.3 and 1% for salmonella and Shigella)

Campylobacter jejuni and C. coli are endemic worldwide and hyperendemic in developing countries.

Infant and young adults are most often infected.

The incidence peak in the summer.

Sporadic outbreaks are associated with contaminated animal products or water.

PathogenesisPathogenesis

Invasion to the epithelial cells and colonization the small and large intestines often occurs, accompanied by blood in stool causing inflamatory diarrhea and fever.

Systematic infections, eg, bacteremia, occur most often in neonates or debilitated adults.

Clinical findingsClinical findings

EnterocolitisEnterocolitis, begins as watery, fuel-smelling diarrhea followed by bloody stools accompanied by fever and severe abdominal pain.

Systemic infections, most commonly bactermia, are caused by C. fetus showing symptoms of fever and malaise.

Detection of C jejuni and related enteric bacteria.

Laboratory diagnosisLaboratory diagnosisfor C. jejunifor C. jejuni

A stool specimen

Blood agar culture

Incubation at 42c in a microaerophilic atmosphere (5% O2 and 10% CO2)

Skirrow’s medium (containing vancomycin, trimethoprim, cephalothin, polymyxin, and amphotericin B.)

Laboratory diagnosisLaboratory diagnosisfor C. jejunifor C. jejuni

Failure to grow at 25 C

Oxidase positive

Sensitivity to nalidixic acid

The identification of C. fetus is confirmed by:

Failure to grow at 42 C

Ability to grow at 25 C

Resistance to nalidixic acid

TreatmentTreatment

Erythromycin in C. jejuni enterocolitis

An aminoglycoside in C. fetus bacteremia

PreventionPrevention

No vaccine

Proper sewage disposal

Personal hygiene (hand washing)

Helicobacter pyloriHelicobacter pylori

Multiple flagella

Urease

Helicobacter pyloriHelicobacter pylori

Microbiology propertiesMotile(darting motility) with lophotrichous

flagellumMicroaerophilic (growing in 5% oxygen)Curved (comma- or S-shaped)Oxidase & Catalase positiveGram-negative rodsNonfermenting

Seventy-two hour culture of H pylori showing typical thin, comma- or S-shaped forms

Virulence factorsVirulence factors

Urease

Cytotoxin

Protease

Flagella

PathogenesisPathogenesis

H. pylori is associated with type B gastritis (antral stomach inflammation/ peptic ulcer).

It shelters from gastric acid in the gastric mucous layer and probably is able to adhere to gastric epithelial cells.

Production of urease and cytotoxin is associated with injury to the gastric epithelium.

EpidemiologyEpidemiologyThe prevalence of infection increases with age.

The source and mode of transmission are not known.

H. pylori is in the mucosa of the stomach of 20% 20% people under 30 years under 30 years but in 40 – 60 % 40 – 60 % of 60 years old60 years old.

Detection methods for H pylori

Laboratory diagnosisLaboratory diagnosis

Using endoscopic biopsy samples endoscopic biopsy samples where the organism can be detectedon histological examinationCulturePCR (polymerase chain reaction)A rapid urease test on the sample

Skirrow’s medium (containing vancomycin, trimethoprim, polymyxin, and amphotericin B.)

Laboratory diagnosisLaboratory diagnosis

Serological tests for antibodies on blood or saliva13C or 14C urea breath tests

Faecal antigen testing

1313C or C or 1414C C urea breath testsurea breath tests(CUBT) for (CUBT) for Helicobacter pylori Helicobacter pylori detectiondetection

The Carbon urea breath test (CUBT)The Carbon urea breath test (CUBT)The breath tests are performed by asking the patient to swallow carbon-labeled urea which is metabolised by H. pylori’s urease to produce labeled carbon dioxide.

Two forms of urea breath tests by using 13C urea or 14C urea is available.

This is absorbed into the blood stream and then exhaled in the breath of infected individuals.

The rapid urease test The rapid urease test Least expensive and can be performed on endoscopic biopsy specimens.

The urease produced by the organism converts urea to ammonia resulting in a PH change detected by phenol red.

The tests usually give a rapid result but typical sensitivity at 1 hour is 71% which increases to 96% at 6 hours.

Serological tests for H. pyloriSerological tests for H. pylori

Elisa

Complement fixation

Latex agglutination

SerologySerology

Testing IgGIgG is the most sensitive as seen in 95%95%..

Testing IgAIgA responses in 68-80%.

Testing IgMIgM responses in only 14% 14% of infected patients.

ControlControl

A three drug treatment for 2 weeks2 weeks:

1. A proton pump inhibitor (such as lansoprazole and omeprazole decreasing stomach's production of acid allowing the ulcer to heal)

2. Methronidasol

3. Tetracycline

BrucellaBrucella

Portals of entry for Brucella species

Spread of Spread of BrucellaBrucella in the body in the body

Brucellosis is a disease of mainly cattle, swine, goats, sheep and dogs. The infection is transmitted to humans by animals through direct contact with infected materials like afterbirth or indirectly by ingestion of animal products and by inhalation of airborne agents. Consumption of raw milk and cheese made from raw milk (fresh cheese) is the major source of infection in man. Most of the fresh cheeses are sheep and goat cheese. Next to this it is considered to be an occupational disease for people who work in the livestock sector. Human-to-human transmission is very rare.