REVIEW OF MEDICAL MICROBIOLOGY
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REVIEW OF MEDICAL MICROBIOLOGY. Infections of Respiratory tract Cardiovascular system Gastrointestinal tract Skin and soft tissue Central nervous system Genitourinary tract. THE RESPIRATORY TRACT. Upper Respiratory Tract Pharyngitis (mostly 2 years through adolescence)

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Review of medical microbiology

REVIEW OF MEDICAL MICROBIOLOGY

Infections of

Respiratory tract

Cardiovascular system

Gastrointestinal tract

Skin and soft tissue

Central nervous system

Genitourinary tract


Review of medical microbiology

THE RESPIRATORY TRACT

Upper Respiratory Tract

Pharyngitis (mostly 2 years through adolescence)

Adenoviruses

Group A Streptococci (S. pyogenes)

Potential for rheumatic fever

Chlamydophila pneumoniae

Neisseria gonorrhoeae

Corynebacterium diphtheriae

Mycoplasma pneumoniae


Review of medical microbiology

THE RESPIRATORY TRACT

Otitis media (infants and young children)

Streptococcus pneumoniae

Haemophilus influenzae

Staphylococcus aureus

Group A streptococcus

Moraxella catarrhalis

Formerly “Branhamella”

Gram-negative cocci

Opportunistic pathogen


Review of medical microbiology

THE RESPIRATORY TRACT

Otitis externa

Staphylococcus aureus

Pseudomonas aeruginosa

Group A Streptococcus

Malignant otitis externa

• In diabetics, elderly & immunocompromised

• Can lead to osteomyelitis and meningitis


Review of medical microbiology

THE RESPIRATORY TRACT

Sinusitis

Streptococcus pneumoniae

Haemophilus influenzae

Staphylococcus aureus

Chlamydophila pneumoniae

Moraxella catarrhalis

Group A Streptococcus

Pseudomonas aeruginosa

Viruses

Oral anaerobic bacteria


Review of medical microbiology

THE RESPIRATORY TRACT

Conjunctivitis

Streptococcus pneumoniae

Group B Streptococcus

Viridans Streptococcus

Staphylococcus aureus

Haemophilus influenzae

Moraxella catarrhalis


Review of medical microbiology

THE RESPIRATORY TRACT

Conjunctivitis (contd)

Pseudomonas aeruginosa

Corynebacterium species

Francisella tularensis

Adenoviruses

Chlamydia trachomatis


Review of medical microbiology

THE RESPIRATORY TRACT

Rhinocerebral mucormycosis

• Life-threatening

• Most common in diabetics

• The fungi Mucor and Rhizopus invade blood

vessels, resulting in necrosis of bone and

thrombosis of the cavernous sinus and internal

carotid artery


Review of medical microbiology

THE RESPIRATORY TRACT

Bacterial epiglottitis

Life-threatening

Haemophilus influenzae type b

Streptococcus pneumoniae

Staphylococcus aureus


Review of medical microbiology

THE RESPIRATORY TRACT

Diphtheria

Corynebacterium diphtheriae

Whooping cough

Bordetella pertussis


Review of medical microbiology

THE RESPIRATORY TRACT

“Common colds”

Rhinoviruses

Adenoviruses

Influenza C

Coronaviruses

Coxsackie viruses


Review of medical microbiology

THE RESPIRATORY TRACT

“Croup”

Respiratory syncytial virus

Influenza virus

Parainfluenza virus


Review of medical microbiology

THE RESPIRATORY TRACT

Lower Respiratory Tract

Community acquired infections

Streptococcus pneumoniae (elderly)

Klebsiella pneumoniae (alcoholics)

Mycoplasma pneumoniae (school-age children)

Mycobacterium tuberculosis

RSV (infants and young children)

Influenza virus


Review of medical microbiology

THE RESPIRATORY TRACT

Lower Respiratory Tract

Community acquired infections

Bronchitis or pneumonia secondary to viral pneumonia

Streptococcus pneumoniae

Haemophilus influenzae

Staphylococcus aureus

Moraxella cararrhalis


Review of medical microbiology

THE RESPIRATORY TRACT

Lower Respiratory Tract

Nosocomial infections

Mycobacterium tuberculosis

RSV in pediatric patients

Methicillin-resistant S. aureus (pneumonia)

Pseudomonas aeruginosa

Legionella spp.


Review of medical microbiology

THE RESPIRATORY TRACT

Lower Respiratory Tract

Patients with underlying lung infections

Chronic obstructive pulmonary disease

P. aeruginosa

S. pneumoniae

H. influenzae

Moraxella cararrhalis

Allergic bronchopulmonary aspergillosis


Review of medical microbiology

THE RESPIRATORY TRACT

Lower Respiratory Tract

Patients with underlying lung infections

Cystic fibrosis

S. aureus

P. aeruginosa

Allergic bronchopulmonary aspergillosis


Review of medical microbiology

THE RESPIRATORY TRACT

Lower Respiratory Tract

Patients with underlying lung infections

Cavitary lung disease (due to prior MTB infection)

Aspergillus spp (Aspergilloma or fungus ball)


Review of medical microbiology

THE RESPIRATORY TRACT

Lower Respiratory Tract

Immunocompromised individuals

At risk for all recognized respiratory tract pathogens

AIDS patients

Pneumocystis carinii

S. pneumoniae

MDR M. tuberculosis


Review of medical microbiology

THE RESPIRATORY TRACT

Lower Respiratory Tract

Immunocompromised individuals

Neutropenic patients

Invasive aspergillosis

Mucormycosis


Review of medical microbiology

THE RESPIRATORY TRACT

Lower Respiratory Tract

Immunocompromised individuals

Transplant patients

Invasive fungi

CMV

HSV

Legionella spp.

Pneumocystis carinii


Review of medical microbiology

A 40-year-old male with multisystem failure secondary to bilateral pneumonia was transferred to our hospital via helicopter.

He had presented to his local physician 3 days previously complaining of fever, malaise, and vague respiratory symptoms.

He was given amantadine for suspected influenza. His condition became progressively worse, with shortness of breath and a fever to 40.5˚C.

From: “Cases in Medical Microbiology and Infectious Disease”


Review of medical microbiology

He was admitted to an outside hospital 24 h prior to transfer.

A laboratory examination revealed abnormal liver and kidney function.

Therapy with Timentin (ticarcillin-clavulanic acid) and trimethoprim-sulfamethoxazole was begun.

He underwent pronchoscopic examination which revealed mildly inflamed airways containing thin, watery secretions.


Review of medical microbiology

A Gram-stain of bronchial washings and culture results are shown in the figure.

Based on these findings, he was begun on appropriate antimicrobial therapy.


Review of medical microbiology

Which organisms are common causes of community-acquired bacterial pneumonia?


Review of medical microbiology

Streptococcus pneumoniae

Haemophilus influenzae

Mycoplasma pneumoniae

Staphylococcus aureus

(frequently following an influenza infection)

Klebsiella pneumoniae

(elderly & alcoholics)

Legionella pneumophila

Chlamydophila pneumoniae


Review of medical microbiology

On the basis of the Gram-stain of bronchial washings, and the patient’s presentation, what is the most likely cause of this patient’s catastrophic infection?

Why must the laboratory be notified if this organism is considered in the differential diagnosis?


Review of medical microbiology

The patient has Legionella pneumophila.

Renal and hepatic dysfunction and thin watery secretions are characteristic of this infection.

Patients with bacterial pneumonia due to most other bacterial agents have thick, purulent secretions.

The laboratory needs to be informed because the organism requires a specific growth medium, buffered charcoal yeast extract (BCYE) agar.


Review of medical microbiology

What techniques other than culture can be used to detect this organism within 24 h?


Review of medical microbiology

DFA


Review of medical microbiology

What is the appropriate antimicrobial agent for the treatment of this infection?

Which other Gram-negative respiratory pathogen is treated with this antibiotic?


Review of medical microbiology

Erythromycin

Can penetrate into white blood cells

Legionella multiplies in macrophages

Bordetella pertussis


Review of medical microbiology

THE CARDIOVASCULAR SYSTEM

Septicemia: Predisposing factors and agents

Abdominal sepsis

Enterobacteria

Bacteroides fragilis

Enterococcus faecalis

Enterococcus faecium

Infected wounds

Staphylococcus aureus

Streptococcus pyogenes

Enterobacteria


Review of medical microbiology

THE CARDIOVASCULAR SYSTEM

Septicemia: Predisposing factors and agents

Osteomyelitis

Staphylococcus aureus

Pneumonia

Streptococcus pyogenes

Food poisoning

Salmonella spp.

Campylobacter spp.


Review of medical microbiology

THE CARDIOVASCULAR SYSTEM

Septicemia: Predisposing factors and agents

Intravascular devices

Staphylococcus aureus

Staphylococcus epidermidis

Enterobacteria

Meningitis

Streptococcus pneumoniae

Neisseria meningitidis

Haemophilus influenzae


Review of medical microbiology

THE CARDIOVASCULAR SYSTEM

Septicemia: Predisposing factors and agents

Immunocompromised patients

Staphylococcus aureus

Enterobacteria


Review of medical microbiology

THE CARDIOVASCULAR SYSTEM

Infective endocarditis

> 80% of cases caused by streptococci

or staphylococci

Total streptococci60%

Viridans group35%

anginosus group

mitis group

mutans group

salivarius group


Review of medical microbiology

THE CARDIOVASCULAR SYSTEM

Infective endocarditis

Total streptococci60%

Total staphylococci25%

S. aureus20%

S. epidermidis 5%


Review of medical microbiology

THE CARDIOVASCULAR SYSTEM

Myocarditis

Corynebacterium diphtheriae

Clostridium perfringens

Group A Streptococcus

Borrelia burgdorferi

Neisseria meningitidis

Staphylocccus aureus


Review of medical microbiology

The patient was a 4-month-old female who was admitted to the hospital in March with sever respiratory distress.

Five days prior to admission she had developed a cough and rhinitis.

Two days later she began wheezing and was noted to have a fever.

She was brought to the emergency room when she became lethargic.

From: “Cases in Medical Microbiology and Infectious Disease”


Review of medical microbiology

One sibling was reported to be coughing, and her father had a “cold”.

On examination she had

a fever of 38.9˚C

tachycardia with a pulse of 220/min

tachypnea with respirations of 80/min

Her throat was clear.


Review of medical microbiology

A chest X-ray revealed interstitial infiltrates.

She was put in respiratory isolation in the pediatric intensive care unit, and was subsequently intubated.

Blood and nasopharyngeal cultures were sent to the bacteriology and virology laboratories.

A rapid diagnostic test was positive and specific antiviral therapy was begun.


Review of medical microbiology

She was also given a bronchodilator (aminophylline) to treat the bronchospasm which was resulting in her wheezing.

She was extubated 5 days later and discharged home on day 8.

1. What are the possible causes for this patient’s pneumonia?


Review of medical microbiology

Parainfluenza virus

Influenza A and B

Respiratory syncytial virus

Mycoplasma pneumoniae

Bordetella pertussis


Review of medical microbiology

Membrane-enzyme immunoassay


Review of medical microbiology

2. What other techniques could one use to identify this microorganism?


Review of medical microbiology

Direct Fluorescence Antibody

“Shell Vial Assay”

Fibroblasts grown on coverslips in a shell vial

Clinical specimens a centrifuged onto the cell monolayer

Incubation for 1-2 days

The monolayer is stained with a fluorescent monoclonal antibody specific for an RSV antigen


Review of medical microbiology

2. What is the epidemiology of the disease?


Review of medical microbiology

RSV is spread by large droplets and on fomites

Can be spread via contaminated hands

Occurs primarily in winter months


Review of medical microbiology

3. What is the pathophysiologic basis for wheezing?


Review of medical microbiology

RSV is tropic for bronchial epithelium

Edema and necrosis can lead to collapse and obstruction of a child’s small bronchioles


Review of medical microbiology

4. What specific therapy should be given after the antigen test gives the diagnosis?


Review of medical microbiology

Only one antiviral agent is available for treatment of RSV in infants

Aerosolized ribavirin

(oral administration can result in hepatic or bone marrow toxicity)

The American Academy of Pediatrics recommends its use in children with congenital heart disease, cystic fibrosis, immunodeficiency or severe illness.


Review of medical microbiology

5. What infection control measures should be taken?


Review of medical microbiology

Patients should be put on respiratory isolation

Gowns and gloves should be used during contact


Review of medical microbiology

6. What can be done to prevent the disease?


Review of medical microbiology

Inactivated RSV vaccine did not work and exacerbated the disease

Immune globulin can be used in children at greatest risk


Review of medical microbiology

THE GASTROINTESTINAL SYSTEM

Two basic mechanisms of diarrheal disease:

Enterotoxin-induced fluid loss

Cholera toxin

Direct damage to the intestinal epithelium

Cytotoxin

Entamoeba histolytica

Invasion of epithelium

Salmonella spp.

Shigella spp.

Campylobacter spp.

Yersinia enterocolitica


Review of medical microbiology

THE GASTROINTESTINAL SYSTEM

Infectious doses

Hundreds of thousands to millions

Salmonella spp.

Vibrio cholerae

Less than 100

Shigella spp.


Review of medical microbiology

THE GASTROINTESTINAL SYSTEM

Bacteria

Invasive diarrhea

Campylobacter spp.

Salmonella spp.

Shigella spp.

Yersinia enterocolitica

Large-volume watery diarrhea

Vibrio spp.


Review of medical microbiology

THE GASTROINTESTINAL SYSTEM

Bacteria

Watery diarrhea

Enterotoxigenic E. coli

Yersinia enterocolitica

Typhoid fever

Salmonella spp.


Review of medical microbiology

THE GASTROINTESTINAL SYSTEM

Bacteria

Traveler’s diarrhea

Enterotoxigenic E. coli

Dysentery

Shigella spp.


Review of medical microbiology

THE GASTROINTESTINAL SYSTEM

Bacteria

Antibiotic-associated diarrhea

Pseudomembranous colitis

Clostridium difficile

Food poisoning

Staphylococcus aureus

Clostridium perfringens

Bacillus cereus

Salmonella spp.


Review of medical microbiology

THE GASTROINTESTINAL SYSTEM

Bacteria

Abdominal abscess

Bacteroides fragilis

Gangrenous lesions of bowel or gall bladder

Clostridium perfringens

Enterohemorrhagic colitis

Enterohemorrhagic E. coli


Review of medical microbiology

THE GASTROINTESTINAL SYSTEM

Viruses

Acute, self-limited hepatitis

Hepatitis A

Acute and chronic hepatitis

Hepatitis B

Hepatitis C


Review of medical microbiology

THE GASTROINTESTINAL SYSTEM

Viruses

Diarrhea

Enterovirus

Rotavirus

Norwalk agent (calicivirus)

Vomiting

Rotavirus

Norwalk agent (“24-hour flu”)


Review of medical microbiology

THE GASTROINTESTINAL SYSTEM

Viruses

Infants

Rotavirus A (most common cause)

Adenovirus 40, 41

Coxsackie A24 virus

Infants, children, and adults

Norwalk agent (“24-hour flu”)

Calicivirus

Reovirus


Review of medical microbiology

SKIN AND SOFT TISSUE

Diffuse erythematous macular rash may be a manifestation of systemic disease

Rocky Mountain spotted fever

Meningococcemia

Entereoviral infection

Toxic shock syndrome

Scarlet fever

Measles

German measles


Review of medical microbiology

SKIN AND SOFT TISSUE

Erythema migrans

Lyme diseases

Vesicular skin lesions

Varicella Zoster virus

Macular, papular or pustular, but not vesicular, skin lesions

Secondary syphilis


Review of medical microbiology

SKIN AND SOFT TISSUE

Important to treat superficial skin infections

Folliculitis caused by Staphylococcus aureus

Cellulitis caused by Streptococcus pyogenes

Delay in treatment may result in invasion of the deeper structures (e.g necrotizing fasciitis)


Review of medical microbiology

SKIN AND SOFT TISSUE

Cat scratch disease, bacillary angiomatosis

Bartonella henselae

Lyme disease

Borrelia burgdorferi

Gas gangrene

Clostridium perfringens

Tetanus

Clostridium tetani


Review of medical microbiology

SKIN AND SOFT TISSUE

Diphtheria and wound diphtheria

Corynebacterium diphtheriae

Cellulitis

Group A streptococci (S. pyogenes)

Group B streptococci (S. agalactiae)

Pasteurella multocida

Staphylococcus aureus

Cryptococcus neoformans


Review of medical microbiology

SKIN AND SOFT TISSUE

Skin infection in burn patients

Pseudomonas aeruginosa

Thrush

Candida albicans

Candida spp.

Cutaneous infection

Blastomyces dermatitidis


Review of medical microbiology

SKIN AND SOFT TISSUE

Infection of keratinized tissue

Epidermophyton floccosum

Microsporum spp.

Trichophyton spp.

Ulcerative skin lesions

Leishmania tropica


Review of medical microbiology

SKIN AND SOFT TISSUE

Exanthem subitum

Human herpesvirus type 6

Oral infections

Herpes simplex virus

Warts

Human papillomavirus


Review of medical microbiology

CENTRAL NERVOUS SYSTEM

The most frequent infections are

Meningitis

Encephalitis

Abscess

Meningitis

Septic: caused by bacteria

CSF cloudy (>1,000 white blood cells/µl)

Aseptic: Viruses, fungi, MTB

CSF clear (100-500 cells/µl)


Review of medical microbiology

CENTRAL NERVOUS SYSTEM

Neonatal meningitis (newborn - 2 months)

Group B streptococci (most common cause)

Listeria monocytogenes

E. coli

Klebsiella pneumoniae

Citrobacter diversus Citrobacter koseri

Treponema pallidum


Review of medical microbiology

CENTRAL NERVOUS SYSTEM

Meningitis (2 months - 5 years)

Haemophilus influenzae type b

Streptococcus pneumoniae

Neisseria meningitidis (all ages)

Meningitis (Patients with head trauma)

Coagulase-negative staphylococci

Staphylococcus aureus

Pseudomonas aeruginosa


Review of medical microbiology

CENTRAL NERVOUS SYSTEM

Aseptic meningitis

Echovirus

Coxsackievirus

Herpes simplex virus

Fungal meningitis

(primarily in the immunocompromised)

Cryptococcus neoformans (in AIDS patients)


Review of medical microbiology

CENTRAL NERVOUS SYSTEM

Viral encephalitis

Herpes simplex virus (most common)

(necrotizing; necrotizing hemorrhagic)

Eastern equine encephalitis virus

Western equine encephalitis virus

St. Louis encephalitis virus

La Crosse encephalitis virus


Review of medical microbiology

CENTRAL NERVOUS SYSTEM

Encephalitis

Toxoplasma gondii

Taenia solium (“cysticercosis”; from pork)

Meningoencephalitis

Cerebral malaria

Naegleria fowleri (an amoeba)

Citrobacter diversus


Review of medical microbiology

CENTRAL NERVOUS SYSTEM

Brain abscesses

Extension from a contiguous site

Hematogenous spread from another site (endocarditis or lung abscess)

Septic emboli (blood clots containing an infectious agent)

In immunocompetent individuals

S. aureus

viridans streptococci

Actinomyces spp.

Anaerobic bacteria


Review of medical microbiology

CENTRAL NERVOUS SYSTEM

Brain abscesses

In immunocompromised individuals

Aspergillus

Mucor

Rhizopus

Nocardia spp.

In diabetic patients

Rhinocerebral mucormycosis


Review of medical microbiology

GENITOURINARY TRACT

Urinary tract infections

Endogenous infections

Nosocomial (catheterization)

Sexually transmitted diseases

Exogenous infections


Review of medical microbiology

GENITOURINARY TRACT

Urinary tract infections

Enterobacter

Enterococcus

Klebsiella pneumoniae

Proteus mirabilis

Pseudomonas aeruginosa

Staphylococcus saprophyticus

Candida spp.


Review of medical microbiology

GENITOURINARY TRACT

Pelvic inflammatory disease

Chlamydia trachomatis (PID)

Neisseria gonorrhoeae (PID)

Actinomyces spp. (endogenous; IUD usage)

Vaginitis

Candida spp. (endogenous)

Trichomonas vaginalis


Review of medical microbiology

GENITOURINARY TRACT

Sexually transmitted diseases

Chlamydia trachomatis (PID)

Neisseria gonorrhoeae (PID)

Treponema pallidum (fetal loss or perinatal infect.)

Herpes simplex virus (fetal loss or perinatal infect.)

HIV

Human papilloma virus

Trichomonas vaginalis


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