Transcript Microbiol Rev w Cases

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)
Adenoviruses
Group A Streptococci (S. pyogenes)
Potential for rheumatic fever
Chlamydophila pneumoniae
Neisseria gonorrhoeae
Corynebacterium diphtheriae
Mycoplasma pneumoniae
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
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
THE RESPIRATORY TRACT
Sinusitis
Streptococcus pneumoniae
Haemophilus influenzae
Staphylococcus aureus
Chlamydophila pneumoniae
Moraxella catarrhalis
Group A Streptococcus
Pseudomonas aeruginosa
Viruses
Oral anaerobic bacteria
THE RESPIRATORY TRACT
Conjunctivitis
Streptococcus pneumoniae
Group B Streptococcus
Viridans Streptococcus
Staphylococcus aureus
Haemophilus influenzae
Moraxella catarrhalis
THE RESPIRATORY TRACT
Conjunctivitis (contd)
Pseudomonas aeruginosa
Corynebacterium species
Francisella tularensis
Adenoviruses
Chlamydia trachomatis
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
THE RESPIRATORY TRACT
Bacterial epiglottitis
Life-threatening
Haemophilus influenzae type b
Streptococcus pneumoniae
Staphylococcus aureus
THE RESPIRATORY TRACT
Diphtheria
Corynebacterium diphtheriae
Whooping cough
Bordetella pertussis
THE RESPIRATORY TRACT
“Common colds”
Rhinoviruses
Adenoviruses
Influenza C
Coronaviruses
Coxsackie viruses
THE RESPIRATORY TRACT
“Croup”
Respiratory syncytial virus
Influenza virus
Parainfluenza virus
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
THE RESPIRATORY TRACT
Lower Respiratory Tract
Community acquired infections
Bronchitis or pneumonia secondary to viral pneumonia
Streptococcus pneumoniae
Haemophilus influenzae
Staphylococcus aureus
Moraxella cararrhalis
THE RESPIRATORY TRACT
Lower Respiratory Tract
Nosocomial infections
Mycobacterium tuberculosis
RSV in pediatric patients
Methicillin-resistant S. aureus (pneumonia)
Pseudomonas aeruginosa
Legionella spp.
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
THE RESPIRATORY TRACT
Lower Respiratory Tract
Patients with underlying lung infections
Cystic fibrosis
S. aureus
P. aeruginosa
Allergic bronchopulmonary aspergillosis
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)
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
THE RESPIRATORY TRACT
Lower Respiratory Tract
Immunocompromised individuals
Neutropenic patients
Invasive aspergillosis
Mucormycosis
THE RESPIRATORY TRACT
Lower Respiratory Tract
Immunocompromised individuals
Transplant patients
Invasive fungi
CMV
HSV
Legionella spp.
Pneumocystis carinii
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”
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.
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.
Which organisms are common causes of communityacquired bacterial pneumonia?
Streptococcus pneumoniae
Haemophilus influenzae
Mycoplasma pneumoniae
Staphylococcus aureus
(frequently following an influenza infection)
Klebsiella pneumoniae
(elderly & alcoholics)
Legionella pneumophila
Chlamydophila pneumoniae
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?
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.
What techniques other than culture can be used to detect
this organism within 24 h?
DFA
What is the appropriate antimicrobial agent for the
treatment of this infection?
Which other Gram-negative respiratory pathogen is
treated with this antibiotic?
Erythromycin
Can penetrate into white blood cells
Legionella multiplies in macrophages
Bordetella pertussis
THE CARDIOVASCULAR SYSTEM
Septicemia: Predisposing factors and agents
Abdominal sepsis
Enterobacteria
Bacteroides fragilis
Enterococcus faecalis
Enterococcus faecium
Infected wounds
Staphylococcus aureus
Streptococcus pyogenes
Enterobacteria
THE CARDIOVASCULAR SYSTEM
Septicemia: Predisposing factors and agents
Osteomyelitis
Staphylococcus aureus
Pneumonia
Streptococcus pyogenes
Food poisoning
Salmonella spp.
Campylobacter spp.
THE CARDIOVASCULAR SYSTEM
Septicemia: Predisposing factors and agents
Intravascular devices
Staphylococcus aureus
Staphylococcus epidermidis
Enterobacteria
Meningitis
Streptococcus pneumoniae
Neisseria meningitidis
Haemophilus influenzae
THE CARDIOVASCULAR SYSTEM
Septicemia: Predisposing factors and agents
Immunocompromised patients
Staphylococcus aureus
Enterobacteria
THE CARDIOVASCULAR SYSTEM
Infective endocarditis
> 80% of cases caused by streptococci
or staphylococci
Total streptococci
Viridans group
anginosus group
mitis group
mutans group
salivarius group
60%
35%
THE CARDIOVASCULAR SYSTEM
Infective endocarditis
Total streptococci
60%
Total staphylococci
S. aureus
S. epidermidis
25%
20%
5%
THE CARDIOVASCULAR SYSTEM
Myocarditis
Corynebacterium diphtheriae
Clostridium perfringens
Group A Streptococcus
Borrelia burgdorferi
Neisseria meningitidis
Staphylocccus aureus
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”
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.
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.
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?
Parainfluenza virus
Influenza A and B
Respiratory syncytial virus
Mycoplasma pneumoniae
Bordetella pertussis
Membrane-enzyme immunoassay
2. What other techniques could one use to identify this
microorganism?
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
2. What is the epidemiology of the disease?
RSV is spread by large droplets and on fomites
Can be spread via contaminated hands
Occurs primarily in winter months
3. What is the pathophysiologic basis for wheezing?
RSV is tropic for bronchial epithelium
Edema and necrosis can lead to collapse and obstruction of
a child’s small bronchioles
4. What specific therapy should be given after the antigen
test gives the diagnosis?
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.
5. What infection control measures should be taken?
Patients should be put on respiratory isolation
Gowns and gloves should be used during contact
6. What can be done to prevent the disease?
Inactivated RSV vaccine did not work and exacerbated the
disease
Immune globulin can be used in children at greatest risk
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
THE GASTROINTESTINAL SYSTEM
Infectious doses
Hundreds of thousands to millions
Salmonella spp.
Vibrio cholerae
Less than 100
Shigella spp.
THE GASTROINTESTINAL SYSTEM
Bacteria
Invasive diarrhea
Campylobacter spp.
Salmonella spp.
Shigella spp.
Yersinia enterocolitica
Large-volume watery diarrhea
Vibrio spp.
THE GASTROINTESTINAL SYSTEM
Bacteria
Watery diarrhea
Enterotoxigenic E. coli
Yersinia enterocolitica
Typhoid fever
Salmonella spp.
THE GASTROINTESTINAL SYSTEM
Bacteria
Traveler’s diarrhea
Enterotoxigenic E. coli
Dysentery
Shigella spp.
THE GASTROINTESTINAL SYSTEM
Bacteria
Antibiotic-associated diarrhea
Pseudomembranous colitis
Clostridium difficile
Food poisoning
Staphylococcus aureus
Clostridium perfringens
Bacillus cereus
Salmonella spp.
THE GASTROINTESTINAL SYSTEM
Bacteria
Abdominal abscess
Bacteroides fragilis
Gangrenous lesions of bowel or gall bladder
Clostridium perfringens
Enterohemorrhagic colitis
Enterohemorrhagic E. coli
THE GASTROINTESTINAL SYSTEM
Viruses
Acute, self-limited hepatitis
Hepatitis A
Acute and chronic hepatitis
Hepatitis B
Hepatitis C
THE GASTROINTESTINAL SYSTEM
Viruses
Diarrhea
Enterovirus
Rotavirus
Norwalk agent (calicivirus)
Vomiting
Rotavirus
Norwalk agent (“24-hour flu”)
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
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
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
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)
SKIN AND SOFT TISSUE
Cat scratch disease, bacillary angiomatosis
Bartonella henselae
Lyme disease
Borrelia burgdorferi
Gas gangrene
Clostridium perfringens
Tetanus
Clostridium tetani
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
SKIN AND SOFT TISSUE
Skin infection in burn patients
Pseudomonas aeruginosa
Thrush
Candida albicans
Candida spp.
Cutaneous infection
Blastomyces dermatitidis
SKIN AND SOFT TISSUE
Infection of keratinized tissue
Epidermophyton floccosum
Microsporum spp.
Trichophyton spp.
Ulcerative skin lesions
Leishmania tropica
SKIN AND SOFT TISSUE
Exanthem subitum
Human herpesvirus type 6
Oral infections
Herpes simplex virus
Warts
Human papillomavirus
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)
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
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
CENTRAL NERVOUS SYSTEM
Aseptic meningitis
Echovirus
Coxsackievirus
Herpes simplex virus
Fungal meningitis
(primarily in the immunocompromised)
Cryptococcus neoformans (in AIDS patients)
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
CENTRAL NERVOUS SYSTEM
Encephalitis
Toxoplasma gondii
Taenia solium (“cysticercosis”; from pork)
Meningoencephalitis
Cerebral malaria
Naegleria fowleri (an amoeba)
Citrobacter diversus
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
CENTRAL NERVOUS SYSTEM
Brain abscesses
In immunocompromised individuals
Aspergillus
Mucor
Rhizopus
Nocardia spp.
In diabetic patients
Rhinocerebral mucormycosis
GENITOURINARY TRACT
Urinary tract infections
Endogenous infections
Nosocomial (catheterization)
Sexually transmitted diseases
Exogenous infections
GENITOURINARY TRACT
Urinary tract infections
Enterobacter
Enterococcus
Klebsiella pneumoniae
Proteus mirabilis
Pseudomonas aeruginosa
Staphylococcus saprophyticus
Candida spp.
GENITOURINARY TRACT
Pelvic inflammatory disease
Chlamydia trachomatis (PID)
Neisseria gonorrhoeae (PID)
Actinomyces spp. (endogenous; IUD usage)
Vaginitis
Candida spp. (endogenous)
Trichomonas vaginalis
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