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 community acquired 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 Total staphylococci S. aureus S. epidermidis 60% 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