REVIEW OF MEDICAL MICROBIOLOGY Infections of Respiratory tract Cardiovascular system...
Transcript of REVIEW OF MEDICAL MICROBIOLOGY Infections of Respiratory tract Cardiovascular system...
REVIEW OF MEDICAL MICROBIOLOGY
Infections ofRespiratory tractCardiovascular systemGastrointestinal tractSkin and soft tissueCentral nervous systemGenitourinary tract
THE RESPIRATORY TRACT
Upper Respiratory Tract
Pharyngitis (mostly 2 years through adolescence)AdenovirusesGroup A Streptococci (S. pyogenes)
Potential for rheumatic feverChlamydophila pneumoniaeNeisseria gonorrhoeaeCorynebacterium diphtheriaeMycoplasma pneumoniae
THE RESPIRATORY TRACT
Otitis media (infants and young children)Streptococcus pneumoniaeHaemophilus influenzaeStaphylococcus aureusGroup A streptococcusMoraxella catarrhalis
Formerly “Branhamella”Gram-negative cocciOpportunistic pathogen
THE RESPIRATORY TRACT
Otitis externaStaphylococcus aureusPseudomonas aeruginosaGroup A Streptococcus
Malignant otitis externa• In diabetics, elderly & immunocompromised• Can lead to osteomyelitis and meningitis
THE RESPIRATORY TRACT
SinusitisStreptococcus pneumoniaeHaemophilus influenzaeStaphylococcus aureusChlamydophila pneumoniaeMoraxella catarrhalisGroup A StreptococcusPseudomonas aeruginosaVirusesOral anaerobic bacteria
ConjunctivitisStreptococcus pneumoniaeGroup B StreptococcusViridans StreptococcusStaphylococcus aureusHaemophilus influenzaeMoraxella catarrhalis
THE RESPIRATORY TRACT
Conjunctivitis (contd)Pseudomonas aeruginosaCorynebacterium speciesFrancisella tularensisAdenovirusesChlamydia trachomatis
THE RESPIRATORY TRACT
Rhinocerebral mucormycosis• Life-threatening• Most common in diabetics• The fungi Mucor and Rhizopus invade bloodvessels, resulting in necrosis of bone andthrombosis of the cavernous sinus and internalcarotid artery
THE RESPIRATORY TRACT
Bacterial epiglottitisLife-threateningHaemophilus influenzae type bStreptococcus pneumoniaeStaphylococcus aureus
THE RESPIRATORY TRACT
DiphtheriaCorynebacterium diphtheriae
Whooping coughBordetella pertussis
THE RESPIRATORY TRACT
“Common colds”RhinovirusesAdenovirusesInfluenza CCoronavirusesCoxsackie viruses
THE RESPIRATORY TRACT
“Croup”Respiratory syncytial virusInfluenza virusParainfluenza virus
THE RESPIRATORY TRACT
THE RESPIRATORY TRACT
Lower Respiratory Tract
Community acquired infectionsStreptococcus pneumoniae (elderly)Klebsiella pneumoniae (alcoholics)Mycoplasma pneumoniae (school-age children)Mycobacterium tuberculosisRSV (infants and young children)Influenza virus
THE RESPIRATORY TRACT
Lower Respiratory Tract
Community acquired infectionsBronchitis or pneumonia secondary to viral pneumonia
Streptococcus pneumoniaeHaemophilus influenzaeStaphylococcus aureusMoraxella cararrhalis
THE RESPIRATORY TRACT
Lower Respiratory Tract
Nosocomial infectionsMycobacterium tuberculosisRSV in pediatric patientsMethicillin-resistant S. aureus (pneumonia)Pseudomonas aeruginosaLegionella spp.
THE RESPIRATORY TRACT
Lower Respiratory Tract
Patients with underlying lung infectionsChronic obstructive pulmonary disease
P. aeruginosaS. pneumoniaeH. influenzaeMoraxella cararrhalisAllergic bronchopulmonary aspergillosis
THE RESPIRATORY TRACT
Lower Respiratory Tract
Patients with underlying lung infectionsCystic fibrosis
S. aureusP. aeruginosaAllergic bronchopulmonary aspergillosis
THE RESPIRATORY TRACT
Lower Respiratory Tract
Patients with underlying lung infectionsCavitary lung disease (due to prior MTB infection)
Aspergillus spp (Aspergilloma or fungus ball)
THE RESPIRATORY TRACT
Lower Respiratory Tract
Immunocompromised individualsAt risk for all recognized respiratory tract pathogens
AIDS patientsPneumocystis cariniiS. pneumoniaeMDR M. tuberculosis
THE RESPIRATORY TRACT
Lower Respiratory Tract
Immunocompromised individuals
Neutropenic patientsInvasive aspergillosisMucormycosis
THE RESPIRATORY TRACT
Lower Respiratory Tract
Immunocompromised individuals
Transplant patientsInvasive fungiCMVHSVLegionella 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 pneumoniaeHaemophilus influenzaeMycoplasma pneumoniaeStaphylococcus aureus
(frequently following an influenza infection)Klebsiella pneumoniae
(elderly & alcoholics)Legionella pneumophilaChlamydophila 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?
ErythromycinCan penetrate into white blood cellsLegionella multiplies in macrophages
Bordetella pertussis
THE CARDIOVASCULAR SYSTEM
Septicemia: Predisposing factors and agents
Abdominal sepsisEnterobacteriaBacteroides fragilisEnterococcus faecalisEnterococcus faecium
Infected woundsStaphylococcus aureusStreptococcus pyogenesEnterobacteria
THE CARDIOVASCULAR SYSTEM
Septicemia: Predisposing factors and agents
OsteomyelitisStaphylococcus aureus
PneumoniaStreptococcus pyogenes
Food poisoningSalmonella spp.Campylobacter spp.
THE CARDIOVASCULAR SYSTEM
Septicemia: Predisposing factors and agents
Intravascular devicesStaphylococcus aureusStaphylococcus epidermidisEnterobacteria
MeningitisStreptococcus pneumoniaeNeisseria meningitidisHaemophilus influenzae
THE CARDIOVASCULAR SYSTEM
Septicemia: Predisposing factors and agents
Immunocompromised patientsStaphylococcus aureusEnterobacteria
THE CARDIOVASCULAR SYSTEM
Infective endocarditis
> 80% of cases caused by streptococcior staphylococci
Total streptococci 60%Viridans group 35%
anginosus groupmitis groupmutans groupsalivarius group
THE CARDIOVASCULAR SYSTEM
Infective endocarditis
Total streptococci 60%
Total staphylococci 25%S. aureus 20%S. epidermidis 5%
THE CARDIOVASCULAR SYSTEM
Myocarditis
Corynebacterium diphtheriaeClostridium perfringensGroup A StreptococcusBorrelia burgdorferiNeisseria meningitidisStaphylocccus 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 hada fever of 38.9˚Ctachycardia with a pulse of 220/mintachypnea 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 virusInfluenza A and BRespiratory syncytial virusMycoplasma pneumoniaeBordetella 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 vialClinical specimens a centrifuged onto the cell monolayerIncubation for 1-2 daysThe 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 toxinDirect damage to the intestinal epithelium
CytotoxinEntamoeba histolytica
Invasion of epitheliumSalmonella spp.Shigella spp.Campylobacter spp.Yersinia enterocolitica
THE GASTROINTESTINAL SYSTEM
Infectious doses
Hundreds of thousands to millionsSalmonella spp.Vibrio cholerae
Less than 100Shigella spp.
THE GASTROINTESTINAL SYSTEM
Bacteria
Invasive diarrheaCampylobacter spp.Salmonella spp.Shigella spp.Yersinia enterocolitica
Large-volume watery diarrheaVibrio spp.
THE GASTROINTESTINAL SYSTEM
Bacteria
Watery diarrheaEnterotoxigenic E. coliYersinia enterocolitica
Typhoid feverSalmonella spp.
THE GASTROINTESTINAL SYSTEM
Bacteria
Traveler’s diarrheaEnterotoxigenic E. coli
DysenteryShigella spp.
THE GASTROINTESTINAL SYSTEM
Bacteria
Antibiotic-associated diarrheaPseudomembranous colitis
Clostridium difficile
Food poisoningStaphylococcus aureusClostridium perfringensBacillus cereusSalmonella spp.
THE GASTROINTESTINAL SYSTEM
Bacteria
Abdominal abscessBacteroides fragilis
Gangrenous lesions of bowel or gall bladderClostridium perfringens
Enterohemorrhagic colitis Enterohemorrhagic E. coli
THE GASTROINTESTINAL SYSTEM
Viruses
Acute, self-limited hepatitisHepatitis A
Acute and chronic hepatitisHepatitis BHepatitis C
THE GASTROINTESTINAL SYSTEM
Viruses
DiarrheaEnterovirusRotavirusNorwalk agent (calicivirus)
VomitingRotavirusNorwalk agent (“24-hour flu”)
THE GASTROINTESTINAL SYSTEM
Viruses
InfantsRotavirus A (most common cause)Adenovirus 40, 41Coxsackie A24 virus
Infants, children, and adultsNorwalk agent (“24-hour flu”)CalicivirusReovirus
SKIN AND SOFT TISSUE
Diffuse erythematous macular rash may be a manifestation of systemic disease
Rocky Mountain spotted feverMeningococcemiaEntereoviral infectionToxic shock syndromeScarlet feverMeaslesGerman measles
SKIN AND SOFT TISSUE
Erythema migransLyme diseases
Vesicular skin lesionsVaricella Zoster virus
Macular, papular or pustular, but not vesicular, skin lesions
Secondary syphilis
SKIN AND SOFT TISSUE
Important to treat superficial skin infectionsFolliculitis caused by Staphylococcus aureusCellulitis 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 angiomatosisBartonella henselae
Lyme diseaseBorrelia burgdorferi
Gas gangreneClostridium perfringens
TetanusClostridium tetani
SKIN AND SOFT TISSUE
Diphtheria and wound diphtheriaCorynebacterium diphtheriae
CellulitisGroup A streptococci (S. pyogenes)Group B streptococci (S. agalactiae)Pasteurella multocidaStaphylococcus aureusCryptococcus neoformans
SKIN AND SOFT TISSUE
Skin infection in burn patientsPseudomonas aeruginosa
ThrushCandida albicansCandida spp.
Cutaneous infectionBlastomyces dermatitidis
SKIN AND SOFT TISSUE
Infection of keratinized tissueEpidermophyton floccosumMicrosporum spp.Trichophyton spp.
Ulcerative skin lesionsLeishmania tropica
SKIN AND SOFT TISSUE
Exanthem subitumHuman herpesvirus type 6
Oral infectionsHerpes simplex virus
WartsHuman papillomavirus
CENTRAL NERVOUS SYSTEM
The most frequent infections areMeningitisEncephalitisAbscess
MeningitisSeptic: 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 monocytogenesE. coliKlebsiella pneumoniaeCitrobacter diversus Citrobacter koseriTreponema pallidum
CENTRAL NERVOUS SYSTEM
Meningitis (2 months - 5 years)Haemophilus influenzae type bStreptococcus pneumoniaeNeisseria meningitidis (all ages)
Meningitis (Patients with head trauma)Coagulase-negative staphylococciStaphylococcus aureusPseudomonas aeruginosa
CENTRAL NERVOUS SYSTEM
Aseptic meningitisEchovirusCoxsackievirusHerpes simplex virus
Fungal meningitis(primarily in the immunocompromised)Cryptococcus neoformans (in AIDS patients)
CENTRAL NERVOUS SYSTEM
Viral encephalitisHerpes simplex virus (most common)
(necrotizing; necrotizing hemorrhagic)Eastern equine encephalitis virusWestern equine encephalitis virusSt. Louis encephalitis virusLa Crosse encephalitis virus
CENTRAL NERVOUS SYSTEM
EncephalitisToxoplasma gondiiTaenia solium (“cysticercosis”; from pork)
MeningoencephalitisCerebral malariaNaegleria fowleri (an amoeba)Citrobacter diversus
CENTRAL NERVOUS SYSTEM
Brain abscessesExtension from a contiguous siteHematogenous spread from another site (endocarditis or lung abscess)
Septic emboli (blood clots containing an infectious agent)
In immunocompetent individualsS. aureusviridans streptococciActinomyces spp.Anaerobic bacteria
CENTRAL NERVOUS SYSTEM
Brain abscesses
In immunocompromised individualsAspergillusMucorRhizopusNocardia spp.
In diabetic patientsRhinocerebral mucormycosis
GENITOURINARY TRACT
Urinary tract infectionsEndogenous infectionsNosocomial (catheterization)
Sexually transmitted diseasesExogenous infections
GENITOURINARY TRACT
Urinary tract infectionsEnterobacterEnterococcusKlebsiella pneumoniaeProteus mirabilisPseudomonas aeruginosaStaphylococcus saprophyticusCandida spp.
GENITOURINARY TRACT
Pelvic inflammatory diseaseChlamydia trachomatis (PID)Neisseria gonorrhoeae (PID)Actinomyces spp. (endogenous; IUD usage)
VaginitisCandida 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.)HIVHuman papilloma virusTrichomonas vaginalis