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Introduction to Infectious Disease
T. Davis
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Sample Question A marked increase in the incidence of cases of tuberculosis in New York City in the 1980s was due to: A. multiply drug-resistant M. tuberculosis B. resistance to INH C. genes for capsule production D. virulent strains from Thailand E. more homeless and AIDS patients
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Sample question 2 A special stain that will demonstrate bacteria, fungi, parasites and viral inclusions is: A. Gram stain B. Acid-fast stain C. Modified acid-fast stain D. Giemsa stain E. Silver (GMS) stain
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ID Outbreaks in the U.S. Polio Legionnaire’s Disease
Toxic Shock Syndrome Lyme Disease Human papillomavirus Tuberculosis Hantavirus SARS and Anthrax HIV/AIDS *MRSA *Clostridium difficile * often hospital-acquired
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“Emerging” Infectious Diseases
Microorganisms do not change much Human behavior changes a lot
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PARALYTIC POLIO Poor Sanitation (U.S. in 1800) childhood diarrhea
enterovirus infection and immunity paralysis rare Good Sanitation (U.S. in 1900) children not infected and do not become immune young adults infected receptors on anterior horn cells- paralysis
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Red areas exhibit the highest rates of paralytic polio
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Legionaire’s Disease Legionella is present in fresh water ponds, plumbing systems and aerosols (humidifiers) Sporadic cases occur American Legion convention with many elderly attendees with chronic lung disease New tools developed to identify Legionella- DFA, urine antigen test and DNA probes Hyper-chlorination or superheating of water in hospitals prevents Legionaire’s Disease Hospital water monitored for Legionella
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Legionella DFA
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Toxic Shock Syndrome Staphylococcus aureus with TSST-1 toxin
1980s- Use of hyperabsorbent tampons (RELY brand) caused an epidemic of cases Toxic shock still seen sporadically caused by both staphylococci and streptococci
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Rash of Toxic Shock Syndrome
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Lyme Disease Borrelia burgdorferi- rash, arthritis, (meningitis and myocarditis) deer tick and white-tail deer reservoir rat tick and woodrat reservoir in California more deer-more ticks-more people wildlife protection-housing development
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Tuberculosis Mycobacterium tuberculosis
In the U.S. the people at risk are: homeless, elderly in nursing homes, prisoners and AIDS patients If people are poor, malnourished, and have crowded living conditions, tuberculosis will flourish
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U.S. Born: Whites and Blacks most common
Foreign Born: Asians and Hispanics most common
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Tuberculosis is a communicable disease
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LN Ghon Lesion Ghon Complex or Promary Complex (LN and peripheral lesion)
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TB in the upper lobe- caseous granulomas
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Hantavirus 4 corners area (SW USA)
flu-like illness to hemorrhagic fever with sudden death (carried by deer mice) excess rain leads to bumper crop of pinon nuts deer mice eat nuts and population increases Navajos harvest pinon nuts
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The deermouse and family
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MRSA and C. difficile MRSA Wide use beta-lactams
Poor handwashing- more patients per nurse/doctor Real-time PCR for diagnosis Clostridium difficile Use of Clindamycin Use of proton pump inhibitors Use of quinolones (gattifloxacin, moxifloxacin) Real-time PCR for diagnosis
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Emerging Diseases ?? The human population changes behavior
Microorganisms do not change behavior
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How Do Microorganisms Cause Disease?
Direct contact with cell death (Streptococcus produces cellulase) Release of toxins that enter the blood and kill target tissue (C. diphtheriae) The host response, such as abscess (staphylococci) or granuloma (TB), that destroys host tissue
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Release and Transmission
Contact- wound, body fluids or mucosal surfaces (as in STDs) Cough with aerosol as in TB Insect vectors as in malaria Diseases spread from person to person are said to be contagious or COMMUNICABLE Diseases acquired in the hospital are NOSOCOMIAL
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Viral Surface Protein Receptors
EBV- **CD21 (CR2) receptor on B-cells and perhaps macrophages; atypical lymphocytes in blood are mainly CD8+** Rabies- acetylcholine receptor on neurons Rhinovirus- ICAM-1 on mucosal cells HIV- CD4 , CXCR4 or CCR-5
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FIGURE 8-5 Robbins
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HIV Kills CD4 (Helper) T- Lymphocytes
Only 1/100,000 CD4 lymphocytes are infected Infected cells induce non-infected cells to commit suicide by APOPTOSIS and other mechanisms
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Bacterial Injury Virulence genes
Salmonella and E. coli have similar virulence genes but E. coli lacks genes for attachment and invasion Helicobacter pylori and Corynebacterium diphtheriae strains that do NOT produce toxins are not pathogenic
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Bacterial Adhesins (Robbins Figure 8-2)
Lipoteichoic acids on Streptococci bind tightly to blood cells and oral epithelial cells Pili on GN rods and cocci- proteins at the tips of the pili bind sugars
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FIGURE 8-2 Robbins
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Bacterial Targets Unlike viruses that invade many cell types bacteria primarily infect epithelial cells (Shigella, E. coli), macrophages (TB) or both (Salmonella, Listeria) Macrophages- receptors for Ab or C’ Epithelial Cells- many bacteria bind to integrins such as CR3 (complement iC3b)
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Bacterial Toxins Endotoxin Exotoxin Enterotoxin
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Immune Evasion 1. Inaccessibility- C. difficile in the intestinal lumen 2. Block phagocytosis- S. pneumoniae’s mucopolysaccharide capsule 3. Antigenic Variation- influenza virus and rhinovirus 4. Immunosuppression- HIV and EBV
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Diagnosing Infectious Diseases
Special Stains Laboratory Culture Nucleic acid probes (DNA probes) Amplified nucleic acid probes Clinical History
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Special Stains for Microorganisms
Gram Stain- G+ and G- bacteria; Candida Giemsa Stain- bacteria, fungi (all), viral inclusions, parasites Silver Stain (GMS)- fungi and a few bacteria (Modified)-Acid-Fast Stain- mycobacteria and Nocardia
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GRAM STAIN Any fluid or tissue Screen for or identify bacteria
30 minute turnaround GPC, GPR, GNC, GNR and yeast Poor sensitivity for filamentous fungi, mycobacteria, parasites and viral inclusions
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Gram-negative bacilli
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Gram stain of Clostridium perfringens
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Gram Stain of Candida albicans
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Giemsa Stain or Diff-Quick (rapid Giemsa) Stain
Any tissue or fluid Works best on smears Bacteria, fungi, parasites, viral inclusions Rapid preparation (1 minute)
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Giemsa Stain of a perispinal abscess shows many intracellular cocci
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Giemsa stain of Histoplasma capsulatum
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Giemsa stain of Cytomegallo Virus (CMV)
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* Giemsa Stain of Bronchoalveolar Lavage- * Pneumocystis cyst with 8 trophozoites
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MICROWAVE GMS (Silver) STAIN
Any tissue or fluid- 30 minutes All fungi including Pneumocystis Histoplasma, Cryptococcus, Mucor, Aspergillus Most sensitive stain for fungi Poor for bacteria and mycobacteria O.K. for Nocardia and Actinomyces
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Silver Stain of H. capsulatum
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GMS Stain- Cryptococcus neoformans in a chest wall biopsy
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GMS (silver) Stain
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Empty spherule Endospores Spherule with endospores GMS (silver) Stain of C. immitis
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GMS Stain shows cysts (“cups, targets, grooves”)
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ACID-FAST STAINS (Kinyoun, Ziel-Neelsen, etc.)
Carbolfucsin or fluorescent (more sensitive) “modified” AFB for Nocardia- weak acid wash Mycobacterium, Nocardia, Rhodococcus, Cryptosporidium Sputum must be decontaminated and concentrated for high sensitivity
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Fluorescent Acid-Fast Stain of M. tuberculosis
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Mycobacterium avium in a lymph node biopsy; Acid-fast Stain
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Acid-fast Stain of M. tuberculosis demonstrating “cording”
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Nocardia is partially acid-fast and may grow on “TB” media
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Filamentous Nocardia on a Gram Stain (gram positive filaments)
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Nocardia demonstrated by a modified-acid-fast stain
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SPECIAL SILVER STAINS Warthin Starry, Dieterle Treponema pallidum
Legionella Bartonella
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Dieterle/Warthin-Starry Stain shows Treponema pallidum
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DIRECT FLUORESCENT ANTIBODY STAIN
Sputum or respiratory washings Legionella, Bordetella persussis Herpes virus and others **Currently we are identifying Influenza A by PCR or DFA and most are H1N1 (by PCR)
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Fluorescent antibody stain demonstates Herpes-infected cells
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Laboratory Cultue Solid Media- wounds, throat, urine, sputum
Broth- blood and sterile body fluids Tissue Culture- virus, Chlamydia (rare)
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DNA Probes GC and Chlamydia from urogenital specimens *(including Pap Smears) ID of bacterial, fungal and mycobacterial growth in broth and on solid media Candida, Gardnerella and Trichomonas from vaginal discharges
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DNA Probe
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DNA Probe
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Amplified DNA Probes PCR, LCR, TMA, SDA
GC and Chlamydia- urogenital swabs or urines M. tuberculosis in respiratory specimens- we now offer a direct PCR that identifies M. tuberculosis and Rifampin/INH resistance
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SDA
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TMA
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Real-time PCR for MRSA, GBS and C. difficile
Results in 1-2 hours (short as 45 minutes) Methicillin-resistant Staphylococcus aureus, C. difficile (MRSA) and Group-B streptococcus/ S. agalactiae (GBS) are FDA-approved tests that are done directly on the specimen (no culture)
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IDI-MRSA™ Provides a Definitive Result
MSSA SCCmec orfX Primers Junction Region for Detection Staphylococcal Chromosomes DNA detection of the SCCmec-orfX junction found only in MRSA provides definitive identification of MRSA Only molecular method to definitively identify MRSA in specimens which contain methicillin-resistant coagulase negative Staphylococci and mecA negative S. aureus. Normally such a combination would yield false-positives in other PCR methods Detects both HA-MRSA and CA-MRSA strains (i.e. USA300)
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Rapid IDI-MRSA/MSSA Assay*
Assay under development, allowing the direct detection of MRSA and MSSA in under 2 hours of laboratory time Plan to validate four different specimen types: Positive blood bottles, wound swabs, nasal swabs, and rectal swabs MRSA Positive MSSA Positive Standard Antibiotics Definitive On-screen Results Swab of Suspect Site MRSA/MSSA Analysis * Under development
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Inflammatory Response to Infectious Diseases
Host Dependent- eg. Greatly reduced in AIDS PMNs- pyogenic response to many bacteria: staphylococci, streptococci, GNRs Granulomatous- tuberculosis, histoplasmosis
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Inflammatory Response To Infection
Bacteria- usually neutrophils (PMNs); liquefactive necrosis; abscess Fungi- usually macrophages/lymphocytes; granulomas Virus- usually lymphocytes; may show cytopathic effect (CPE) Immune Deficient Host- there may be absence of the normal inflammatory response and high numbers of microorganisms (eg. M. avium in AIDS)
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Bacterial abscess in the brain
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Giemsa Stain of a perispinal abscess shows many intracellular cocci
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TB Granuloma
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Inflammatory Response (2)
Cytopathic- viral inclusions in Herpes and CMV or dysplastic changes in HPV Necrosis- Clostridium perfringens in gas gangrene
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Koilocytosis of HPV
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Giemsa stain of Cytomegallovirus (CMV)
* * * Viral inclusions in the nuclei
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