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