Lower Respiratory Infections

8/2/2019 Lower Respiratory Infections

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Dr.T.V.Rao MD

LOWER RESPIRATORY

BACTERIAL INFECTIONS

AETIOLOGY, DIAGNOSIS

DR.T.V.RAO MD 1


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RESPIRATORY SYSTEM

ENVIRONMENT IS DIVERSE

Upper respiratory system

Nose, pharynx, associated structures

Purpose: to take in, warm and moisten air Most common site of infections

Lower respiratory system

Larynx, trachea, bronchi, alveoli

Purpose: ventilation, gas exchange

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ANATOMY OF THE RESPIRATORY

SYSTEM (AND SITES OF INFECTION)

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CLINICAL PRESENTATION:

LOWER RESPIRATORY TRACT INFECTION

Acute Infection:

Fever, chills

Back pain, myalgias, arthralgias

Headache, malaise, chills

Nausea, vomiting

Chest Infection:

Cough

Chest pain

Rales, wheezing, noisy chest

Characteristic changes on chest x-rays

Increasing respiratory distress, may require mechanical ventilation

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LOWER RESPIRATORY TRACT INFECTIONS

EPIDEMIOLOGY

Pneumonia is the sixth leadingcause of death in US

Increasing numbers of patients at risk Aging population

Increase in patients with

immunocompromising conditions


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DIAGNOSIS DEPENDS ON CLINICAL

PRESENTATION AND AGE TOO

Most of these cases diagnosis depends on

clinical presentation and minimum laboratory

and radiologic investigations may be needed

most of these cases recovered smoothly with

appropriate management unless an underlying

lung pathological or systemic disease may

worsen the condition or continue with chronicityappropriate follow-up of these patients in OPC is

appreciated especially after discharge from

hospitalDR.T.V.RAO MD 6


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Infections of the lowerrespiratory tract are the

leading cause of cause

of mortality world wide.

Streptococcus

pneumoniae is the

leading bacterial agent

of community acquiredpneumonia along with

Haemophilus

influenza and

Moraxella catarrhalis

LOWER RESPIRATORY TRACT

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Pneumococcus is the

most common bacterial

pathogen causing

febrile pneumonia inchildren and adults

The clinical syndrome

is characteristic and

distinctive : acute

onset of high, spiking

fever, with chills, cough,

and sputum production

PNEUMOCOCCUS A SIGNIFICANT PATHOGEN

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Acute bronchitis

Community

acquired pneumonia Hospital acquired

pneumonia

Pneumonia in theimmunocompromisedhost

CATEGORIES OF LOWER

RESPIRATORY TRACT INFECTIONS

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COMMUNITY ACQUIRED PNEUMONIA

ETIOLOGIC AGENTS

Pathogen Frequency (%)Streptococcus pneumoniae 66

Haemophilus influenza 1-12

M catarrhalis 10

Legionellaspecies 2-15Mycoplasma pneumoniae 2-14

Klebsiellaspecies 3-14

Enteric gram negative bacilli 6-9

Staphylococcus aureus 3-14

Chlamydiaspecies 5-15

Influenza viruses 5-12

Other viruses


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SPECIMEN COLLECTION:

The patient should be standing, If possible or sitting upright in

bed.

He or she should take deep breath to full the lungs, and emptythen in one breath, coughing as hard and as deeply as

possible.

Sputum brought up should be spit into screw capped

container.Visually inspect the specimen.

Tighten the cap of the container and send immediately to lab.

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Sputum of less than 2ml

should not be processed

unless obviously purulent

Only 1 sputum per 24hr.submitted

Some scoring system

should be used to reject

specimen that re oralcontamination.

SPUTUM COLLECTION

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TRANSPORTATION OF SPUTUM

Transportation in


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INDUCED SPUTUM

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Patients who are unable to produce sputum may beassisted by respiratory therapy technician. Aerosolinduced specimen are collected by allowing thepatient to breath aerosolized droplets of a solution

of 15% sodium chloride and 10% glycerin forapproximately 10 minute obtaining suchspecimen may avoid the need for a more invasiveprocedures ,such as bronchoscopy or needle

aspiration, in many cases.


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BRONCHOALVEOLAR LAVAGE (BAL)

SPECIMEN ACCEPTABILITY

Microscopic examination of Gram-stained smear

Acceptable

1% of cells present are squamous epithelial

cells

Thorpe JE et. al. 1987. Bronchoalveolar lavage for diagnosing acute bacterialpneumonia. J. Infect. Dis. 155:855-861DR.T.V.RAO MD 15


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METHODS OF COLLECTION IS

IMPORTANT..

Sputum collected under supervision of nurse or resident

Samples were processed immediately

Screened for epithelial cells

Screened for predominant morphotype (> 75% of the

organisms seen)

Sputum planted to blood agar, chocolate agar and MacConkey

agar Strictly defined clinical and diagnostic parameters

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Prepare a gram stain smear for

all lower respiratory tract

specimens to determine the

presence of oropharyngeal

contamination (indicated by

squamous epithelial cells) andlower respiratory tract secretions

(indicated by WBCs) as well as

to identity the most likely

pathogens (Indicated by the

predominant organismsassociated with WBCs).

MICROSCOPIC EXAMINATION

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SPUTUM GRAM STAIN

Good quality specimens

Quantify number and types of inflammatory cells

Note presence of bronchial epithelial cells

Concentrate on areas with WBCs when looking for

organisms

Determine if there is a predominant organism (> 10 per oil

immersion field) Semiquantitate and report organism with descriptive

If no predominant organism is present, report mixed gram

positive and gram negative floraDR.T.V.RAO MD 18


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SPUTUM GRAM STAIN IS HELPFUL - YES

Proponents

Demonstration ofpredominant

morphotype on Gramstain guides therapy

Accuracy is good when

strict criteria are used Cheap, so why not?

Antagonists

Poor specimen collection

Intralaboratory variability

(Gram stain interpretation) Low sensitivity and

specificity

Empiric treatment

guidelines Do much dependence ???

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STUDIES PROVE ... Overall sensitivity and specificity for pneumococcal

pneumonia: 57% and 97%

Overall sensitivity and specificity forH. influenza

pneumonia: 82 % and 99%

Gram stain gave presumptive diagnosis in 80% of

patients who had a good specimen submitted

> 95% of patients in whom a predominant morphotypewas seen on Gram stain received monotherapy

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REPORT GRAM STAINING WITH

CAUTION

Be as descriptive as possible

Moderate neutrophils

Moderate Gram positive diplococcic suggestiveofStreptococcus pneumoniae

Few bacteria suggestive of oral flora

Keep report shortavoid line listing of all

morphotypes present

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If no squamous epithelial cell are

found, report No epithelial cells

seen

If only a few epithelial cells are

found report Few epithelial cellsseen

If abundant epithelial cells seen,

indicating oropharyngeal

contamination, such specimens

are graded as unsatisfactorysample.

SQUAMOUS EPITHELIAL CELLS

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If no WBC are foundreport No WBCs

seen

If WBCs are present

in any amount state

as few, moderate or

numerous WBCsseen.

REPORTING THE PRESENCE OF LEUCOCYTES:

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INTERPRETATION OF GRAM STAIN:

None Few Moderate Numerous

Squamous epithelial cells/ LPF* 0 1-9 10-24 >25

Neutrophils/LPF* 0 1-9 10-24 >25

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GRAM STAINING REPORTING MICROBIAL

OBSERVATIONS

Type / Number of organisms / HPF**

Gram-positive cocci

Gram-negative cocci

Gram-negative rods

Gram-positive rods

PF*: (low power field) x 10 (examine 10-20 fields)

HPF**: (high power field) oil immersion

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PROCESSING SPECIMENS FOR CULTURE

Process specimens in biological safety cabinet, asaerosol can result in laboratory-squired respiratoryinfections.

Process all specimens as rapidly as possible,

especially specimen from emergency department, andinpatients. Select the most purulent or most blood-tinged portion of the specimen. Significant growthabove the cutoff should be reported; however if more

than one pathogen is isolated than it is suggestive oforopharyngeal contamination and clinical correlationshould be done before reporting the samples.

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Sheep Blood

Agar

MacConkeyagar

Chocolateagar

CHOOSING CULTURE MEDIA:

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Most of the commonlysought etiologic agents oflower respiratory tractinfection will isolated on

routinely used media : 5%sheep blood agar,MacConkey agar forisolation and differentiationof gram-negative bacilli

,and chocolate agar forNeisseria spp andHaemophilus .

ROUTINE CULTURE

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CONTAMINATION WITH ORAL FLORA

INTERFERES RESULTS

Because of contaminating oral flora ,sputum specimens,

specimens obtained by bronchial washing, and lavage

tracheostomy, or endotracheal tube aspirates are not

inoculated to enriched broth or incubated anaerobically.Only specimens obtained by percutaneous aspiration

(including trans tracheal aspiration )and by protected

bronchial brush are suitable for anaerobic culture: he

latter must be done quantitatively for properinterpretation.

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CULTURING SPECIMENS FROM CYSTIC


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CULTURING SPECIMENS FROM CYSTIC

FIBROSIS

Sputum specimens from patients known tohave cystic fibrosis should be inoculated to

selective agar ,such as manitol salt agar for

recovery ofS .aureus and selective horseblood-bacitracin ,incubated anaerobically and

aerobically ,for recovery ofH,influenzae that

may be obscured by the mucoid

P,aeroginosa on routine media.

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SPUTUM AND ENDOTRACHEAL SUCTIONCULTURE EVALUATION

Identify and perform susceptibility testing on 2-3 potentialpathogens seen as predominant on Gram stain

Alpha streprule out S. pneumoniae

Yeastrule out Cryptococcus neoformans only

S. aureus, Gram negative bacilli

< normal flora, quantify and limit ID; no susceptibility

Add comment that organism not predominant on stain

ID mould, Mycobacteria orNocardia spp.

Modified from Sharp SE, et. Al. 2003. Cumitech 7B. ASM Press.DR.T.V.RAO MD 31


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INTERPRETATION OF QUANTITATIVE

PSB/BAL

Dilution Method

Quantify each morphotype present and express as CFU/ml

Calibrated Loop Method

Quantify each morphotype present and express as log10 colonycount ranges

Thresholds for significance

PSB > 103 CFU/ml

BAL > 104 CFU/ml

Baselski and Wunderink. 1994. ClinMicro Rev7:547

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EXAMINE FOR AND ALWAYS REPORT.

Streptococcus pyogenes

Group B streptococci in pediatric population

Francisella tularensis

Bordetella spp., especially Bordetella bronchiseptica

Yersinia pestis

Nocardia spp.

Bacillus anthracis

Cryptococcus neoformans

Molds, not considered saprophytic contaminants

Neisseria gonorrhoeaeDR.T.V.RAO MD 33


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Streptococcuspneumoniae

Haemophilusinfluenza reportbeta-lactamase

ALWAYS REPORT, BUT DO NOT MAKE AN EFFORT TO FIND

LOW NUMBERS, UNLESS THEY ARE SEEN IN THE SMEAR.

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REPORT IF PRESENT IN SIGNIFICANT

AMOUNTS, EVEN IF NOT PREDOMINANT

1 Moraxella catarrhalis

2 Neisseria meningitides

Report the following for nosocomialinfections:

3. Pseudomonas aeruginosa

4. Stenotrophomonas maltophilia

5. Acinotobacterspp.

6. Burkholderia spp.DR.T.V.RAO MD 35


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REPORT IF PRESENT IN SIGNIFICANT AMOUNT AND IF IT IS

THE PREDOMINANT ORGANISM IN THE CULTURE,

PARTICULARLY IF SUGGESTS INFECTION WITH

MORPHOLOGY CONSISTENT WITH ISOLATE.

Staphylococcus aureus

Beta-hemolytic streptococcus B (adults), C, or G

Single morphotype of gram-negative rod (especiallyKlebsiella pneumoniae)

Fastidious gram-negative rods; usually report beta-lactamase

Corynebacterium spp. if urea positive or from ICU

Rhodococcus equiin immunocompromised patients

DR.T.V.RAO MD 36

ATS GUIDELINES


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ATS GUIDELINES

DIAGNOSTIC TESTS FOR CAP

Empiric therapy for outpatients

Macrolide or tetracycline

Hospitalized patients with CAP

2 sets of pre-treatment blood cultures Pleural fluid Gram stain/culture when appropriate

Studies for Legionella, Mtb, fungi in select patients

Sputum Gram stain/culture only if resistant or unusual pathogen issuspected

Avoid extensive testing

ATS. 2001.Am J Respir Crit Care Med163: 1730-1754.

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CRITERIA FOR REJECTING


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CRITERIA FOR REJECTING

SAMPLES

DR.T.V.RAO MD 38

Mismatch of information on the label and the request

Inappropriate transport temperature

Excessive delay in transportation

Inappropriate transport medium

specimen received in a fixative

dry specimen

sample with questionable relevance

Insufficient quantity

Leakage

IM

MUNOCOMPROMISED PATIENTS


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Aerobic Gram stainquantitative bacterialculture

Fungal stain and culture

Mycobacterial stain andculture

Viral culture/RespiratoryDFA

Pneumocystis DFA

Legionella culture

IMMUNOCOMPROMISED PATIENTS

SUGGESTED BAL PROTOCOL

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MANY OTHER CAUSES OF PNEUMONIA WITH

ACUTE RESPIRATORY DISEASE & FEVER

Plague Tularemia RICIN toxin

StaphylococcalEnterotoxin B

TBLegionella

SARS

S.Pneumoniae


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SUMMARY Respiratory system can host a variety of microbes

Normal flora in restricted areas

Susceptibility depends on age, immune system

Some organisms are adept at evading immune

system

Damage generally due to cytotoxicity andinflammation

Vaccines are available for some organismsDR.T.V.RAO MD 41

CHILDHOOD IMMUNIZATIONS CAN REDUCE


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CHILDHOOD IMMUNIZATIONS CAN REDUCERESPIRATORY INFECTIONS FOLLOW THE SCHEDULES

Birth 1m 2m 3m 4m 6m 12m 15m 18m 4-6y 11-12y

HBV3

DTP

HBV1HBV2

DTP

DTP DTP

Hib

Hib

Hib Hib

Polio Polio Polio

MMR MMR or MMR

Varicella Varicella


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DO REMEMBER

The culture of lower respiratory

specimens may result in more

unnecessary microbiologic effort

than any other type of

specimen.Raymond C Bartlett

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Programme created byDr.T.V.Rao MD for Medical and

Health Workers in theDeveloping World

Email

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Lower Respiratory Infections