Case StudyPathogenic Bacteriology

2009

Case 51Anthony Obisesan

Tania GuevaraEdmund yeo

Case Summary

A 53 year-old man with non-insulin-dependent diabetes and hypertension presents symptoms of fever, chills, and a cough

with green sputum. Gram stain, blood culture, biochemical test, chest x-ray were performed to identify the causative agent. Streptococcus Pneumoniae was isolated and identified. This

organism is by far the most common cause of bacterial pneumonia, particularly in the elderly.

Key Information Pointing to Diagnosis

Degree of resistance to host:

Age: 53 year old

Gender: Male

Physical Health: Mellitus diabetes and Hypertension, 2 packs of cigarettes daily for 40 years.

Symptoms: fatigue, fever, chills, dyspnea, left-sided pleuritic chest pain, and cough with green sputum.

Gram Staining and blood culture to role out other organism

The Diagnosis for Case 51 •Based on the patient’s symptoms (green sputum) and findings from physical examination (crackles in lung fields) Pneumonia is suspected.

•Chest X-ray: •Chest X-ray is typically used for diagnosis in hospitals•Right lower lobe, left lingular, and left lower lobe infiltrates

Computed tomography of chest (lung window) shows two large cavities with air

fluid level.

After 4 weeks in hospital, multiple cavities with air-fluid level are seen in right lung

One week into admission, there is segmental infiltrate

within right upper lobe.

Diagnosis• Blood Culture: Significant in ruling out other

gram (+) organism that cause pneumonia such as staph. aureus, and strep. agalactiae an important cause of pneumonia (especially in new borns).

• Gram stain: Strep Pneumoniae present & Normal Respiratory Flora• High white blood cell count indicates the presence

of an infection or inflammation.• staining: Gram (+)• Catalase (+)• Coagulase (-)• Staph Epidermidis Present, NF in upper

respiratory tract.

Classification,Gram Stain Results, and Microscopic Appearance of

Streptococcus Pneumoniae• Classification: Streptococcus – a major cause of human

infections. They are untypable in the Lancefield classification which is based on the antigenicity of a carbohydrate which is soluble in dilute acid and called the C carbohydrate. They can, however, be subdivided into more than 80 serological types on the basis of antigenic differences in their capsular polysaccharide. For pneumococcal pneumonia, 23 types are the cause of 90% of the case

Morphology and General Characteristics: a gram (+), apha-hemolytic diplococcus, aerotolerant anaerobe.

Gram Stain Results: Gram positive diplococcus

Streptococcus pneumoniae Gram-stain of blood broth culture. CDC

Diseases and Pathogenesis of Disease Caused by Streptococcus

PneumoniaeDiseases: Lobar Pneumonia, meningitis, Otitis media, Septicemia, endocarditis and so on.

In the elderly or in other individuals whose ciliary activity or respiratory drainage is likely to be impaired the organism can reach its pathogenic site in the lung and cause serious disease. Those most susceptible would be the bedridden, heavy smokers, alcoholics, or individuals who had suffered a recent respiratory viral infection or toxic damage to the mucociliary escalator..

Transmission: Person to person by direct inoculation from shared respiratory equipment has been documented, other medical equipment might be cause to infection, and transmission via HCW

PathogenesisVirulence Factors: The capsule of the pneumococci is its most potent virulence factor.

•The antiphagocytic properties of the capsule allow the pneumococci to grow in the lung. This results in an inflammatory response in which fluid accumulates in the lung.

Other virulence factors include: the cell wall; choline-binding proteins; pneumococcal surface proteins A and C (PspA and PspC); the LPXTG-anchored neuraminidase proteins; hyaluronate lyase (Hyl); pneumococcal adhesion and virulence A (PavA); enolase (Eno); pneumolysin; autolysin A (LytA); and the metal-binding proteins pneumococcal surface antigen A (PsaA), pneumococcal iron acquisition A (PiaA) and pneumococcal iron uptake A (PiuA).

Common Disease & Symptoms caused by Streptococcus

PneumoniaeSepticemia

Pneumonia

Fever Hypotension

Acute confusion

Chills Dyspnea Tachypnea

Headache Tachycardia Bacteremia

Fever Dyspnea Lung consolidation

Hemoptysis chills Chest pain

Cyanosis malaise Rust colored sputum

Diagnosis/Isolation/Identification/ of Streptococcus Pneumoniae

•Isolation: Isolation can be done on Columbia Blood Agar (CBA)

•Identification: Gram staining; Pneumococci are differentiated in the laboratory from other alpha hemolytic streptococci by virtue of their sensitivity to optichin. This is usually tested by means of an impregnated disc, the P disk, placed on a lawn of the bacteria on a blood agar plate, and sensitivity demonstrated by a zone of no growth around the disc.

Test for Bile solubility also

Therapy, Prevention and Prognosis of Patient Infected with

Streptococcus Pneumoniae•Prevention: Vaccination is recommended for individuals over 10 years of age who are at risk; i.e., those with sickle cell disease, splenic malfunction, congestive heart failure, alcoholism, diabetes, confinement in a nursing home.•Sterilized hospital equipment and the use of personal safety equipment (gloves, gowns etc) by healthcare worker will reduce transmission.

Between 5 and 10 million people get pneumonia in the United States each year, and more than 1 million people are hospitalized due to the condition. As a result, pneumonia is the third most frequent cause of hospitalizations (births are first, and heart disease is second). About 500,000 children are hospitalized for respiratory infections each year, and a third of them have pneumonia. Although the majority of pneumonias respond well to treatment, the infection kills 40,000 - 70,000 people each year.

A recent disturbing finding is that about 25% of isolates of S. pneumoniae are now resistant to one or more antibiotics. The penicillin resistance in this organism is usually not due to beta lactamase, but rather to mutations in penicillin binding proteins. Sensitivity testing is necessary

Primary Research Article Contributing to the Understanding

of the Disease caused by Streptococcus PneumoniaeKwan, S.K. et al, 2009, “Changes of serotype and genotype in

Streptococcus pneumoniae isolates from a Korean hospital in 2007”, Diagnostic Microbiology and Infectious Disease, vol 63: 271 - 278.

Experimental set up: Capsular quellung method: To determine serotypes of Strep. pneumoniae (154 isolates) from sputum, blood, tracheal aspirate, nasal swab, and pus. 104 were invasiveIn vitro susceptibility testing was performed by broth microdilution (MIC). 8 antimicrobial agents were tested: penicillin, erythromycin, amoxixillin-clavulanate, levofloxacin, ciprofloxacin, clarithromycin, clindamycin and trimethoprim-sulfamethoxazole.Multilocus sequence typing was performed to determine the genotypes of all isolates.Erythromycin-resistant genes in isolates were determined by duplex PCR method.

FindingsNew serotypes found

Antimicrobial Resistance in isolates between 1998-2000 and 2007

Conclusion

Conclusion:Helpful information on local vaccine serotype expansion or replacement in Korea

Emergence of new serotypes with time

Resistance to antimicrobials

Changes in serotype and genotype in Streptococcus pneumoniae is unfavorable to preventing pneumoniae especially in hospital patients. With these changes, resistant serotypes emerge and are a major threat to human lives.

Take Home MessagePneumonia is a common illness which occurs in all age groups, and is a leading cause of death among the elderly and people who are chronically and terminally ill

Typical symptoms are fatigue, fever, chills, dyspnea, left-sided pleuritic chest pain, and cough with green sputum.

Pathogen is Streptococus pneumoniae, a gram (+), apha-hemolytic diplococcus, aerotolerant anaerobe

Diagnostics include test gram staining, optochin susceptibility & bile solubilty, blood culture, and X-ray

Therapy is based on vaccination, vaccination to prevent certain strains are available

Prognosis: with treatment, pneumonia can be cleared within two to four weeks. The eventual outcome of an episode depends on how ill the person is when he or she is first diagnosed

• Prevention is via vaccination for individuals over 10 years of age who are at risk; i.e., those with sickle cell disease, splenic malfunction, congestive heart failure, alcoholism, diabetes, confinement in a nursing home.Sterilized hospital equipment and the use of personal safety equipment (gloves, gowns etc) by healthcare worker will reduce transmission

Transmission is via Person to person by direct inoculation from shared respiratory equipment has been documented, other medical equipment might be cause to infection, and transmission via HCW

Threat is Changes in serotype and genotype in Streptococcus pneumoniae is unfavorable to preventing pneumoniae especially in hospital patients. With these changes, resistant serotypes emerge and are a major threat to human lives

References

Kwan, S.K. et al, 2009, “Changes of serotype and genotype in Streptococcus pneumoniae isolates from a Korean hospital in 2007”, Diagnostic Microbiology and Infectious Disease, vol 63: 271 - 278.

http://www.cdc.gov/ncidod/biotech/strep/strepindex.htm accessed on March 11, 2008

Point SpreadCase summary 5

Key Information pointing to Diagnosis 10

Diagnosis 5

Microbiology of Pathogen 10

Pathogenesis of the disease 10

Diagnostic tests 5

Therapy and Prognosis 5

Prevention 5

Epidemiology and threats 5

Primary research article (last 5 years) 20

Take home message 5

Are all questions addressed? 5

Appearance 5

Presentation skills (individual) 5

Total 100