FINAL BSI group b3,d3 department of microbiology.pptx

Laboratory diagnostics, treatment, etiology,

1. BLOOD STREAM INFECTIONS Prepared by B3 & D3 batch Microbiology Department Internal Assessment 2023-24

2. BLOOD STREAM INFECTIONS Blood stream infections (BSI) refers to the presence of organisms in blood which are threat to every organ in the body. It causes shock, multiple organ failure and DIC (Disseminated Intravascular Coagulation). The presence of bacteria in blood is called Bacteremia . The bacteria circulate and actively multiply in the blood stream is called Septicemia. The presence of virus in blood is called Viremia . The presence of parasite in blood is called Parasitemia . The presence of fungi in blood is called Fungemia .

3. Types of bacteremia 1. Transient Bacteremia It is the sudden destruction of the tissue. It occur during brushing teeth, chewing food, manipulation of infected tissues, devices inserted through contaminated mucosal surface, surgery in non- sterile sites. 2. Continuous Bacteremia Here the organism released into the bloodstream at fairly constant rate. It occurs in the early stages of certain infections such as typhoid fever, brucellosis & leptospirosis .

4. Types of bacteremia 3. Intermittent bacteremia Here the organism released into the blood stream at various time intervals. It is found in patients with undrained abscess. It occurs in the early stages of meningitis, pneumoniae , pyrogenic arthritis and osteomyelitis .

5. Etiological agents

6. Types of blood stream infections They are 2 types: Intravascular and extravascular Intravascular – from within the cardiovascular system for e.g. Infective Endocarditis, Catheter Related BSI (CRBSI), Vasculitis Extravascular – those entering the bloodstream through the lymphatic system from other sites of infection or from infective foci elsewhere. For e.g. Disseminated Intravascular Clot (DIC)

7. Fever : accompanied by chills and rigors. Hypotension : In severe cases may manifest as dizziness, lightheadedness, or even fainting. Tachycardia Hypothermia Respiratory Alkalosis Altered mental status : confusion, disorientation, or altered consciousness. Localized signs of infection : redness, warmth, swelling, or pus discharge. Skin manifestations : petechiae, purpura, or ecchymosis. Hepatic and renal dysfunction : jaundice, elevated liver enzymes, oliguria, or anuria. Shock CLINICAL FEATURES

8. 1. Enteric Fever Caused by – S. Typhi , S. Paratyphi A.B,C C haracteristic typhoid ulcers Complications : i ) Intestinal perforation ii) Hemorrhage Clinical features Incubation period: 10–14 days S tep-ladder pyrexia , abdominal pain, myalgia, headache, anorexia and diarrhea (more common than constipation) Rose spots Universities Press Pvt Ltd Fig. 20.7 Rose-coloured spots on the abdomen in a case of typhoid ( Source: Centres for Disease Control and Prevention [CDC], Public Health Image Library [PHIL], Image ID 2214)

9. Laboratory Diagnosis Specimens: Blood – BHI Broth/ BacT /Alert U rine – MacConkey agar Biochemical Identification – Catalase(+) , oxidase(+) , indole(-) , citrate(+/-) , urease(-) , TSI(K/A, gas +) Feces culture: Selenite F and tetrathionate broth are the enrichment media Serotyping by agglutination Serology- Widal test: A gglutination tests to detect H and O agglutinins for typhoid and paratyphoid fever Titres of TO >80 and TH >160: Indicative of early infection Demonstration of a rise in titre: M ore meaningful Universities Press Pvt Ltd Fig. A typical culture medium for Salmonella on xylose lysine deoxycholate (XLD) media (on the left) and Salmonella-Shigella (SSA) agar (on the right)

10. 2. SCRUB TYPHUS Caused by Orientia tsutsugamushi (Rickettsia) Occurs in scrub vegetation where low lying trees and bushes are found. Vector - Bite of infected tromviculid mites of genus Leptotrombidium Larva(chiggers) are the only stage that feed on humans. Transmission - Occurs through transovarian route. Clinical Manifestation - Triad consist of – Eschar, regional lymphadenopathy and macupapular rash . Non specific manifestations – fever , headache,myalgia,cough and GIT symptoms . Complications encephalitis and interstitial pneumonia may occur rarely.

11. Serology - In primary infection IgM antibodies appear by the end of 1st week, and IgG by end of 2 nd week. Weil-Felix : Non specific ,detects high titer of heterophile antibodies . Indirect Immunofluorescence Antibody(IFA)- Considered as gold standard serological test. ELISA - Performed using 56– kDa recombinant major surface antigens. Cost effective and alternative to IFA . Molecular Test - PCR is developed in which targeting specific genes such as major 56-kDa gene, 46-kDa gene and 16S rRNA gene . Laboratory Diagnosis

12. 3. Clabsi (Central line associated blood stream infection) A central line is an intravascular device that terminates in the great vessels. It is needed for various purposes such as central venous pressure monitoring & administration of drugs, nutrition etc. A CLABSI is a primary BSI that develops in a patient with a CVC in place within the 48-hour period before onset of the BSI that is not related to infection at another site.

13. 4. Fungal candidemia Caused by Candida species. Clinical Manifestation- It includes- Mucocutaneous – Oral Candidiasis , Oesophagitis. Cutaneous- Candidal Granuloma Intertrigo. Systemic - Endocarditis, Meningitis and allergic diseases Lab Diagnosis: Samples : - whitish patches from mucous membrane of mouth and sputum Method of collection :- Sterile swabs Direct examination:- KOH wet mount, Gram staining and Other stains: PAS and Gomori’s methenamine silver stain and fungal cultures :- Sabouraud dextrose agar Biochemical tests :- Glucose and Maltose fermented with acid and gas production, sucrose and lactose not fermented Immunodiagnosis :- PCR based tests for candida – DNA detection and ELISA and PHA

14. 5. Infective endocarditis It is the infection of the endocardium. It is characterised by the presence of friable vegetation which is composed of platelets, fibrin, inflammatory cells and entrapped organism. It is mainly caused by viridans streptococci which is a normal inhabitant of oral cavity. It enter into the bloodstream through gingivitis, periodontitis or dental manipulation.

15. Lab Diagnosis of Infective Endocarditis Blood culture confirms diagnosis. Needs m ultiple blood cultures ( possibility of transient bacteraemia) P aired samples collected thrice (with a gap of one hour in between each collection), the total duration not exceeding 24 hours, is the ideal method Antigen detection M ultiplex PCR Echocardiography

16. LABORATORY DIAGNOSIS Specimen collection The blood should be collected before antimicrobial therapy. The skin is wiped with 70% isopropyl alcohol. Using sterile disposable syringe the blood is collected aseptically by veni -puncture. The blood volume is around 10-20 ml for adults and 1-5 ml for infants. The collected blood transported to the laboratory in anticoagulant containing tube. Heparin, EDTA are not used, because it inhibits the growth of organisms. Hence, Sodium polyanethol sulphonate (SPS) is a coagulant for blood culture.

17. BLOOD SPECIMEN COLLECTION STEPS

18. 2. Conventional Blood culture media It consists of nutrient broth and anticoagulant. It includes Trypticase soy broth, Brainheart infusion broth, Columbia or Brucella broth. Biphasic medium is used as a conventional culture medium. 3. Automated system i. BACTEC System BACTEC is a fully automated machine which consists of incubator, shaker and incubator. It consists of a glass permeable flourescene to measure Co2 produced by microorganisms. ii. BacT Alert It is based on the colorimetric detection of Co2. iii. Versa TREK System It is unique agitation system during blood culture inoculation

19. 4. Identification The isolated organism is identified by colony morphology, gram staining, biochemical reactions and serological tests.

20. OTHER TESTS Fig. 20.3 Approach to the diagnosis of bloodstream infections

21. Treatment Enteric Fever Scrub Typhus Fungal candidiasis Infective Endocarditis Ceftriaxone for empirical therapy Doxycycline Topical azole (Oral Thrush) Penicillin G Azithromycin orally 1gm for 5 days Chloramphenicol Oral Fluconazole (Esophageal candidiasis) Gentamycin Fluroquinolones eg.Ciprofloxacin Azithromycin Liposomal amphotericin B Ceftriaxone Drug Regimen for Infective Endocarditis- 1. REGIMEN FOR S.AUREUS IE FOR NATIVE VALVE IE: FOR MSSA ( METHICILLIN SUSCEPTIBLE S.AUREUS ) CLOXACILLIN OR NAFXCILLIN IS GIVEN FOR 6 WEEKS. FOR MRSA ( METHICILLIN RESISTANT S. AUREUS ) : VANCOMYCIN FOR 6 WEEKS . FOR PROSTHETIC VALVE IE: RIFAMPIN AND GENTAMICIN 2 . REGIMEN FOR VIRIDIANS STREPTOCOCCUS AND S. GALLOLYTICUS IE FOR NATIVE VALVE IE: PENICILLIN FOR 4 WEEKS FOR PROSTHETIC VALVE IE : GENTAMICIN FOR 6 WEEKS. 3 FOR HACEK ENDOCARDITIS - CEFTRIAZONE GIVEN FOR 4 WEEKS

22. Reference - Bailey & Scotts; Diagnostic Microbiology Anantanarayan & Paniker ; Textbook of Microbiology Apoorba S Sastry & Sandhya Bhatt; Essentials of medical microbiology