Blood Stream Infections Lecture Notes PDF

G A L A L A U N I V E R S I T Y T H E F U T U R E S T A R T S H E R E Blood stream infections D r. R a s h a S h a l a b y T H E F U T U R E S T A R T S H E R...

G A L A L A U N I V E R S I T Y T H E F U T U R E S T A R T S H E R E Blood stream infections D r. R a s h a S h a l a b y T H E F U T U R E S T A R T S H E R E  Bloodstream infections; 2 types Health care–acquired blood stream infections (HA-BSIs): defined as infection occurring in a patient in a hospital or other health care facility > 48 hours post-admission (positive blood culture) Include device-associated infections (DAIs) such as central line–associated bloodstream infections (CLA-BSIs). Community-acquired bloodstream infections (CA-BSIs) defined as an infection that occurs in the community or before 2 days of admission to the healthcare facility or hospitalization. M Tille, Patricia. "Bailey & Scott’s Diagnostic Microbiology Fourteenth Edition." (2017), Chapter 67 E5ology of bloodstream infec5ons All major groups of microbes can be present in the bloodstream during the course of many diseases: Bacterial Fungal Viral Parasitic M Tille, Patricia. "Bailey & Scott’s Diagnostic Microbiology Fourteenth Edition." (2017), Chapter 67 Types of bloodstream Infections; continued Intravascular Extravascular originate within the bacteria entering the blood cardiovascular system. circulation through the lymphatic system from another site of infection. primary site of infection is the when organisms multiply at a bloodstream. local site of infection such as the lung, they are drained by the lymphatics and reach the bloodstream. M Tille, Patricia. "Bailey & Scott’s Diagnostic Microbiology Fourteenth Edition." (2017), Chapter 67  Bacteremia Defined as the presence of bacteria in the bloodstream. Bacteremia may be transient, continuous, or intermittent. Transient (asymptomatic and a result of a procedure associated with a nonsterile anatomic site) e.g., ØPeople having dental procedures have had oral microbiota gain entry to the bloodstream through breaks in the gums. ØManipulation of infected tissues ØDevices or instrumentation inserted through contaminated mucosal surfaces ØSurgery involving nonsterile sites. M Tille, Patricia. "Bailey & Scott’s Diagnostic Microbiology Fourteenth Edition." (2017), Chapter 67  Bacteremia; continued The most common portals of entry for bacteremia are the: Genitourinary tract (25%) Respiratory tract (20%) Abscesses (10%) Surgical wound infections (5%) Biliary tract (5%) M Tille, Patricia. "Bailey & ScoH’s DiagnosIc Microbiology Fourteenth EdiIon." (2017), Chapter 67  G A L A L A U N I V E R S I T Y T H E F U T U R E S T A R T S H E R E Intravenous catheter–associated infections T H E F U T U R E S T A R T S H E R E  IV catheters are an integral part of the care for many hospitalized patients. For example, central venous catheters are used to administer fluids, medications, antibiotics, and nutrition and for hemodynamic monitoring. M Tille, Patricia. "Bailey & Scott’s Diagnostic Microbiology Fourteenth Edition." (2017), Chapter 67  A major consequence of these medical devices is colonization of the catheter, either bacteria or fungi, which can lead to catheter infection and a serious bloodstream infection. Triple-lumen (channel opening within a tube) central venous catheter M Tille, Patricia. "Bailey & Scott’s Diagnostic Microbiology Fourteenth Edition." (2017), Chapter 67 IV catheter–associated bacteremia (or fungemia) Occur primarily by two routes. Route 1 (extraluminal spread): involves the movement of organisms from the catheter entry site through the patient’s skin and down the external surface of the catheter to the catheter tip within the bloodstream. After arriving at the tip, the organisms multiply and may cause a bacteremia. M Tille, Patricia. "Bailey & Scott’s Diagnostic Microbiology Fourteenth Edition." (2017), Chapter 67  Route 2 (intraluminal spread): by migration of organisms along the inside of the catheter (the lumen) to the catheter tip. The catheter’s hub, where the tubing connects into the IV catheter, is considered the site at which organisms gain access to the patient’s bloodstream through the catheter lumen. M Tille, Patricia. "Bailey & Scott’s Diagnostic Microbiology Fourteenth Edition." (2017), Chapter 67  Microbial etiology The most common e*ologic agents for IV catheter–associated bloodstream infec*ons, regardless of the route of infec*on, are organisms found on the skin. M Tille, Patricia. "Bailey & Scott’s Diagnostic Microbiology Fourteenth Edition." (2017), Chapter 67 Pathophysiology  G A L A L A U N I V E R S I T Y T H E F U T U R E S T A R T S H E R E Fungal blood stream infections T H E F U T U R E S T A R T S H E R E  Fungemia (the presence of fungi in blood) Serious condition. Occurring primarily in immunosuppressed patients and in those with serious or terminal illness. Candida albicans is by far the most common species isolated from bloodstream infections M Tille, Patricia. "Bailey & Sco4’s Diagnos:c Microbiology Fourteenth Edi:on." (2017), Chapter 62  Genus Candida Morphology: oval yeast with a single bud Candida albicans ØIs a species member of the genus Candida ØIt is part of the normal flora of mucous membranes of the upper respiratory, gastrointestinal, and female genital tracts. ØIs a human opportunist pathogen that can grow as yeast, pseudohyphae, or true hyphae in vitro and in vivo, depending on environmental conditions. ØIn tissues, it appears most often as yeasts Light microscopy image showing or as pseudohyphae. Gram-positive yeast cells with pseudohyphae M Tille, Patricia. "Bailey & Scott’s Diagnostic Microbiology Fourteenth Edition." (2017), Chapter 62 Pseudohyphae - resemble elongated yeast cells that remain attached to one another - show a constriction between adjacent cellular compartments True hyphae consist of long tubes with parallel sides and no constrictions. Light microscopy image  Candida spp. are responsible for the most commonly encountered opportunisDc fungal infecUons. Currently, Candida spp. are the fourth most common cause of hospital-acquired bloodstream infecUons (BSIs) in the United States, and a mortality rate as high as 50%. C. albicans is the most commonly isolated yeast, but other, emerging species include Candida glabrata, Candida parapsilosis, Candida tropicalis, and Candida krusei M Tille, Patricia. "Bailey & Scott’s Diagnostic Microbiology Fourteenth Edition." (2017), Chapter 62 Pathophysiology of invasive candidiasis 1- Adherence to the surface before infection. 2- C. Albicans produce proteases leading to an increased ability to cause invasive disease. 3- Ability to undergo phenotypic switching (i.e., the ability to produce pseudohyphae and hyphae). C. albicans is capable of switching to a filamentous form, permitting other pathogenic organisms to set in the filaments and forming a polymicrobial matrix or biofilm. Candida spp. are able to form biofilm (an extracellular polysaccharide material) that permits hematogenous spread of the organism and provides a high level of antibiotic resistance. Pathogenesis of invasive candidiasis Pappas, P. G. et al. (2018) Invasive candidiasis Nat. Rev. Dis. Primers doi:10.1038/nrdp.2018.26 Diagnostic techniques Blood culture remains the gold standard for diagnosis of invasive candidiasis. Drug susceptibility testing Pappas, P. G. et al. (2018) Invasive candidiasis Nat. Rev. Dis. Primers doi:10.1038/nrdp.2018.26 Management two clinical interventions are essential to the successful management of invasive candidiasis: Source control: the elimination of the suspected focus of infection, such as removal of contaminated intravascular catheters and effective drainage of collections of infected material, for example, peritoneal fluid, pleural fluid and/or abscess material. Early effective systemic antifungal treatment. Pappas, P. G. et al. (2018) Invasive candidiasis Nat. Rev. Dis. Primers doi:10.1038/nrdp.2018.26  References: Pappas, Peter G., et al. "Invasive candidiasis." Nature Reviews Disease Primers 4.1 (2018): 1-20 M Tille, Patricia. "Bailey & Scott’s Diagnostic Microbiology Fourteenth Edition." (2017), Chapters 62 & 67 THANK YOU