Bacteremia


Article Author:
David Smith


Article Editor:
Sara Nehring


Editors In Chief:
Sebastiano Cassaro
Joseph Lee
Tanya Egodage


Managing Editors:
Avais Raja
Orawan Chaigasame
Carrie Smith
Abdul Waheed
Khalid Alsayouri
Trevor Nezwek
Radia Jamil
Patrick Le
Anoosh Zafar Gondal
Saad Nazir
William Gossman
Hassam Zulfiqar
Hussain Sajjad
Steve Bhimji
Muhammad Hashmi
John Shell
Matthew Varacallo
Heba Mahdy
Ahmad Malik
Sarosh Vaqar
Mark Pellegrini
James Hughes
Beata Beatty
Beenish Sohail
Nazia Sadiq
Hajira Basit
Phillip Hynes


Updated:
11/15/2018 3:50:00 PM

Introduction

Bacteremia in the strictest sense refers to viable bacteria in the blood. Asymptomatic bacteremia can occur in normal daily activities such as conducting oral hygiene and after minor medical procedures. In a healthy person, these clinically benign infections are transient and cause no further sequelae. However, when immune response mechanisms fail or become overwhelmed, bacteremia becomes a bloodstream infection which can evolve into many clinical spectrums and is differentiated as septicemia. Untreated and clinically significant bacteremia progresses to systemic inflammatory response syndrome (SIRS), sepsis, septic shock, and multiple organ dysfunction syndrome (MODS). [1][2][3]

Etiology

Determining the primary source of infection is critical in the management of a patient with bacteremia, as well as in the identification of the affected patient population. Common sources in hospitalized patients include the respiratory tract and indwelling catheters, specifically central venous catheters. Untreated urinary tract infections most commonly cause community-acquired bacteremia. Soft tissue and intraabdominal infections are not as common and are more prevalent in the post-operative surgical setting. Escherichia coli is the most common cause of gram-negative associated bacteremia, while Staphylococcus aureus is the most common gram-positive organism.[4][5][6]

Epidemiology

 Geographic region, patient population, drug resistance, and infection prevention practices at each institution drive the causative organisms of bloodstream infections. Taking into account that older patients with multiple comorbidities are more likely to reside in community centers and be hospitalized, it is no surprise that they are at an increased risk of developing bacteremia. Traditionally gram-negative bacilli were the driving force for most hospital-acquired bloodstream infections in the United States and are still the most common organism associated with community-acquired bacteremia. However, with the onset of an aging population and device-related procedures, gram-positive aerobes have seen an increase in prevalence over the last two decades. [3][7][8]

Pathophysiology

All bacterial infections are dependent on the host immune system which is affected by its genetic signature, as well as congenital and acquired deficiencies. Cellular innate and adaptive immune responses are responsible for initial microbe clearance, while the liver and spleen filter active bacteria in the circulating blood. In its most basic form bacteria will begin to colonize at its primary source of location. At this point, the bacteria may become transient and clinically insignificant or can escape the host immune response and increase in number and become a local infection that can eventually migrate to other parts of the body. If the bacteria are viable and enter the circulating bloodstream, the infection still may spontaneously clear or progress to septicemia. The first barrier to bacterial invasion is the skin and mucosal surfaces. Conditions which interfere with these natural defense barriers commonly include medical procedures that pass through the skin and anatomical lumina. Additionally, events can precipitate defense breakdown via trauma, burns, ulcers, and the natural elements of aging.[6]

History and Physical

The classical presentation in a bacteremic patient is the presence of a fever. Chills and/or rigors do not need to present; however, the presence of such signs should clue the provider that a febrile patient is now bacteremic. The development of septicemia leading to sepsis and septic shock will commonly cause hypotension, altered mental status,  and decreased urine output due to hypovolemia from leaking capillaries. As the infection disseminates, other organs can become affected causing acute respiratory distress syndrome (ARDS) and acute kidney injury (AKI).

Evaluation

Identifying or presuming the source of infection will dictate the diagnostic measures taken. There should be a low threshold for ordering labs and imaging since time is of the essence in preventing septicemia. Initial labs in all presumed bacteremic patients should include a lactate level and blood cultures; ideally two sets assessing for aerobic and anaerobic organisms from each arm. In the hospital setting, most patients at a minimum will require a chest x-ray and urinalysis with culture. A surgical patient may require CT imaging of the location of their surgery to assess for abscess or collection formation, as well as wound cultures for surgical site infections. Likewise, an intubated or patient presenting with the pulmonary disease will require sputum cultures. Patients with indwelling venous catheters, hemodialysis catheters, or ports should have their lines removed and tips cultured.[9][10]

Treatment / Management

Bacteremia requires urgent and appropriate antibiotics. Delay in the administration of appropriate antibiotics is associated with increased morbidity and mortality. Empiric antibiotics should follow a logical approach based on the patient's history and current disposition, for example, is the infection community or hospital acquired, what is the patient's recent healthcare exposure, recent medical or surgical treatment, and what is the local antibiotic resistance. Gram stain, if applicable. Before a Gram stain is finalized, all patients should receive broad-spectrum antibiotics covering gram-positive and gram-negative bacteria which include extended-generation cephalosporins or a beta-lactamase inhibitor. Pseudomonas coverage is applicable for hospital-acquired bacteremia, as well as in a patient with recent health care exposure. Additionally, vancomycin should be added to cover resistant gram-positive organisms most notably methicillin-resistant resistant Staphylococcus aureus (MRSA). When the practitioner obtains the final cultures, antibiotics should be titrated to directed therapy starting with the gram stain, and eventually, antimicrobial susceptibility. There is no optimal duration of treatment. In most cases, antibiotic treatment should continue for seven to 14 days and should always be administered parenterally. Oral agents are recommended when patients have been afebrile for at least 48 hours and are otherwise clinically stable.[11][12][13]

Complications

  • Meningitis
  • Endocarditis
  • Osteomyelitis
  • Sepsis
  • Cellulitis
  • Peritonitis

Consultations

Infectious disease consultant

Enhancing Healthcare Team Outcomes

As with most infectious diseases, preventive practice is critical in the outpatient and inpatient setting. All healthcare workers play an important role in the prevention of bacterial infections in the workplace. At the most rudimentary level, basic hand hygiene and the adherence to clean and sterile techniques is critical in preventing and decreasing the prevalence of bloodstream infections. Preventative practice starts not only at the beginning of a procedure but also throughout daily maintenance of line care. Even with strict adherence to infection control, many patients will succumb to a blood stream infection. Recognizing the predominant organisms associated within each clinical setting can prevent mortality as blood stream pathogens such as S. aureus, Pseudomonas aeruginosa, and Enterobacter species are associated with a higher mortality rate. Prevention also includes judicious use of antibiotics which must take into effect the risk and reward of antibiotic use. The rising prevalence of multi-drug-resistant bacteria has complicated treatment over the years and will continue to do so. This rise makes education, prevention, and adherence to protocol a necessity to counter the debilitating effects of bloodstream infections. Patient isolation, preventing airborne and contact infections are also key factors that must be controlled. Today, all healthcare facilities have an infectious disease committee which oversees the use of antibiotics, prescribing habits of healthcare providers and ensures that invasive and other bedside procedures are done under sterile conditions. The key to lowering the morbidity of bacteremia is the education of the healthcare provider. [3][14][15](Level V)

Outcomes

Patients with bacteremia who are treated with antibiotics or observed have good outcomes. But rarely the bacteremia may cause endocarditis, osteomyelitis, pneumonia, cellulitis, meningitis sepsis and multiorgan dysfunction, followed by death. Over the past four decades, the availability of better antibiotics and vaccination have resulted in lower mortality rates in people of all ages. Prior to the era of vaccination, the mortality rates from bacteremia were over 20%. Today, the biggest concern in the development of antibiotic resistance which is now common against most organisms. Many guidelines have been developed to manage children and seniors with fever and bacteremia, but the bottom line is that one should always be aware of the potential of harm if the observation is selected as a method of treatment.[16][17][18] (Level V)


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Bacteremia - Questions

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Review of a patient's clinical course reveals that at approximately 2 pm daily, the patient develops an abrupt temperature elevation to 39 C and a chill. Which of the following times would be the best to draw blood cultures from this patient?



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Which child is most susceptible to bacteremia?



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Which of the following skin manifestations is not associated with Pseudomonas bacteremia?



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What is the empiric therapy for a symptomatic patient with blood cultures positive for gram-positive cocci?



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Which of the following criteria would suggest 14 days of total antibiotic therapy would be sufficient in a bacteremic patient?



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A 72-year-old man was brought to the emergency department with a complaint of syncope while on a ladder outside his house that afternoon. He fell 8 feet backward but sustained only minor injuries. He was noted as diaphoretic with a fever of 101.2. With more questioning, he does admit to having a "tremor" off and on over the past few days and feeling dizzy at times. His wife reports that he has had a few episodes in the past 3 days where he was drenched in sweat. His blood cultures turned positive within a day. First, the anaerobic bottle grew "gram-variable rods" and the aerobic bottle grew "gram-positive cocci." At that point, he admitted to having a wound on his buttock that had purulent drainage from it that he had previously not disclosed to the medical staff. What is the most likely explanation for the gram-variable rods in his blood culture?



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A 43-year-old African American male has a recent history of acute renal failure that required placement of a tunneled catheter. It is still in place and being used. He is admitted to hospital for hypotension and fevers. Blood cultures have turned positive for coagulase negative Staphylococcus, 1 of 2 bottles. What is the significance of this finding?



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Bacteremia - References

References

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Dagasso G,Conley J,Parfitt E,Pasquill K,Steele L,Laupland K, Risk factors associated with bloodstream infections in end-stage renal disease patients: a population-based study. Infectious diseases (London, England). 2018 Aug 29     [PubMed]
Arcens M,Stirnemann J,Mayor G,John G, [Epidemiology and strategy to prevent urinary catheters related complications]. Revue medicale suisse. 2018 Aug 29     [PubMed]
Munro APS,Blyth CC,Campbell AJ,Bowen AC, Infection characteristics and treatment of Staphylococcus aureus bacteraemia at a tertiary children's hospital. BMC infectious diseases. 2018 Aug 10     [PubMed]
Antonio M,Gudiol C,Royo-Cebrecos C,Grillo S,Ardanuy C,Carratalà J, Current etiology, clinical features and outcomes of bacteremia in older patients with solid tumors. Journal of geriatric oncology. 2018 Jul 10     [PubMed]
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Lishman H,Costelloe C,Hopkins S,Johnson AP,Hope R,Guy R,Muller-Pebody B,Holmes A,Aylin P, Exploring the relationship between primary care antibiotic prescribing for urinary tract infections, Escherichia coli bacteraemia incidence and antibiotic resistance: an ecological study. International journal of antimicrobial agents. 2018 Aug 23     [PubMed]
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Arientová S,Beran O,Štefan M,Čurdová M,Holub M, Bacteremia due to Staphylococcus aureus - the importance of appropriate management. Epidemiologie, mikrobiologie, imunologie : casopis Spolecnosti pro epidemiologii a mikrobiologii Ceske lekarske spolecnosti J.E. Purkyne. 2018 Spring     [PubMed]
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Beeler C,Dbeibo L,Kelley K,Thatcher L,Webb D,Bah A,Monahan P,Fowler NR,Nicol S,Judy-Malcolm A,Azar J, Assessing patient risk of central line-associated bacteremia via machine learning. American journal of infection control. 2018 Sep     [PubMed]
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Mogle BT,Steele JM,Seabury RW,Dang UJ,Kufel WD, Implementation of a two-point pharmacokinetic AUC-based vancomycin therapeutic drug monitoring approach in patients with methicillin-resistant Staphylococcus aureus bacteremia. International journal of antimicrobial agents. 2018 Aug 31     [PubMed]
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