Infectious Disease Alert Updates
By Carol A. Kemper, MD, FACP
Clinical Associate Professor of Medicine, Stanford University, Division of Infectious Diseases, Santa Clara Valley Medical Center
Bloodstream Infections During COVID-19
SOURCE: Zhu N, Rawson TM, Mookerjee S, et al. Changing patterns of bloodstream infections in the community and acute care across two COVID-19 epidemic waves: A retrospective analysis using data linkage. Clin Infect Dis 2021;Oct 1:ciab869. doi: 10.1093/cid/ciab869. [Online ahead of print].
These authors at the Imperial College Hospital and School of Public Health in London examined patterns of bloodstream infection (BSI), hospital stay, and mortality before and during two waves of COVID-19 between January 2020 and February 2021. The first major wave peaked in April 2020 and the next major wave, which was more serious and deadlier, began in the fall of 2020, peaking in January 2021. During both major pandemic waves in London, hospital personnel and supplies were stretched thin, despite suspension of elective admissions during peak COVID-19 activity, and laboratory support services were truncated.
For the purposes of this analysis, a positive bloodstream infection was defined as two positive cultures with the same species within a 24-hour period; single cultures and those with skin commensals were regarded as contaminates. Positive cultures taken within 48 hours of admission were regarded as community-acquired BSI, and those obtained > 48 hours after admission were considered hospital-onset BSI.
In total, 34,044 blood cultures were obtained in 19.9% of admissions; blood cultures were obtained in 59.9% of those admitted to the intensive care unit (ICU). Despite a decrease in the number of total hospital admissions by 65% during the surges, mostly due to suspension of elective activities, blood cultures were obtained at a rate nearly double that of pre-COVID, up from 86.8/1,000 patient days pre-COVID to 150.7/1,000 patient days during both COVID surges. Of these, 6.8% of blood cultures had bacterial and/or fungal growth, one-third of which were from ICU patients.
Increases in both contaminated and non-contaminated blood cultures were observed during both COVID surges. Coagulase-negative Staphylococcus were isolated in 47.8% of cultures during both surges, up from 24.8% pre-COVID; and overall, 41.3% of cultures were considered contaminated during both surges, up from 31.5% pre-COVID. A total of 1,250 true-positive blood cultures occurred in 1,047 BSI, including 653 (62.4%) community acquired and 394 (37.4%) hospital acquired. Despite the decrease in hospital admissions, hospital-onset BSI increased from 97.3/100,000 patient days pre-COVID to 132.8/100,000 and 190.9/100,000 during the first and second surge, respectively. For those patients in the ICU, the rate of hospital-onset BSI increased from 101.3/100,000 patient days pre-COVID to 421/100,000 patient days during the second wave — a 400% increase.
The rate of hospital-onset BSI was 170.2/100,000 and 90.1/100,000 in those with and without COVID infection, respectively (P < 0.05). The largest observed increase in hospital-acquired bloodstream pathogens was due to methicillin-resistant Staphylococcus aureus (MRSA), up from 0.8 pre-COVID to 4.9 during the first wave and 6.0 during the second wave (per 100,000 patient days).
During both surges, patients with hospital-acquired BSI had an all-cause hospital mortality of 32.1% (101/314), up 24% from that pre-COVID. Length of stay was on average 20.2 days longer in patients with hospital-acquired BSI.
The authors believe that both the increased rate of contaminated cultures and the increase in hospital-acquired BSI can be directly traced to the impact of both COVID surges on the hospital system, with disruptions in care and breakdown of usual infection prevention practices. The severity of illness, prolonged hospital stays, use of mechanical ventilation, and use of immune-modulating agents in people with COVID also may have contributed to the observed increases in hospital-acquired BSI and attendant mortality.
Ventilator-Associated Pneumonia and Probiotics
SOURCE: Johnstone J, Meade M, Lauzier F, et al. Effect of probiotics on incident ventilator-associated pneumonia in critically ill patients. A randomized clinical trial. JAMA 2021;326:1024-1033.
This double-blind randomized study using probiotics in patients requiring mechanical ventilation was conducted at 44 different intensive care units (ICUs) throughout Canada, the United States, and Saudi Arabia from 2013-2019 (pre-COVID). The primary objective of the study was the reduction of ventilator-associated pneumonia (VAP), as well as secondary outcomes, including frequency of diarrhea, incidence of Clostridioides difficile enterocolitis, total use of antimicrobials, length of stay, and adverse events. All outcomes were reviewed by blinded adjudicants; VAP was defined as a new progressive or persistent infiltrate on chest radiograph more than two days following mechanical ventilation with at least two of the following: fever, leukocytosis, or purulent sputum.
Adults older than 18 years of age requiring mechanical ventilation for > 72 hours were randomized to receive (1:1) enteral Lactobacillus rhamnosus GG (LRGG) or an identical enteral placebo (1 × 1010 colony forming units) daily during study. Exclusion criteria included those already receiving mechanical ventilation for > 72 hours, immune suppression or receipt of chemotherapy in the previous three months, human immunodeficiency virus infection, severe acute pancreatitis, or requirement for percutaneous enteral feedings.
A total of 2,653 participants were enrolled, with an average age of 59.8 years; 40% were female. At baseline, all of the participants were intubated/requiring mechanical ventilation, 61% required pressor support, and 8% required dialysis or renal substitute. In all, 70.8% were admitted to the ICU with an active infection, including 59.5% with pneumonia, and 82.5% were receiving antibacterials. Participants received LRGG for a median of nine days. Their median length of mechanical ventilation was seven days, and the median ICU stay was 12 days.
No statistically significant difference was observed in the primary outcome of VAP or in any of the secondary outcomes between the two groups. VAP developed in 21.9% of those receiving LRGG compared with 21.3% of those not receiving it (P = NS). Diarrhea occurred in 81.4% of study participants, with no difference between the two groups. C. difficile infection occurred in 2.4% of those receiving LRGG vs. 2.1% of controls (P = NS). Sixteen patients had positive cultures for Lactobacillus from a sterile site (or the predominant organism from a non-sterile site), including 11 bloodstream infections, one liver abscess, two abdominal infections, one urinary infection, and one pleural infection. Twelve isolates were available for sequencing and were LRGG.
Administration of LRGG probiotic in this critically ill patient group did not appear to reduce the occurrence of VAP, antibiotic-associated diarrhea, or risk of C. difficile infection compared with blinded placebo. A rate of VAP infection may have been helpful in this study; the overall observed frequency of VAP was high in both probiotic and placebo groups. Complicating LRGG infection was observed in 1.1% of those receiving the probiotic for a median of nine days.
Simplified Recommendations for Pneumococcal Vaccination
SOURCE: Kobayashi M, Farrar JL, Gierke R, et al. Use of 15-valent pneumococcal conjugate vaccine and 20-valent pneumococcal conjugate vaccine among U.S. Adults; Updated recommendations of the Advisory Committee on Immunization Practices — United States, 2022. MMWR Morb Mortal Wkly Rep 2022;71:109-117.
Something this year actually got easier. On Oct. 20, 2021, the Advisory Committee on Immunization Practices (ACIP) recommended a simpler approach to pneumococcal vaccination of adults in hopes that vaccine coverage would improve. They spent the last year reviewing the epidemiology of pneumococcal disease from 2007-2019 and the available data for the use of the newer 20-valent pneumococcal conjugate vaccine (PCV20) and the 15-valent pneumococcal conjugate vaccine (PCV15). The findings of the Working Group are summarized in this MMWR publication. (See Table 1.)
Table 1. 2022 Revised Recommendations for Pneumococcal Vaccination in Adults
Adults ≥ 65 years of age with no history of pneumococcal vaccine or whose history is unknown
One dose of of PCV20 OR one dose of PCV15 followed by a dose of PPSV23 ≥ one year later
Adults 19-64 years of age with underlying medical conditions or other risk factors (see list)
(Risk factors: Alcoholism, chronic heart disease, chronic liver disease, chronic lung disease, cigarette smoking, diabetes mellitus, cochlear implant, cerebrospinal fluid leak, congenital or acquired asplenia, sickle cell disease or other hemoglobinopathies, chronic renal failure, congenital or acquired immunodeficiencies, generalized malignancy, human immunodeficiency virus infection, Hodgkin disease, iatrogenic immunosuppression, leukemia, lymphoma, multiple myeloma, nephrotic syndrome, solid organ transplant)
One dose of PCV20 OR one dose of PCV15 followed by a dose of PPSV23 ≥ one year later
Previously, the recommendations varied by age and risk group, as well as previous vaccine status, with complicating booster doses. Now, the recommendations are for one dose of PCV20 OR one dose of PCV15 followed by the 23-valent pneumococcal polysaccharide vaccine (PPSV23). The key here is — go ahead and give vaccine, even if the previous vaccine history is unknown. The group also considered recommending vaccination for all adults > 50 years of age, but this idea was rejected for several reasons, including concerns about waning vaccine immunity with advancing age.
Bloodstream Infections During COVID-19; Ventilator-Associated Pneumonia and Probiotics; Simplified Recommendations for Pneumococcal Vaccination
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