Sites of blood collection and topical antiseptics associated with contaminated cultures: prospective observational study

Sites of blood collection and topical disinfectants associated with contaminated cultures: An ambidirectional cohort study

Background

We aimed to determine whether puncture sites for blood sampling and topical disinfectants are associated with rates of contaminated blood cultures in the emergency department (ED) of a single institution.

Methods

This single-center, ambidirectional cohort study of 548 consecutive patients ≥20 years of age was performed in the ED of a university hospital in Japan over a 13-month period. Pairs of blood samples were collected for aerobic and anaerobic cultures from patients in the ED. Physicians selected puncture sites and topical disinfectants according to their personal preference.

Results

Potential contamination was identified in 110 of the 548 patients (20.1%). One hundred fourteen (20.8%) patients showed true-positive results for bacteremia, and 324 (59.1%) patients showed true-negative results. Multivariate analysis revealed more frequent contamination when puncture sites were disinfected with povidone-iodine (PVI) than with alcohol/chlorhexidine (ACHX) (adjusted risk difference, 19.1%; 95% confidence interval [CI]), 15.7-22.6; p < 0.001). In terms of blood collection sites, femoral and central venous (CV) catheter with PVI disinfection showed more frequent contamination than venous sites with ACHX (adjusted risk differences: 26.6%, 95% CI 21.3-31.9, p < 0.001 and 41.1%, 95% CI 22.2-59.9, p < 0.001, respectively).

Conclusion

Rates of contaminated blood cultures were significantly higher when blood was collected from the CV catheter or femoral sites with PVI as the topical disinfectant.

Equine blood cultures: Can we do better?

Blood culture is considered the gold standard test for documenting bacteraemia in patients with suspected bacterial sepsis in veterinary and human medicine. However, blood culture often fails to yield bacterial growth even though the clinical picture is strongly suggestive of bacterial sepsis, or contaminating organisms can overgrow the true pathogen, making accurate diagnosis and appropriate management of this life-threatening condition very challenging. Methodology for collecting blood cultures in equine medicine, and even in human hospitals, is not standardised, and many variables can affect the yield and type of microorganisms cultured. Microbiological culture techniques used in the laboratory and specific sample collection techniques, including volume of blood collected, aseptic technique utilised, and the site, timing and frequency of sample collection, all have substantial impact on the accuracy of blood culture results. In addition, patient-specific factors such as husbandry factors, the anatomical site of the primary infection, and changing microflora in different geographic locations, also can impact blood cultures. Thus, blood cultures obtained in practice may not always accurately define the presence or absence of, or specific organisms causing, bacteraemia in horses and foals with suspected sepsis. Erroneous blood culture results can lead to inappropriate antimicrobial use, which can result in poor outcomes for individual patients and contribute to the development of antimicrobial resistance in the patient's microflora and the environmental microcosm. This review summarises current indications and methodology, and specific factors that may be optimised, for equine blood culture, with particular focus on available literature from neonatal foals with suspected bacterial sepsis. To standardise and optimise blood culture techniques in horses and foals, future research in this area should be aimed at determining the optimal volume of blood that should be collected for culture, and the ideal site, timing, and frequency of sample collection.

Effect of the introduction of a management bundle for blood culture collection

BACKGROUND

Inappropriate blood collection subjected to blood culture (BC) causes BC contamination and may complicate the diagnose is of infectious diseases. Therefore, we developed a bundle based on the guideline recommendations for appropriate blood collection and examined the effects of bundle introduction.

METHODS

We performed a retrospective analysis of BC samples to determine the contamination rates before and after introducing the BC bundle. We also analyzed the correlation between the compliance rate of the bundle and contamination rate, and between each bundle element and contamination.

RESULTS

After the introduction of the bundle, the contamination rate was significantly reduced from 5.4% ± 0.9% to 1.7± 0.7% (P < .01). The compliance rate of the bundle was significantly associated with a lower contamination rate (P < .01). Multivariable logistic regression showed that collection from superficial veins of the cubital fossa (odds ratio [OR], 0.25; 95% confidence interval [CI], 0.13-0.51, P < .01) and disinfection of the skin at the blood collection site with 1% chlorhexidine alcohol swab (OR, 0.41; 95% CI, 0.25-0.68, P < .01) were significantly associated with lower contamination.

CONCLUSIONS

This study suggests that the introduction of the BC bundle significantly reduced the contamination rate, and bundle compliance was associated with a lower contamination rate.

High yield of blood cultures in the etiologic diagnosis of cellulitis, erysipelas, and cutaneous abscess in elderly patients

Background

Cellulitis is a common disease in the elderly, and detecting etiologic organisms with blood cultures is difficult because of the low positive rate and occasional skin contamination. Therefore, routine blood cultures are not recommended for uncomplicated cellulitis. However, it is unclear whether blood culture collection for the diagnosis of cellulitis in elderly patients is useful.

Methods

This single hospital–based observational study was performed between April 2012 and March 2015 in Okinawa, Japan. All enrolled patients were aged 15 years or older and admitted to the Division of Infectious Diseases with suspected cellulitis, erysipelas, and cutaneous abscess. Two routine sets of blood cultures were obtained.

Results

Two hundred and twenty-one patients were enrolled. The median age was 77 years. The proportion of bacteremia was 21.7% for all patients (48/221), 8.5% (4/47) for those <65 years, and 25.3% (44/174) for those ≥65 years old (P = .013). The skin contamination rate was 0.9% (2/221). The most common pathogen was Streptococcus dysgalactiae (62.5%). Gram-negative bacteremia not susceptible to cefazolin was detected in 8.3%. Cefazolin and ampicillin were the first- and second-most commonly used therapies. Anti–methicillin-resistant Staphylococcus aureus therapy was required in 3.6% of patients. In addition to age and severe infection, shaking chills and white blood count ≥13 000 cells/µL were independent risk factors of bacteremia.

Conclusions

Two routine sets of blood cultures are recommended for the precise diagnosis and appropriate treatment of cellulitis in elderly patients, especially in patients with shaking chills or leukocytosis.

Regression discontinuity of blood culture contamination rate after changing of disinfectants: retrospective observational study

Blood cultures are indispensable for detecting life-threatening bacteremia. Little is known about associations between contamination rates and topical disinfectants for blood collection in adults. We sought to determine whether a change in topical disinfectants was associated with the rates of contaminated blood cultures in the emergency department of a single institution. This single-center, retrospective observational study of consecutive patients aged 20 years or older was conducted in the emergency department (ED) of a university hospital in Japan between August 1, 2018 and September 30, 2020. Pairs of blood samples were collected for aerobic and anaerobic culture from the patients in the ED. Physicians selected topical disinfectants according to their personal preference before September 1, 2019; alcohol/chlorhexidine gluconate (ACHX) was mandatory thereafter, unless the patient was allergic to alcohol. Regression discontinuity analysis was used to detect the effect of the mandatory usage of ACHX on rates of contaminated blood cultures. We collected 2141 blood culture samples from 1097 patients and found 164 (7.7%) potentially contaminated blood cultures. Among these, 445 (20.8%) were true bacteremia and 1532 (71.6%) were true negatives. Puncture site disinfection was performed with ACHX for 1345 (62.8%) cases and with povidone-iodine (PVI) for 767 (35.8%) cases. The regression discontinuity analysis showed that mandatory ACHX usage was significantly associated with lower rates of contaminated blood cultures by 9.6% (95% confidence interval (CI): 5.0%–14.2%, P < 0.001). Rates of contaminated blood cultures were significantly lower when ACHX was used as the topical disinfectant.