A guideline identifying when inpatients with penicillin or cephalosporin antibiotic allergy labels (PCAAL) can receive β-lactam antibiotics increased β-lactam receipt at a large northeastern US health care system.
To report outcomes of implementing a similar guideline and electronic order set (OS) at an independent academic health care system.
Penicillin/cephalosporin receipt (percentage of inpatients receiving full doses) and alternative antibiotic use (days of therapy per 1000 patient-days [DOT/1000PD]) were compared over 3 periods before (February 1, 2017, to January 31, 2018) and after guideline implementation (February 1, 2018, to January 31, 2019), and after OS implementation (February 1, 2019, to January 31, 2020) among inpatients with PCAAL admitted on medical services with access to guideline/OS and education (Medical-PCAAL, n = 8721), surgical services with access to guideline/OS without education (Surgical-PCAAL, n = 5069), and obstetrics/gynecology services without interventions (Ob/Gyn-PCAAL, n = 798) and inpatients without PCAAL admitted on the same services (Medical-No-PCAAL, n = 50,840; Surgical-No-PCAAL, n = 29,845; Ob/Gyn-No-PCAAL, n = 6109). χ2 tests were used to compare categorical variables, and analysis of variance was used to compare continuous and interrupted time series analyses (ITSA) to investigate the guideline/OS implementation effect on penicillin/cephalosporin receipt.
In the Medical-PCAAL group, penicillin/cephalosporin receipt increased (58%-68%, P < .001), specifically for cefazolin (8%-11%, P = .02) and third- to fifth-generation cephalosporins (43%-48%, P = .04), and aztreonam use decreased (12 DOT/1000PD, P = .03). In the Medical-No-PCAAL group, penicillin/cephalosporin receipt increased (88%-90%, P = .004), specifically for penicillin (40%-44%, P < .001), without changes in aztreonam use. Significant changes were not observed in these outcomes on surgical or obstetrics/gynecology services. Per ITSA, guideline/OS implementation was associated with increased penicillin/cephalosporin receipt in the Medical-PCAAL group only.
Guideline and OS implementation was associated with improved antibiotic stewardship on inpatient services that also received allergy education.

Pseudomonas aeruginosa is related to nosocomial infections, and it tends to become resistant during or after antimicrobial treatment. The ability to develop carbapenems resistance makes it difficult to treat. P. aeruginosa infections are often associated with high mortality, morbidity and treatment costs. A group of Chinese experts drafted a consensus for treatment of extensively drug-resistant Gram-negative bacilli (XDR-GNB) including extensively drug-resistant P. aeruginosa (XDR-PA). In this study, we studied the antibacterial activities of different antibiotic combinations against six carbapenems-resistant P. aeruginosa (CRPA) strains in vitro, and the results indicated that the combination of ceftazidime with cefoperazone-sulbatam was the best combination with excellent synergistic rate (100%). Besides, some combinations exhibited better effects than using antibiotics alone, reducing the MICs of both drugs significantly, such as ceftazidime/piperacillin-tazobactam and ceftazidime/aztreonam etc. However, there are also some combinations that showed no additional or synergistic effects, suggesting that not all combinations recommended by the guideline have the same effect against resistant P. aeruginosa. Our study screened out some effective combinations against six CRPA strains which might help to prevent the spread of antibiotic resistance through improving antibiotic effectiveness. SIGNIFICANCE AND IMPACT OF THE STUDY: This study measured the synergistic interactions between various antibiotics in vitro recommended by Chinese consensus statement against carbapenems-resistant Pseudomonas aeruginosa. The results of this study provide valuable evidence that some combinations may be a promising option for clinical treatment.

UNASSIGNED: Patients reporting penicillin allergy often receive unnecessary and costly broad-spectrum alternatives such as aztreonam with negative consequences. Penicillin allergy testing improves antimicrobial therapy but is not broadly used in hospitals due to insufficient testing resources and short-term expenses. We describe a clinical decision support (CDS) tool promoting pharmacist-administered penicillin allergy testing in patients receiving aztreonam and its benefits toward antimicrobial stewardship and costs.
UNASSIGNED: A CDS tool was incorporated into the electronic medical record, directing providers to order penicillin allergy testing for patients receiving aztreonam. An allergy-trained pharmacist reviewed orders placed through this new guideline and performed skin testing and oral challenges to determine whether these patients could safely take penicillin. Data on tests performed, antibiotic utilization, and cost-savings were compared with patients tested outside the new guideline as part of our institution\'s standard stewardship program.
UNASSIGNED: The guideline significantly increased penicillin allergy testing among patients receiving aztreonam from 24% to 85% (P < .001) while reducing the median delay between admission and testing completion from 3.31 to 1.05 days (P = 0.008). Patients tested under the guideline saw a 58% increase in penicillin exposure (P = .046). Institutional aztreonam administration declined from 2.54 to 1.47 administrations per 1000 patient-days (P = .016). Average antibiotic costs per patient tested before and after CDS decreased from $1265.81 to $592.08 USD, a 53% savings.
UNASSIGNED: Targeting penicillin allergy testing to patients on aztreonam yields therapeutic and economic benefits during a single admission. This provides a cost-effective model for inpatient testing.

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In vitro activity of aztreonam was compared with that of ceftazidime, cefotaxime, cefoperazone, piperacillin, and ticarcillin against 656 representative bacterial pathogens. Aztreonam was not active against gram-positive cocci but was as active as the third-generation cephalosporins against the Enterobacteriaceae, Haemophilus influenzae, and Neisseria gonorrhoeae. Additional data for 5,262 gram-negative bacilli isolated in four separate medical centers documented the low incidence of resistance to aztreonam; 97.2% of 4,312 isolates of Enterobacteriaceae and 79% of 854 isolates of Pseudomonas aeruginosa were inhibited by less than or equal to 8.0 micrograms of aztreonam/ml. Additional studies confirmed the stability of aztreonam in the presence of seven different beta-lactamases. For disk-diffusion susceptibility tests, 30-micrograms disks are recommended, with interpretive breakpoints of less than or equal to 15 mm for resistance (MIC greater than or equal to 32 micrograms/ml), 16-21 mm for intermediate susceptibility (MIC, 16 micrograms/ml), and greater than or equal to 22 mm for susceptibility (MIC less than 8.0 micrograms/ml). For quality control of tests with 30-micrograms disks, zone-size limits for Escherichia coli (ATCC 25922) should be 28-36 mm and those for P. aeruginosa (ATCC 27853) should be 23-29 mm.

Carumonam 30-microgram disk diffusion tests with 342 gram-negative organisms suggested modifying earlier interpretive zone criteria, i.e., a susceptibility zone diameter of greater than or equal to 23 mm (less than or equal to 8.0 micrograms/ml MIC correlate) and a resistance zone diameter of less than or equal to 17 mm (greater than or equal to 32 micrograms/ml MIC correlate). Quality assurance guidelines were determined by multilaboratory investigations. Recommended limits were calculated for the gram-negative quality control organisms only. For Escherichia coli ATCC 25922, the recommended limits are 30 to 36 mm and 0.03 to 0.25 micrograms/ml, and for Pseudomonas aeruginosa ATCC 27853, they are 24 to 32 mm and 1.0 to 4.0 micrograms/ml.