Time to positivity of blood culture is predictive for nosocomial infection and infectious endocarditis instead of other clinical characteristics and prognosis in Acintobacter baumannii bloodstream infection

Value of Time to Positivity of Blood Culture in Children with Bloodstream Infections

Objective

This study was to investigate the microbiological characteristics and the relationship between the time to positivity (TTP) of blood cultures and different bacterial species and to assess the clinical value of TTP in children with bloodstream infections (BSIs).

Methods

The TTP of all the blood cultures from children with suspected BSIs was retrospectively collected in 2016. The microbiological characteristics and the relationship between the TTP of blood cultures and different bacterial species were also analyzed.

Results

A total of 808 strains were isolated from 15835 blood cultures collected, and 145 (17.9%) were Gram-negative, 636 (78.7%) were Gram-positive, and 27 (3.3%) were fungi. The bacteria were divided into definite pathogens (174), possible pathogens (592), fungi (27), and contaminants (15). The average TTP of all positive blood cultures was 30.97 and ranged from 3.23 h to 92.73 h. The TTP of Gram-negative strains was significantly shorter than that of Gram-positive strains (P < 0.001) and fungi (P = 0.032). The mean TTP for E. coli (15.60 h) was shortest within the group of Gram-negative isolates, and the mean TTP for Streptococcus (17.34 h) within the group of Gram-positive isolates. Significant difference of the TTP was detected in methicillin-resistant vs methicillin-susceptible S. aureus, extended-spectrum beta-lactamases (ESBLs) positive vs negative Enterobacteriaceae, and extensive drug-resistant and non-XDR A. baumannii. The median TTP in patients with BSI was significantly shorter than in those without it (P < 0.001). ROC curve analysis indicated that the TTP cutoff value of CoNS, S. aureus, E. coli, and K. pneumoniae was 22.72 h, 19.6 h, 18.58 h, and 16.43 h, respectively, with most sensitive and specific predictor of BSIs.

Conclusions

Our data acknowledged that TTP is a valuable index for the early prognosis of BSIs. TTP not only provides additional utility as a general predictor of bacteria with smear result but also provides the implication of drug-resistant organisms.

Evaluation of Polymyxin B Susceptibility Profile and Detection of Drug Resistance Genes among Acinetobacter Baumannii Clinical Isolates in Tehran, Iran during 2015-2016

Acinetobacter baumannii is an important opportunistic pathogen, responsible for approximately 10% of all gram-negative nosocomial infection. The aim of this study was to determine aminoglycoside and quinolone resistance genes and their antimicrobial susceptibility profile in the clinically A. baumannii. In this cross-sectional study, a total of 100 nonduplicative A. baumannii isolates were collected from different clinical samples. Antimicrobial susceptibility test was performed by disk diffusion method. QnrA, anrB, qnrS, aac(3)-IIa, and aac(6')-Ib genes were identified using PCR method. The results of antibiotic susceptibility test showed that polymyxin B was the most effective antimicrobial against A. baumannii. 97%, 95% and 82% of isolates were resistant to cefepime, ceftriaxone, and amikacin, respectively. The molecular distribution of aac(3)-IIa, aac(6')-Ib, and qnrA genes were 45%, 50%, and 50% of isolates, respectively. However, qnrB and qnrS genes could not be detected in any strain. This study showed that polymyxin B was the best drug against A. baumannii clinical isolates. This data is also valid for polymyxin E (colistin), which is mostly used in clinics. There is a high level of resistance genes among clinical A. baumannii isolates. This high prevalence rate highlights the necessity for the development of rapid diagnostic assays and continuous monitoring of antibiotic resistance.