Controlled comparison of bioMérieux VITAL and BACTEC NR-660 systems for detection of bacteremia and fungemia in pediatric patients

Evaluation of the Effects of Probiotics and Prebiotics on the Salmonella typhi Infections

Typhoid fever is one of the most commonly disseminated diseases and is considered to be linked to poor sanitation. It is responsible for 2-5% of all deaths, and its causative agent is Salmonella typhi. The current study aimed to investigate the antibacterial activity of prebiotics (inulin and starch) and probiotics against multidrug resistance of S. typhi bacterial isolates. Determination of the inhibitory effect of probiotics and prebiotics against S. typhi isolates was performed by agar well diffusion method and minimal inhibitory concentration. Body samples of all eligible patients were collected and cultured. Finally, 50 (25%) out of the total cultured samples were S. Typhi bacteria isolated from different samples. The bacteria were mainly found in blood, followed by stool and fluid (74%, 24%, and 2%, respectively). On differential medium, xylose lysine deoxycholate agar, the colonies appear red with black centers, while on MacConkey agar, the colonies appear smooth, pale, transparent, colorless, and raised. Regarding the inhibition zone values of bacteriocins of Lactobacillus from Yogurt against S. typhi in plate, significant differences were identified between the ones with and without prebiotic addition. Accordingly, the value of the inhibition zone for those without prebiotic addition (13.18±7.403) was significantly lower than that of cutoff values of 20 with a significant difference of -6.820 (t= -6.514, df 49, P=0.000). Moreover, the inhibition effect of prebiotics (inulin and starch) against S. typhi at 37 °C for 24 h in part dish glucose as control, only the mean of inulin was found to be significantly lower than that of the cutoff value of 18 with the mean difference of -3.900 (t=-4.115, df 49, P=0.000). Other prebiotics of glucose and starch in 24 h showed negative inhibition. Probiotics are live microorganisms that have beneficial host effects by enhancing microbial balance in the intestine, whereas prebiotics are indigestible food components having beneficial effects by enhancing the activity and growth of one or more colonic bacteria. Lactobacillus filtrates had considerable effects against the test S. typhi isolates.

Update on blood cultures: how to obtain, process, report, and interpret

The detection and identification of microorganisms circulating in the bloodstream of patients is arguably one of the most important functions of the clinical microbiology laboratory. Effective implementation of this function requires careful consideration of specimen collection and processing, culture techniques, result reporting, and, perhaps most importantly, result interpretation by the physician. The purpose of this review is to provide a synopsis of the current state of the art for each of these areas, with the intention of providing adequate information to enable clinical laboratory personnel and physicians to critically evaluate and, if required, improve their current blood culture practices.

Controlled evaluation of Bactec Peds Plus/F and Bactec lytic/10 anaerobic/F media for isolation of Salmonella enterica serovars typhi and paratyphi A from blood

We compared anaerobic lytic (AL) and pediatric aerobic resin-containing (Peds Plus/F) blood culture media for the isolation of Salmonella enterica serotype Typhi or Paratyphi A from children. The yields from AL and Peds Plus/F media were the same with equal volumes of blood, but recovery was faster from AL medium than Peds Plus/F medium (10.7 and 16.4 h, respectively) (P < 0.001).

Detection of group B streptococcal bacteremia in simulated intrapartum antimicrobial prophylaxis

The diagnostic value of negative blood cultures from neonates whose mothers receive intrapartum antimicrobial prophylaxis for prevention of perinatal group B streptococcal disease is uncertain. We investigated whether blood culture medium containing resin designed to adsorb antibiotic improved group B streptococcal detection following simulated intrapartum antimicrobial prophylaxis. Group B streptococcus (Streptococcus agalactiae) was preincubated with varying antibiotic concentrations before inoculation into BACTEC Peds Plus resin-containing medium, BACTEC Standard, or Trek ESP 80A. In the presence of 10 mcg/mL ampicillin, detection of both low (<500 CFU/mL) and high (>500 CFU/mL) S. agalactiae inocula ranged between 75-100% of resin-containing medium bottles; detection rates in both non-resin-containing media were lower. When S. agalactiae was detected, it was detected sooner with resin-containing medium. The addition of gentamicin to ampicillin did not affect sensitivity of resin-containing medium for S. agalactiae. In our model, resin-containing medium more consistently and more rapidly detected S. agalactiae than did either of two non-resin-containing media, in the presence of antibiotic levels likely present in fetal sera following intrapartum antimicrobial prophylaxis.

Evaluation of the VITAL (bioMérieux) automated blood culture system using blind subculture

OBJECTIVE

This study was performed to determine the ability of the VITAL system to detect and allow recovery of microorganisms that are difficult to grow, such as Brucella spp., yeasts, or anaerobes, as well as to determine the need for blind subcultures after the incubation period.

METHODS

A prospective evaluation of the system was performed, and 8247 blood culture bottles were processed. The standard was blind subculture from all the bottles after 5 days of incubation.

RESULTS

There were 3.2% false-positive and 0.6% false-negative results (72% of clinical importance). The system sensitivity for yeasts was 41%. The mean time for detection of Neisseria meningitidis was 31.9 +/- 2.8 h, for Brucella spp. 119.7 +/- 2 h, and for yeast 51.5 +/- 27.8 h.

CONCLUSIONS

The VITAL system poses has serious difficulties in the detection of N. meningitidis, Brucella spp., yeast and methicillin- and aminoglycoside-resistant Staphylococcus aureus (MARSA). The low system sensitivity for yeast detection makes the blind subculture necessary after the incubation period.

Controlled clinical comparison of bioMérieux VITAL and BACTEC NR-660 blood culture systems for detection of bacteremia and fungemia in adults

A total of 9,446 blood cultures were collected from adult patients at three university-affiliated hospitals. Of these, 8,943 cultures were received with both aerobic bottles filled adequately; 885 yielded 1,016 microorganisms, including 622 isolates (61%) that were the cause of sepsis, 337 isolates (33%) that were contaminants, and 57 isolates (6%) that were indeterminate as the cause of sepsis. With the exception of Staphylococcus aureus, which was recovered more often from VITAL aerobic bottles, more pathogenic microorganisms were recovered from BACTEC NR6 (aerobic) bottles than from VITAL aerobic bottles. Growth of pathogenic microorganisms was detected earlier in VITAL aerobic bottles. A total of 8,647 blood cultures were received with both anaerobic bottles filled adequately; 655 yielded 740 microorganisms, including 486 isolates (66%) that were the cause of sepsis, 215 isolates (29%) that were contaminants, and 39 isolates (6%) that were indeterminate as the cause of sepsis. More pathogenic microorganisms were recovered from VITAL anaerobic bottles than from BACTEC NR7 (anaerobic) bottles. Growth of pathogenic microorganisms was detected earlier in VITAL anaerobic bottles. In 8,500 sets all four bottles were received adequately filled. When paired aerobic and anaerobic bottle sets (systems) were compared, more pathogenic microorganisms (again with the exception of S. aureus) were recovered from the BACTEC system. For the 304 septic episodes (253 unimicrobial and 51 polymicrobial), significantly more were detected by the BACTEC system. We conclude that VITAL requires modification to improve recovery of pathogenic microorganisms to make it competitive with other commercially available blood culture systems.

Experience of changing between signal and Bactec 9240 blood culture systems in a children's hospital

AIM

To compare experience of positive blood cultures in successive years before and after changing from Signal (Unipath) to Bactec 9240 (Becton Dickinson) blood culture systems.

METHODS

Analysis of data collected prospectively on 7967 Signal and 7062 Bactec blood culture sets.

RESULTS

Significant growths occurred in 5.7% of Signal and 8.9% of Bactec cultures; 33.0% more significant isolates and 24.0% more episodes of bacteraemia were detected in the second year, following introduction of the Bactec system. Inpatient hospital activity increased by 8.2% between the first and second years, although the numbers of blood cultures received actually fell by 11.4%. There were striking increases in numbers of isolates of coagulase negative staphylococci (47.7%) and Enterobacteriaceae (56.8%) from Bactec cultures. Two anaerobic bacteraemias were detected in Signal blood cultures, whereas none was detected by the Bactec system, despite 12.1% of sets including an anaerobic bottle. Of significant positive cultures, 90.2% were detected within one day with the Bactec 9240, compared with only 50.0% of Signal cultures; 20.7% of significant positive Signal blood cultures were detected only on terminal subculture. Microorganisms that were not significant were isolated from 5.1% Signal and 3.8% Bactec cultures.

CONCLUSIONS

Compared with the Signal system, the Bactec 9240 offers markedly more rapid and sensitive detection of bacteraemia, together with a lower rate of non-significant isolates. However, using a single PEDS PLUS/F bottle the few episodes of anaerobic bacteraemia that occur in children are likely to be missed.

Evaluation of the BacT/Alert and VITAL blood culture systems for the diagnosis of bacteremia

OBJECTIVE: To evaluate the detection of bacterial growth in the BacT/Alert (Organon Teknika) and VITAL (bioMérieux) automated blood culture systems. METHODS: In accordance with the protocol of study, 1021 blood sample pairs for culture were obtained from adult patients admitted to the Emergency Room and Intensive Care Unit. RESULTS: In total, 139 (13.6%) clinically significant blood cultures were detected, of which 79 (56.8%) were detected by both systems, 48 (34.5%) only by BacT/Alert and 12 (8.6%) only by VITAL (P cent0.0001). The BacT/Alert system detected positive blood cultures more rapidly for all groups of microorganisms. The VITAL system showed six false-negative blood cultures, while the BacT/Alert system showed none (P50.03). There was no significant difference between the number of false-positive blood cultures detected by the two systems. CONCLUSIONS: In our study, overall the BacT/Alert system achieved a better recovery of microorganisms than the VITAL system.