Oxoid Signal Blood Culture Research Articles

Susceptibility Pattern of Pathogens Causing Blood Stream Infections in a Tertiary Care Hospital: A Two-year Retrospective Study from Southern Nigeria

Aim: Bloodstream infections are a major cause of morbidity and mortality worldwide. The prevalence of causative microorganisms varies from one geographical region to another. This study was aimed at determining the etiological agents prevalent in our environment and their susceptibility profile.
 Study design: This is a retrospective study carried out at the University of Calabar Teaching Hospital, Calabar, Nigeria.
 Methodology: Blood culture results of patients documented over a two-year period were retrieved and analyzed. Blood culture positive isolates were detected using conventional method and Oxoid signal blood culture systems. Antimicrobial sensitivity tests were carried out by Kirby-Bauer disc diffusion method. Methicillin resistance in Staphylococcus aureus and coagulase negative Staphylococcus species (CoNS) was detected by disk diffusion method using 30 µg cefoxitin disk. ESBL production was detected by phenotypic confirmatory disc diffusion test (PCDDT) and the double disc synergy test (DDST).
 Results: A total of 413 blood culture antimicrobial susceptibility test results were analyzed, of which 116 (28.09%) were identified as culture positive. Sixty-nine (59%) of the positive isolates were from female patients. Out of 116 positive cultures, 58.62% (68/116) were Gram positive organisms, 40.52% (47/116) were Gram negative organisms, non albicans Candida accounted for 0.86% (1/116). Staphylococcus aureus (n=41, 35.3%) was the predominant isolate and showed high sensitivity to levofloxacin (100%), Linezolid (100%) and Amikacin (100%). Twelve isolates of S. aureus were methicillin resistant, while 1 isolate was inducible clindamycin resistant. Of the 116 isolates identified in this study, forty-three (43) were multidrug resistant with highest number of multidrug resistant isolates from Staphylococcus aureus (n=20). 21.28% (n=10) of the Gram-negative isolates were positive for extended spectrum beta lactamases.
 Conclusion: A high rate of antimicrobial resistance is observed among microorganisms causing blood stream infections. This emphasizes the need for antimicrobial sensitivity testing in the management of blood stream infections.

Prevalence and Bacteriology of Bacteremia Associated With Cleft Lip and Palate Surgery

The aim of the study was to determine the prevalence and bacteriology of bacteremia associated with cleft lip and palate (CLP) surgery. Three venous blood samples were obtained from 90 eligible subjects who presented for CLP surgery: before surgical incision, 1 minute after placement of the last suture, and 15 minutes thereafter. The samples were injected into an Oxoid Signal blood culture and transported to the laboratory for gram-positive/negative and aerobic/anaerobic bacteria analysis. Prevalence of bacteremia associated with cleft surgery was 38.1%. Prevalence rates of bacteremia in cleft lip surgery, cleft palate surgery, and alveoloplasty were 40.9%, 33.3%, and 50%, respectively. There was no significant difference in prevalence rate of positive blood culture in cleft lip surgery, cleft palate surgery, and alveoloplasty (P = 0.69). Positive blood culture was detected most frequently (47%) 1 minute after placement of the last suture. Of the 23 subjects who had positive blood culture at 1 minute, bacteremia persisted in 8 (35%) of them after 15 minutes. The most common bacteria isolated were coagulase-negative staphylococcus, Acinetobacter lwoffii, and coagulase-positive Staphylococcus aureus. Sex and age of the subjects, duration of surgery, blood loss, and type of cleft surgery were not significantly associated with positive blood culture. Bacteremia associated with CLP surgery is polymicrobial and persisted for at least 15 minutes after surgery in 35% of cases. This may reinforce the need for prophylactic antibiotics to protect at-risk patients from developing focal infection of the heart by oral flora.

Bacterial Bloodstream Infections in HIV-infected Adults Attending a Lagos Teaching Hospital

An investigation was carried out during October 2005-September 2006 to determine the prevalence of bloodstream infections in patients attending the outpatient department of the HIV/AIDS clinic at the Lagos University Teaching Hospital in Nigeria. Two hundred and one patients--86 males and 115 females--aged 14-65 years were recruited for the study. Serological diagnosis was carried out on them to confirm their HIV status. Their CD4 counts were done using the micromagnetic bead method. Twenty mL of venous blood sample collected from each patient was inoculated into a pair of Oxoid Signal blood culture bottles for 2-14 days. Thereafter, 0.1 mL of the sample was plated in duplicates on MacConkey, blood and chocolate agar media and incubated at 37 degrees C for 18-24 hours. The CD4+ counts were generally low as 67% of 140 patients sampled had < 200 cells/microL of blood. Twenty-six bacterial isolates were obtained from the blood samples and comprised 15 (58%) coagulase-negative staphylococci as follows: Staphylococcus epidermidis (7), S. cohnii cohnii (1), S. cohnii urealyticum (2), S. chromogenes (1), S. warneri (2), S. scuri (1), and S. xylosus (1). Others were 6 (23%) Gram-negative non-typhoid Salmonella spp., S. Typhimurium (4), S. Enteritidis (2); Pseudomonas fluorescens (1), Escherichia coli (1), Ochrobactrum anthropi (1), Moraxella sp. (1), and Chryseobacterium meningosepticum. Results of antimicrobial susceptibility tests showed that coagulase-negative staphylococci had good sensitivities to vancomycin and most other antibiotics screened but were resistant mainly to ampicilin and tetracycline. The Gram-negative organisms isolated also showed resistance to ampicillin, tetracycline, chloramphenicol, and septrin. This study demonstrates that coagulase-negative staphylococci and non-typhoidal Salmonellae are the most common aetiological agents of bacteraemia among HIV-infected adults attending the Lagos University Teaching Hospital, Nigeria. The organisms were resistant to older-generation antibiotics often prescribed in this environment but were sensitive to vancomycin, cefotaxime, cefuroxime, and other new-generation antibiotics.

Blood culture examinations at a community hospital without a microbiology laboratory: using an automated blood culture system and performing a Gram stain on positive culture bottles in the institution.

To elucidate the existence of microorganisms from blood culture bottles in hospitals without a microbiology laboratory, we changed the system of blood culture examinations. The Oxoid signal blood culture system and submission of all blood cultures to the clinical testing industry was used from July 2002 to December 2002 (first period). Use of the BacT/Alert system and performing of Gram stain for positive culture bottles in our institutions was conducted from January 2003 to June 2003 (latter period). A total of 210 and 193 blood cultures were processed during the first and latter periods, respectively. There were 40 (19.0%) positive cultures in the first period and 32 (16.6%) positive cultures in the latter period. The times from the specimen collection to the Gram stain result that were required were 3.8 and 1.0 days in the first period and the latter period, respectively. The times required for the final report of the blood cultures in the first period and in the latter period were 5.8 and 4.9 days, respectively. We conclude that using a continuous monitoring, automated blood culture system and performing Gram stain for positive culture bottles in institutions without microbiology laboratories may be useful for medical doctors to rapidly determine the existence of microorganisms and to begin adequate antiinfective therapy.

Review on evaluations of currently available blood-culture systems.

Review on evaluations of currently available blood-culture systems.

Comparative evaluation of nonradiometric BACTEC and improved oxoid signal blood culture systems in a clinical laboratory

The BACTEC NR660 blood culture system, which uses infrared spectroscopy to detect carbon dioxide generated by bacterial growth, was compared with the new medium formulation of the Oxoid Signal system. Two trials were conducted: a comparative study of 88 organisms in simulated blood cultures and a clinical trial of 3,321 paired patient blood culture samples. Both trials showed that overall the BACTEC system performed better in the recovery of organisms. The Oxoid system was unable to detect by signal the growth of the majority of yeasts, nonfermentative gram-negative bacilli, Neisseria meningitidis, Nocardia spp., and Corynebacterium jeikeium. There were no significant differences in the yield of Staphylococcus spp., members of the family Enterobacteriaceae, Streptococcus spp., or anaerobic organisms. BACTEC detected growth more quickly than did the Oxoid system; 61% of the isolates were detected by BACTEC at 24 h, while 49% of the isolates were detected by Oxoid. The Oxoid system had a high proportion (58.5%) of false-positives, compared with 7.7% for the BACTEC system. Despite the new medium formulation of the Oxoid system, its performance is still not equivalent to that of the BACTEC system.

Effect of altered headspace atmosphere on yield and speed of detection of the Oxoid Signal blood culture system versus the BACTEC radiometric system

The one-bottle Oxoid Signal blood culture system altered to provide a more aerobic bottle headspace was reassessed in a comparative study versus the two-bottle BACTEC radiometric system in 5,426 blood cultures. The BACTEC system detected more microorganisms (P less than 0.02), particularly anaerobes (P less than 0.05) and fungi (P less than 0.05).

Comparison of Oxoid Signal and Biphasic Blood Culture Systems in Clinical Practice

The 1-bottle Oxoid Signal blood culture system was compared with a biphasic 2-bottle system in a clinical trial. A total of 851 routine blood samples were processed in the study which was run as a multicenter study at 4 university hospitals. Microorganisms were isolated from 104 (12.2%) blood cultures by one or both methods. 75 (72%) were clinically significant isolates, 61 of them were recovered in both systems, 9 in Oxoid Signal only and 5 in the biphasic system only. 29 isolates (28%) were judged as contaminants, 6 of them were found in both systems, 18 in Oxoid Signal only and 5 in the biphasic system only. The Oxoid Signal System had many advantages although it sometimes gave false positive signals in the device. The growth of pathogens was equally good, 93% versus 88% positive cultures.

Comparative evaluation of the BCB Roche and Oxoid Signal blood culture systems

The agar-slide blood culture system BCB Roche was compared with the Oxoid Signal blood culture system using 2,266 paired blood cultures. A total of 271 (12%) paired sets were culture-positive, including 222 (9.8%) yielding pathogens associated with septicemia and 50 (2.2%) yielding likely contaminants. In the recovery of the total 235 isolates considered as pathogens, the BCB Roche system yielded 202 (85.9%), the Oxoid Signal 211 (89.8%); 178 (75.7%) were cultured by both systems. There was no statistically significant difference between the two systems in their sensitivity, contamination-rate and detection time, except for gram-positive organisms, which were detected earlier by the Oxoid Signal system. Both systems performed well and were easy to handle.

Comments on Oxoid Signal blood culture system.

Comments on Oxoid Signal blood culture system.

Aetiology of bacteraemia among adult AIDS patients attending Lagos University Teaching Hospital (LUTH), Lagos, Nigeria

Bacteraemia is a relatively common event in HIV-infected patients, especially in late infection. Studies in Africa have shown that more than 23% of AIDS patients have bacteraemia but there is paucity of data from Nigeria. Blood samples from 67 consecutive patients with AIDS attending the Lagos University Teaching Hospital between April and August 2000 were cultured. Temperature, ESR, Full blood count, and where possible CD4 counts were obtained. Socio-demographic details were also recorded. Thirty apparently healthy people were randomly selected from a low-risk population to act as non-AIDS controls. The Oxoid Signal Blood Culture System was used to investigate bacteraemia. Antibiotic sensitivity tests were carried out on all isolates. Twenty-two (33%) of the 67 AIDS patients were culture positive. Non-typhoidal Salmonella spp (45.5%), coagulase-negative staphylococci (22.7%) and Staphylococcus aureus (18.2%) were most commonly isolated. One isolate each of Klebsiella pneumoniae, Pseudomonas aeruginosa and Bacillus spp were identified. All bacteraemic patients had temperatures above 38 degrees C and white blood cell counts ranged between 2,700-13,500/mm(3). There was a high rate of antibiotic resistance particularly to chloramphenicol, tetracyclines, cotrimoxazole and beta-lactam antibiotics. However, most isolates were still susceptible to gentamicin and the fluoroquinolones. There was no significant difference in the socio-demographics of the bacteraemic AIDS and non-bacteraemic AIDS patients. Salmonella spp. were the most common aetiological agent of bacteraemia among AIDS patients seen at the Lagos University Teaching Hospital (LUTH), Nigeria. A high temperature was a pointer to the presence of bactaeraemia while total white blood cell counts were not useful. It is recommended that blood culture should be done for AIDS patients with elevated temperature irrespective of the total white blood cell count.