Assessment of the BACTEC NR660 blood culture system for the detection of bacteremia in young children

Group B streptococcal neonatal infections in Rio Grande do Sul, Brazil

Group B Streptococcus is the most common pathogen found in neonatal sepsis in North America.

OBJECTIVES

We describe 15 cases of neonatal infections by Group B Streptococcus (Streptococcus agalactiae) at a Neonatal Intensive Care Unit of a public and teaching hospital.

METHODS

We conducted a study at Hospital de Clínicas de Porto Alegre, from January 1st, 1996 to June 30, 1999. Diagnosis of neonatal infection was established according to the findings of Group B Streptococcus in blood culture associated with alterations resembling sepsis on the basis of clinical picture and laboratory findings.

RESULTS

Fifteen cases of neonatal infections by Group B Streptococcus were detected. Eleven cases consisted of early-onset sepsis, 2 cases of occult bacteremia and 2 cases of late-onset sepsis. Eight cases had septic shock (53%), 8 cases had pneumonia (53%), and 4 cases had meningitis (27%). Fourteen cases were diagnosed from a positive blood culture, and 1 case from evidence of these bacteria in pulmonary anatomopathological examination. Thirteen cases (87%) were diagnosed before 72 hours of life. We had 3 deaths (20%), and 3 cases of meningitis developing neurological deficits.

CONCLUSIONS

Streptococcus Group B is one of the most important pathogens in the etiology of early-onset neonatal sepsis at our hospital, with high mortality and morbidity. However, we do not know the incidence of GBS neonatal infections at other hospitals. More data are needed to establish a basis for trials of different strategies to reduce these infections.

Use of C-reactive protein to guide duration of empiric antibiotic therapy in suspected early neonatal sepsis

BACKGROUND

Serial C-reactive protein (CRP) measurements have been shown to be useful for guiding duration of antibiotic therapy in neonates. This study sought to determine whether this is a safe and practical approach in a developing country.

METHODS

The study was conducted at the Johannesburg Hospital between September 15, 1998, and January 15, 1999. Subjects included all neonates evaluated for suspected sepsis in the first 24 h of life who had negative initial and repeat CRP values (< or = 10 mg/l) [corrected]. Repeat CRP measurements were performed between 24 and 48 h after birth. Antibiotic therapy was stopped in these infants at 24 to 48 h, and they were observed until 72 h, when the final blood culture results were available. The number of positive blood cultures in this group was determined.

RESULTS

The repeat CRP estimation correctly identified 99 of 100 infants in the study as not requiring further antibiotic therapy (negative predictive value, 99%; 95% confidence intervals, 95.6 to 99.97%). The 1 infant with a positive blood culture was premature with a gestational age of 31 weeks. Eight babies required repeat evaluation for suspected sepsis, 4 presented on Day 3 to 4 and one of these babies died. All these neonates were of < or =33 weeks gestation.

CONCLUSION

The use of serial CRP measurements to guide antibiotic therapy is a safe and practical approach in neonates with suspected sepsis in a developing country.

Isolation and characterization of a species-specific DNA fragment for detection of Candida albicans by polymerase chain reaction

A 2-kbp DNA fragment, EO3, that was present in multiple copies in the Candida albicans genome was isolated for use in developing a detection method for C. albicans by polymerase chain reaction (PCR). Dot blot hybridization revealed that EO3 was specific for the 40 isolates of C. albicans serotypes A and B used. Using a set of primers (20-mer each) derived from the nucleotide sequence of EO3, we performed specific amplification of a 1.8-kbp DNA fragment within EO3 by PCR. All 40 isolates belonging to C. albicans serotypes A and B contained amplifiable 1.8-bkp fragments, although the DNA of the amplified products exhibited small variations in size, yielding three different fragment groups. Southern blot hybridization probed with EO3 showed that these 1.8-kbp fragments were derived from the EO3 region. Conversely, the 1.8-kbp fragment was not amplified from 38 isolates belonging to seven other medically important Candida species or from isolates of Cryptococcus neoformans, Saccharomyces cerevisiae, various bacteria, and a human cell line. The detection limit of the PCR assay for C. albicans with the EO3 fragment was shown to be approximately 2 to 10 cells and 100 cells in saline and human urine, respectively, by ethidium bromide staining and 2 and 10 cells, respectively, by Southern blot analysis. In addition, EO3 was assumed to originate from mitochondrial DNA on the basis of the results of its characterizations. These results indicate that the PCR system using the 1.8-kbp fragment as a target is a reliable method for identifying C. albicans isolates, thereby suggesting its potentials for specific and sensitive detection of C. albicans in samples from patients with candidiasis.

Determination of growth value thresholds for BACTEC PLUS aerobic blood culture vials

Growth value thresholds used to identify positive blood culture vials can be defined by users for each BACTEC NR-660 bacteremia detection instrument. Growth values were compared with the recovery of organisms from vials flagged as positive during the testing of 3.056 high-volume vials containing aerobic (BACTEC PLUS 26) medium over a 2-month period. Results showed that optimal threshold values for our use of these vials varied from those recommended by the manufacturer; if the thresholds defined from these data had been used during the study period, total vials flagged as positive from which no organisms were recovered (false alarms) would have been reduced from 181 (5.9/100 vials tested) to 71 (2.3/100 vials tested), with a minimal decrease in the identification of vials containing usual or occasional pathogens (hits). Adjustments of growth value thresholds by the individual user can make the use of BACTEC instruments more efficient by decreasing further processing of vials from which no organisms are recovered.