Comparison of Xpert GBS v. culture for rapid detection of group B streptococcus in pregnant women : sensitivity, specificity and predictive values

BACKGROUND. Group B streptococcus (GBS) is a leading cause of invasive disease, particularly in newborns. Seventy-five percent of neonates will be colonised by mothers carrying the organism. Confirmation of maternal colonisation with GBS is essential for prompt treatment and prevention of neonatal sepsis. The current gold standard of culture for isolation of GBS has a disadvantage of long turnaround time (24 - 72 hours). Rapid assays are required to determine maternal carriage of GBS. OBJECTIVES. To determine the usefulness of the Xpert GBS technology v. culture methods to detect GBS carriage in pregnant women. METHODS. This was a prospective observational study of 284 pregnant women between 26 and 37 weeks’ gestation. Two vaginorectal swabs were collected from each participant. One swab was processed using the gold-standard culture method, while the second swab was processed using the Xpert GBS assay. The performance of the Xpert GBS assay was then compared with that of the culture method. RESULTS. Two swabs were processed from each of 284 pregnant women between 26 and 37 weeks’ gestation. Culture detected 70 GBS isolates from a total of 279 specimens (25.1%), whereas the Xpert GBS detected 66 positive specimens (23.7%). The Xpert GBS assay had a sensitivity of 87% and specificity of 98%, with a positive predictive value of 92% and a negative predictive value of 96%. CONCLUSIONS. The Xpert GBS assay is a rapid and sensitive tool for prenatal detection of GBS. The assay should ideally be available in every labour ward, where women can be screened for GBS on arrival.The research described in this article was an MMed project of MS, the main author.A National Health Laboratory Services Research Grant (no. 94443) in fulfilment of MS’s MMed project.http://www.samj.org.zaam2019Medical MicrobiologyObstetrics and Gynaecolog

Antimicrobial susceptibility and serotype distribution of Streptococcus agalactiae rectovaginal colonising isolates from pregnant women at a tertiary hospital in Pretoria, South Africa : an observational descriptive study

BACKGROUND. Streptococcus agalactiae or group B streptococcus (GBS) is a significant cause of neonatal sepsis. Intrapartum antibiotic prophylaxis is recommended for pregnant women identified to be rectovaginally colonised between 34 and 37 weeks’ gestational age to decrease the risk of invasive disease in their newborns. An effective multivalent GBS vaccine may prevent a broader scope of GBS-associated diseases, such as GBS early-onset disease, GBS late-onset disease, spontaneous abortion, stillbirth and maternal bacteraemia. Serotype distribution of GBS isolates is essential to determine the efficacy of such a vaccine. OBJECTIVES. To investigate serotype distribution and antimicrobial susceptibility patterns of GBS isolates cultured from rectovaginal specimens during pregnancy. METHODS. Sixty-nine archived maternal colonising isolates were tested against penicillin, erythromycin, clindamycin, vancomycin and levofloxacin. Minimum inhibitory concentration testing was performed using the ETEST method. Serotyping was performed by the latex agglutination method. RESULTS. The most common serotypes detected were Ia (54%), III (20%), V (16%), II (6%), IV (2%) and Ib (1%). All isolates were fully susceptible to penicillin, vancomycin and levofloxacin. Eight (11%) and 50 (56%) isolates showed intermediate resistance to erythromycin and clindamycin, respectively, and 1 isolate was resistant to erythromycin. The macrolide-lincosamide-streptogramin B (MLSB) phenomenon was noted in 3 (4%) of the isolates. CONCLUSIONS. GBS-colonising isolates remain susceptible to penicillin, which remains the drug of choice for intrapartum antibiotic prophylaxis and treatment of invasive disease in newborns. Macrolides should only be used if clinically indicated due to the high prevalence of intermediate resistance. A pentavalent GBS vaccine currently in phase I trials should provide coverage for 97% of the isolates identified in this study.The National Health Laboratory Service (NHLS) and the Respiratory and Meningeal Pathogens Research Unit, University of the Witwatersrand, Johannesburg.http://www.samj.org.zaam2021Medical Microbiolog

Meningococcal infections in hospitalised patients in Pretoria

We report on 13 patients diagnosed with meningococcal infections in patients attending state-owned hospitals serving an indigent population in Pretoria in 2009. The case fatality rate was 27%. Ceftriaxone was the main antibiotic (9 out of 13 patients) for therapy. Five isolates (39%) were serogroup B and 4 (31%) serogroup W135. Most isolates (12/13) were fully susceptible to penicillin (MIC range 0.016 - 0.047 μg/ml). A single isolate was intermediately resistant to penicillin (MIC, 0.125 μg/ml) while all isolates were uniformly susceptible to ceftriaxone, ciprofloxacin and rifampicin. This pattern reveals a shift in serogroups with an increase of serogroup B disease in the Pretoria region, and the need for ongoing monitoring of antimicrobial susceptibility profiles and the value of ceftriaxone for favourable therapeutic outcome.http://www.samj.org.z

Antifungal susceptibility profile of yeast isolates from sterile sites at a tertiary hospital in South Africa

Invasive infections caused by yeasts are associated with high mortality and morbidity, and resistance to antifungal agents is increasing. Candida spp. has emerged as the leading cause of systemic nosocomial fungal infections. The aim of this study was to identify yeast isolates from sterile site specimens to species level, and to determine their susceptibility to fluconazole and voriconazole, at the National Health Laboratory, Service Dr George Mukhari Tertiary Laboratory from March to August 2007. Candida isolates were identified to species level using a germ tube test and/or Api® ID 32C kits. Antifungal susceptibility testing to fluconazole and voriconazole was performed using the disc diffusion method in accordance with the Clinical and Laboratory Standards Institute guidelines. All of the Candida isolates were from the neonatal intensive care unit (NICU), with the exception of two. The distribution of yeast isolates was as follows: C. krusei (41.9%), C. albicans (32.3%), C. inconspicua (5.5%), C. parapsilosis (2%), C. tropicalis (1.5%), C. sake (1.5%), C. lambica (1.5%), and C. valida (0.5%). Cryptococcus neoformans (11%), C. albidus (0.5%), Rhodotorula glutinis (1%), and C. humicola (0.5%) were also isolated. Of the isolated C. albicans, 61% were susceptible to fluconazole. A possible C. krusei outbreak could have occurred in the NICU during the study period. Voriconazole was the most susceptible antifungal agent to various yeast pathogens. The results of this study on azoles susceptibility testing of yeasts show that voriconazole may prove to be a valuable alternative antifungal agent in this tertiary hospital for the treatment of infections caused by yeasts, including Candida spp.http://www.sajei.co.za/index.php/SAJEI 2312-0053hb201

Antimicrobial susceptibility patterns of gonococcal isolates in Pretoria, South Africa, over a 20-year period (1984-2004)

This paper reviews the susceptibility profiles of Neisseria gonorrhoeae over a 20-year period in the Pretoria region. Endourethral specimens were collected from adult men with symptoms of urethritis attending primary health care clinics and private medical practitioners. These swabs were plated on enriched media for isolation of N. gonorrhoeae. Antimicrobial susceptibility of the organisms was performed using the disc diffusion and agar dilution methods. Plasmid analyses were performed on beta-lactamase-producing isolates. Penicillase-producing N. gonorrhoeae strains increased from 4% to 16%, whilst chromosomally mediated penicillin-resistant strains increased dramatically from 0% to 16% from 1984 to 2004. There was an equal distribution of the 3.2 MDa African and 4.4 MDa Asian plasmids. High-level tetracycline-resistant strains (36%) were detected for the first time in 2004. Ciprofloxacin resistance emerged at 7% in the same year. Gonococcal isolates remained susceptible to cefoxitin, ceftriaxone, cefpodoxime, and spectinomycin. However, the minimum inhibitory concentration values for spectinomycin were very close to the breakpoint. We have shown a continuing increase in resistance to penicillin (plasmid and chromosomal), the emergence of high-level tetracycline resistance and an emergence of resistance to ciprofloxacin. Susceptibility testing is essential for successful therapeutic outcomes and needs to be performed in an ongoing basis