ABSTRACT
BACKGROUND AND OBJECTIVES: Commercial Aspergillus IgG antibody assays have become pivotal in the current diagnosis of chronic pulmonary aspergillosis (CPA). However, diagnostic cutoffs have been found to vary from manufactures' recommendations in different settings. This study aimed to establish the Aspergillus IgG reference range among Nigerians and determine a diagnostic cutoff for CPA. METHODS: Sera from 519 prospectively recruited healthy blood donors and 39 previously confirmed cases of CPA were analysed for Aspergillus IgG levels using the Bordier test kit (Bordier Affinity Products SA, Crissier, Switzerland). Accuracy versus cutoff profile and receiver operating characteristics (ROC) curve were analysed for both CPA cases and controls using the R-Studio (2020), (Window desktop, version 4.0.2 software with R packages "nnet" and "ROCR"). RESULTS: Among healthy blood donors, 141 (27.2%) were aged 16-25 years with median (interquartile range, IQR) of 22 (20-24) years; 304 (58.6%) were aged 26-40 years with median (IQR) of 32 (29-36) years; while 74 (14.2%) were aged 41-60 years with median (IQR) of 46 (44-49.75). Median IgG level in respective age groups were 0.069 (0.009-0.181), 0.044 (0.014-0.202) and 0.056 (0.01-0.265) with no significant difference found in the three age categories (p = 0.69). The overall diagnostic cutoff for the diagnosis of CPA was 0.821 with an accuracy of 97.1% and area under the curve (AUC) = 0.986. CONCLUSION: The optimal diagnostic cutoff for diagnosing CPA in Nigerians using the Bordier kit was 0.821 which is lower than the manufacturer's recommended cutoff of 1.0. The determination of this cutoff among Nigerians will significantly enhance accurate identification of CPA and assessment of its true burden in Nigeria.
ABSTRACT
OBJECTIVES: The presence of carbapenemase-producing bacterial isolates is found not only in hospital and community settings but also in the environment. Carbapenemase production may be related to acquired, usually plasmid-borne, ß-lactamase genes or to chromosomal genes intrinsic to various species. The aim of this study was to evaluate the occurrence of such carbapenemase-producing bacterial isolates among environmental samples from Nigeria. METHODS: A total of 122 environmental samples were plated on carbapenem-containing media. A total of 259 isolates were recovered, among which 124 were carbapenemase-producers according to the results of the Rapidec® Carba NP test. RESULTS: The majority of isolates (n=112) recovered corresponded to natural producers of carbapenemases, i.e. Stenotrophomonas maltophilia (n=108), Burkholderia cepacia (n=1), Shewanella sp. (n=1), Sphingobacterium sp. (n=1) and Chryseobacterium gleum (n=1). Ten isolates (mainly Enterobacteriaceae and Acinetobacter baumannii) produced an acquired carbapenemase, most commonly of the NDM type. In addition, two Pseudomonas otitidis isolates were identified as producing the Ambler class B carbapenemase POM-1, further confirming that this carbapenemase is naturally produced in this environmental species. Finally, several isolates co-producing 16S rRNA methylases (ArmA, RmtC) and/or extended-spectrum ß-lactamases (CTX-M-9, CTX-M-15) were also identified. CONCLUSION: This study revealed the presence and diversity of clinically-relevant antimicrobial-resistant bacteria in the environment in Nigeria.
