Field diagnostic kits: a solution for developing countries?

Seroprevalence and Risk Factors Associated with Contagious Caprine Pleuropneumonia in Western Amhara, Northwest Ethiopia

Contagious caprine pleuropneumonia (CCPP) has been identified as a significant problem in goat production, especially in the arid and semiarid lowland areas of Ethiopia. Even though CCPP was reported in most of the goat rearing areas of the country, there is no adequate information on the disease in the Amhara Region. Cross-sectional study was conducted from November 2016 to April 2017 in the districts of Western Amhara to estimate the seroprevalence and identify the associated risk factors for occurrence of the CCPP. The risk factors considered included age, sex, agroclimate, and districts. A competitive enzyme-linked immunosorbent assay (cELISA) was carried out on a total of 400 goat sera samples, out of which 34 samples were found seropositive for specific antibodies against CCPP, with the overall seroprevalence of 8.5% (95% confidence interval (CI) =5.8, 11.2). Among the epidemiological factors considered, age and sex of the goats were not significantly associated with CCPP seroprevalence (p>0.05). However, the seropositivity was slightly higher in adults (9.9%) and female goats (9.0%) compared to young (6.3%) and male (7.5%) goats, respectively. The analysis of seroprevalence by district shows that the seroprevalence of CCPP in Metema (OR=14.34; 95%CI= 1.80, 114.09; p=0.012) and Fogera (OR=9.99; 95%CI= 1.10, 91.16; p= 0.041) was significantly higher compared to other study districts. Multivariable logistic regression analysis also identified the district as a risk factor for the occurrence of a high seroprevalence of CCPP. The present study revealed the seroprevalence and the distribution of CCPP in Western Amhara districts, and hence appropriate control measures including regular investigation and vaccination should be implemented to alleviate the problem.

Contagious caprine pleuropneumonia - a comprehensive review

Contagious caprine pleuropneumonia (CCPP) is a serious disease of goats, occasionally sheep and wild ruminants, caused by Mycoplasma capricolum subspecies capripneumoniae (Mccp). The disease is characterized by severe serofibrinous pleuropneumonia, very high morbidity (∼100%), and mortality (80–100%). CCPP affects goats in more than 40 countries of the world thereby posing a serious threat to goat farming around the globe. The characteristic clinical signs of CCPP are severe respiratory distress associated with sero-mucoid nasal discharge, coughing, dyspnea, pyrexia, pleurodynia, and general malaise. In later stages, severe lobar fibrinous pleuropneumonia, profuse fluid accumulation in pleural cavity, severe congestion of lungs and adhesion formation is observed. Mycoplasmal antigen interactions with host immune system and its role in CCPP pathogenesis are not clearly understood. CCPP is not a zoonotic disease. Diagnosis has overcome cumbersome and lengthy conventional tests involving culture, isolation, and identification by advanced serological (LAT, cELISA) or gene-based amplification of DNA (PCR, RFLP, and hybridization) and sequencing. The latex agglutination test (LAT) is rapid, simple, and better test for field and real-time diagnosis applicable to whole blood or serum and is more sensitive than the CFT and easier than the cELISA. Moreover, the studies on antibiotic sensitivity and exploration of novel antibiotics (fluoroquinolones, macrolides) can help in better therapeutic management besides preventing menace of antibiotic resistance. Re-visiting conventional prophylactic measures focussing on developing novel strain-based or recombinant vaccines using specific antigens (capsular or cellular) should be the most important strategy for controlling the disease worldwide.

16S rRNA Gene Sequence-Based Identification of Bacteria in Automatically Incubated Blood Culture Materials from Tropical Sub-Saharan Africa

BACKGROUND

The quality of microbiological diagnostic procedures depends on pre-analytic conditions. We compared the results of 16S rRNA gene PCR and sequencing from automatically incubated blood culture materials from tropical Ghana with the results of cultural growth after automated incubation.

METHODS

Real-time 16S rRNA gene PCR and subsequent sequencing were applied to 1500 retained blood culture samples of Ghanaian patients admitted to a hospital with an unknown febrile illness after enrichment by automated culture.

RESULTS

Out of all 1500 samples, 191 were culture-positive and 98 isolates were considered etiologically relevant. Out of the 191 culture-positive samples, 16S rRNA gene PCR and sequencing led to concordant results in 65 cases at species level and an additional 62 cases at genus level. PCR was positive in further 360 out of 1309 culture-negative samples, sequencing results of which suggested etiologically relevant pathogen detections in 62 instances, detections of uncertain relevance in 50 instances, and DNA contamination due to sample preparation in 248 instances. In two instances, PCR failed to detect contaminants from the skin flora that were culturally detectable. Pre-analytical errors caused many Enterobacteriaceae to be missed by culture.

CONCLUSIONS

Potentially correctable pre-analytical conditions and not the fastidious nature of the bacteria caused most of the discrepancies. Although 16S rRNA gene PCR and sequencing in addition to culture led to an increase in detections of presumably etiologically relevant blood culture pathogens, the application of this procedure to samples from the tropics was hampered by a high contamination rate. Careful interpretation of diagnostic results is required.

Fluorescence in situ hybridization (FISH) for rapid identification of Salmonella spp. from agar and blood culture broth--an option for the tropics?

BACKGROUND

Salmonella enterica is an important cause of diarrhea with the potential to cause systemic infection including sepsis, particularly in the tropics. Sepsis in particular requires quick and reliable identification to allow a rapid optimization of antibiotic therapy. We describe the establishment and evaluation of fluorescence in situ hybridization (FISH) as a rapid and easy-to-perform molecular identification procedure from agar and blood culture broths.

METHODS

Two newly developed FISH probes with specificity for Salmonella spp. were evaluated with 10 reference strains, 448 clinical isolates of Gram-negative bacteria from Germany and Ghana including 316 Salmonella spp. strains, and 39 environmental Salmonella spp. isolates from rivers and streams in Ghana. One FISH probe was further tested with 207 pre-incubated blood culture broths from Germany with Gram-negative rod-shaped bacteria in Gram stain.

RESULTS

Evaluation of the newly designed FISH probes demonstrated sensitivity of 99.2% and specificity of 98.4% for clinical isolates, sensitivity of 97.4% for environmental Salmonella spp. isolates, and sensitivity of 100% and specificity of 99.5% for blood culture materials.

CONCLUSIONS

FISH proved to be highly reliable for a rapid identification of Salmonella spp. directly from pre-incubated blood culture broths as well as after growth on agar. The inexpensive and easy-to-perform procedure is particularly suitable for resource-limited areas where more sophisticated procedures are not available.