ABSTRACT
The contamination of ready to eat foods (RTE) products due to Listeria monocytogenes could compromise the products safety becoming a great risk for the consumers. The high presence of L. monocytogenes in RTE products has been described worldwide, but few data are available about these products from African countries. The aims of this study were to report the presence of L. monocytogenes in Zambian RTE products, providing genomic characterization and data on similarity with African circulating strains using whole genome sequencing (WGS). A total of 304 RTE products, produced by different Zambian manufacturers, were purchased at retail, from major supermarkets located in Lusaka, Zambia, comprising 130 dairy and 174 meat products. L. monocytogenes was detected only in 18 (10.3%) RTE meat products of the 174 samples tested. The MLST analysis grouped the 18 L. monocytogenes isolates in 7 clonal complexes (CCs): CC1 (n = 5), CC2 (n = 4), CC9 (n = 4), CC5 (n = 2), CC121 (n = 1), CC155 (n = 1), and CC3 (n = 1). According to the cgMLST results, several clusters were detected, in particular belonging to hyper-virulent clones CC1 and CC2. Regarding the virulence factors, a complete L. monocytogenes Pathogenicity Island 3 (LIPI-3) was present both in the CC1 and CC3, in addition to LIPI-1. Several resistance genes and mobile genetic elements were detected, including Stress Islands, the bcrABC cassette and Tn6188_qac transposon, plasmids and intact prophages. Despite being a first preliminary work with a limited number of samples and isolates, this study helped to increase existing knowledge on contaminated RTE products in Zambia, confirming the presence of hyper-virulent L. monocytogenes CCs, which could play an important role in human diseases, posing a public health concern for consumers.
ABSTRACT
BACKGROUND: Contagious bovine pleuropneumonia (CBPP) caused by Mycoplasma mycoides subspecies mycoides (Mmm) is an important disease of cattle that causes serious economic losses. With the known effectiveness of new generation macrolides, tulathromycin and gamithromycin were assessed in comparison with oxytetracycline as a positive control and saline as a negative control for effectiveness in inhibiting lung lesion development, promoting resolution, preventing spread and bacteriological clearance in susceptible local cattle breeds in two separate studies in Kenya and Zambia. Animals were monitored for clinical signs, sero-conversion as well as detailed post-mortem examination for CBPP lesions. RESULTS: Using the Hudson and Turner score for lesion type and size, tulathromycin protected 90%, gamithromycin 80%, and oxytetracycline 88% of treated animals in Kenya. In Zambia, all animals (100%) treated with macrolides were free of lung lesions, while oxytetracycline protected 77.5%. Using the mean adapted Hudson and Turner score, which includes clinical signs, post-mortem findings and serology, tulathromycin protected 82%, gamithromycin 56% and oxytetracycline 80% of the animals in Kenya whereas in Zambia, tulathromycin protected 98%, gamithromycin 94% and oxytetracycline 80%. The saline-treated groups had 93 and 92% lesions in Kenya and Zambia respectively, with Mmm recovered from 5/14 in Kenya and 10/13 animals in Zambia. Whereas the groups treated with macrolides were free from lesions in Zambia, in Kenya 5/15 tulathromycin-treated animals and 6/15 gamithromycin-treated animals showed lesions. Oxytetracycline-treated animals showed similarities with 3/14 and 4/15 showing lesions in Zambia and Kenya respectively and Mmm recovery from one animal in Kenya and six in Zambia. In both studies, lesion scores of saline-treated groups were significantly higher than those of the antibiotic treated groups (p < 0.001). In sentinel animals, CBPP lesions were detected and Mmm recovered from one and two animals mixed with the saline-treated groups in Kenya and Zambia respectively. CONCLUSIONS: This study demonstrated that tulathromycin, a mycoplasmacidal, can achieve metaphylactic protection of up to 80%, while non-recovery of Mmm from sentinels suggests macrolides effectiveness in preventing spread of Mmm. It is recommended that further studies are conducted to evaluate strategies comparing vaccination alone or combining vaccination and antibiotics to control or eradicate CBPP.
