Molecular Epidemiology of Thermophilic Campylobacter Infection in Poultry, Cattle and Humans in Plateau State, Nigeria

Abstract

Occurrence of Campylobacter species was investigated in poultry, cattle and humans in Plateau state. Cloacal swabs, rectal swabs and faeces from apparently healthy broilers, cattle and humans in selected farms and Hospitals respectively were cultured for Campylobacter organisms on modified charcoal cefoperazone deoxycholate agar (MCCDA). Characterization of Campylobacter isolates was done by using standard biochemical tests and further confirmed by polymerase chain reaction (PCR). Multilocus sequence typing was done by amplifying and sequencing 7 house keeping genes. Out of the overall 1, 012 samples tested, 228 (22.2%) were positive for Campylobacter species. One hundred and seventy five (76.8%) were identified as C. jejuni while 53 (23.2%) were C. coli. Out of the 360 samples from poultry tested, 129 (35.8%) were positive for Campylobacter species, with 105 (81.4%) as C. jejuni and 24 (18.6%) as C. coli. Of the 352 samples from cattle, 65 (18.5%) were positive with 52 (80%) as C.jejuni and 13 (20%) as C. coli. Similarly, of the 300 samples from humans tested, 34 (11.3%) were positive with 18 (52.9%) as C. jejuni while 16 (47.1%) were C. coli. The results of the study also showed that the prevalence was significantly higher in calves (25%) than in adults (12.2%) (P<0.05). Similarly, the prevalence was significantly higher (P < 0.05) in children (15.8%) than adults (7.1%). Susceptibility to 10 antimicrobial agents was evaluated using the disc diffusion technique. Of the 145 Campylobacter isolates from all sources tested, 115(79.3%) were resistant to one or more of the ten antimicrobial agents. Overall, the highest resistance was observed to nalidixic acid (60.7%), followed by tetracycline (57.2%), ciprofloxacin (53.1%), sulphamethoxazole/trimethoprim (46.2%) and erythromycin (41.4%). The low resistance was observed to azithromycin (27.6%), streptomycin (13.1%), gentamicin (6.9%) and chloramphenicol (4.8%). All the isolates were susceptible to clindamycin. Considering the overall resistance by species, C. coli was generally more resistant than C. jejuni to most of the antimicrobial agents. Overall, 81 (55.9%) of the isolates were multiresistant with nalidixic acid as the most frequently occurring antimicrobial agent, being found in 25 of the 29 multiresistant patterns. Out of the 125 Campylobacter isolates tested by PCR, 112 (89.6%) were correctly confirmed as C. jejuni and C. coli. Like the biochemical tests, none of the isolate was confirmed as C. lari. Out of the 60 isolates sequenced by MLST, 36 were C. jejuni while 24 were C. coli. The number of unique alleles at each locus varied from 5 for the asp and unc locus to 8 for the gly locus for the C. jejuni isolates while the number of unique alleles at each locus for the C. coli isolates varied from 2 for the gln locus to 5 for the gly locus. A high degree of variability was observed at locus tkt, which was caused by a unique allele tkt-3 characteristic of C. jejuni, but present in 2 of our C. coli isolates. Out of the 43 sequence types identified, 23 (53.5%) were novel. The remaining 20 (46.5%) had been previously reported. From the 36 Campylobacter jejuni isolates sequenced, a total of 21 sequence types were identified with 9 (42.9%) being new. The new sequence types were ST4036, ST4037, ST4038, ST4039, ST4040, ST4041, ST4064, ST4066 and ST4220. The most common sequence type was ST1932 which comprised of 6 isolates (28.6%), followed by ST1036 and ST607 with 3 isolates (14.3%) each and ST3554, ST460, ST4041, ST523, ST354 and ST4064 with 2 isolates (9.5%) each. From the 24 Campylobacter coli isolates sequenced, a total of 22 sequence types were identified with 14 (63.6%) being novel. The 43 STs were grouped in to 8 previously defined clonal complexes (CC). The clonal complexes were CC-460, CC-607, CC-353, CC-354, CC-658, CC-574, CC-22 and CC-828. Nine (20.9%) STs found in the isolates were unassigned. CC-828 (n = 16; 26.7%) was the most prevalent followed by CC-460 (n = 14; 23.3%) and CC 353 (n = 5; 10%). CC 828, CC460 and CC353 overlap among the poultry, cattle and human isolates. CC-607 was associated with poultry and human isolates only while CC-354 and CC-574 were associated with poultry isolates only. CC-658 was associated with poultry and cattle isolates only while CC-22 was found in the human isolates only. The results of this study revealed that Campylobacter species is prevalent in poultry, cattle and humans in Plateau state. The study also revealed that most of the isolates were resistant to most of the antimicrobial agents used with C. coli being more resistant than C. jejuni. The Campylobacter strains showed high level of genetic diversity with C. jejuni isolates being more diverse than C.coli. Genetic exchange between C.jejuni and C. coli was also determined in this study. This study also revealed that certain STs and CCs are associated with source of isolation which is an important epidemiological finding in tracing back sources of infection.