Resistance in bacteria of the food chain: epidemiology and control strategies

Antimicrobial Usage, Susceptibility Profiles, and Resistance Genes in Campylobacter Isolated from Cattle, Chicken, and Water Samples in Kajiado County, Kenya

Campylobacter organisms are the major cause of bacterial gastroenteritis and diarrhoeal illness in man and livestock. Campylobacter is growingly becoming resistant to critically crucial antibiotics; thereby presenting public health challenge. This study aimed at establishing antimicrobial use, susceptibility profiles, and resistance genes in Campylobacter isolates recovered from chicken, cattle, and cattle-trough water samples. The study was conducted between October 2020 and May 2022 and involved the revival of cryopreserved Campylobacter isolates confirmed by PCR from a previous prevalence study in Kajiado County, Kenya. Data on antimicrobial use and animal health-seeking behaviour among livestock owners (from the same farms where sampling was done for the prevalence study) were collected through interview using a pretested semistructured questionnaire. One hundred and three isolates (29 C. coli (16 cattle isolates, 9 chicken isolates, and 4 water isolates) and 74 C. jejuni (38 cattle isolates, 30 chicken isolates, and 6 water isolates)) were assayed for phenotypic antibiotic susceptibility profile using the Kirby-Bauer disk diffusion method for ampicillin (AX), tetracycline (TE), gentamicin (GEN), erythromycin (E), ciprofloxacin (CIP), and nalidixic acid (NA). Furthermore, detection of genes conferring resistance to tetracyclines (tet (O), β-lactams (bla _OXA-61), aminoglycosides (aph-3-1), (fluoro)quinolones (gyrA), and multidrug efflux pump (cmeB) encoding resistance to multiple antibiotics was detected by mPCR and confirmed by DNA sequencing. The correlation between antibiotic use and resistance phenotypes was determined using the Pearson's correlation coefficient (r) method. Tetracyclines, aminoglycosides, and β-lactam-based antibiotics were the most commonly used antimicrobials; with most farms generally reported using antimicrobials in chicken production systems than in cattle. The highest resistance amongst isolates was recorded in ampicillin (100%), followed by tetracycline (97.1%), erythromycin (75.7%), and ciprofloxacin (63.1%). Multidrug resistance (MDR) profile was observed in 99 of 103 (96.1%) isolates; with all the Campylobacter coli isolates displaying MDR. All chicken isolates (39/39, 100%) exhibited multidrug resistance. The AX-TE-E-CIP was the most common MDR pattern at 29.1%. The antibiotic resistance genes were detected as follows: tet (O), gyrA, cmeB, bla _OXA-61 , and aph-3-1 genes were detected at 93.2%, 61.2%, 54.4%, 36.9%, and 22.3% of all Campylobacter isolates, respectively. The highest correlations were found between tet (O) and tetracycline-resistant phenotypes for C. coli (96.4%) and C. jejuni (95.8%). A moderate level of concordance was observed between the Kirby-Bauer disk diffusion method (phenotypic assay) and PCR (genotypic assay) for tetracycline in both C. coli (kappa coefficient = 0.65) and C. jejuni (kappa coefficient = 0.55). The study discloses relatively high resistance profiles and multidrug resistance to antibiotics of critical importance in humans. The evolution of the multidrug-resistantCampylobacter isolates has been linked to the use and misuse of antimicrobials. This poses a potential hazard to public and animal health, necessitating need to reduce the use of antibiotics in livestock husbandry practice coupled with stringent biosecurity measures to mitigate antimicrobial resistance.

High Levels of Antibiotic Resistance in Isolates From Diseased Livestock

Overuse of antimicrobials in livestock health and production beyond therapeutic needs has been highlighted in recent years as one of the major risk factors for the acceleration of antimicrobial resistance (AMR) of bacteria in both humans and animals. While there is an abundance of reports on AMR in clinical isolates from humans, information regarding the patterns of resistance in clinical isolates from animals is scarce. Hence, a situational analysis of AMR based on clinical isolates from a veterinary diagnostic laboratory was performed to examine the extent and patterns of resistance demonstrated by isolates from diseased food animals. Between 2015 and 2017, 241 cases of diseased livestock were received. Clinical specimens from ruminants (cattle, goats and sheep), and non-ruminants (pigs and chicken) were received for culture and sensitivity testing. A total of 701 isolates were recovered from these specimens. From ruminants, Escherichia coli (n = 77, 19.3%) predominated, followed by Staphylococcus aureus (n = 73, 18.3%). Antibiotic sensitivity testing (AST) revealed that E. coli resistance was highest for penicillin, streptomycin, and neomycin (77-93%). In addition, S. aureus was highly resistant to neomycin, followed by streptomycin and ampicillin (68-82%). More than 67% of E. coli isolates were multi-drug resistant (MDR) and only 2.6% were susceptible to all the tested antibiotics. Similarly, 65.6% of S. aureus isolates were MDR and only 5.5% were susceptible to all tested antibiotics. From non-ruminants, a total of 301 isolates were recovered. Escherichia coli (n = 108, 35.9%) and Staphylococcus spp. (n = 27, 9%) were the most frequent isolates obtained. For E. coli, the highest resistance was against amoxicillin, erythromycin, tetracycline, and neomycin (95-100%). Staphylococcus spp. had a high level of resistance to streptomycin, trimethoprim/sulfamethoxazole, tetracycline and gentamicin (80-100%). The MDR levels of E. coli and Staphylococcus spp. isolates from non-ruminants were 72.2 and 74.1%, respectively. Significantly higher resistance level were observed among isolates from non-ruminants compared to ruminants for tetracycline, amoxicillin, enrofloxacin, and trimethoprim/sulfamethoxazole.

Prevalence and Antimicrobial Resistance of Campylobacter Isolated from Dressed Beef Carcasses and Raw Milk in Tanzania

Campylobacter species are commonly transmitted to humans through consumption of contaminated foods such as milk and meat. The aim of this study was to investigate the prevalence, antimicrobial resistance, and genetic determinants of resistance of Campylobacter isolated from raw milk and beef carcasses in Tanzania. The antimicrobial resistance genes tested included blaOXA-61 (ampicillin), aph-3-1 (aminoglycoside), tet(O) (tetracycline), and cmeB (multi-drug efflux pump). The prevalence of Campylobacter was 9.5% in beef carcasses and 13.4% in raw milk, respectively. Using multiplex-polymerase chain reaction (PCR), we identified 58.1% of the isolates as Campylobacter jejuni, 30.7% as Campylobacter coli, and 9.7% as other Campylobacter spp. One isolate (1.6%) was positive for both C. jejuni and C. coli specific PCR. Antimicrobial susceptibility testing using the disk diffusion assay and the broth microdilution method showed resistance to: ampicillin (63% and 94.1%), ciprofloxacin (9.3% and 11.8%), erythromycin (53.7% and 70.6%), gentamicin (0% and 15.7%), streptomycin (35.2% and 84.3%), and tetracycline (18.5% and 17.7%), respectively. Resistance to azithromycin (42.6%), nalidixic acid (64.8%), and chloramphenicol (13%) was determined using the disk diffusion assay only, while resistance to tylosin (90.2%) was quantified using the broth microdilution method. The blaOXA-61 (52.6% and 28.1%), cmeB (26.3% and 31.3%), tet(O) (26.3% and 31.3%), and aph-3-1 (5.3% and 3.0%) were detected in C. coli and C. jejuni. These findings highlight the extent of antimicrobial resistance in Campylobacter occurring in important foods in Tanzania. The potential risks to consumers emphasize the need for adequate control approaches, including the prudent use of antimicrobials to minimize the spread of antimicrobial-resistant Campylobacter.