Virulence attributes and antimicrobial profile of pasteurella multocida isolated from pneumonic goats in Northern Tanzania
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Date
2024
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Sokoine University of Agriculture
Abstract
Pneumonic pasteurellosis, stemming from Pasteurella multocida,
poses a significant economic threat to small-scale goat farmers in
northern Tanzania. This study aimed to assess the prevalence of
antimicrobial resistance and virulence genes within Pasteurella
multocida isolates collected from goats displaying clinical symptoms
of the disease. A total of 200 nasal swab samples were obtained from
goats exhibiting signs of pneumonic pasteurellosis. In the laboratory,
these samples underwent culture on blood agar enriched with 5%
horse blood at 37°C and 5% carbon dioxide for 24-48 hours. Isolates
displaying characteristics resembling Pasteurella multocida were
subjected to gram staining and biochemical tests, including indole,
oxidase, and catalase. Among the presumptive Pasteurella multocida
isolates, 10 were initially identified, later confirmed using specific
molecular primers, Pm0762 and Pm1231, with only five isolates
ultimately confirming the presence of either or both genes. The
confirmed isolates were then subjected to susceptibility testing
against ten antibiotics. Additionally, screening for the presence of
virulence genes, including ptfhA, ptfA, fimA, exbD, and exbB, was
conducted. Moreover, antimicrobial resistance genes (sul1, sul2,
blaTEM, aac(3)-1, tetA, and acrA) were investigated. Out of the 200
analyzed nasal swab samples, Pasteurella multocida was isolated in
only 2.5%. This seemingly low prevalence may be attributed to the
larger sample size utilized in this study compared to prior
investigations or the influence of geographic and environmental
factors. Serogrouping revealed that 20% of the isolates belonged to
serogroup A, while a substantial 80% defied classification, posing
challenges for surveillance and control efforts. Further analysis
uncovered the presence of virulence genes crucial for iron acquisition
(exbD found in 100% of isolates) and adhesion (ptfA in 60%), pivotal
for bacterial survival and respiratory tract infection. However, despite
their significance, all isolates exhibited resistance to a broad
spectrum of antimicrobials, including commonly used drugs such as
ampicillin, amoxicillin and erythromycin. Resistance extended to
cephalosporins (cefotaxime), sulfamethoxazole/trimethoprim, and
even macrolides. This widespread resistance underscores the need
for judicious antibiotic use in veterinary medicine to curb the emergence of multidrug-resistant strains. Notably, susceptibility was
retained against gentamicin and ciprofloxacin, suggesting potential
alternative treatment options. Nevertheless, the prevalence of
multidrug resistance across all isolates (100%) emphasizes the
urgency for innovative strategies to combat pneumonic pasteurellosis.
Additionally, the identification of antimicrobial resistance genes like
blaTEM and sul1 in some isolates further accentuates the evolving
threat of resistance. Moreover, the prevalence of untypable strains
underscores the necessity for further research to understand their
implications and devise alternative typing methodologies for effective
control. In summary, this study reveals a concerning landscape of
antimicrobial resistance and virulence in Pasteurella multocida among
goats in northern Tanzania. Addressing challenges such as low
isolation rates, untypable strains, and widespread resistance
necessitates a multifaceted approach involving prudent antibiotic use,
exploration of novel treatment modalities and diagnostics, and
collaboration among public health authorities, veterinarians, and
livestock producers. Only through concerted efforts can we effectively
combat pneumonic pasteurellosis and safeguard the health and
livelihoods of small-scale goat farmers in the region.
Description
Dissertation
Keywords
Pasteurella multocida, Pneumonic pasteurellosis, Goat, Tanzania