OCCURRENCE AND MOLECULAR CHARACTERIZATION OF METHICILLIN RESISTANT Staphylococcus aureus (MRSA) IN BOVINE MASTITIS IN SETTLED FULANI HERDS IN KADUNA STATE, NIGERIA
OCCURRENCE AND MOLECULAR CHARACTERIZATION OF METHICILLIN RESISTANT Staphylococcus aureus (MRSA) IN BOVINE MASTITIS IN SETTLED FULANI HERDS IN KADUNA STATE, NIGERIA
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Date
2019-04
Authors
UMARU, Gali Abaka
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Abstract
Staphylococcus aureus is an important pathogen causing superficial and systemic
infections in humans and animals as nosocomial or community-acquired. S. aureus is
a common causative agent of bovine mastitis in dairy herds. The persistent emergence
of multidrug resistant S. aureus, particularly methicillin-resistant S. aureus, has caused
high economic burden and concerns for public health, due to limited options of
treatment of MRSA infections. Therefore, this study was designed to determine the
occurrence and molecular characterization of Methicillin-resistant Staphylococcus
aureus (MRSA) from bovine mastitis in settled Fulani herds in Kaduna State. A crosssectional
study was conducted to determine the prevalence of methicillin-resistant
Staphylococcus aureus (MRSA) and the molecular epidemiology of S. aureus and
MRSA from bovine mastitis in settled Fulani herds in Kaduna State. Three hundred
and sixty milk samples were collected from randomly selected herds or farms in
Kaduna South, Igabi, Kagarko, Sabon-Gari and Zaria and examined for
Staphylococcus species by phenotypic and molecular methods. The results revealed
that the prevalence of mastitis at cow level was 26.9% (97/360), out of which 3.1%
(11/360) were clinical mastitis and 23.9% (86/360) were subclinical mastitis
respectively (P<0.05). The results also showed that out of the 97 mastitis positive
samples, 44.3% (43/97) were associated with S. aureus and 24.7% (24/97) with
coagulase negative staphylococci respectively. Of the 360 cow milk samples
examined, 55 (15.3%) were positive for S. aureus, out of which 28 (7.8%) were found
to be MRSA. Twelve (42.9%) of MRSA were associated with mastitis (4 each from Kaduna South and Kagarko, 2 from Zaria and one each from Giwa and Igabi
respectively). The resistance patterns of the 28 MRSA isolates showed high resistance
to penicillin 28 (100.0%), amoxicillin 23 (89.3%), ampicillin 23 (89.3%), tetracycline
24 (85.7%) and erythromycin 20 (71.1%). The multiple drug resistance indices of the
MRSA strains revealed that all the 28 MRSA strains were resistant to 5 or more
antibiotics tested, 6 (21.4%) strains were resistant to 6 antibiotics, 6 (21.4%) were
resistant to 7 antibiotics, 8 (28.6%) were resistant to 8 antibiotics and 4 (14.3%) were
resistant to 9 antibiotics. Twenty six of the 28 MRSA (92.9%) exhibited unique
resistance patterns with only 4 exhibiting similar patterns of multiple resistance. The
two patterns encountered were AML,AMP,C,CN,E,NA,P,S,TE exhibited by isolates
K23 and K42, and AML,AMP,E,P,TE,VA,W exhibited by isolates K3 and S26. The
multiple antibiotic resistance classification results showed that significant number
(P<0.05) exhibited the extensive drug classification pattern, while the MIC values of
the antibiotics showed that all (100%) had values greater than 256 μg/mL against
oxacillin, 15 (53.6%) had values greater than 256 μg/mL against vancomycin
respectively. Of the 28 MRSA isolates examined by multiplex PCR for the presence of
mec A, mec C and fem B genes, 3 were positive for fem B. None was positive for mec
A and mec C genes respectively. Typing using MLST revealed that all the 3 isolates
were MLST types 1 (ST 1) and clonal complex (CC) 1. All the 3 isolates
(23448_1#128, 23448_1#129. 23448_1#131) were isolated from cases of subclinical
mastitis and exhibited multidrug and extensive drug resistance (XDR) patterns. The
three strains were 100 % homologous to each other with no divergence within the specie level. The occurrence of mastitis coupled with the isolation of ST 1 (CC1) S.
aureus; CONS and MRSA are of great public health concern and requires strict
control and preventive measures. The study recommends proper hygienic measures
during milking, environmental sanitation and culling of infected cows to prevent the
spread of pathogens to uninfected cows and humans.
Description
A THESIS SUBMITTED TO THE SCHOOL OF POSTGRADUATE STUDIES,
AHMADU BELLO UNIVERSITYIN PARTIAL FULFILLMENT FOR THE
AWARD OF DOCTOR OF PHILOSOPHY (Ph.D) IN VETERINARY PUBLIC
HEALTH AND PREVENTIVE MEDICINE
DEPARTMENT OF VETERINARY PUBLIC HEALTH AND PREVENTIVE,
FACULTY OF VETERINARY MEDECINE,
AHMADU BELLO UNIVERSITY,
ZARIA, NIGERIA
Keywords
OCCURRENCE,, MOLECULAR CHARACTERIZATION,, METHICILLIN RESISTANT,, Staphylococcus aureus,, BOVINE MASTITIS,, SETTLED FULANI HERDS,, KADUNA STATE,, NIGERIA