'Prevalence and antimicrobial susceptibility of Listeria monocytogenes and methicillin-resistant Staphylococcus aureus strains from raw meat and meat products in Zaria, Nigeria.

UNLABELLED: The bacterial genera Listeria and Staphylococcus have been frequently isolated from food products and are responsible for a number of animal and human diseases. The aim of the study was to simultaneously isolate and characterize L. monocytogenes and Staphylococcus species from 300 samples of raw meat and meat products, to determine the susceptibility of the organisms to commonly used antimicrobial agents and to determine the presence of haemolysin A (hyl) virulence gene in L. monocytogenes and staphylococcal cassette chromosome mecA (SCCmec) gene in the Staph. aureus isolates using PCR. Of the 85 Listeria isolates tested, 12 L. monocytogenes were identified and tested for their sensitivity to 14 antimicrobial agents. All the 12 isolates (100%) were resistant to nine antimicrobial agents, but however sensitive to gentamicin. Only one isolate was found to harbour the hylA gene. Twenty-nine isolates were confirmed as Staph. aureus by the Microbact 12S identification system and were all presumptively identified as methicillin-resistant Staph. aureus species using oxacillin-resistant Staph. aureus basal medium (ORSAB). The 29 Staph. aureus isolates were tested for their sensitivity to 16 antimicrobial agents, and 11 were resistant to methicillin. None of the 11 Staph. aureus isolates harboured the methicillin resistance, mecA gene. SIGNIFICANCE AND IMPACT OF THE STUDY: Listeria monocytogenes and Staphylococcus aureus are important agents of foodborne diseases. Occurrence of these infectious agents was established in meat and meat products in Zaria, Nigeria. Majority of isolates obtained from this study, displayed multidrug resistance to commonly used antimicrobial agents, including methicillin resistance among the Staph. aureus isolates. The potential virulence of L. monocytogenes found in ready-to-eat food was documented by the carriage of hly A gene by one of the isolates. A different mechanism of methicillin resistance or different homologue of mec A gene may be circulating among Nigerian isolates.

Economic and Health Perspectives of Mycotoxins: A Review

Due to their potent toxicity; mycotoxins have attracted worldwide attention over the years and recently; there has been an increasing disquietness on the part of governments; producers; processors; marketers and consumers over the health and economic significance. The diversity in occurrence; structure and chemistry of mycotoxins make their impact more complex to diagnose. Owing to their usual environmental conditions of production in countries with warm and humid climates as well as poor conditions of storage and handling; agricultural commodities are susceptible to fungal colonization and development which can lead to the accumulation of mycotoxins. As part of drying process; agricultural produce are exposed to contamination by ubiquitous mycoflora that grow; develop and produce some toxic metabolites that are harmful to the consumers. Food is already a limited commodity; especially in developing countries of the world and consumers therefore; either as a matter of choice or for the relative cheapness and affordability during periods of scarcity; opt for the over-fresh produce; sometimes not aware of the adverse health implications such foods pose. In the quest to ensure regular and continuous availability of certain perishable farm produce; especially in developing nations; local farmers and traders resort to unscientific and faulty storage conditions to preserve commodities; thereby pre-disposing produce to fungal colonization and mycotoxin production. Thus; commodities such as groundnuts; maize; sorghum; rice; yam; cassava; tiger nut; soyabeans; cotton seeds; fruits; vegetables spices can be contaminated with toxins of fungal origin such as aflatoxins; ochratoxins; fumonisins; patulin; sterigmatocystin; deoxynivalenol; zearalenone and other mycotoxins which pose serious economic and health risks. This review presents some mycotoxins commonly found on agricultural commodities both in temperate and tropic regions of the world. The acute and chronic toxic effects of these toxins in humans and animals are highlighted. Control measures include education of the populace on the risks of exposure to mycotoxins through skin contact; inhalation and ingestion; early harvesting; rapid appropriate drying; sequestration of diseased seeds from sound seeds; sanitation; use of good agronomic practices; insect control; the use of botanicals and synthetics as storage protectants; biological control and detoxification of mycotoxin-contaminated commodities. Probable related health implications are also discussed with a view to creating better public awareness and providing scientific basis for appreciating the challenges; while proactively promoting the development and implementation of policies at mitigating risk factors. Some mycotoxins; their producer fungi and toxic effects are further presented

Characterisation and screening for antimicrobial substances of slaughtered cattle in Zaria, Nigeria.

The occurrence of antimicrobial drug residues in 500 routinely slaughtered cattle in Zaria, Nigeria, was determined. A microbial inhibition test with Micrococcus luteus ATCC9341 was used to test urine at the time of slaughter for the presence of antimicrobial substances. Thirty-seven (7.4%) of the urine samples were positive for antimicrobial substances. Positive cases were not distributed according to breed (P>0.05), but occurred significantly more in male cattle aged 3-9 years and in those with good body condition score (P<0.05). Thirty-eight cases, in the form of 16 different pathological conditions, were seen from visual inspection of carcasses. Lymphadenopathy was seen in 10 (23.7%) carcasses including one antimicrobial substances positive carcass. Dermatophilosis and emaciation constituted 15.8 and 13.2% of pathological conditions observed, respectively.

Antibiogram of staphylococcal strains isolated from milk and milk-products.

A study of the resistance patterns of 248 staphylococcal isolates from milk and milk products to eight antimicrobial agents using the disc method showed that 80 (32.3%) were resistant to sulphafurazole, 75 (30.2%) to penicillin G, 63 (25.4%) to ampicillin, 23 (9.3%) to cloxacillin, 19 (7.7%) to tetracycline, 17 (6.9%) to streptomycin, 14 (5.6%) to erythromycin and 12 (4.8%) to chloramphenicol. One hundred and sixteen (46.8%) of the 248 staphylococcal isolates were sensitive to all the agents tested. A significant percentage (P less than 0.05) of the isolates from raw milk were resistant to erythromycin, sulphafurazole, cloxacillin, penicillin G and streptomycin compared to isolates from fermented milk. The minimum inhibitory concentrations (MIC) as determined by the tube method for isolates resistant by the disc method, were greater than or equal to 16 micrograms for ampicillin in 5 (11.9%) isolates; greater than or equal to 40 micrograms for cloxacillin, 9 (36.0%) and greater than or equal to 12 international units for penicillin G amongst 12 (22.2%) isolates. MIC values of greater than or equal to 40 micrograms were recorded for 9 (90.0%), 9 (69.2%), 8 (73.7%) and 7 (70.0%) isolates to chloramphenicol, streptomycin, erythromycin and tetracycline respectively. The relatively high level of resistance to antimicrobial agents is a reflection of misuse or abuse of these agents in the environment.

The occurrence of Staphylococcus aureus in fermented milk products (fura and manshanu) in Nigeria.

Ninety-three samples of fermented milk cereal (Fura) and 79 of local butter (Manshanu) were collected from four different markets around Zaria. For Fura the mean content of Staphylococci for each of the four markets ranged from 4.5 x 10(3) to 4.3 x 10(4) cfu/ml and the mean aerobic mesophilic plate count from 5.6 x 10(5) to 2.7 x 10(6) cfu/ml. For Manshanu the mean staphylococcal count and aerobic mesophilic plate count ranged from 3.4 x 10(2) to 2.2 x 10(3) cfu/ml and 6.7 x 10(4) to 1.1 x 10(6) cfu/ml respectively. Significant differences were seen between the different markets.

Enterotoxigenicity of staphylococci isolated from raw milk obtained from settled and nomadic herds around Zaria, Nigeria.

Staphylococcal isolates from 135 raw milk samples obtained from settled herds (42) and nomadic herds (93), were characterized and assayed for enterotoxin production. Of the 42 samples from settled herds, 13 (31%) were California Mastitis Test (CMT)-positive, but all the samples contained staphylococci. Only 3 (3.2%) of the 93 raw milk samples from nomadic herds were CMT-positive but 58 (62.4%) contained staphylococci. Of the 13 isolates from CMT-positive milk obtained from settled herds, one produced enterotoxin A, while amongst the 29 from CMT-positive milk, 4 elaborated enterotoxin A and 3 produced type D. None of the isolates from milk obtained from nomadic herds was enterotoxigenic.

Enterotoxin Production by Staphylococcal Isolates from Nigerian Fermented Milk Products.

A total of 369 samples of nono, furanono and manshanu were purchased from four different markets around Zaria, Nigeria. Five hundred and sixty-eight staphylococcal isolates were obtained from the three products of which a total of 37 (6.5%) were enterotoxigenic comprising 21 (10.7%) from nono samples and 16 (17.2%) from fura samples. The staphylococcal count, pH and titratable acidity of all the samples that contained enterotoxigenic staphylococci ranged from 5.4 × 103 to 6.3 × 104 CFU/ml, 3.89 to 4.21 and 0.47 to 0.74, respectively. Of all the staphylococcal isolates, 6.5% produced enterotoxin. Of the enterotoxigenic strains encountered 73.0% produced enterotoxin A, 10.8% B, 10.8% C and 2.7% produced combinations of A and B and A and C each. Statistical analysis revealed no correlation between either coagulase, thermonuclease, hemolysin production and enterotoxin production.

Isolation of Yersinia enterocolitica from milk and milk products in Zaria, Nigeria.

Fourteen isolates of Yersinia enterocolitica were obtained from a total of 319 samples of raw milk and milk products. None of the isolates produced heat-stable enterotoxin as measured by infant mouse test. All the isolates were sensitive to tetracycline, gentamicin, sulfamethoxazole trimethoprim and resistant to cephaloridine, ampicillin, nitrofurantoin and carbenicillin. Most of the isolates were probably environmental strains. This paper reports isolation of Y. enterocolitica from milk and milk products for the first time in Nigeria.