Listeria Research Articles

Bacterial surveillance of apheresis platelets in South Africa (January 2011 to December 2016)

BackgroundGlobally, bacterial contamination of platelets remains the major transfusion‐related infectious risk. Limited data are available from low‐middle income countries. The South African National Blood Service routinely tests a percentage of apheresis platelets for bacterial contamination. We report on contamination rates from January 2011 to December 2016.MethodsA retrospective analysis of the surveillance data from apheresis platelets was performed. Two to 4 ml of each apheresis product was collected aseptically and divided equally into an aerobic and anaerobic culture bottle using the BacT/ALERT (bioMerieux) or BACTEC™ (Beckton Dickinson) systems. Bacterial identification was done using the MicroScan (Beckman Coulter) system.ResultsA total of 87 841 apheresis platelets were collected between 2011 and 2016 of which 18% were tested. The average positive culture rate was 2·7%, ranging between 0·6% (2011) and 5·22% (2015). Gram‐positive bacteria constituted 94% of all isolates (269/285), ten (4%) gram‐negative bacteria and 6 (2%) fungi were detected. The most common bacterial isolates were Cutibacterium acnes (35%), coagulase‐negative Staphylococci (26%), Bacillus spp. (8%), Corynebacteria spp. (8%). A total of nine highly pathogenic bacteria were isolated: two Acinetobacter spp, one each of Enterobacter spp., Serratia spp., Klebsiella spp., one Staphylococcus aureus and three Listeria spp. Average time to positivity for bacteria was 5·9 days. No cases of sepsis or death were reported during this time.ConclusionBacterial contamination rates, mostly due to gram‐positive bacteria, increased since 2011. Bacterial screening must be aligned with international recommendations, and novel technologies should be explored to reduce the residual risk.

Listeria monocytogenes meningitis in 17 immunocompetent children

Objective To summarize the clinical characteristics and treatment of 17 children with Listeria monocytogenes(LM) meningitis (LMM). Methods Case histories (including clinical features, laboratory examination, treatment, prognosis ) of 17 LMM children who were hospitalized at the Department of Infectious Disease of Beijing Children′s Hospital from January 1, 2013 to December 31, 2017 were analyzed retrospectively.The age ranged from 7 months to 10 years, with an average of 3 years and 5 months. Among them, 1 case 3-<6 years old, and 4 cases≥6 years old. Related literatures were summarized. Results All of 17 patients were diagnosed by a positive cerebrospinal fluid culture of LM.All patients had fever.Other symptoms included seizures, headache and vomiting were found during the course of disease; infectious symptoms were relatively mild.The symptoms presented 7 to 50 days before admission.None of the patients was known to have immune deficiencies or any other underlying diseases.Five cases underwent strain typing, all resulting from strain type 1/2a.All patients used cephalosporin antibiotics before the diagnosis.After the diagnosis was confirmed, sensitive antibiotics were used according to the drug sensitivity test, including Penicillin, Meropenem, Vancomycin, Linezolid, and Sulfamethoxazole-trimethoprim (SMZ), etc.Out of the 17 patients, 2 case had hydrocephalus, of which 1 cases had clinical symptoms, and underwent surgery for a ventriculoperitoneal shunt.All patients were followed up for 1 year, with good prognosis and no neurological sequela. Conclusions LMM is rare in children, especially in children with no immune deficiencies.LMM in children can present with hydrocephalus.Ampicillin remains the first choice of treatment, while meropenem, SMZ and Linezolid can be used as substitution drugs. Key words: Child; Listeria monocytogenes; Meningitis

Prevalence and antimicrobial resistance of Listeria species and subtyping and virulence factors of Listeria monocytogenes from retail meat

AbstractIn this study, of 124 samples of ground beef and chicken meat, 101 (81.5%) were positive for Listeria spp. Listeria innocua (35.5%) and Listeria monocytogenes (26.6%) were the most frequently isolated species. All 33 (100%) L. monocytogenes isolates were positive for the virulence genes hlyA, actA, inlA, inlB, inlC, inlJ, prfA, plcA, and iap. Serotype 1/2a, which is one of the listeriosis‐associated serotypes, was the most predominant serotype (57.6%), followed by 1/2c (39.4%) and 3c (3%). In polymerase chain reaction‐restriction fragment length polymorphism (PCR‐RFLP) analysis of inlA for subtyping of the L. monocytogenes strains, the AluI and MluCI enzymes generated two different profiles. Almost all chicken strains were grouped in similar PCR‐RFLP profiles with both restriction enzymes. Most Listeria isolates were resistant to ceftriaxone (79.7%), fusidic acid (63.3%), and clindamycin (47.7%). Resistance to penicillin and ampicillin occurred in 1.6 and 17.9% of the isolates, respectively. The percentage of resistance to three or more agents was 48.1%.Practical applicationThe presence of Listeria spp., especially L. monocytogenes, in foods is inevitable because of the ubiquitous nature of Listeria spp. Illnesses resulting from the consumption of contaminated food severely affect sensitive groups, especially pregnant women, unborn fetuses and newborns as a result of transmission across the placenta or during delivery. Immunosuppressed adults are also sensitive to infection. Listeria grows well at cold temperatures, so storage of contaminated food in the refrigerator can also increase the risk of infections for consumers. In particular, limiting the exposure of pregnant women and immunosuppressed patients to potential sources of Listeria such as raw and undercooked meats is recommended.

Clinical analysis of Listeria monocytogenes meningitis in 11 meonates

目的 探讨新生儿李斯特菌脑膜炎的临床表现、治疗及转归。 方法 对2013年3月至2016年6月山西省儿童医院收治的11例新生儿李斯特菌脑膜炎患儿的临床资料进行回顾性分析，并进行随访。 结果 11例患儿中，早发型9例(82%)，晚发型2例(18%)。11例患儿中8例(73%)出现神经系统并发症，均为早发型患儿。5例患儿入院前曾应用头孢类抗生素，疗效差。明确病原菌后所有患儿均予青霉素/氨苄西林，其中6例联合美罗培南治疗。10例患儿获随访，随访时间为7～47个月，2例患儿(早发型)出现语言运动发育落后，其余8例正常。 结论 新生儿李斯特菌脑膜炎临床表现缺乏特异性，早发型多见，且易出现神经系统并发症及后遗症。做好产前预防、早期诊断并及时应用敏感抗生素，可提高治愈率、改善预后。

Epistatic control of intrinsic resistance by virulence genes in Listeria.

Elucidating the relationships between antimicrobial resistance and virulence is key to understanding the evolution and population dynamics of resistant pathogens. Here, we show that the susceptibility of the gram-positive bacterium Listeria monocytogenes to the antibiotic fosfomycin is a complex trait involving interactions between resistance and virulence genes and the environment. We found that a FosX enzyme encoded in the listerial core genome confers intrinsic fosfomycin resistance to both pathogenic and non-pathogenic Listeria spp. However, in the genomic context of the pathogenic L. monocytogenes, FosX-mediated resistance is epistatically suppressed by two members of the PrfA virulence regulon, hpt and prfA, which upon activation by host signals induce increased fosfomycin influx into the bacterial cell. Consequently, in infection conditions, most L. monocytogenes isolates become susceptible to fosfomycin despite possessing a gene that confers high-level resistance to the drug. Our study establishes the molecular basis of an epistatic interaction between virulence and resistance genes controlling bacterial susceptibility to an antibiotic. The reported findings provide the rationale for the introduction of fosfomycin in the treatment of Listeria infections even though these bacteria are intrinsically resistant to the antibiotic in vitro.

Clinical features and outcome analysis of 16 cases of Listeria infection in neonates

目的 探讨新生儿期李斯特菌感染的临床特征、结局及其影响因素，为临床早发现、早治疗提供依据，改善新生儿预后。 方法 回顾性分析2014年4月至2017年4月郑州大学第三附属医院确诊的16例李斯特菌感染新生儿的临床资料，对李斯特菌感染的临床表现、治疗情况、围生期因素及预后进行分析总结。 结果 16例李斯特菌感染新生儿中，早产儿14例、足月儿2例，5 min Apgar评分≤7分7例。15例血培养阳性，4例脑脊液培养阳性，2例痰培养阳性，均为早发感染。首发表现中呼吸困难7例，窒息后呼吸衰竭5例；病程中均有呼吸异常表现，发热7例，腹胀6例；生后1 h内CRP升高15例。初选抗生素有8例为哌拉西林/他唑巴坦，8例头孢类抗生素。母亲先兆早产11例，产前发热10例，宫内窘迫9例，产前外周血WBC或CRP升高14例。6例母亲血或(和)阴道分泌物培养为单核细胞增生性李斯特菌。16例新生儿中，治愈7例，好转要求出院4例，生后24 h内放弃治疗3例，死亡2例，2例死亡病例首选药物均为头孢类抗生素。4例化脓性脑膜炎中，1例治愈，1例好转要求出院，1例外院治疗20 d转入者遗留脑积水，1例生后3 d死亡。 结论 李斯特菌感染新生儿以早产儿为主，多为早发型。对有先兆早产、产前发热、宫内窘迫及产前感染指标升高的孕产妇及其新生儿均应警惕李斯特菌感染，首选敏感抗生素治疗至关重要。

Influence of the cleaning system of conveyor belts on microbiological quality of poultry meat

ABSTRACT This study focused on assessing the microbiology of conveyor belts surfaces, cleaned or not with pressurized water, and verification of the influence of this process on the microbiological quality of poultry meat. A reduction on mesophilic, psychrotrophic and Enterobacteriaceae counts (P&lt;0.05) on dry conveyor belts compared to wet ones was observed. For the chicken leg (consisting of drumstick and thigh) samples, no statistically significant differences were detected on counts of indicators of microorganisms on poultry legs (composed by drumstick and thigh). For poultry meat conducted on wet or dry conveyor belts, 99% and 86%, were positive for Listeria spp, respectively. Only one sample of chicken leg was positive for presence of L. monocytogenes. These results demonstrate that there is no need to use water for cleaning conveyor belts during processing, which allows a reduction on the use of potable water in poultry slaughterhouses without jeopardizing food safety and public health.

Incidence of Listeria spp. in Ready-to-Eat Food Processing Plant Environments Regulated by the U.S. Food Safety and Inspection Service and the U.S. Food and Drug Administration

A multiyear survey of 31 ready-to-eat (RTE) food processing plants in the United States was conducted to determine the incidence of Listeria spp. in various RTE production environments. Samples were collected from 22 RTE plants regulated by the U.S. Department of Agriculture's Food Safety and Inspection Service (FSIS) and from 9 RTE food plants regulated by the U.S. Department of Health and Human Services' Food and Drug Administration (FDA). Only nonfood contact surfaces in the RTE manufacturing areas with exposed RTE product were sampled. Each sample was individually analyzed for the presence of Listeria spp. by using a PCR-based rapid assay. In total, 4,829 samples were collected from various locations, including freezers, equipment framework, floors, walls, wall-floor junctures, drains, floor mats, doors, and cleaning tools. Nine (29%) of the facilities had zero samples positive for Listeria spp. in the production environment, whereas 22 (71%) had one or more samples positive for Listeria spp. The total incidence of Listeria spp. in all RTE food plants was 4.5%. The positive rate in plants regulated by the FSIS ranged from 0 to 9.7%, whereas the positive rate in plants regulated by the FDA ranged from 1.2 to 36%.

Synthesis, antimicrobial activity and conformational analysis of the class IIa bacteriocin pediocin PA-1 and analogs thereof

The antimicrobial peptide pediocin PA-1 is a class IIa bacteriocin that inhibits several clinically relevant pathogens including Listeria spp. Here we report the synthesis and characterization of whole pediocin PA-1 and novel analogs thereof using a combination of solid- and solution-phase strategies to overcome difficulties due to instability and undesired reactions. Pediocin PA-1 thus synthesized was a potent inhibitor of Listeria monocytogenes (MIC = 6.8 nM), similar to the bacteriocin produced naturally by Pediococcus acidilactici. Of particular interest is that linear analogs lacking both of the disulfide bridges characterizing pediocin PA-1 were as potent. One linear analog was also a strong inhibitor of Clostridium perfringens, another important food-borne pathogen. These results are discussed in light of conformational information derived from circular dichroism, solution NMR spectroscopy and structure-activity relationship studies.

Phenotypic and genotypic characterization of listeria species isolated from poultry and milk products

Listeria monocytogenes has become increasingly important as a food-associated pathogen. It cancause a rare but serious disease called listeriosis with high fatality rates (20–30%) compared withother foodborne microbial pathogens. To estimate the incidence and levels of Listeria spp. indifferent food sources, A total of 200 random samples which collected from different sources 65samples isolated from poultry , 45 from poultry byproducts (Frozen chicken meat balls (kofta),Frozen chicken burger and frozen chicken sausages), 20 from pasteurized milk ,30 from milkproducts (Feta cheese ,cream cheese )and 40 from poultry eggs .Only 7 of total 200 samples (14%)that collected from suspected isolates and detected on Oxford agar, PALCAM agar and ALOA agarwere suspected to be Listeria spp. In poultry, poultry byproducts, pasteurized milk, milk byproductsand poultry eggs, listeria percentage were 0/65(0%), 4/45(1.8), 0/20(0%), 0/30(0%), 3/40(1.2%)isolates, respectively. The in-vitro antimicrobial sensitivity test showed that the isolated L.monocytogenes were sensitive to Sulphamethoxazole /trimethoprim, Gentamycin, Ceftazidime andCephazoline followed by Sulphamethoxazole, ceftriaxone , weak sensitivity to Penicillin . Whilethey were resistant to Erythromycin, Clindamycin, Ampicillin. The results of virulence tests forisolated listeria strains appeared that all of L .monocytogenes were virulent strains as all of themwere positive to CAMP test; showed narrow zone of β–hemolysis on sheep blood agar .The PCRresults for Listeria isolates showed that all strains are L. monoctogenes and have Inl A and hly Agenes positive as virulence genes while negative Inl B, iap and prf A genes.

Foodborne pathogens in unpasteurized milk in Sweden

Raw milk may be a risk for public health if it is contaminated with zoonotic pathogens. To study the prevalence in unpasteurized milk from Swedish farms, bovine and small ruminant dairy farms were sampled. Since the sampling method and transport conditions may influence the outcome of analyses, efforts were made to optimize the methodology. Culturing of bacteria was done from in-line milk filters collected from the milk pipe at the point where it enters the milk bulk tank at the farms and this way of sampling was compared to sampling bulk tank milk (BTM) directly. Analysing milk filters were found to be superior to analysing BTM directly. Conditions for transport of milk filter samples were further improved by the addition of Cary Blair transport medium, which significantly increased the number of positive samples for pathogenic bacteria. The isolation of several foodborne pathogens from milk filters was demonstrated. The prevalence of samples with Staphylococcus aureus was 71% and 64%, and Listeria spp. 21% and 29% from dairy cow and goat/sheep farms, respectively. Campylobacter jejuni, Yersinia enterocolitica and verotoxigenic Escherichia coli (VTEC) O157 were detected in 9%, 2% and 2% of samples from bovine milk, respectively.We conclude that the choice of sampling method and sample handling influence the results of bacterial culturing. From the results of this study, we strongly recommend to sample in-line milk filters instead of BTM directly and to use Cary Blair medium during transport, especially if the samples are to be analysed for Campylobacter spp. and/or Listeria spp. The findings also show that unpasteurized milk from Swedish farms occasionally contain bacteria with zoonotic potential.

Disulfiram-based disulfides as narrow-spectrum antibacterial agents

Sixteen disulfides derived from disulfiram (Antabuse™) were evaluated as antibacterial agents. Derivatives with hydrocarbon chains of seven and eight carbons in length exhibited antibacterial activity against Gram-positive Staphylococcus, Streptococcus, Enterococcus, Bacillus, and Listeria spp. A comparison of the cytotoxicity and microsomal stability with disulfiram further revealed that the eight carbon chain analog was of lower toxicity to human hepatocytes and has a longer metabolic half-life. In the final analysis, this investigation concluded that the S-octylthio derivative is a more effective growth inhibitor of Gram-positive bacteria than disulfiram and exhibits more favorable cytotoxic and metabolic parameters over disulfiram.

DETECTION OF LISTERIA SPP. IN RAW MILK AND DAIRY PRODUCTS RETAILED IN ANKARA

The objective of this study was to determine the prevalence of Listeria species in raw milk, and dairy products. A total of 110 samples were obtained from randomly selected retail stores and local bazaars located in Ankara. Using TS EN ISO 11290-1 method, 23 samples were found positive for Listeria spp. The overall prevalence of Listeria spp. was 20.91%, in which L. innocua was the most commonly recovered species (6.36%). The remaining isolates were identified as L ivanovii (5.45%), L. monocytogenes (4.55%), and L welshimeri (4.55%). The L monocytogenes isolates were positive for the presence of hlyA gene. The highest prevalence of Listeria spp. was found in homemade cheese (9.09%), followed by raw milk (8.19%), and white cheese (3.64%). L monocytogenes was isolated from raw milk and homemade cheese in this study. In conclusion, the low hygienic quality dairy products may lead to listeriosis surveillance in Ankara.

The prevalence and antimicrobial resistance of Listeria spp in raw milk and traditional dairy products delivered in Yazd, central Iran (2016)

Listeria monocytogenes is an important foodborne pathogen which its data in Iranian dairy products is limited. A total of 545 samples of traditional dairy products (raw milk, traditional cheese, traditional butter, traditional curd, and traditional ice cream) were collected from traditional dairy shops located in Yazd, Iran. L. monocytogenes was isolated, and positive samples were confirmed by polymerase chain reaction. Antibiotic sensitivity test was conducted to determine the antibiotic resistance. Listeria species were isolated from 11.7% samples. 4.03% samples were identified as L. monocytogenes, 5.6% as L. innocua, 1.8% as L. seeligeri, and 0.18% L. murrayi. All L. monocytogenes isolates were resistant to tetracycline, chloramphenicol, penicillin, and amoxicillin/clavulanic acid. Consumption of raw milk and its traditional products prepared inadequate heat treatment and the lack of appropriate control measures might lead to serious health problems. As our results show, the Iranian food safety authorities should set up an effective standard to screen all susceptible food for the presence of Listeria spp.

Prevalence and Characterization of Listeria Species from Raw Milk and Dairy Products from Çanakkale Province

The objective of this study was to determine the prevalence of Listeria species, specifically Listeria monocytogenes, in raw milk, pasteurized milk, white cheese, and homemade cheese. A total of 200 food samples were collected and analyzed to examine the presence of Listeria spp. The EN ISO 11290-1 method was used for isolation of Listeria. API Listeria test kit was used for biochemically characterization. Listeria spp. were isolated in 25 of the 200 samples (12.5%). The largest number of Listeria spp. was detected in homemade cheese (24%), followed by raw milk (18%), and white cheese (8%). Listeria spp. were not isolated from the pasteurized milk. The most common species isolated were Listeria innocua (5.5%); the remaining Listeria isolates were Listeria ivanovi (3.5%), Listeria welshimeri (3%), and Listeria monocytogenes (0.5%). Listeria monocytogenes was detected in only raw milk.

Effect of Serving Time on Microbiological Quality of Food Served (Chicken Dish and Rice) During Wedding Banquet

Ayam masak merah (chicken in tomato sauce) and nasi minyak (flavoured ghee rice) are among the common dish served in Malay wedding banquet. The microbiological quality of these dishes becomes a concern when there was a food poisoning that caused four deaths after attending the wedding banquet. Therefore, the aim of this work is to investigate the microbiological quality of ayam masak merah and nasi minyak during the serving time (0, 1, 2, 3 and 4 hours) at the wedding banquet. The microbiological analysis were; total plate count (TPC), total coliform, Escherichia coli , Staphylococcus aureus, Bacillus cereus, Salmonella spp., and Listeria spp. The results showed that ayam masak merah has the highest count for TPC, total coliform, Escherichia coli, Staphylococcus aureus, but low count in Listeria spp. and Salmonella spp. was not detected. Highest TPC was observed at the first hour of serving time, 7.33 log CFU/g, while for total coliforms and Staphylococcus aureus was at the 4 hours of serving time, 7.44 log CFU/g and 7.27 log CFU/g respectively.

Prevalence, Antimicrobial Resistance, and Genetic Diversity of Listeria spp. Isolated from Raw Chicken Meat and Chicken-Related Products in Malaysia

Listeria spp. are ubiquitous in nature and can be found in various environmental niches such as soil, sewage, river water, plants, and foods, but the most frequently isolated species are Listeria monocytogenes and Listeria innocua. In this study, the presence of Listeria spp. in raw chicken meat and chicken-related products sold in local markets in Klang Valley, Malaysia was investigated. A total of 44 Listeria strains (42 L. innocua and 2 L. welshimeri) were isolated from 106 samples. Antibiotic susceptibility tests of the L. innocua strains revealed a high prevalence of resistance to clindamycin (92.9%), ceftriaxone (76.2%), ampicillin (73.8%), tetracycline (69%), and penicillin G (66.7%). Overall, 31 L. innocua and 1 L. welshimeri strain were multidrug resistant, i.e., nonsusceptible to at least one antimicrobial agent in three or more antibiotic classes. The majority of the L. innocua strains were placed into five AscI pulsogroups, and overall 26 distinct AscI pulsotypes were identified. The detection of multidrug-resistant Listeria strains from different food sources and locations warrants attention because these strains could serve as reservoirs for antimicrobial resistance genes and may facilitate the spread and emergence of other drug-resistant strains.

Molecular ecology of Listeria spp., Salmonella, Escherichia coli O157:H7 and non-O157 Shiga toxin-producing E.coli in pristine natural environments in Northern Colorado.

Molecular subtyping is commonly used in foodborne disease surveillance and microbial source tracking. There is a knowledge gap regarding the molecular ecology of foodborne pathogens in non-food-associated environments. The objective of this study was to isolate and subtype foodborne pathogens from pristine natural environments with minimal anthropogenic inputs. Five locations (wilderness areas) in Northern Colorado were sampled during the spring, summer and fall over a 2-year period. Soil, water, sediment, surface soil and wildlife faecal samples were microbiologically analysed to detect Listeria, Salmonella and Shiga toxin-producing Escherichia coli (STEC), and resultant isolates were subtyped. Three samples tested positive for Listeria monocytogenes and 19 samples contained other Listeria spp. Salmonella was isolated from two samples, five samples contained non-O157 STEC, and E.coli O157:H7 was not detected. Two L. monocytogenes isolates from faecal samples collected from the same wilderness area over a year apart shared the same PFGE pattern, while all other isolates had a unique type. Our data indicate that (i) there was a rare presence of human foodborne pathogens in pristine natural environments in Northern Colorado, (ii) there was genetic diversity between organisms isolated within a given wilderness area, and (iii) the Northern Colorado climate and topography may contribute to the low occurrence of these organisms. Relatively little is known about the molecular ecology of foodborne pathogens in pristine natural environments. While foodborne pathogens were rarely detected in wildlife faecal and environmental samples from the wilderness areas in this study, some isolates shared DNA fingerprint types with human clinical isolates from same region during the same time frame, highlighting the need for environmental isolate subtype data. The availability of molecular subtyping data for non-food-associated foodborne pathogen isolates can facilitate epidemiological and microbial source tracking investigations.

Saúde Animal, Biossegurança e Segurança dos alimentos

Pork meat and processed pork meat products may carry some hazards that threaten the consumer’s health. These hazards are related with animal health or with the way in which the raw materials are manipulated during slaughtering and manufacturing until the consumption. Substances having anabolic effects, the residues of veterinary drugs and chemical contaminants, some of them with origin in animal production but others produced during the transformation processes should be considered among chemical hazards. Concerning biological hazards, we can mention some parasites like Toxoplasma gondii, Trichinella spiralis, Taenia solium and also some bacteria like Salmonella spp., Campylobacter spp., Yersinia enterocolitica and Listeria monocytogenes. The physicochemical characteristics of fresh meat further facilitate the growth of various microorganisms, other than those mentioned above, which turns it into a highly perishable product. Several transformation processes of the raw material, provide different food products to consumers and constitute ways to increase its shelf-life. Drying, fermentation and cure are among these processing methods. In Portugal there is a wide variety of processed meat products, such as Chourico, Paio, Presunto, Salsichao and Catalao many of them manufactured according to traditional techniques of their regions of origin. Some of these products have been studied at the Universidade de Evora. Some results, which show the favourable effect of a range of transformation processes in controlling some of the mentioned biological hazards, will be presented.

Public Health Implications of Waste Dump to Inhabitants in the Environment

Dump sites are naturally associated with foul odour which obviously is product of microbial activities. The bacterial agents responsible for this decomposition may be injurious to humans. In order to determine the genera of bacteria responsible, Petri dishes containing three different types of media, nutrient, MacConkey and blood agars were exposed for fifteen minutes, and incubated at 37°C for 24 hours. Organisms that grew were analyzed to determine if they are pathogens. Five plates of each media were exposed, and the mean of the colony counts were expressed as colony forming units per millitre (cfu/ml). Three different dump sites were studied, namely school waste dump (SWD), Village waste dump (VWD) and Market waste dump (MWD). Results of Petri dish exposure for 15 mins showed mean cfu/ml of 300, 250 and 300 on nutrient agar for SWD, VWD and MWD respectively. 100, 120 and 150 on MacConkey agar for SWD, VWD and MWD respectively then 20, 15 and 25 on blood agar for SWD, VWD and MWD respectively. Cultural characteristics of the isolates revealed diverse shapes, margins, colours and sizes. Phenotypic characterization showed the Grain reaction, catalase, coagulase, motility, indole, oxidase tests, glucose fermentation, capsule and spore tests results of the isolates. Isolates were tentatively identified to be Listeria spp, Streptococcus spp, Escherischia spp, Staphylococcus spp, Bacillus spp, Shigella spp and Micrococcus spp, by Bergey’s manual of determinative bacteriology. Virulence test by haemolysis assay showed both Streptococcus spp and Listeria spp to be α- haemolysis negative and β-haemolysis positive. Their zones of inhibition were 2-2.5 mm and 3.0-3.5 mm for Streptococcus spp, while Listeria spp was 1.5 mm. Capsule stain was positive for Streptococcus spp and Escherischia spp. Spore stain was positive only for Bacilluis spp. These finds show that pathogenic bacteria are associated with waste dumps and therefore can be injurious to public health.