Safety Properties of Escherichia coli O157:H7 Specific Bacteriophages: Recent Advances for Food Safety.

Shiga-toxin-producing Escherichia coli (STEC) is typically detected on food products mainly due to cross-contamination with faecal matter. The serotype O157:H7 has been of major public health concern due to the severity of illness caused, prevalence, and management. In the food chain, the main methods of controlling contamination by foodborne pathogens often involve the application of antimicrobial agents, which are now becoming less efficient. There is a growing need for the development of new approaches to combat these pathogens, especially those that harbour antimicrobial resistant and virulent determinants. Strategies to also limit their presence on food contact surfaces and food matrices are needed to prevent their transmission. Recent studies have revealed that bacteriophages are useful non-antibiotic options for biocontrol of E. coli O157:H7 in both animals and humans. Phage biocontrol can significantly reduce E. coli O157:H7, thereby improving food safety. However, before being certified as potential biocontrol agents, the safety of the phage candidates must be resolved to satisfy regulatory standards, particularly regarding phage resistance, antigenic properties, and toxigenic properties. In this review, we provide a general description of the main virulence elements of E. coli O157:H7 and present detailed reports that support the proposals that phages infecting E. coli O157:H7 are potential biocontrol agents. This paper also outlines the mechanism of E. coli O157:H7 resistance to phages and the safety concerns associated with the use of phages as a biocontrol.

Antimicrobial Potential and Phytochemical Screening of Clathria sp. 1 and Tedania (Tedania) stylonychaeta Sponge Crude Extracts Obtained from the South East Coast of South Africa.

Scientists have continuously searched for novel bioactive compounds to overcome the inherent problems associated with drug resistance, the evolution of unknown diseases, and the toxicity of currently used compounds. The ocean has been considered a rich source of compounds that possess unique chemical structures and novel biological capabilities. Biologically active molecules isolated from marine flora and fauna have shown significant advancement over the past century in the pharmaceutical industry. Marine natural products (MNPs) have been used as nanomedicine, cosmetics, wound healing, antimicrobial agents, anticancer agents, and anti-inflammatory agents. The physicochemical parameters of the collection site were also recorded. This study's marine sponge species were collected from Phillip's Reef, South Africa, at 12 m during the spring season. Ethyl acetate (EA) and dichloromethane : methanol (DCM : ME, 1 : 1) were used as extraction solvents. Crude extracts of the marine sponges were tested against MRSA, P. aeruginosa, C. difficile, A. fumigatus, and C. albicans. Phytochemical screening was conducted to identify seven critical phytochemical groups. A pH reading of 8.01 and a temperature of 15.45°C were recorded at the sampling site. Clathria sp. 1 and Tedania (Tedania) stylonychaeta EA crude extracts showed bioactivity against all five test pathogens. The DCM : ME crude extract of Clathria sp. 1 was the only bioactive crude extract from DCM : ME extracts. This crude extract was only bioactive against C. albicans as no activity was observed against the other four pathogens. EA crude extracts of Clathria sp. 1 yielded more significant inhibition zones against both fungal pathogens. These EA crude extracts performed better than fluconazole as inhibition zones of 35 ± 0 mm at 24 mg/ml, 31 ± 0 mm at 19 mg/ml, 31 ± 0 mm at 14.4 mg/ml, 30 ± 0 mm at 9.6 mg/ml, and 25 ± 0 mm at 7.2 mg/ml were recorded. Clathria sp. 1 crude extracts exhibited higher inhibition zones compared to Tedania (Tedania) stylonychaeta. The antibiotic imipenem (26 ± 0.7 mm at 10 µg) and ciprofloxacin (30 ± 0.3 mm at 5 µg) exhibited higher zones of inhibition than EA crude extracts of Tedania (Tedania) stylonychaeta at all test concentrations. In this study, Clathria sp. 1 was observed to have broad-spectrum bioactivity as EA crude extracts were bioactive against MRSA, P. aeruginosa, C. difficile, A. fumigatus, and C. albicans. In addition to this, the EA crude extract of Clathria sp. 1 was bacteriostatic (9.6 mg/ml). Clathria sp. 1 DCM : ME crude extract only tested positive for the presence of terpenoids. In contrast, EA crude extracts did not test positive for the existence of any of the seven phytochemicals. Our study has revealed that Tedania (Tedania) stylonychaeta and Clathria sp. 1 sponge species collected from Phillip's Reef in South Africa can produce bioactive compounds useful against bacterial and fungal species.

Duodenal ulcer promoting gene (DupA), plasticity region genes and sigma factors in H. pyloristrains from Nigeria.

INTRODUCTION: Helicobacter pylori is a principal cause of gastric cancer. The aim of this study was to determine the prevalence and contribution of duodenal ulcer promoting gene A (dupA), the plasticity region genes and sigma factors in relation to their pathological expression of H. pylori infections in the Nigerian population. METHODOLOGY: Polymerase Chain Reaction was used to analyze a total of forty-nine H. pylori strains isolated from patients attending various endoscopic units in tertiary hospitals in Nigeria for complete dupA (G27 variant), jhp0917, jhp0918, other plasticity region genes jhp 914/917, jhp0914, jhp0940 and sigma factors. RESULTS: PCR results indicated that the prevalence of complete dupA (G27 variants), jhp0917, jhp0918 and other plasticity region genes jhp0914, jhp0914/0917 and jhp0940 in the H. pylori strains were 4%, 53%, 88%, 73%, 12% and 0% respectively. The prevalence values of the sigma factors were 96%, 92%, 80% for rpoN,  fliA and rpoD respectively. However, the endoscopic findings showed that erosion, normal mucosal, ulcer, hyperaemic stomach, mucosal atrophy and oedematous stomach in the patients where the H. pylori strains were isolated were 40.8%, 32.7%, 10.2%, 8.2%, 2.0% and 6.1% respectively. There was significant association between jhp0917, jhp914/917 and G27 variant and the endoscopic findings, while other plasticity genes showed no association with the endoscopic findings. CONCLUSION: These results suggest that the presence of jhp0917, jhp0914/917 and G27 variant could be used as marker to predict the pathological effect of severity in Nigeria patients with H. pylori infection.

Antibiotic Susceptibility of Non-Cholera Vibrios Isolated from Farmed and Wild Marine Fish (Argyrosomus japonicus), Implications for Public Health.

This study aimed to evaluate the antibiogram and antibiotic resistance genes (ARGs) of Vibrio isolates recovered from a marine fish (Argyrosomus japonicus) and water samples from two commercial dusky kob aquaculture farms and the Kariega estuary, South Africa, and to evaluate these findings for their public health implications. A total of 277 molecularly confirmed Vibrio isolates consisting of 126 Vibrio fluvialis, 45 Vibrio vulnificus, 30 Vibrio Parahaemolyticus, and 76 vibrios belonging to species of the genus other than Vibrio cholerae were subjected to susceptibility testing to 15 antibiotics by the disc diffusion method. Multiple antibiotic resistance index (MARI) was used to determine the antibiotic resistance-associated health risk, while polymerase chain reaction was used to evaluate the presence of 14 ARGs for nonsusceptible strains. Highest resistances were recorded to amoxicillin (76.2%), ampicillin (67.5%), erythromycin (38.3%), and doxycycline (35.0%), while susceptibilities were highest to gentamicin (100%), followed by norfloxacin (97.8%), florfenicol (90.3%), tetracycline (87.7%), and chloramphenicol (87.4%). We recorded a 58.5% multidrug resistance (resistance to ≥2 antimicrobial classes). MARI did not vary significantly between sites (p > 0.05); however, values of >0.2 were recorded in 40% (108/277) of all strains tested. ARG markers, ampC, blaOXA, tetA, tetM, dfr1, sul1, sul2, ermB, nptII, strA, and SXT integrase, were detected in one or more strains with ermB (82.5%), sul2 (53.8%), strA (44%), dfr1 (42.3%), and tetM (38.3%) being the most abundant. Healthy marine finfish (dusky kob) and their environment can serve as reservoirs for antibiotic resistant vibrios and ARGs, which could be disseminated to humans and other susceptible bacteria and this therefore becomes a public health concern.

Occurrence of Virulence Genes Associated with Human Pathogenic Vibrios Isolated from Two Commercial Dusky Kob (Argyrosmus japonicus) Farms and Kareiga Estuary in the Eastern Cape Province, South Africa.

Background: Seafood-borne Vibrio infections, often linked to contaminated seafood and water, are of increasing global public health concern. The aim of this study was to evaluate the prevalence of human pathogenic vibrios and their associated virulence genes isolated from fish and water samples from 2 commercial dusky kob farms and Kareiga estuary, South Africa. Methods: A total of 200 samples including dusky kob fish (n = 120) and seawater (n = 80) were subjected to Vibrio screening on thiosulfate-citrate-bile salts-sucrose agar (TCBS). Presumptive isolates were confirmed and delineated to V. cholerae, V. parahaemolyticus, V. vulnificus, and V. fluvialis by PCR. Various pathogenic gene markers were screened: V. parahaemolyticus (trh and tdh), V. vulnificus (vcgE and vcgC) and V. fluvialis (stn, vfh,hupO, vfpA). Restriction Fragment Length Polymorphism (RFLP) of the vvhA gene of V. vulnificus strains was performed to determine the associated biotypes. Results: Total Vibrio prevalence was 59.4% (606/1020) of which V. fluvialis was the most predominant 193 (31.85%), followed by Vibrio vulnificus 74 (12.21%) and V. parahaemolyticus 33 (5.45%). No V. cholerae strain was detected. One of the V. parahaemolyticus strains possessed the trh gene 7 (9.46%) while most (91.9%; 68/74) V. vulnificus isolates were of the E-type genotype. V. fluvialis virulence genes detected were stn (13.5%), hupO (10.4%) and vfpA (1.0%). 12.16% (9/74) of V. vulnificus strains exhibited a biotype 3 RFLP pattern. Conclusions: This is the first report of potentially pathogenic vibrios from healthy marine fish in the study area, and therefore a public health concern.

Antimicrobial Susceptibility of Staphylococcus aureus Isolated from Recreational Waters and Beach Sand in Eastern Cape Province of South Africa.

Background: Resistance of Staphylococcus aureus to commonly used antibiotics is linked to their ability to acquire and disseminate antimicrobial-resistant determinants in nature, and the marine environment may serve as a reservoir for antibiotic-resistant bacteria. This study determined the antibiotic sensitivity profile of S.aureus isolated from selected beach water and intertidal beach sand in the Eastern Cape Province of South Africa. Methods: Two hundred and forty-nine beach sand and water samples were obtained from 10 beaches from April 2015 to April 2016. Staphylococcus aureus was isolated from the samples using standard microbiological methods and subjected to susceptibility testing to 15 antibiotics. Methicillin-resistant Staphylococcus aureus (MRSA) was detected by susceptibility to oxacillin and growth on Brilliance MRSA II agar. Antibiotic resistance genes including mecA, femA rpoB, blaZ, ermB, ermA, ermC, vanA, vanB, tetK and tetM were screened. Results: Thirty isolates (12.3%) were positive for S. aureus by PCR with over 50% showing phenotypic resistance to methicillin. Resistance of S. aureus to antibiotics varied considerably with the highest resistance recorded to ampicillin and penicillin (96.7%), rifampicin and clindamycin (80%), oxacillin (73.3%) and erythromycin (70%). S.aureus revealed varying susceptibility to imipenem (96.7%), levofloxacin (86.7%), chloramphenicol (83.3%), cefoxitin (76.7%), ciprofloxacin (66.7%), gentamycin (63.3%), tetracycline and sulfamethoxazole-trimethoprim (56.7%), and vancomycin and doxycycline (50%). All 30 (100%) S. aureus isolates showed multiple antibiotic-resistant patterns (resistant to three or more antibiotics). The mecA, femA, rpoB, blaZ, ermB and tetM genes were detected in 5 (22.7%), 16 (53.3%), 11 (45.8%), 16 (55.2%), 15 (71.4%), and 8 (72.7%) isolates respectively; Conclusions: Results from this study indicate that beach water and sand from the Eastern Cape Province of South Africa may be potential reservoirs of antibiotic-resistant S. aureus which could be transmitted to exposed humans and animals.

Multi-drug resistant toxigenic Vibrio cholerae O1 is persistent in water sources in New Bell-Douala, Cameroon.

BACKGROUND: Cholera has been endemic in Douala, since 1971 when it was first recorded in Cameroon. Outbreaks have often started in slum areas of the city including New Bell. Despite the devastating nature of outbreaks, always resulting in high mortality and morbidity, a paucity of information exists on the reservoirs of the causative agent, V. cholerae, and factors maintaining its persistence. This has complicated disease prevention, resulting in frequent outbreaks of cholera. We investigated water sources in New Bell for contamination with V. cholerae O1 with pathogenic potential, to highlight their role in disease transmission. Antibiotic susceptibility pattern of isolates and the environmental factors maintaining its persistence were investigated. METHOD: Water samples from various sources (taps, dug wells, streams) were analyzed for contamination with V. cholerae O1 using standard methods. Antibiotic susceptibility was determined by disc diffusion method. Pathogenic potential of isolates was determined by analyzing for genes for cholera toxin (ctx), toxin co-regulated pilus (tcpA), and zonula occludens toxin (zot) by PCR. Physico-chemical characteristics of water (pH, temperature and salinity) were investigated using standard methods. The Spearman's Rank correlation was used to analyze the relationship between physico-chemical factors and the occurrence of V. cholerae O1. Differences were considered significant at P≤0.05. RESULTS: Twenty-five V. cholerae O1 strains were isolated from stream and well samples in both dry and rainy seasons. Twenty-three (92%) isolates were multidrug resistant. All isolates had genes for at least one virulence factor. Cholera toxin gene was detected in 7 isolates. Of the 15 isolates positive for tcpA gene, two had Classical type tcpA while 13 had tcpA El Tor. All tcpA Classical positive isolates were positive for ctx gene. Isolates were grouped into nine genotypes based on the genes analyzed. pH and salinity significantly correlated with isolation of V. cholerae O1. CONCLUSION: Multidrug resistant Vibrio cholerae O1 with pathogenic potential is present in some wells and streams in study area. pH and salinity are among the factors maintaining the persistence of the organism. Findings indicate an urgent need for potable water supply in study area and in addition, regular disinfection of water from contaminated sources to prevent outbreak of cholera.