aureus isolated from food poisoning outbreaks in Egypt

BACKGROUND

Staphylococcus aureus (S. aureus), especially methicillin-resistant S. aureus (MRSA), is a known disease-causing bacteria with many associated health hazards. Staphylococcal food poisoning can result from staphylococcal enterotoxins (SEs).

METHODS

In this study, 50 S. aureus isolates were isolated from the gastrointestinal tract (GIT) clinical samples of patients with food poisoning in clinical laboratories at Mansoura University Hospital, Egypt. For determination their antibiogram, these isolates were tested for antimicrobial sensitivity against 12 antimicrobial agents using the agar disk diffusion test. After DNA extraction from the isolates, conventional polymerase chain reaction (PCR) was used to detect mecA and SEs genes.

RESULTS

As a result, all isolates were ampicillin and cefoxitin-resistant, while 86% (43 of 50) of the tested isolates exhibited multidrug resistance (MDR). In contrast, the highest sensitivity was confirmed against vancomycin, linezolid and quinolones, namely ciprofloxacin and norfloxacin. Although 100% of the isolates were mecA positive, staphylococcal enterotoxin genes set-A, set-B, set-C, set-G, set-M, and set-O genes were detected in 56%, 20%, 8%, 32%, 16%, and 24%, of the tested isolates, respectively. Finally, isolates encompassing SEs genes were used to validate a microarray chip, indicating its potential for a better methodological approach for detecting and identifying SEs in human samples.

CONCLUSION

The genotypic findings of this study may help explain the enterotoxigenic patterns in S. aureus among Egyptian patients with food poisoning.

Detection of genes encoding enterotoxins (SEA-D) in Staphylococcus aureus strains isolated from workers' nasal samples and creamy pastries of Shiraz confectioneries

Background and Objectives

Staphylococcus aureus is responsible for the majority of food poisoning all around the world. Nasal carriers of S. aureus and foodstuffs need for handling are important sources and vehicles to transmit this pathogen to ready-to-eat foods. According to hygienic standards, confectioners should not be contaminated with S. aureus. This study aimed to detect nasal carriers and creamy pastries contaminated with enterotoxigenic S. aureus in confectioneries of Shiraz, Iran.

Materials and Methods

From the confectioneries of Shiraz city, 27 places in the north, south, center, west, and east areas were selected randomly then 100 creamy pastries samples and 117 nasal swabs were collected. Bacteriological and biochemical tests were performed to isolate S. aureus. The polymerase chain reaction (PCR) test was used to identify the virulence and enterotoxins genes of the S. aureus isolates. Agar disk diffusion was performed to find out the antibiotic resistance of the isolates.

Results

Results revealed that 16.24 and 33 percent of workers and creamy pastries were contaminated with S. aureus respectively. Also, 100%, 37%, 58%, and 6% of nasal samples harbored femA, mecA, sea, and sec genes respectively. According to the results 97%, 70%, 54.5%, and 6% of creamy pastries isolates harbored femA, mecA, sea, and sec genes respectively. No isolate carried seb and sed genes. The results also showed that 41.5% of nasals and 5.5% of creamy pastry isolates harbored both sea and sec genes. The sea was the most common enterotoxin gene observed in nasal and creamy pastries. The results of the antimicrobial resistance test showed that 68.42% of nasal and 48.48% of creamy pastry isolates were resistant to cefocxitn (FOX) respectively. Both nasal (89%) and creamy pastry (82%) isolates presented the highest resistance to penicillin (P) and the most sensitivity to trimethoprim-sulphamethoxazole (SXT) (94%). Most of the isolates were sensitive to erythromycin (E), aztreonam (AZM), tetracycline (TE), trimethoprim (TMP), and ciprofloxacin (CP). Isolates of S. aureus harboring multi-enterotoxin genes were resistant to more antibiotics than others.

Conclusion

The presence of enterotoxigenic S. aureus in the workers' nasal samples and creamy pastries of Shiraz confectioneries was high which is a potential public health hazard.

Aeromonas spp. diversity in U.S. mid-Atlantic surface and reclaimed water, seasonal dynamics, virulence gene patterns and attachment to lettuce

Aeromonas, a ubiquitous taxon in water environments, is emerging as a foodborne pathogen of concern that remains understudied and under-reported. We evaluated the distribution of 331 Aeromonas spp. isolates collected from irrigation water over one year and characterised their virulence profile, attachment and ability to persist on lettuce. Water sources included non-tidal and tidal river, farm pond and reclaimed water. Twenty Aeromonas species were identified; A. veronii, A. hydrophila and A. jandaei predominated in all water types and seasons, comprising ~63% of isolates. Species distribution was most affected by water type. The highest and lowest diversity were detected in river and pond water, respectively. A. hydrophila and A. veronii ranked highest in frequency in fresh river and reclaimed water, while A. jandaei ranked first in pond water. Only two isolates carried all five virulence genes tested, while 46% of A. hydrophila (n = 50), 54% of A. veronii (n = 61) and 50% of A. jandaei (n = 32) isolates harboured multiple enterotoxin genes. Detection of alt and ast genes was more likely in summer collections, while ast detection was less likely in tidal brackish river and pond water isolates. Season was a factor in attachment to polystyrene, being strongest in spring isolates. The gene flaA was associated with strong attachment and was more likely to be detected in non-tidal fresh river isolates. A. hydrophila and A. jandaei isolates persisted on lettuce leaves for 24 h, but populations dwindled over 120 h, while loosely and strongly attached cells of A. veronii isolates persisted for 120 h. This study provides comprehensive data on Aeromonas species distribution and environmental traits. The associations revealed among diversity, water type, season, virulence factors and phyllosphere attachment capacity can inform agricultural water standards in novel ways. Moreover, understanding Aeromonas-plant interactions is an important step in advancing food safety of fruit and vegetables.

Detection and molecular characterisation of methicillin-resistant Staphylococcus aureus isolated from raw meat in the retail market

OBJECTIVES

This study aimed to detect and characterise methicillin-resistant Staphylococcus aureus (MRSA) from retail meat in the Czech Republic.

METHODS

Isolates were identified by PCR detection of the S. aureus-specific fragment Sa442 and mecA gene. spa typing, MLST, detection of genes encoding staphylococcal enterotoxins, Panton-Valentine leukocidin (pvl), exfoliative toxins A and B (eta and etb), toxic shock syndrome toxin (tst) and staphylokinase (sak), detection of φSa3 prophage and antimicrobial susceptibility testing were performed.

RESULTS

Of 65 raw meat samples examined (poultry, beef, pork and rabbit), 23 (35.4%) were positive for MRSA. Twelve positive samples originated from poultry (12/33; 36.4%), while the remaining eleven came from pork (9/9; 100%) and pork/beef mixed minced meat (2/5; 40.0%). Eight spa types belonging to five different sequence types (STs) were identified. ST398 was the most frequent (28/36; 77.8%), presenting spa types t011, t034, t2576, t4132, t588 and t899. Other livestock-associated MRSA STs (ST9-t899, ST5-t002, ST692-t8646 or the newly described ST4034-t899) were also sporadically identified. In seven isolates (19.4%), one or more staphylococcal enterotoxin genes were detected, with sea, seg and sei prevailing. Three isolates from turkey [ST398-t899 (n = 2) and ST398-t011] harboured the sak gene, and the latter also harboured the sea gene. Seven isolates from poultry harboured the φSa3 prophage and were resistant to tetracycline.

CONCLUSION

Specific kinds of meat appear to be a possible source of MRSA, although the risk to humans is hard to define. Therefore, surveillance of MRSA in meat as well as hygienic practices should be improved.

Antibiogram and phylogenetic diversity of enterotoxigenic Staphylococcus aureus strains from milk products and public health implications

Food poisoning caused by Staphylococcus aureus (S. aureus) toxins is considered one of the foremost public health threat that usually occurs through the ingestion of raw milk contaminated with staphylococcal enterotoxins. The current study spotlights on the prevalence, antibiogram and genetic diversity of S. aureus enterotoxin genes. One hundred and fifty of raw milk (90) and ice cream (60) samples were randomly collected from local markets from Sadat city, Egypt. S. aureus was recovered from 44% of raw milk and 20% of ice cream samples. The identification for the obtained S. aureus isolates was confirmed through targeting the nuc gene. Antibiogram pattern of 32 S. aureus isolates showed high resistance to Cefoxitin, Sulpha/Trimethoprim, Tetracycline, Norfloxacin, Penicillin and Cephradine. However, high susceptibility to Gentamycin and Vancomycin were observed. Multiplex PCR was a competent practise for the recognition of Staphylococcus enterotoxin (SE) genes (SEA, SEB and SED). The phylogenetic analysis of the SED gene of enterotoxigenic S. aureus strains showed identical similarity with 100% to each other and high similarity with other international isolates in GenBank from different localities and sources. The frequency of enterotoxigenic S. aureus strains in milk products could have serious hazardous effects on humans. These results suggested possible strains transmission between different geographical areas through the food and milk product trades.

High prevalence of methicillin resistant and enterotoxin gene-positive Staphylococcus aureus among nasally colonized food handlers in central Iran

This study defined the prevalence of enterotoxin gene-positive Staphylococcus aureus strains among food handlers and non-food processing healthy nasal S. aureus carriers in central Iran. Meticillin-resistant S. aureus (MRSA) strains were diagnosed by cefoxitin disk diffusion. PCR was used to detect the mecA, Sa442, and enterotoxin genes. Out of the 1113 food handlers, 224 (20.1%) were nasal carriers of S. aureus and 157 (70.1%) of these isolates were positive for one or more enterotoxin genes. The most prevalent enterotoxin gene was sei (40.2%), followed by seg (35.3%), sea (23.5%), seb (15.2%), sec (5.5%), and seh (2.7%). See and sed genes were not found. Sixty seven (42.7%) of enterotoxin gene-positive isolates possessed a single enterotoxin gene, and 64 (40.8%), 23 (14.7%), and 3 (1.9%) contained two, three, or four enterotoxin genes, respectively. The most frequently detected gene combination was sei/seg (n = 35, 22.3%). Thirty seven (16.5%) isolates were diagnosed as MRSA, and 27 (73%) of these strains were positive for at least one enterotoxin gene. Out of 546 healthy controls, 100 individuals were identified as S. aureus nasal carriers; among the strains, 39 (39%) were positive for at least one enterotoxin gene. Only one (1%) CA-MRSA was identified among the strains from the volunteers. A high prevalence of meticillin resistant and enterotoxin-positive S. aureus were documented in food handlers. We suggest that this may be due to the frequent handling of contaminated foodstuffs and that this is possibly related to the elevated frequencies of acquired staphylococcal food poisoning in this population.

Prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in retail food in Singapore

We characterised 227 Staphylococcus aureus isolates from retail food and food handlers’ gloves samples obtained through food surveillance and risk assessment studies between 2011 and 2014. Of 227 isolates, five (2.2%) were methicillin-resistant and belonged to sequence types ST80 (n = 3) and ST6 (n = 2). All five isolates belonged to SCCmec type IV, were Panton-Valentine leukocidin (pvl)-negative and staphylococcal enterotoxin genes-positive. Resistance to azithromycin was found in ST80 isolates, in addition to resistance to beta-lactams. Our finding of two clinically relevant methicillin-resistant S. aureus (MRSA) strains (ST80 and ST6) in ready-to-eat food and food contact surfaces at retail in Singapore suggests food and food contact surfaces as potential environmental sources of MRSA in the community.

Detection of biofilm related genes, classical enterotoxin genes and agr typing among Staphylococcus aureus isolated from bovine with subclinical mastitis in southwest of Iran

Staphylococcus aureus by producing biofilm and facilitating chronic infection is a common cause of mastitis in cows and thereby can cause food poisoning by production of enterotoxins in milk. The agr typing method is an important tool for epidemiological investigation about S. aureus. The aims of the present study were to detect biofilm related genes, 5 classical enterotoxin genes and the agr types among S. aureus isolates. The ability of S. aureus isolates to produce biofilm was evaluated by modified CRA plate. Six biofilm related adhesion genes (icaD, icaA, fnbA, bap, clfA and cna), five classical enterotoxin genes (sea, seb, sec, sed and see) and tst-1 gene were detected by PCR methods. Multiplex-PCR was used to determination of the agr groups. 55 out of 80(68.8%) S. aureus isolates were biofilm producer. The icaD gene was detected in 70 (87.5%) of isolates. The prevalence rates of fnbA, icaA, clfA, cna and bap were 72.5, 56.25, 50, 22.5, and 5% respectively. The agr group I and III were detected in 57.5% 25% of studied isolates. The sea, sed and tst-1 genes were found in 10%, 7.5% and 1.25% of isolates respectively. The majority of S. aureus were able to produce biofilm. Significant associations were observed between presence of the icaD, icaA, fnbA, clfA and the cna genes as well as biofilm formation. The present study revealed that isolates with the agr type III are more potent for biofilm production. Our data supported a possible link between the agr types and certain SE genes.

Food handlers as potential sources of dissemination of virulent strains of Staphylococcus aureus in the community

Food handlers may constitute a reservoir of virulent strains of Staphylococcus aureus and may be vehicles of their transmission to food. One hundred and sixty-two volunteers were assessed for the presence of S. aureus on the hands and in the nose. S. aureus was isolated by routine procedures, and the isolates were tested for susceptibility against a panel of nine antimicrobial agents. The isolates were further characterized by SmaI-PFGE profiling and the presence of virulence factors.

RESULTS

The prevalence of S. aureus was 19.8% in the nose and 11.1% on the hands; 6.2% of the individuals carried S. aureus both in their noses and hands, and three individuals had the same strain (PFGE type) in the nose and on the hands. Although 82% of the isolates were resistant to at least one antibiotic, none demonstrated the presence of either mecA gene or resistance to oxacillin (none identified as MRSA). Sixty-eight percent of the isolates from the nose and hands possessed enterotoxin genes. This study revealed a high prevalence of antibiotic resistance and virulence determinants among the isolates, including not only classical and novel enterotoxin genes but also major virulence factors such as tst. Potential dissemination of these strains in the community is a matter of concern.