Heterotrophic bacteria in drinking water: evaluating antibiotic resistance and the presence of virulence genes

Heterotrophic bacteria, impacting those with infections or compromised immunity, pose heightened health risks when resistant to antibiotics. This study investigates heterotrophic plate count bacteria in water from North West-C (NWC) and North West-G (NWG) facilities, revealing prevalent β-hemolysis (NWC 82.5%, NWG 86.7%), enzyme production (98%), and antibiotic resistance, especially in NWC. NWG exhibits variations in hemolysin (P = 0.013), lipase (P = 0.009), and DNase activity (P = 0.006). Antibiotics, including ciprofloxacin, persist throughout treatment, with high resistance to β-lactams and trimethoprim (47%-100%), predominantly in NWC. Multiple antibiotic resistance index indicates that 90% of values exceed 0.20, signifying isolates from high antibiotic usage sources. Whole genome sequencing reveals diverse antibiotic resistance genes in heterotrophic strains, emphasizing their prevalence and health risks in water.IMPORTANCEThis study's findings are a stark reminder of a significant health concern: our water sources harbor antibiotic-resistant heterotrophic bacteria, which can potentially cause illness, especially in individuals with weakened immune systems or underlying infections. Antibiotic resistance among these bacteria is deeply concerning, as it threatens the effectiveness of antibiotics, critical for treating various infections. Moreover, detecting virulence factors in a notable proportion of these bacteria highlights their elevated risk to public health. This research underscores the immediate need for enhanced water treatment processes, rigorous water quality monitoring, and the development of strategies to combat antibiotic resistance in the environment. Safeguarding the safety of our drinking water is imperative to protect public health and mitigate the spread of antibiotic-resistant infections, making these findings a compelling call to action for policymakers and public health authorities alike.

Pathogenic Potential and Antibiotic Susceptibility: A Comprehensive Study of Enterococci from Different Ecological Settings

The pathway and the lifestyle of known enterococcus species are too complicated. The aim of the present study is to trace the path of pathogenicity of enterococci isolated from seven habitats (Cornu aspersum intestine; Bulgarian yoghurt; goat and cow feta cheese-mature and young, respectively; Arabian street food-doner kebab; cow milk; and human breast milk) by comparing their pathogenic potential. In total, 72 enterococcal strains were isolated and identified by MALDI-TOF, sequencing, and PCR. Hemolytic and gelatinase activity were biochemically determined. PCR was carried out for detection of virulence factors (cylB, esp, gls24, nucl, psaA, agg, gelE, and ace) and antibiotic resistance (erm, ermB, blaZ, vanA, aphA, mefA, gyrA, catpIP501, and aac6'-aph2″). Phenotypic antibiotic resistance was assigned according to EUCAST. Eleven representatives of the genus Enterococcus were identified: E. mundtii, E. casseliflavus, E. gilvus, E. pseudoavium, E. pallens, E. malodoratus, E. devriesei, E. gallinarum, E. durans, E. faecium, and E. faecalis. Twenty-two strains expressed α-hemolysis. Thirteen strains had the cylB gene. Only two strains expressed α-hemolysis and possessed the cylB gene simultaneously. Positive amplification for gelE was found in 35% of the isolates, but phenotypic gelatinase activity was observed only in three strains. All isolates showed varying antibiotic resistance. Only E. faecalis BM15 showed multiple resistance (AMP-HLSR-RP). Correlation between genotypic and phenotypic macrolide resistance was revealed for two E. faecalis strains.

In vivo characterization of the novel ebolavirus Bombali virus suggests a low pathogenic potential for humans

Ebolaviruses cause outbreaks of haemorrhagic fever in Central and West Africa. Some members of this genus such as Ebola virus (EBOV) are highly pathogenic, with case fatality rates of up to 90%, whereas others such as Reston virus (RESTV) are apathogenic for humans. Bombali virus (BOMV) is a novel ebolavirus for which complete genome sequences were recently found in free-tailed bats, although no infectious virus could be isolated. Its pathogenic potential for humans is unknown. To address this question, we first determined whether proteins encoded by the available BOMV sequence found in Chaerephon pumilus were functional in in vitro assays. The correction of an apparent sequencing error in the glycoprotein based on these data then allowed us to generate infectious BOMV using reverse genetics and characterize its infection of human cells. Furthermore, we used HLA-A2-transgenic, NOD-scid-IL-2γ receptor-knockout (NSG-A2) mice reconstituted with human haematopoiesis as a model to evaluate the pathogenicity of BOMV in vivo in a human-like immune environment. These data demonstrate that not only does BOMV show a slower growth rate than EBOV in vitro, but it also shows low pathogenicity in humanized mice, comparable to previous studies using RESTV. Taken together, these findings suggest a low pathogenic potential of BOMV for humans.

Thermal and pigment characterization of environmental fungi in the urban heat island of Baltimore City

One of the major barriers of fungal infections of mammals is the inability to grow and/or survive at mammalian body temperature, typically around 37°C. This has provided mammals an advantage over fungi. However, environmental fungi may soon adapt to persist at higher temperatures, consistent with mammalian body temperature, due to thermal selection pressures imposed by climate change, global warming, and increased frequency of extreme heat events. Consequently, there is a need for more updated information about the thermal tolerance range of fungi near humans, such as in urban areas. The heat island effect suggests that cities are up to 8°C warmer than their suburban counterparts because of increased heat production, asphalt coatings and reduced greenspace among other factors, and it is more common in lower income and marginalized urban communities. Thus, urban centers are at increased risk for the emergence of heat tolerant fungi. In this study, we developed a methodology to collect and archive fungal isolates from sidewalk and soil samples in both warmer and cooler neighborhoods in Baltimore, Maryland. We demonstrate a novel methodology for fungal sample collection from sidewalks, employing the use of standardized and commercially available taffy. Analysis of fungal isolates collected from warmer neighborhoods revealed greater thermal tolerance and lower pigmentation, suggesting local adaptation to heat. Lower pigmentation in hotter areas is consistent with the notion that fungi use pigmentation to help regulate their temperature. Further, we identified the robust presence of the polyextremotolerant fungus Aureobasidium pullalans from the warmest neighborhood in Baltimore, further showing that the extreme conditions of cities can drive proliferation of extremotolerant fungi. This study develops new techniques for environmental fungal collection and provides insight on the fungal census in an urban setting that can inform future work to study how urban environments may drive stress/thermotolerance in fungi, which could alter fungal interactions with humans and impact human health.

Prevalence, Virulence Potential, and Growth in Cheese of Bacillus cereus Strains Isolated from Fresh and Short-Ripened Cheeses Sold on the Italian Market

This study investigated B. cereus presence in 122 samples belonging to 34 typologies of fresh or short-ripened cheeses made from cow, sheep, goat, or buffalo pasteurized milk, and sold on the Italian market. B. cereus was isolated at a prevalence of 9.8%, with a marked variability among cheese categories, and at low counts (always below 2.26 Log CFU/g). Twelve isolates were identified by MALDI-TOF analysis and typified by RAPD PCR as belonging to different B. cereus strains. All the strains were tested for the production of hemolysin BL, phosphatidylcholine-specific phospholipase C, proteases, and biofilm formation, and for the presence of chromosomal toxin-encoding genes (sph, plcA, cytK, entFM, bcet, nheA, nheB, nheC). Overall, 92% of strains harbored bcet, 75% the three genes nheA, nheB, and nheC, as well as plcA and sph, 67% entFM, and 33% cytK. All strains showed biofilm-forming ability. A chemical-physical characterization of the cheeses was also performed to show their suitability as substrates for B. cereus growth, showing high heterogeneity in terms of pH, aw, salt content, and concentration of organic acids. Finally, the ability to support spore germination and vegetative cell growth of a selected cheese was investigated in spores-inoculated samples maintained at 10 °C and 15 °C, showing the inhibitory effect of low storage temperatures.

In Vitro Cytopathogenic Activities of Acanthamoeba T3 and T4 Genotypes on HeLa Cell Monolayer

Amoebic keratitis and encephalitis are mainly caused by free-living amoebae of the genus Acanthamoeba, which consists of both pathogenic and nonpathogenic species. The global distribution, amphizoic properties and the severity of the disease caused by Acanthamoeba species have inspired the scientific community to put more effort into the isolation of Acanthamoeba, besides exploring the direct and indirect parameters that could signify a pathogenic potential. Therefore, this study was performed to characterize the pathogenic potential of Acanthamoeba isolated from contact lens paraphernalia and water sources in Malaysia. Various methodologies were utilized to analyze the thermotolerance and osmotolerance, the secretion level of proteases and the cytopathic effect of trophozoites on the cell monolayer. In addition, the in vitro cytopathogenicity of these isolates was assessed using the LDH-release assay. A total of 14 Acanthamoeba isolates were classified as thermo- and osmotolerant and had presence of serine proteases with a molecular weight of 45-230 kDa. Four T4 genotypes isolated from contact lens paraphernalia recorded the presence of serine-type proteases of 107 kDa and 133 kDa. In contrast, all T3 genotypes isolated from environmental samples showed the presence of a 56 kDa proteolytic enzyme. Remarkably, eight T4 and a single T3 genotype isolates demonstrated a high adhesion percentage of greater than 90%. Moreover, the use of the HeLa cell monolayer showed that four T4 isolates and one T3 isolate achieved a cytopathic effect in the range of 44.9-59.4%, indicating an intermediate-to-high cytotoxicity level. Apart from that, the LDH-release assay revealed that three T4 isolates (CL5, CL54 and CL149) and one T3 isolate (SKA5-SK35) measured an exceptional toxicity level of higher than 40% compared to other isolates. In short, the presence of Acanthamoeba T3 and T4 genotypes with significant pathogenic potential in this study reiterates the essential need to reassess the functionality of other genotypes that were previously classified as nonpathogenic isolates in past research.

Hortaea werneckii isolates exhibit different pathogenic potential in the invertebrate infection model Galleria mellonella

Hortaea werneckii is a black yeast with a remarkable tolerance to salt. Most studies have been dedicated to understanding how H. werneckii adapts to hypersaline environments. H. werneckii has an unconventional cell cycle in which it alternates between fission and budding, which is modulated by cell density. Additionally, H. werneckii can cause superficial mycosis of the palm and sole of humans. Here, we determine the impact of salt concentration on the EXF-2000 strain's cell division pattern and morphology by performing timelapse microscopy at different salt concentrations. At low density and no salt, EXF-2000 primarily grows as pseudohyphae dividing mainly by septation. When grown in the presence of salt at a similar concentration to saltwater or hypersaline environments, we observe it grows first by undergoing fission followed by budding at the poles. Then, we examined a collection of 16 isolates in the presence of 0.6M NaCl, including isolates from marine and hypersaline environments and isolates from patients. These isolates exhibit a wide diversity in colony shape and cellular morphology. The isolates grew as yeast, pseudohyphae, and true hyphae, indicating that isolates can exhibit various cell morphologies under similar environmental conditions. We used the insect larvae Galleria mellonella to determine the pathogenic potential of our isolates. We observe that only a subset of isolates can cause death in our model, and there was no correlation between H. werneckii morphology and capacity to cause disease. Taken together, H. werneckii genomic and phenotypic diversity can serve as a model to better understand how phenotypes and pathogenic potential evolve in environmental fungi.

The pathogenic potential and genetic attributes of Escherichia coli in milk from dairy cows with subclinical mastitis

The centrality of milk and dairy products to the human diet allows potential pathogens to pose a threat to human health. Pathogenic Escherichia coli is a zoonotic foodborne pathogen with many virulence genes which cause variations in its pathogenicity. The current study aimed to investigate the pathogenic potential of E. coli from milk of dairy cows with subclinical mastitis and evaluate the genetic relatedness to E. coli from human sources. The majority of the E. coli isolates belonged to the A (55.0%) and B2 (22.5%) phylogenetic groups and the most prevalent virulence genes were colV (90.0%), fyuA (75.0%) and vat (42.5%). Mice injected with G4-BD23 (P < 0.05) and G5-BD3 had lower survival rates than controls and visible pathological changes to lung and kidney. Nineteen MLST types were identified in 40 dairy E. coli isolates and three STs (ST10, ST48 and ST942) were shared with those from human sources. Some dairy E. coli isolates were phylogenetically related to human E. coli isolates indicating pathogenic potential.

Escherichia coli Specific Virulence-Gene Markers Analysis for Quality Control of Ovine Cheese in Slovakia

Shiga toxin-producing and extra-intestinal pathogenic Escherichia coli (E. coli) have the potential to spread through faecal waste, resulting in contamination of food and causing foodborne disease outbreaks. With the aim of characterizing unpasteurized ovine cheese in Slovakia, a total of 92 E. coli strains were examined for eleven representative virulence genes typical for (extra-)intestinal pathogenic E. coli and phylogenetic grouping. Phylogenetic groups B1 (36%) and A (32%) were the most dominant, followed by groups C (14%) and D (13%), while the lowest incidence was recorded for F (4%), and E (1%), and 43 (47%) samples carried at least one virulent gene, i.e., potential pathogens. Isolates present in groups E, F and D showed higher presence of virulence genes (100%, 75%, and 67%), versus 55%, 39%, and 28% in commensal B1, C, and A, respectively. Occurrence of papC and fyuA (both 24%) was highest, followed by tsh, iss, stx2, cnf1, kpsII, cvaC, stx1, iutA and eaeA. Nine E. coli strains (almost 10% of all tested and around 21% of our virulence-gene-associated isolates) harboured stx1, stx2 or eae. Ovine cheeses in Slovakia are highly contaminated with E. coli including potentially pathogenic strains capable of causing intestinal and/or extra-intestinal diseases, and thus may pose a threat to public health while unpasteurized.

Pathogenic potential assessment of the Shiga toxin-producing Escherichia coli by a source attribution-considered machine learning model

Instead of conventional serotyping and virulence gene combination methods, methods have been developed to evaluate the pathogenic potential of newly emerging pathogens. Among them, the machine learning (ML)-based method using whole-genome sequencing (WGS) data are getting attention because of the recent advances in ML algorithms and sequencing technologies. Here, we developed various ML models to predict the pathogenicity of Shiga toxin-producing Escherichia coli (STEC) isolates using their WGS data. The input dataset for the ML models was generated using distinct gene repertoires from positive (pathogenic) and negative (nonpathogenic) control groups in which each STEC isolate was designated based on the source attribution, the relative risk potential of the isolation sources. Among the various ML models examined, a model using the support vector machine (SVM) algorithm, the SVM model, discriminated between the two control groups most accurately. The SVM model successfully predicted the pathogenicity of the isolates from the major sources of STEC outbreaks, the isolates with the history of outbreaks, and the isolates that cannot be assessed by conventional methods. Furthermore, the SVM model effectively differentiated the pathogenic potentials of the isolates at a finer resolution. Permutation importance analyses of the input dataset further revealed the genes important for the estimation, proposing the genes potentially essential for the pathogenicity of STEC. Altogether, these results suggest that the SVM model is a more reliable and broadly applicable method to evaluate the pathogenic potential of STEC isolates compared with conventional methods.

An Assessment of Siderophore Production, Mucoviscosity, and Mouse Infection Models for Defining the Virulence Spectrum of Hypervirulent Klebsiella pneumoniae

Hypervirulent Klebsiella pneumoniae (hvKp) bacteria are more virulent than classical K. pneumoniae (cKp) with resultant differences in clinical manifestations and management. It is unclear whether all hvKp isolates share a similar pathogenic potential. This report assessed the utility of siderophore production, mucoviscosity, and murine infection for defining the virulence spectrum of hvKp. Three strain cohorts were identified and defined based on the CD1 mouse subcutaneous (SQ) challenge model: (i) fully virulent hvKp strains (_fvhvKp), lethal at a challenge inoculum (CI) of ≤10³ CFU; (ii) partially virulent hvKp strains (_pvhvKp), lethal at a CI of >10³ to 10⁷ CFU; (iii) classical K. pneumoniae, not lethal at a CI of 10⁷ CFU. Quantitative siderophore and mucoviscosity assays differentiated _fvhvKp and _pvhvKp strains from cKp strains but were unable to differentiate between the _fvhvKP and _pvhvKP strain cohorts. However, SQ challenge of CD1 mice and intraperitoneal (IP) challenge of CD1 and BALB/c mice, but not C57BL/6 mice, were able to discriminate between an _fvhvKp and a _pvhvKp strain; SQ challenge of CD1 mice may have the greatest sensitivity. cKp was differentiated from hvKp both by SQ challenge of CD1 mice and IP challenge of all three mouse strains. These data identify a means to define the relative virulence of hvKP strains. It remains unclear whether the observed differences of hvKp virulence in mice translates to human infection. However, these data can be used to sort random collections of K. pneumoniae strains into _fvhvKp and _pvhvKp strain cohorts and assess for differences in clinical manifestations and outcomes.

IMPORTANCE The pathogenic potential of hvKp strains is primarily mediated by a large virulence plasmid. The minimal set of genes required for the full expression of the hypervirulent phenotype is undefined. A number of reports describe hvKp strains possessing only a portion of the virulence plasmid; the clinical consequences of this are unclear. Therefore, the goal of this report was to determine whether virulence among hvKp strains varied and, if so, how to best identify the relative virulence of hvKp isolates. Data demonstrate hvKp pathogenic potential varies in CD1 and BALB/c murine infection models. In contrast, measurements of siderophore production and mucoviscosity were unable to discriminate the differences in hvKp isolate virulence observed in mice. This information can be used in future studies to determine the mechanisms responsible for differences between fully virulent hvKp and partially virulent hvKp and whether the differences observed in mice translate to disease in humans.

Preparing for invasion: Assessing risk of infection by chytrid fungi in southeastern plethodontid salamanders

Understanding the responses of naïve communities to the invasion of multihost pathogens requires accurate estimates of susceptibility across taxa. In the Americas, the likely emergence of a second amphibian pathogenic fungus (Batrachochytrium salamandrivorans, Bsal) calls for new ways of prioritizing disease mitigation among species due to the high diversity of naïve hosts with prior B. dendrobatidis (Bd) infections. Here, we applied the concept of pathogenic potential to quantify the virulence of chytrid fungi on naïve amphibians and evaluate species for conservation efforts in the event of an outbreak. The benefit of this measure is that it combines and summarizes the variation in disease effects into a single numerical index, allowing for comparisons across species, populations or groups of individuals that may inherently exhibit differences in susceptibility. As a proof of concept, we obtained standardized responses of disease severity by performing experimental infections with Bsal on five plethodontid salamanders from southeastern United States. Four out of five species carried natural infections of Bd at the start of the experiments. We showed that Bsal exhibited its highest value of pathogenic potential in a species that is already declining (Desmognathus auriculatus). We find that this index provides additional information beyond the standard measures of disease prevalence, intensity, and mortality, because it leveraged these disease parameters within each categorical group. Scientists and practitioners could use this measure to justify research, funding, trade, or conservation measures.

Isolation of Acanthamoeba T5 from Water: Characterization of Its Pathogenic Potential, Including the Production of Extracellular Vesicles

Acanthamoeba is a genus of free-living amoebae widely distributed in nature, associated with the development of encephalitis and keratitis. Despite the fact that it is common to find genotype T5 in environmental samples, only a few cases have been associated with clinical cases in humans. The wide distribution of Acanthamoeba, the characteristic of being amphizoic and the severity of the disease motivate researchers to focus on the isolation of these organisms, but also in demonstrating direct and indirect factors that could indicate a possible pathogenic potential. Here, we performed the characterization of the pathogenic potential of an Acanthamoeba T5 isolate collected from a water source in a hospital. Osmo- and thermotolerance, the secretion of proteases and the effect of trophozoites over cell monolayers were analyzed by different methodologies. Additionally, we confirm the secretion of extracellular vesicles (EVs) of this isolate incubated at two different temperatures, and the presence of serine and cysteine proteases in these vesicles. Finally, using atomic force microscopy, we determined some nanomechanical properties of the secreted vesicles and found a higher value of adhesion in the EVs obtained at 37 °C, which could have implications in the parasite´s survival and damaging potential in two different biological environments.

The Other Side of the Coin: What Beneficial Microbes Can Teach Us about Pathogenic Potential

Koch's postulates and molecular Koch's postulates have made an indelible mark on how we study and classify microbes, particularly pathogens. However, rigid adherence to these historic postulates constrains our view of not only microbial pathogenesis but also host-microbe relationships in general. Collectively, the postulates imply that a "microbial pathogen" is a clearly identifiable organism with the exclusive capacity to elicit disease through an arsenal of pathogen-specific "virulence factors." This narrow definition has been repeatedly contradicted. Advances in DNA sequencing technologies and new experimental systems have revealed that the outcomes of host-microbe interactions are highly contextual and dynamic, especially those involving resident microbiota and variable aspects of host biology. Clarifying what differentiates pathogenic from non-pathogenic microbes, including their paradoxical ability to masquerade as one another, is critical to developing targeted diagnostics and treatments for infectious disease. Such endeavors will also inform the design of therapeutic strategies based on microbiome engineering by providing insights into how manipulating entire host-microbe systems may directly or indirectly alter the pathogenic potential of microbial communities. With these goals in mind, we discuss the need to develop experimental models that better capture the contexts that determine the nature of host-microbe relationships. To demonstrate the potential of one such model-the zebrafish and its resident microbiota-we describe recent work that has revealed the thin line between pathogenic and mutualistic relationships, how the intestine physically shapes bacterial populations and inflammation, and the ability of microbial transmission to override the host's innate immune system.

Establishment of Listeria monocytogenes in the Gastrointestinal Tract

Listeria monocytogenes is a Gram positive foodborne pathogen that can colonize the gastrointestinal tract of a number of hosts, including humans. These environments contain numerous stressors such as bile, low oxygen and acidic pH, which may impact the level of colonization and persistence of this organism within the GI tract. The ability of L. monocytogenes to establish infections and colonize the gastrointestinal tract is directly related to its ability to overcome these stressors, which is mediated by the efficient expression of several stress response mechanisms during its passage. This review will focus upon how and when this occurs and how this impacts the outcome of foodborne disease.

Transmission and Toxigenic Potential of Vibrio cholerae in Hilsha Fish (Tenualosa ilisha) for Human Consumption in Bangladesh

Fish have been considered natural reservoirs of Vibrio cholerae, the deadly diarrheal pathogen. However, little is known about the role of fish in the transmission of V. cholerae from the Bay of Bengal to the households of rural and urban Bangladesh. This study analyzes the incidence and pathogenic potential of V. cholerae in Hilsha (Tenualosa ilisha), a commonly caught and consumed fish that exhibits a life cycle in both freshwater and marine environments in Bangladesh. During the period from October 2014 to October 2015, samples from the gills, recta, intestines, and scale swabs of a total of 48 fish were analyzed. The fish were collected both at local markets in the capital city Dhaka and directly from fishermen at the river. PCR analysis by targeting V. cholerae species-specific ompW gene revealed that 39 of 48 (81%) fish were positive in at least one of the sample types. Real-time PCR analysis demonstrated that the cholera-causing ctxA gene was detected in 20% (8 of 39) of V. cholerae-positive fish. A total of 158 V. cholerae isolates were obtained which were categorized into 35 genotypic groups. Altogether, 25 O1 and 133 non-O1/O139 strains were isolated, which were negative for the cholera toxin gene. Other pathogenic genes such as stn/sto, hlyA, chxA, SXT, rtxC, and HA-P were detected. The type three secretion system gene cluster (TTSS) was present in 18% (24 of 133) of non-O1/O139 isolates. The antibiotic susceptibility test revealed that the isolates conferred high resistance to sulfamethoxazole-trimethoprim and kanamycin. Both O1 and non-O1/O139 strains were able to accumulate fluid in rabbit ileal loops and caused distinctive cell death in HeLa cell. Multilocus sequence typing (MLST) showed clonal diversity among fish isolates with pandemic clones. Our data suggest a high prevalence of V. cholerae in Hilsha fish, which indicates that this fish could serve as a potential vehicle for V. cholerae transmission. Moreover, the indigenous V. cholerae strains isolated from Hilsha fish possess considerable virulence potential despite being quite diverse from current epidemic strains. This represents the first study of the population structure of V. cholerae associated with fish in Bangladesh.

Evaluation of the pathogenic potential, antimicrobial susceptibility, and genomic relations of Yersinia enterocolitica strains from food and human origin

Yersinia enterocolitica is a food-borne pathogen that causes gastroenteritis with occasional postinfection sequels. This study was aimed to determinate the pathogenic potential, antimicrobial susceptibility, and genomic relationships of Y. enterocolitica strains of different bioserotypes (B/O) isolated from foods and human samples in San Luis, Argentina. Strains obtained by culture were bioserotyped and characterized by phenotypic and genotypic virulence markers, antimicrobial susceptibility, and pulsed-field gel electrophoresis (PFGE). Yersinia enterocolitica was detected in 9.2% of 380 samples, with a distribution of 10.6% (30/284) for food products and 5.2% (5/96) for human samples. Regarding the pathogenic potential, B1A strains of different serotypes were virF(-) ail(-), of which 72.0% (13/18) were ystB(+) with virulence-related phenotypic characteristics. Among B2/O:9 isolates, 75.0% (9/12) exhibited the genotype virF(+) ail(+) ystB(-) along with phenotypic traits associated with virulence; the same genotype was observed in 80.0% (4/5) of B3/O:3 and B3/O:5 strains. By PFGE, it was possible to separate Y. enterocolitica biotypes into 4 clonal groups (A to D) with 23 genomic types, generating a discriminatory index of 0.96. All isolates were susceptible to antimicrobials used for clinical treatment. This study highlights the presence of pathogenic bioserotypes and the high genomic diversity of the Y. enterocolitica strains isolated in our region.

Epidemiology and identification of potential fungal pathogens causing invasive fungal infections in a tertiary care hospital in northeast Thailand

Invasive fungal infections (IFIs) are life threatening and associated with a high mortality rate. Here, we describe the distribution of pathogens, host risk factors, and significance of fungi isolated from patients with IFIs. The study included 861 fungal isolates recovered between 2006 and 2011 from 802 patients at Srinagarind Hospital, Thailand. Based on the European Organization for Research and Treatment of Cancer/Invasive Fungal Infections Cooperative Group and the National Institute of Allergy and Infectious Diseases Mycoses Study Group 2008 criteria, 28.5% (245/861 isolates) of the fungal isolates were considered to be causative agents of IFIs. The most common fungus was Candida albicans (46%, 396/861 isolates). However, the most common yeast causing IFIs was Cryptococcus neoformans (34.7%, 85/245 isolates), while the most common mould was Penicillium marneffei (10.6%, 26/245 isolates). Cryptococcosis was significantly associated with human immunodeficiency virus infections (P < 0.001). Trend analysis revealed that there was no significant increase in IFI cases (P = 0.34) from 2006 to 2011 or from 2007 to 2011 (P = 0.05), but there was a trend toward significant increases in candidiasis (P = 0.04). The fungal isolates were categorized according to the positive predictive value of their recovery in cultures as being true (>95%), moderate (5%-95%), and rare (<5%) pathogens. This classification system could facilitate the prediction of the likelihood of diseases caused by the isolated fungi.

Pathogenic potential and genetic diversity of environmental and clinical isolates of Pseudomonas aeruginosa

The aim of this study was to investigate the occurrence of virulence genes among clinical and environmental isolates of Pseudomonas aeruginosa and to establish their genetic relationships by Enterobacterial Repetitive Intergenic Consensus PCR (ERIC-PCR). A total of 60 P. aeruginosa isolates from environmental and clinical sources were studied. Of these, 20 bacterial isolates were from soil, 20 from water, and 20 from patients with cystic fibrosis. Analysis of ERIC-PCR demonstrated that the isolates of P. aeruginosa showed a considerable genetic variability, regardless of their habitat. Numerous virulence genes were detected in both clinical and environmental isolates, reinforcing the possible pathogenic potential of soil and water isolates. The results showed that the environmental P. aeruginosa has all the apparatus needed to cause disease in humans and animals.