Non-clinical Strains Research Articles

FLO11 expression in clinical and non-clinical Saccharomyces cerevisiae strains and its association with virulence

In Saccharomyces cerevisiae, FLO11 encodes a protein associated with phenotypic traits considered important for virulence. Here, we report the analysis of FLO11 gene expression using RT-LightCycler PCR in several S. cerevisiae strains of different origin (clinical and non-clinical) and with different degrees of in vivo virulence. An association between in vivo virulence and FLO11 expression was observed for the majority of strains when cells were grown at 37 °C in brain heart infusion (BHI) broth to mimic conditions encountered during brain colonization. However, there was a lack of correlation for two of the strains and this was probably due to the loss of a repression sequence in the FLO11 promoter and/or to changes in repetitive sequences in the ORF. The results indicate that the method proposed here, in conjunction with determination of other virulence factors, could usefully predict which S. cerevisiae strains are better suited to colonize in vivo systems.

High Frequency of Virulence Factor Genes tdh , trh , and tlh in Vibrio parahaemolyticus Strains Isolated from a Pristine Estuary

Virulence factor genes encoding the thermostable direct hemolysin (tdh) and the thermostable direct hemolysin-related hemolysin (trh) are strongly correlated with virulence of the emergent human pathogen Vibrio parahaemolyticus. The gene encoding the thermolabile hemolysin (tlh) is also considered a signature molecular marker for the species. These genes are typically reported in very low percentages (1 to 2%) of nonclinical strains. V. parahaemolyticus strains were isolated from various niches within a pristine estuary (North Inlet, SC) and were screened for these genes using both newly designed PCR primers and more commonly used primers. DNA sequences of tdh and trh were recovered from 48% and 8.3%, respectively, of these North Inlet strains. The recovery of pathogenic V. parahaemolyticus strains in such high proportions from an estuarine ecosystem that is virtually free of anthropogenic influences indicates the potential for additional, perhaps environmental roles of the tdh and trh genes.

Identification and distribution of putative virulence genes in clinical strains ofYersinia enterocoliticabiovar 1A by suppression subtractive hybridization

To detect putative virulence genes in clinical strains of Yersinia enterocolitica biovar 1A by suppression subtractive hybridization between two closely related strains of clinical and nonclinical origin having the same serotype (O:6,30-6,31). Suppression Subtractive Hybridization (SSH) was used to identify genomic differences between clinical (serotype O:6,30-6,31, from diarrhoeic human stools) and nonclinical (serotype O:6,30-6,31, from wastewater) strains of Y. enterocolitica biovar 1A. Following genomic subtraction and DNA sequencing, nine DNA sequences that were present only in clinical biovar 1A strains were identified. The sequences identified using SSH showed similarity to conserved hypothetical proteins, proteins related to iron acquisition and haemin storage, type 1 secretion proteins, flagellar hook proteins, exported protein and ABC transport system. All these sequences showed high similarity with Y. enterocolitica 8081 (biovar 1B). The distribution of these genes was further analysed using PCR in 26 clinical strains of Y. enterocolitica biovar 1A. The results revealed that the distribution of these genes was not uniform. Genes related to iron acquisition and storage, and flagellar proteins might be responsible for virulence of some of the clinical strains of Y. enterocolitica biovar 1A. Genes identified in this study might be useful in understanding the pathogenic potential of clinical strains of Y. enterocolitica biovar 1A.

Comparative genomic analysis of bovine, environmental, and human strains ofPseudomonas aeruginosa

Genomic analyses on versatility of the ubiquitous opportunistic pathogen Pseudomonas aeruginosa have been focusing on clinical strains from humans but much less on animal and environmental strains. Here, we aimed to compare genomic patterns of bovine, environmental, and human strains of P. aeruginosa. A collection of 71 strains, equally representing bovine (non-clinical), environmental (aquatic), and human (clinical) isolates from all main subregions of Hungary was genotyped by PCR microarray. Results were interpreted in comparison with internationally established human clinical and environmental clones, based on single nucleotide polymorphisms, on di- and multiallelic loci (fliC and fpvA) of the conserved core genome, and on genetic markers for the flexible accessory genome. As a result, a total of 33 clones were identified, with one bovine, 10 environmental, and five human clones regarded as new ones. In spite of general clonal diversity, bovine and human clones seemed to be habitat related. Bovine strains were characterized by significant overrepresentation of type III FpvA pyoverdine receptor, while the environmental and human strains showed the dominance of type I FpvA. Genotypes of non-clinical bovine strains of P. aeruginosa differed from those of human clinical strains, supporting the hypothesis about specific groups of strains colonizing specific habitats.

The pathogenic potential of Yersinia enterocolitica 1A

Yersinia enterocolitica 1A strains are generally considered apathogenic. However, besides environmental sources, foods and animals, they are repeatedly isolated from patients with gastrointestinal symptoms typical to those evoked by Yersinia of the virulent 1B and 2–4 biotypes. Also, at least 2 gastrointestinal outbreaks associated with 1A strains have been reported. There is a general controversy concerning the pathogenic potential of 1A isolates of clinical and non-clinical origin. To address the 1A puzzle, we have determined the genome sequences of 2 1A strains, a nosocomial O:5 and environmental O:36 isolates, and compared them to each other and to O:8/1B and O:3/4 representatives of the virulent serobiotypes. 1A isolates have mosaic genomes and share genes both with serobiotypes O:8/1B and O:3/4 that implies their common descent. Besides the pYV virulence plasmid, 1A strains lack the classical virulence markers, like the Ail adhesin, the YstA enterotoxin, and the virulence-associated protein C. However, they still possess genes encoding such known and suspect virulence-associated determinants like the YstB enterotoxin, the InvA invasin, the mucoid Yersinia factor MyfA, and the enterochelin utilisation fepBDGC/ fepA/ fes gene cluster. In contrast to previous studies, we have found that the strains of the 1A group possess the MyfA antigen although with limited similarity to the highly conserved MyfA in the virulent serobiotypes. In turn, the MyfB chaperone coevolved with the MyfA fibrillae, while the MyfC usher retains 90% identity to its MyfC counterparts in O:3/O:8 group. The only notable difference between clinical and non-clinical 1A strains was the presence of a truncated Rtx toxin-like gene cluster and remnants of a P2-like prophage in the hospital O:5 isolate. Taken together, Y. enterocolitica BT 1A group represents opportunistic pathogens whose opportunity to establish infection seems to rely mainly on the state of the host defence system. However, presence of known and putative virulence-associated features shared with the pathogenic serobiotypes compels to reconsider properly the pathogenic potential of this group of emerging pathogens.

Tn1546 structures and multilocus sequence typing of vanA-containing enterococci of animal, human and food origin

To characterize the Tn1546 structure and to perform the genetic typing of 51 PFGE-unrelated vanA-containing enterococci of different origin (clinical, food and faecal samples of healthy humans and healthy poultry). Tn1546 structure was characterized by a PCR primer walking strategy and sequencing. Multilocus sequence typing (MLST) was performed for Enterococcus faecium and Enterococcus faecalis strains, and esp and hyl genes were detected by PCR. Nine different Tn1546 structures were identified in the studied strains. Type I was the most prevalent structure (75%) (identical to GenBank M97297). Two new Tn1546 structures were identified (in three clinical and animal strains), containing two new insertion sequences (ISs; ISEfa11 disrupting vanS and ISEfa10 disrupting orf1). An additional new Tn1546 structure was found in one animal strain, containing ISEf1 interrupting vanY and IS1542 in the orf2-vanR region. A high diversity of sequence types (STs) was detected among clinical (6 ST/18 strains) and non-clinical E. faecium strains (18 ST/24 strains). STs associated with clonal complexes CC17 and CC9 were mainly detected among clinical and non-clinical E. faecium strains, respectively. Seven new STs were identified in non-clinical strains. The esp and hyl genes were only found among clinical E. faecium strains. A moderate variability in Tn1546 structure has been detected among unrelated vanA-containing enterococci of different origins, showing three new structures including two new ISs. A high diversity of STs was detected among E. faecium strains, especially among non-clinical strains, and new STs have been identified.

Genetic relationships between clinical and non-clinical strains of Yersinia enterocolitica biovar 1A as revealed by multilocus enzyme electrophoresis and multilocus restriction typing

BackgroundGenetic relationships among 81 strains of Y. enterocolitica biovar 1A isolated from clinical and non-clinical sources were discerned by multilocus enzyme electrophoresis (MLEE) and multilocus restriction typing (MLRT) using six loci each. Such studies may reveal associations between the genotypes of the strains and their sources of isolation.ResultsAll loci were polymorphic and generated 62 electrophoretic types (ETs) and 12 restriction types (RTs). The mean genetic diversity (H) of the strains by MLEE and MLRT was 0.566 and 0.441 respectively. MLEE (DI = 0.98) was more discriminatory and clustered Y. enterocolitica biovar 1A strains into four groups, while MLRT (DI = 0.77) identified two distinct groups. BURST (Based Upon Related Sequence Types) analysis of the MLRT data suggested aquatic serotype O:6,30-6,31 isolates to be the ancestral strains from which, clinical O:6,30-6,31 strains might have originated by host adaptation and genetic change.ConclusionMLEE revealed greater genetic diversity among strains of Y. enterocolitica biovar 1A and clustered strains in four groups, while MLRT grouped the strains into two groups. BURST analysis of MLRT data nevertheless provided newer insights into the probable evolution of clinical strains from aquatic strains.

Quantitative agar-invasion assay

A new method for quantification of yeast invasion into the agar medium was developed. Classical agar-invasion assays have been the methods of choice for determination of yeast invasion, but their main disadvantage is the lack of quantification. Our new Quantitative yeast agar-invasion test allows for quantitative measurements and enables sorting strains by their degree of invasiveness. The invasion abilities were measured for 10 clinical and non-clinical Saccharomyces cerevisiae strains and a strain of Candida albicans. Finally, the correlation between the degrees of strains invasiveness and their reported virulence was observed, proposing our assay as a method for quick determination of yeast virulence potential.

Hepatic nitroreduction, toxicity and toxicokinetics of the anti-tumour prodrug CB 1954 in mouse and rat

5-(Aziridin-1-yl)-2,4-dinitrobenzamide (CB 1954), a promising anti-tumour compound, is associated with clinical hepatotoxicity. We have previously demonstrated that human liver preparations are capable of endogenous 2- and 4-nitroreduction of CB 1954 to generate highly potent cytotoxins. The present study initially examined the in vitro metabolism of CB 1954 in S9 preparations of several non-clinical species and strains. The CD-1 nu/ nu mouse and Sprague–Dawley rat were subsequently chosen for further assessment of in vivo metabolism and hepatotoxicity of CB 1954, as well as the mechanisms that may be involved. Animals were administered the maximum tolerated dose (MTD). At 562 μmol/kg, the mouse exhibited transaminase elevation and centrilobular hepatocyte injury. Moreover, thiol adducts as well as hepatic glutathione depletion paralleled temporally by maximal nitroreduction were observed. The rat had a much lower MTD of 40 μmol/kg and showed signs of gastro-intestinal disturbances. In contrast to mouse, peri-portal damage and biliary changes were observed in rat without any alterations in plasma biomarkers or hepatic glutathione levels. Immunohistochemical analysis did not reveal any correlation between the location of injury and expression of cytochrome P450 reductase and NAD(P)H quinone oxidoreductase 1, two enzymes implicated in the bioactivation of this drug. In conclusion, the present study showed that following administration of CB 1954 at the respective MTDs, hepatotoxicity was observed in both mouse and rat. However, the degree of sensitivity to the drug and the mechanisms of toxicity involved appear to be widely different between CD-1 nu/ nu mice and Sprague–Dawley rats.

Characteristics of β-lactamases and their genes (blaA and blaB) in Yersinia intermedia and Y. frederiksenii

BackgroundThe presence of β-lactamases in Y. enterocolitica has been reported to vary with serovars, biovars and geographical origin of the isolates. An understanding of the β-lactamases in other related species is important for an overall perception of antibiotic resistance in yersiniae. The objective of this work was to study the characteristics of β-lactamases and their genes in strains of Y. intermedia and Y. frederiksenii, isolated from clinical and non-clinical sources in India.ResultsThe enzymes, Bla-A (a constitutive class A penicillinase) and Bla-B (an inducible class C cephalosporinase) were found to be present in all the clinical and non-clinical strains of Y. intermedia and Y. frederiksenii by double disc diffusion method. The results showed differential expression of Bla-A as indicated by presence/absence of synergy whereas expression of Bla-B was quite consistent. The presence of these enzymes was also reflected in the high minimum inhibitory concentrations, MIC50 (126–1024 mg/L) and MIC90 (256–1024 mg/L) of β-lactam antibiotics against these species. Restriction fragment length polymorphism (RFLP) revealed heterogeneity in both blaA and blaB genes of Y. intermedia and Y. frederiksenii. The blaA gene of Y. intermedia shared significant sequence identity (87–96%) with blaA of Y. enterocolitica biovars 1A, 1B and 4. The sequence identity of blaA of Y. frederiksenii with these biovars was 77–79%. The sequence identity of blaB gene of Y. intermedia and Y. frederiksenii was more (85%) with that of Y. enterocolitica biovars 1A, 1B and 2 compared to other species viz., Y. bercovieri, Y. aldovae and Y. ruckeri. Isoelectric focusing data further revealed that both Y. intermedia and Y. frederiksenii produced Bla-A (pI 8.7) and "Bla-B like" (pI 5.5–7.1) enzymes.ConclusionBoth Y. intermedia and Y. frederiksenii showed presence of blaA and blaB genes and unequivocal expression of the two β-lactamases. Limited heterogeneity was detected in blaA and blaB genes as judged by PCR-RFLP. Phylogenetic relationships showed that the two species shared a high degree of identity in their bla genes. This is the first study reporting characteristics of β-lactamases and their genes in strains of Y. intermedia and Y. frederiksenii isolated from Asian region.

The rrn locus and gyrB genotyping confirm the existence of two clonal groups in strains of Yersinia enterocolitica subspecies palearctica biovar 1A

Eighty-one strains of Yersinia enterocolitica biovar 1A representing several serotypes isolated from India, France, Germany and the USA were analyzed using ribotyping, 16S–23S rDNA intergenic spacer length polymorphism analysis (PCR-ribotyping) and gyrB restriction fragment length polymorphism. Ribotyping with BglI, NciI and EcoRV distinguished 81 strains into 4, 3 and 2 ribotypes respectively. BglI- NciI combination gave the highest Simpson's diversity index (DI = 0.43). Strains with identical ribotypes were further differentiated by PCR-ribotyping. The combination of BglI- NciI ribotyping with PCR ribotyping increased DI to 0.72. This suggested that the combination of the two may be used for molecular epidemiological studies of Y. enterocolitica biovar 1A. This approach clearly resolved the strains into two clonal groups, each comprising strains isolated from humans, swine, pork and wastewater. PCR-RFLP of the gyrB gene using three enzymes ( AluI, MspI and HinfI) distinguished strains into seven types and confirmed the existence of two clonal groups. Thus, assessment of heterogeneity based on chromosomal restriction analysis (ribotyping), rRNA spacer length polymorphism (PCR-ribotyping) and gyrB gene analysis were in concordance and provided unequivocal evidence for the presence of two groups amongst strains of Y. enterocolitica biovar 1A despite their diverse geographic origins. These data also grouped clinical and non-clinical strains of serotype O:6,30–6,31 into discrete subgroups.

Distribution of virulence-associated genes inYersinia enterocoliticabiovar 1A correlates with clonal groups and not the source of isolation

Yersinia enterocolitica, an important food- and water-borne enteric pathogen, is represented by six biovars viz. 1A, 1B and 2-5. Some biovar 1A strains, despite lacking virulence plasmid (pYV) and chromosomal virulence genes, have been reported to cause symptoms similar to that produced by isolates belonging to known pathogenic biovars. Virulence-associated genes viz. ail, virF, inv, myfA, ystA, ystB, ystC, tccC, hreP, fepA, fepD, fes, ymoA and sat were studied in 81 clinical and nonclinical strains of Y. enterocolitica biovar 1A by PCR amplification. All strains lacked ail, virF, ystA and ystC genes. The distribution of other genes with respect to clonal groups revealed that four genes viz. ystB, hreP, myfA and sat were associated exclusively with strains belonging to clonal group A. The clonal groups A and B were differentiated previously based on rep (REP-/ERIC) - PCR genomic fingerprinting. The distribution of virulence-associated genes, however, did not differ significantly between clinical and nonclinical strains. In strains of Y. enterocolitica biovar 1A, clonal groups seem to reflect virulence potential better than the source (clinical vs. nonclinical) of isolation.

Food and probiotic strains from the Saccharomyces cerevisiae species as a possible origin of human systemic infections

We report four cases of blood cultures testing positive for yeast strains belonging to the species Saccharomyces cerevisiae. Using molecular techniques, RFLP of mtDNA and δ-PCR amplification, we show the association of two of the isolates with non-clinical strains. Specifically, with two commercial bread-making strains and the therapeutic S. boulardii strain. The association of S. boulardii with cases of fungemia has been reported previously. Nevertheless, this is the first time that a baker's yeast has been isolated from blood.

Differential inlA and inlB expression and interaction with human intestinal and liver cells by Listeria monocytogenes strains of different origins.

In this study, a number of Listeria monocytogenes strains of different origins were evaluated for in vitro invasion capacity for various human cell types (monocytic THP-1, enterocytic Caco-2, and hepatocytic HepG2 cells) and for expression levels of specific virulence genes. For THP-1 cells, no differences between clinical and nonclinical L. monocytogenes strains in invasion capacity or in production of the proinflammatory cytokine interleukin-8 (IL-8) were observed, whereas for the Caco-2 and HepG2 cells, significant differences in invasion capacity were noticed. On average, the clinical strains showed a significantly lower invasion capacity than the nonclinical L. monocytogenes strains. Furthermore, it was shown that the clinical strains induce lower IL-8 levels in HepG2 cells than do the nonclinical strains. This observation led us to study the mRNA expression levels of inlA, inlB, and ami, important virulence genes mediating adhesion and invasion of eukaryotic cells, by real-time reverse transcription-PCR for 27 clinical and 37 nonclinical L. monocytogenes strains. Significant differences in inlA and inlB expression were observed, with clinical strains showing a lower expression level than nonclinical strains. These observations were in accordance with in vitro invasion of Caco-2 and HepG2 cells, respectively. The results of this study indicate that differential expression levels of inlA and inlB possibly play a role in the virulence capacities of L. monocytogenes strains. The lower capacity of clinical strains to invade HepG2 cells and to induce IL-8 is possibly a mechanism of immune evasion used by specific L. monocytogenes strains.

Detection and assay of beta-lactamases in clinical and non-clinical strains of Yersinia enterocolitica biovar 1A.

To detect beta-lactamases (A & B) and extended-spectrum beta-lactamases (ESBLs) in clinical and non-clinical isolates of Yersinia enterocolitica biovar 1A, and to determine their activity in the presence of specific lactamase inhibitors. The presence of beta-lactamases and ESBLs was detected by disc diffusion in 219 (36 clinical, 183 non-clinical) isolates. beta-Lactamase activity was assayed spectrophotometrically in all 36 clinical and 10 representative non-clinical isolates using nitrocefin as the substrate. Inhibition of beta-lactamases was studied by clavulanic acid, aztreonam and cloxacillin. Of the 219 isolates, all except two non-clinical isolates indicated the presence of beta-lactamase A (Bla-A) based on the smaller (2-8 mm) radius of the inhibition zone around the ticarcillin disc. Synergy between ticarcillin and co-amoxiclav discs was, however, observed in only 34% of isolates of non-clinical origin. beta-Lactamase B (Bla-B) was found to be consistently positive among all the clinical and non-clinical isolates, as indicated by its characteristic appearance of flattening of the zone of inhibition around the cefotaxime disc adjacent to an imipenem disc. Bla-B was induced more strongly in clinical than in non-clinical isolates. Inhibition of enzyme A by clavulanic acid, aztreonam and cloxacillin was found to be similar, whereas enzyme B was inhibited more strongly by aztreonam and cloxacillin. None of the isolates showed the unequivocal presence of ESBL. This is the first report on beta-lactamases of Yersinia enterocolitica biovar 1A from Asia. Y. enterocolitica biovar 1A expressed both Bla-A and Bla-B. Heterogeneity was, however, discerned in the expression of Bla-A and by induction of Bla-B among clinical and non-clinical isolates of Y. enterocolitica biovar 1A.

Molecular Characterization of Clinical Saccharomyces cerevisiae Isolates and their Association with Non-Clinical Strains

We assessed the molecular characterization of 96 clinical isolates of S. cerevisiae from a Spanish medical institution and we compared them with 6 non-clinical strains isolated from wine, beer and bread and 1 S. boulardii strain collected from a commercial preparation. The strains were subjected to HinfI mtDNA restriction analysis and PCR amplification of delta sequences. Although both techniques are appropriate for routine clinical analysis, that based on PCR turned out to be the most discriminating. This study, apart from providing tools for clinical application, deals with the relationships between clinical and non-clinical strains. The two baker's yeasts analysed shared mtDNA and PCR patterns with a group of 31 clinical isolates. An exogenous entry of a strain was also reflected in the case of 19 clinical isolates and the therapeutic strain S. boulardii. Both baker's yeasts and S. boulardii were identified respectively among 32.3% and 19.8% of the clinical isolates and there seemed to be a connection between their ability to colonize humans and their ability to cause vaginal infection. The rest of food isolates were not grouped with clinical strains.

Pharmacology Review

Linezolid is an oxazolidinone antibiotic recently approved for treatment of infections due to antibiotic-resistant strains of Enterococcus faecium , Staphylococcus aureus, and Streptococcus pneumoniae. Because infections with these organisms, particularly vancomycin-resistant E faecium (VREF) and methicillin-resistant S aureus (MRSA), are becoming more common in critically ill neonates, linezolid is likely to play an increasingly important role in the antibiotic treatment of neonates who have antibiotic-resistant gram-positive infections. ### Mechanism of Action Oxazolidinone antibiotics, including linezolid, inhibit bacterial protein translation through a unique mechanism. Linezolid binds to the 23S subunit of the bacterial 50S ribosome. In doing so, the antibiotic blocks formation of the 70S translation initiation complex. Not surprisingly, nonclinical strains that have 23S rRNA mutations have shown linezolid resistance in vitro. ### Spectrum of Action Organisms against which linezolid has proven antibacterial efficacy include: E faecium (vancomycin-resistant strains only), S aureus (including methicillin-resistant strains), S agalactiae , S pneumoniae, and S pyogenes. Linezolid also shows in vitro activity against E faecalis (including vancomycin-resistant strains), E faecium (vancomycin-susceptible strains), S epidermidis (including methicillin-resistant strains), S haemolyticus , S pneumonia (penicillin-resistant strains), viridans-group streptococci, and Pasteurella multocida. In general, linezolid is bacteriostatic for staphylococci and enterococci, but is bactericidal for streptococci. Linezolid has activity against methicillin-sensitive and -resistant strains of S aureus and reportedly is active even against glycopeptide-intermediate and -resistant S aureus strains. ### Absorption Linezolid is administered either intravenously or orally. The intravenous preparation contains 2 mg/mL linezolid in an isotonic citrate buffer; the oral suspension contains 20 mg/mL linezolid. The oral bioavailability of linezolid suspension in older children and adults is 100% and is not altered by food. Neither preparation contains alcohol. No data on oral absorption in neonates are available. ### Distribution Linezolid distributes to well-perfused tissues and has low plasma protein binding (approximately 31%). Studies have shown that linezolid penetrates into osteoarticular tissues well, exceeding the minimum inhibitory …

Sequence polymorphism of the 16S rRNA gene of Vibrio vulnificus is a possible indicator of strain virulence.

Vibrio vulnificus exhibits considerable strain-to-strain variation in virulence. Attempts to associate phenotypic or genotypic characteristics with strain virulence have been largely unsuccessful. Based on a 17-nucleotide difference throughout the sequence of the small subunit 16S rRNA gene, there are two major groups of V. vulnificus designated types A and B. In a survey of the 16S rRNA genotype in 67 V. vulnificus human clinical and nonclinical strains, we determined that the majority of nonclinical isolates are type A (31 of 33) and that there is a statistically significant association between the type B genotype and human clinical strains (26 of 34).

Release of monocyte chemoattractant protein (MCP)-1 by a human alveolar epithelial cell line in response to Mycobacterium avium

Clinical strains of Mycobacterium avium isolated from patients with acquired immunodeficiency syndrome, but not a non-clinical laboratory strain (ATCC 25291), were found to stimulate the human alveolar epithelial cell line A549, to produce monocyte chemoattractant protein (MCP)-1. A549 cells were also found to produce elevated levels of MCP-1 in response to sonicates of the clinical strains of M. avium, and surprisingly, the non-clinical strain as well. However, sonic extracts of the clinical strains were found to induce significantly higher levels of MCP-1 production compared to extracts of the non-clinical strain ( P<0.001). These data suggest the existence of strain-related differences in antigen expression by M. avium. The clinical and non-clinical strains of M. avium were found to attach and invade, but not replicate in A549 cells indicating that MCP-1 production by A549 cells does require the presence of viable, replicating organisms. Activation of alveolar epithelial cells by exposure to M. avium resulting in the production of chemokines which recruit inflammatory cells to the site of infection may be an important regulatory pathway for the activation of pulmonary host defense.

Release of monocyte chemoattractant protein (MCP)-1 by a human alveolar epithelial cell line in response to mycobacterium avium.

Clinical strains of Mycobacterium avium isolated from patients with acquired immunodeficiency syndrome, but not a non-clinical laboratory strain (ATCC 25291), were found to stimulate the human alveolar epithelial cell line A549, to produce monocyte chemoattractant protein (MCP)-1. A549 cells were also found to produce elevated levels of MCP-1 in response to sonicates of the clinical strains of M. avium, and surprisingly, the non-clinical strain as well. However, sonic extracts of the clinical strains were found to induce significantly higher levels of MCP-1 production compared to extracts of the non-clinical strain (P < 0.001). These data suggest the existence of strain-related differences in antigen expression by M. avium. The clinical and non-clinical strains of M. avium were found to attach and invade, but not replicate in A549 cells indicating that MCP-1 production by A549 cells does require the presence of viable, replicating organisms. Activation of alveolar epithelial cells by exposure to M. avium resulting in the production of chemokines which recruit inflammatory cells to the site of infection may be an important regulatory pathway for the activation of pulmonary host defense.