Stefania Anna Lucia Zanetti

Detection and Isolation of Mycobacterium avium Subspecies paratuberculosis from Intestinal Mucosal Biopsies of Patients with and without Crohn's Disease in Sardinia

OBJECTIVES:Sardinia is an island community of 1.6 million people. There are also about 3.5 million sheep and one hundred thousand cattle in which Johnes disease and Mycobacterium avium subspecies paratuberculosis infection are endemic. The present study was designed to determine what proportion of people in Sardinia attending for ileocolonoscopy with or without Crohns disease were infected with this pathogen.METHODS:Mycobacterium avium subspecies paratuberculosis was detected by IS900 PCR on DNA extracts of fresh intestinal mucosal biopsies as well as by isolation in culture using supplemented MGIT media followed by PCR with amplicon sequencing.RESULTS:Twenty five patients (83.3%) with Crohns disease and 3 control patients (10.3%) were IS900 PCR positive (p = 0.000001; Odds ratio 43.3). Mycobacterium avium subspecies paratuberculosis grew in cultures from 19 Crohns patients (63.3%) and from 3 control patients (10.3%) (p = 0.00001; Odds ratio 14.9). All patients positive by culture had previously been positive by PCR. Mycobacterium avium subspecies paratuberculosis first appeared in the liquid cultures in a Ziehl Neelsen (ZN) staining negative form and partially reverted through a rhodamine-auramine positive staining form to the classical ZN positive form. This resulted in a stable mixed culture of all 3 forms illustrating the phenotypic versatility of these complex chronic enteric pathogens.CONCLUSIONS:Mycobacterium avium subspecies paratuberculosis was detected in the majority of Sardinian Crohns disease patients. The finding of the organism colonizing a proportion of people without Crohns disease is consistent with what occurs in other conditions caused by a primary bacterial pathogen in susceptible hosts.

Rv1818c‐encoded PE_PGRS protein of Mycobacterium tuberculosis is surface exposed and influences bacterial cell structure

Identification of the novel PE multigene family was an unexpected finding of the genomic sequencing of Mycobacterium tuberculosis. Presently, the biological role of the PE and PE_PGRS proteins encoded by this unique family of mycobacterial genes remains unknown. In this report, a representative PE_PGRS gene (Rv1818c/PE_PGRS33) was selected to investigate the role of these proteins. Cell fractionation studies and fluorescence analysis of recombinant strains of Mycobacterium smegmatis and M. tuberculosis expressing green fluorescent protein (GFP)‐tagged proteins indicated that the Rv1818c gene product localized in the mycobacterial cell wall, mostly at the bacterial cell poles, where it is exposed to the extracellular milieu. Further analysis of this PE_PGRS protein showed that the PE domain is necessary for subcellular localization. In addition, the PGRS domain, but not PE, affects bacterial shape and colony morphology when Rv1818c is overexpressed in M. smegmatis and M. tuberculosis. Taken together, the results indicate that PE_PGRS and PE proteins can be associated with the mycobacterial cell wall and influence cellular structure as well as the formation of mycobacterial colonies. Regulated expression of PE genes could have implications for the survival and pathogenesis of mycobacteria within the human host and in other environmental niches.

Mycobacterium avium Subspecies paratuberculosis Infection in Cases of Irritable Bowel Syndrome and Comparison with Crohn's Disease and Johne's Disease: Common Neural and Immune Pathogenicities

ABSTRACT Mycobacterium avium subsp. paratuberculosis causes Johnes disease, a systemic infection and chronic inflammation of the intestine that affects many species, including primates. Infection is widespread in livestock, and human populations are exposed. Johnes disease is associated with immune dysregulation, with involvement of the enteric nervous system overlapping with features of irritable bowel syndrome in humans. The present study was designed to look for an association between Mycobacterium avium subsp. paratuberculosis infection and irritable bowel syndrome. Mucosal biopsy specimens from the ileum and the ascending and descending colon were obtained from patients with irritable bowel syndrome attending the University of Sassari, Sassari, Sardinia, Italy. Crohns disease and healthy control groups were also included. Mycobacterium avium subsp. paratuberculosis was detected by IS900 PCR with amplicon sequencing. Data on the potential risk factors for human exposure to these pathogens and on isolates from Sardinian dairy sheep were also obtained. Mycobacterium avium subsp. paratuberculosis was detected in 15 of 20 (75%) patients with irritable bowel syndrome, 3 of 20 (15%) healthy controls, and 20 of 23 (87%) people with Crohns disease (P = 0.0003 for irritable bowel syndrome patients versus healthy controls and P = 0.0000 for Crohns disease patients versus healthy controls). One subject in each group had a conserved single-nucleotide polymorphism at position 247 of IS900 that was also found in isolates from seven of eight dairy sheep. There was a significant association (P = 0.0018) between Mycobacterium avium subsp. paratuberculosis infection and the consumption of hand-made cheese. Mycobacterium avium subsp. paratuberculosis is a candidate pathogen in the causation of a proportion of cases of irritable bowel syndrome as well as in Crohns disease.

Evaluation of BACTEC Mycobacteria Growth Indicator Tube (MGIT 960) Automated System for Drug Susceptibility Testing of Mycobacterium tuberculosis

ABSTRACT The reliability of the BACTEC MGIT 960 system, an automated version of the Mycobacteria Growth Indicator Tube (MGIT), for antimicrobial susceptibility testing of Mycobacterium tuberculosis was evaluated on 78 clinical isolates. Rifampin (RMP), isoniazid (INH), streptomycin (SM), and ethambutol (EMB) were tested at the following concentrations: 1.0 μg/ml for RMP, 0.1 and 0.4 μg/ml for INH, 1.0 and 4.0 μg/ml for SM, and 5.0 and 7.5 μg/ml for EMB. Results were compared with those obtained by the BACTEC 460 TB radiometric system. Initially the reproducibility study showed 99.5% agreement on repeat testing with all the four drugs. With susceptibility testing of clinical isolates, excellent agreement between the two systems was found for all the drugs. A total of nine major errors were observed for only three isolates, resistant according to BACTEC MGIT 960 and susceptible according to BACTEC 460 TB, to SM (4.0 μg/ml), INH (0.1 μg/ml), and EMB (5.0 μg/ml) (one isolate) and to SM (1.0 μg/ml), INH (0.4 μg/ml), and EMB (5.0 μg/ml) (two isolates). When these isolates were tested by using the conventional proportion method on Löwenstein-Jensen medium, agreement with BACTEC MGIT 960 was found for five results and with BACTEC 460 TB for the remainder. The time to report results was 7.9 days by MGIT 960 and 7.3 days by BACTEC 460 TB, which was not found statistically significant (P > 0.05). In conclusion, the performance of BACTEC MGIT 960 was found similar to that of BACTEC 460 TB and this new system can be considered a good alternative to the radiometric method for routine susceptibility testing of M. tuberculosis.

Antibacterial activity of ozonized sunflower oil (OLEOZON)

L.A. SECHI, I. LEZCANO, N. NUNEZ, M. ESPIM, I. DUPRÈ, A. PINNA, P. MOLICOTTI, G. FADDA AND S. ZANETTI. 2001.

Novel substituted quinoxaline 1,4-dioxides with in vitro antimycobacterial and anticandida activity.

Thirty-six 6(7)-substituted-3-methyl- or 3-halogenomethyl-2-phenylthio-phenylsulphonyl-chloro-quinoxaline 1,4-dioxides belonging to series 3-6 were synthesised and submitted to a preliminary in vitro evaluation for antimycobacterial, anticandida and antibacterial activities. Antitubercular screening showed a generally good activity of 3-methyl-2-phenylthioquinoxaline 1,4-dioxides (3d,e,h-j) against Mycobacterium tuberculosis, and exhibited MIC between 0.39 and 0.78 microg mL(-1) (rifampicin MIC=0.25 microg mL(-1)), whereas in compounds 4d,e, 5a,b,d,e,l and 6b-e,j,l MIC ranged between 1.56 and 6.25 microg mL(-1). Results of the antibacterial and anticandida screening showed that 6e and 6l exhibited MIC=0.4 and 1.9 microg mL(-1), respectively, against Candida krusei (miconazole MIC=0.9 microg mL(-1)), and 4i, 5b,d, 6e, MIC=3.9 microg mL(-1) against Candida glabrata (miconazole MIC=0.4 microg mL(-1)), while compounds 3d,l, 5e,l, and 6b,d,e,l showed MIC=15.6 microg mL(-1) against Vibrio alginolyticus.

Identification and antibiotic susceptibility of coagulase negative staphylococci isolated in corneal/external infections

AIMS To identify and determine antibiotic susceptibility of coagulase negative staphylococci (CoNS) isolated from patients with chronic blepharitis, purulent conjunctivitis, and suppurative keratitis. METHODS A retrospective review of all culture positive cases of chronic blepharitis, purulent conjunctivitis, and suppurative keratitis between July 1995 and December 1996 was performed. Cases in which CoNS were the sole isolates were analysed. Species identification was performed by using a commercially available standardised biochemical test system. Antibiotic susceptibility to penicillin, gentamicin, tetracycline, erythromycin, ciprofloxacin, and teicoplanin was determined by agar disc diffusion (Kirby–Bauer method). Teicoplanin resistance was confirmed by agar dilution. RESULTS 42Staphylococcus epidermidis, fourS warneri, three S capitis, two S hominis, one each ofS xylosus, S simulans, S equorum, andS lugdunensis were identified. 37 CoNS were penicillin resistant, 12 gentamicin resistant, 28 tetracycline resistant, 18 erythromycin resistant, four ciprofloxacin resistant, and one teicoplanin resistant (MIC, 32 μg/ml). In total, 16 strains were resistant to three or more antibiotics. CONCLUSION Species of CoNS apart from S epidermidis may be isolated from patients with corneal and external infection. Antibiotic susceptibility of CoNS is unpredictable and multiresistant strains are common. As a result, antibiotic susceptibility testing should be performed in all cases of clinically significant ocular infections caused by CoNS.

Distribution of virulence genes in Aeromonas spp. isolated from Sardinian waters and from patients with diarrhoea

Aims: To characterize 46 isolates of different Aeromonas spp. strains (26 Aeromonas hydrophila, 13 Aeromonas sobria and 7 Aeromonas salmonicida) isolated from coastal water and clinical sources in Sardinia, Italy.

In vitro susceptibility of Vibrio spp. isolated from the environment

Bacteria of the genus Vibrio include harmless aquatic strains as well as strains capable of causing epidemics of cholera and human intestinal diseases. Some of these species may show resistance to different antibiotics including cefotaxime, tetracycline and chloramphenicol. The susceptibility to different antibiotics was tested using 40 Vibrio alginolyticus, eight V. parahaemolyticus and six V. vulnificus strains isolated in the coastal waters of Northern Sardinia (Italy). The frequency of resistance to beta-lactams was unexpectedly high. More than 80% of Vibrio isolates were resistant to ampicillin and 2.5% of V. alginolyticus were resistant to ceftazidime and cefotetan. Forty percent of V. alginolyticus and three V. vulnificus isolates gave a positive nitrocefin test. PCR was also performed using selected primers chosen for having common sequences of bla(TEM) and bla(SHV) genes.

Characterization of clinical isolates of Enterobacteriaceae from Italy by the BD Phoenix extended-spectrum beta-lactamase detection method.

ABSTRACT Production of extended-spectrum β-lactamases (ESBLs) is an important mechanism of β-lactam resistance in Enterobacteriaceae. Identification of ESBLs based on phenotypic tests is the strategy most commonly used in clinical microbiology laboratories. The Phoenix ESBL test (BD Diagnostic Systems, Sparks, Md.) is a recently developed automated system for detection of ESBL-producing gram-negative bacteria. An algorithm based on phenotypic responses to a panel of cephalosporins (ceftazidime plus clavulanic acid, ceftazidime, cefotaxime plus clavulanic acid, cefpodoxime, and ceftriaxone plus clavulanic acid) was used to test 510 clinical isolates of Escherichia coli, Klebsiella pneumoniae, Klebsiella oxytoca, Proteus mirabilis, Providencia stuartii, Morganella morganii, Enterobacter aerogenes, Enterobacter cloacae, Serratia marcescens, Citrobacter freundii, and Citrobacter koseri. Of these isolates, 319 were identified as ESBL producers, and the remaining 191 were identified as non-ESBL producers based on the results of current phenotypic tests. Combined use of isoelectric focusing, PCR, and/or DNA sequencing demonstrated that 288 isolates possessed blaTEM-1- and/or blaSHV-1-derived genes, and 28 had a blaCTX-M gene. Among the 191 non-ESBL-producing isolates, 77 isolates produced an AmpC-type enzyme, 110 isolates possessed TEM-1, TEM-2, or SHV-1 β-lactamases, and the remaining four isolates (all K. oxytoca strains) hyperproduced K1 chromosomal β-lactamase. The Phoenix ESBL test system gave positive results for all the 319 ESBL-producing isolates and also for two of the four K1-hyperproducing isolates of K. oxytoca. Compared with the phenotypic tests and molecular analyses, the Phoenix system displayed 100% sensitivity and 98.9% specificity. These findings suggest that the Phoenix ESBL test can be a rapid and reliable method for laboratory detection of ESBL resistance in gram-negative bacteria.