Maria Carbone

Distribution of potentially pathogenic bacteria as free living and plankton associated in a marine coastal zone

Aims:  To determine the abundance of faecal and nonfaecal bacteria related to human and animal health, as free living or associated with small (>64 μm) and large (>200 μm) plankton, samples were collected monthly from the coastal zone at Messina (Italy).

Detection of Arcobacter spp. in the Coastal Environment of the Mediterranean Sea

ABSTRACT The occurrence of Arcobacter spp. was studied in seawater and plankton samples collected from the Straits of Messina, Italy, during an annual period of observation by using cultural and molecular techniques. A PCR assay with three pairs of primers targeting the 16S and 23S rRNA genes was used for detection and identification of Arcobacter butzleri, Arcobacter cryaerophilus, and Arcobacter skirrowii in cultures and environmental samples. Only one of the Arcobacter species, A. butzleri, was isolated from seawater and plankton samples. With some samples the A. butzleri PCR assay gave amplified products when cultures were negative. A. cryaerophilus and A. skirrowii were never detected by culture on selective agar plates; they were detected only by PCR performed directly with environmental samples. Collectively, our data suggest that culturable and nonculturable forms of Arcobacter are present in marine environments. The assay was useful for detecting Arcobacter spp. both as free forms and intimately associated with plankton. This is the first report showing both direct isolation of A. butzleri and the presence of nonculturable Arcobacter spp. in the coastal environment of the Mediterranean Sea.

In vitro susceptibility of Arcobacter butzleri and Arcobacter cryaerophilus to different antimicrobial agents.

Seventeen strains of Arcobacter butzleri and thirteen of Arcobacter cryaerophilus, were tested for their antimicrobial susceptibility to 26 antimicrobial agents. Among beta-lactams agents in this study, imipenem was the most active agent against both A. butzleri and A. cryaerophilus isolates with MIC(90) values of 2 and 4 mg/l, respectively. The most active cephalosporin tested was cefepime, although it was more active against A. butzleri (MIC(90) 8 mg/l) than A. cryaerophilus (MIC(90) 64 mg/l). Levofloxacin, marbofloxacin, enrofloxacin and ciprofloxacin were the best-performing fluoroquinolones against these species. Of the aminoglycosides, amikacin was the most active agent against both A. butzleri and A. cryaerophilus strains with MIC(90) values of 64 and 16 mg/l, respectively. All isolates showed high levels of resistance to penicillins, macrolides, chloramphenicol, trimethoprim and vancomycin.

Pet cats as carriers of Arcobacter spp. in Southern Italy

Aims:  To evaluate the presence of Arcobacter spp. in different biological samples from domestic cats in Southern Italy by using a species‐specific PCR assay and thus to elucidate their potential significance as sources of human infection.

Neonatal Hypersusceptibility to Endotoxin Correlates with Increased Tumor Necrosis Factor Production in Mice

Septic shock is a major cause of mortality in neonates. The hypothesis was tested that neonatal age is associated with altered sensitivity to shock-inducing bacterial products or proinflammatory cytokines (or both). Mice of different ages were inoculated with various doses of lipopolysaccharide (LPS), superantigenic staphylococcal enterotoxin B (SEB), or recombinant tumor necrosis factor-alpha (rTNF-alpha), alone or in combination with the sensitizing agent D-galactosamine. Neonatal mice were markedly more susceptible to LPS-induced lethality but more resistant to SEB than were adults (P < .05). Mice of different ages did not differ, however, in their sensitivity to lethal activities of rTNF-alpha. Neonatal susceptibility to LPS and SEB correlated directly with plasma TNF-alpha but not IFN-gamma levels, which was confirmed by TNF-alpha and IFN-gamma blockade experiments. These data document marked age-related differences in the pathophysiology of septic shock and suggest that IFN-gamma is not an obligatory mediator of either LPS- or SEB-induced lethality in neonates.

Occurrence of Helicobacter pylori DNA in the coastal environment of southern Italy (Straits of Messina)

Aims:  The occurrence of Helicobacter pylori in the coastal zone of the Straits of Messina (Italy) as free‐living and associated with plankton was studied.

Induction and Resuscitation of Viable Nonculturable Arcobacter butzleri Cells

ABSTRACT Two strains of Arcobacter butzleri, ATCC 49616 and an environmental isolate, became nonculturable in seawater microcosms at 4°C by 20 days and at room temperature by 14 days. Nonculturable cells were viable for up to 270 days of incubation in microcosms. Resuscitation of A. butzleri cells from microcosms at both temperatures was achieved 9 days after nutrient addition.

Adherence of environmental Arcobacter butzleri and Vibrio spp. isolates to epithelial cells in vitro

The objective of this study was to explore the ability of environmental Arcobacter butzleri and Vibrio spp. strains to adhere and induce cytotoxicity in cultured epithelial cells. A total of 27 of marine environment isolates, 17 A. butzleri and 10 Vibrio spp., were tested individually for the adhesive capacity to HEp-2 and HeLa line cells. Next, the ability of these strains to secrete toxic factors capable of producing morphological changes on Vero cells, was tested. Only six out of 17 of the A. butzleri strains were able to adhere to both cell lines. 57% of the V. alginolyticus strains were able to adhere to HEp-2 and HeLa cell lines. None of the Vibrio strains produced toxic factors. However, five out of the six of the A. butzleri strains that were shown to adhere both cell lines, also secreted toxic factors. It is apparent from this study that toxigenic and adhesive strains of A. butzleri can be isolated from aquatic environments in Messina (Italy).

Activity and postantibiotic effect of marbofloxacin, enrofloxacin, difloxacin and ciprofloxacin against feline Bordetella bronchiseptica isolates

The minimum inhibitory concentration (MIC) and postantibiotic effect (PAE) of marbofloxacin, enrofloxacin, difloxacin and ciprofloxacin were evaluated in vitro against 43 feline-source Bordetella bronchiseptica strains. All strains tested were susceptible to marbofloxacin and enrofloxacin (MIC90 0.5mg/l), while 93 and 84% of the strains were susceptible, respectively, to ciprofloxacin and difloxacin with MIC(90) values of, respectively, 1 and 8mg/l. The PAE was studied in 10 strains by exposure of bacteria to marbofloxacin, enrofloxacin, difloxacin and ciprofloxacin at 5 and 10 times minimum inhibitory concentration (MIC) for 1 and 2h. Regrowth was determined by measuring the viable counts after drug removal by a 10(3) dilution procedure. PAEs increased as a function of concentration and exposure time. The mean duration of PAEs varied between 1.1 and 8.2h, showing the following order: marbofloxacin>enrofloxacin>ciprofloxacin>difloxacin. These data are encouraging since fluoroquinolones have a possible role in the clinical treatment of B. bronchiseptica infections, and the strong PAE caused by quinolones may contribute to the in vivo efficacy of these drugs.

Antimicrobial activity and postantibiotic effect of flurithromycin against Helicobacter pylori strains.

The minimal inhibitory concentrations (MIC) of flurithromycin on 49 clinical isolates of Helicobacter pylori was investigated. The MICs were determined using an agar dilution technique. Flurithromycin inhibited the growth of H. pylori strains with MIC(50) and MIC(90) values of 0.156 and 0.625 mg/l, respectively. The postantibiotic effects (PAE) were studied on ten strains, by exposure of the bacteria to flurithromycin at five and ten times MIC for 1 or 2 h. Regrowth was determined by measuring the viable counts after drug removal by a 10(3) dilution procedure. All PAEs increased as a function of concentration and time of exposure. The mean duration of PAEs varied between 1.5 and 6 h. These data are encouraging since macrolides play a key role in the clinical treatment of H. pylori infections, and the strong PAE caused by flurithromycin may contribute to the in vivo efficacy of this drug.