The molecular epidemiology of multidrug-resistant Acinetobacter baumannii was investigated in the medicalsurgical intensive care unit (ICU) of a university hospital in Italy during two window periods in which two sequential A. baumannii epidemics occurred. Genotype analysis by pulsed-field gel electrophoresis (PFGE) of A. baumannii isolates from 131 patients identified nine distinct PFGE patterns. Of these, PFGE clones B and I predominated and occurred sequentially during the two epidemics. A. baumannii epidemic clones showed a multidrug-resistant antibiotype, being clone B resistant to all antimicrobials tested except the carbapenems and clone I resistant to all antimicrobials except ampicillin-sulbactam and gentamicin. Type 1 integrons of 2.5 and 2.2 kb were amplified from the chromosomal DNA of epidemic PFGE clones B and I, respectively, but not from the chromosomal DNA of the nonepidemic clones. Nucleotide analysis of clone B integron identified four gene cassettes: aacC1, which confers resistance to gentamicin; two open reading frames (ORFs) coding for unknown products; and aadA1a, which confers resistance to spectinomycin and streptomycin. The integron of clone I contained three gene cassettes: aacA4, which confers resistance to amikacin, netilmicin, and tobramycin; an unknown ORF; and bla OXA-20 , which codes for a class D -lactamase that confers resistance to amoxicillin, ticarcillin, oxacillin, and cloxacillin. Also, the bla IMP allele was amplified from chromosomal DNA of A. baumannii strains of PFGE type I. Class 1 integrons carrying antimicrobial resistance genes and bla IMP allele in A. baumannii epidemic strains correlated with the high use rates of broad-spectrum cephalosporins, carbapenems, and aminoglycosides in the ICU during the study period.
The spread of the aac(6')-Ie-aph(2'')-Ia gene was responsible for high-level resistance to gentamicin and amikacin among enterococci isolated from patients in our geographical area.
Outbreaks caused by S marcescens are very difficult to eradicate. An infection control program that includes molecular typing of microorganisms and the proper dissemination among staff members of the typing results is likely to be very effective in reducing NICU-acquired infections and in controlling outbreaks caused by S marcescens, as well as other multiresistant bacteria.
A total of 103 isolates of Aeromonas spp. were obtained over a 3-year period from a natural mineral water and from surface streams located within the boundaries of the watershed of the natural mineral water wells and were typed by macrorestriction analysis of genomic DNA with XbaI and by pulsed-field gel electrophoresis. All Aeromonas caviae isolates from the natural mineral water belonged to the same clone, and an analogous clonal identity was found among Aeromonas hydrophila isolates. These two clones expressed no hemolytic or cytotoxic activities. Aeromonas isolates from surface waters showed high molecular heterogeneity and were not related to the clones found in the natural mineral water. The presence of aeromonads chronically found in the natural mineral water was a likely consequence of a localized development of a biofilm, with no exogenous contamination of the aquifer. Molecular fingerprinting of drinking water isolates is a useful tool in explaining possible reasons for bacterial occurrences.The health consequences of the presence of motile species of the genus Aeromonas in drinking water are the subject of much debate (7,11,12,20,25). Recent studies have demonstrated that the presence of Aeromonas spp. in drinking water is a potential risk, since these microorganisms can produce a wide range of virulence factors (10,13,15,18,20,26). The difficulty in assigning an unequivocal health hazard to motile aeromonads in drinking water stems from the facts that these microorganisms are heterogeneous and that only specific strains may be pathogenic (14,16,23).There have been attempts in some countries, such as The Netherlands, Canada, and Italy, to introduce guideline standards for the presence of Aeromonas spp. in drinking water (4,8,9,26). In Italy, provisional and cautionary limits were established in 1997 for natural mineral waters at their origin (10 CFU/100 ml) and after being bottled (100 CFU/100 ml) and maintained until the end of 1998.These new health regulations aimed at the bottled-water industry compelled Italian public health professionals to make decisions about the safety of bottled mineral waters containing small quantities of Aeromonas spp., even after the cautionary limits were removed. In this paper we show how macrorestriction analysis of genomic DNAs of Aeromonas isolates with pulsed-field gel electrophoresis (PFGE) was useful in clarifying the reasons for the chronic occurrence of Aeromonas spp. in an Italian brand of bottled natural mineral water and the reasons these organisms are not presumed to be a hazard to human health. The natural mineral water described in this study is a natural sparkling water obtained from wells drilled to depths between 60 and 100 m. Groundwater is first collected into stainless steel pipes leading to a single mixing tank and then pumped to four separate bottling lines. The average production volume of the plant is 2 million liters per day.Microbiological analyses conducted during 1998 revealed none of the indicators set by the European health regulations for ...
A survey was carried out in Italy to ascertain the prevalence of Aeromonas spp. in ready-to-eat foods (vegetables, cheeses, meat products, and ice creams) and the level of molecular heterogeneity of the isolates found by macrorestriction analysis of genomic DNA with pulsed-field gel electrophoresis (PFGE). In total, 46 (14.4%) of the 320 food samples examined were found positive for Aeromonas spp. The highest percentages of isolation were discovered in vegetables, particularly lettuce (45.0%), endive (40.0%), and rucola (20.0%). Ricotta was the only cheese type analyzed that showed a high frequency of isolation (45.0%). Among meat products, salami and raw ham (25.0% of samples positive) and, to a lesser extent, baloney (5.0%) were found positive for Aeromonas spp. Aeromonas hydrophila was the most common isolate from foods of animal origin, whereas Aeromonas caviae was the dominant species in vegetables. No motile aeromonads were found in ice cream samples. Aeromonas isolates showed a high level of genetic heterogeneity, because 24 PFGE patterns were identified among 27 A. hydrophila strains and 20 PFGE patterns were found in 23 A. caviae isolates. In conclusion, consumers of ready-to-eat foods in Italy are regularly exposed to many genetically distinct strains of A. hydrophila and A. caviae without evident signs of malaise, and therefore, few of these strains, if any, are likely to be pathogenic.
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