Pierluigi Nicoletti

Emergence in Italy of Klebsiella pneumoniae Sequence Type 258 Producing KPC-3 Carbapenemase

KPC-type carbapenemases are emerging resistance determinants in Klebsiella pneumoniae and other gram-negative pathogens, being an increasingly important mechanism of acquired resistance to carbapenems and other β-lactams ([9][1], [10][2]). KPC producers have recently undergone an important

Intestinal flora in breast- and bottle-fed infants

We verified whether an adapted formula, which presents poly-oligosaccharides containing maltose, promotes intestinal implantation of bacterial microflora to the extent that breast milk does, as an epidemiological link exists between newborn feeding methods and infant health. Stool specimens were taken and cultured at the fourth day of life from vaginally born neonates. Twenty-two were breast-fed and 20 were fed with formula. In breast-fed infants, the Bifidobacterium was significantly prevalent expressed in percentage (47.6% vs 15%) and in mean bacterial fecal counts/g (7.1 +/- 0.8 vs 5.3 +/- 0.6). Enterococci prevailed in formula-fed infants (mean counts 6.7 +/- 0.9 vs 7.4 +/- 0.5). Of interest is the significant and simultaneous presence of Bifidobacteria and Bacteroides in breast-fed infants. Our study indicates that flora with a diet-dependent pattern is present from the fourth day of life. These results support a preference for breast feeding over formula feeding, even though renewed.

Characterization of Listeria monocytogenes Isolates from Human Listeriosis Cases in Italy

ABSTRACT The objective of this study was to characterize by serotyping, pulsed-field gel electrophoresis (PFGE), and PCR amplification of virulence genes and markers of epidemic clones I, II, and III (ECI, ECII, and ECIII) 54 human isolates from apparently sporadic cases of infection occurring in the Lombardy region and in the province of Florence, Tuscany, Italy, in the years 1996 to 2007. Listeria monocytogenes isolates were provided by the clinical microbiology laboratories of the Lombardy region and the “Careggi” Hospital of Florence, Tuscany, Italy. Serotyping, PFGE after digestion with the AscI and ApaI enzymes, and PCR amplification for the inlA, inlC, and inlJ genes and ECI, ECII, and ECIII markers were performed according to procedures described previously. Twenty-five (46.3%) L. monocytogenes isolates were assigned to serotype 1/2a, 23 (42.6%) to serotype 4b, and 6 (11.1%) to serotype 1/2b. Thirty-one AscI pulsotypes were recognized among the 54 human isolates. Eleven molecular subtype clusters, of which eight included indistinguishable pulsotypes and three included closely related pulsotypes, were shared by two to seven isolates. Fifteen isolates exhibited unique AscI pulsotypes. Three groups of clustered isolates and two apparently sporadic isolates generated EC amplicons. All strains tested positive for the inlA, inlC, and inlJ genes. Based on the results of serotyping and molecular typing, there were 11 occasions when L. monocytogenes strains with the same subtype were isolated from more than one listeriosis case. A total of 39 out of 54 isolates (72.2%) were attributed to molecular subtype clusters. The results of the study suggest that routine subtyping of L. monocytogenes strains from human listeriosis cases could allow more-timely detection of outbreaks possibly caused by food-borne isolates from a common source and could lead to control of ongoing food exposure, thus preventing the occurrence of more cases.

Molecular epidemiological investigation of an outbreak of Pseudomonas aeruginosa infection in an SCT unit

From May to October 2006, six severe Pseudomonas aeruginosa infections were diagnosed in patients undergoing SCT in the SCT unit of the Careggi hospital (Florence, Italy). Four of the infected patients were treated consecutively in the same room (room N). On the hypothesis of a possible environmental source of infection, samples were collected from different sites that had potential for cross-contamination throughout the SCT unit, including the electrolytic chloroxidant disinfectant used for hand washing (Irgasan) and the disinfectant used for facilities cleaning. Four of the environmental samples were positive for P. aeruginosa: three Irgansan soap samples and a tap swab sample from the staff cleaning and dressing room. The AFLP (amplified fragment length polymorphism) typing method employed to evaluate strain clonality showed that the isolates from the patients who had shared the same room and an isolate from Irgasan soap had a significant molecular similarity (dice index higher than 0.93). After adequate control measures, no subsequent environmental sample proved positive for P. aeruginosa. These data strongly support the hypothesis of the clonal origin of the infective strains and suggest an environmental source of infection. The AFLP method was fast enough to allow a ‘real-time’ monitoring of the outbreak, permitting additional preventive measures.

Distribution and antibiotic resistance of isolates from lower respiratory tract and blood cultures from patients in three Italian intensive care units: a 2-year comparison

The distribution and antibiotic resistance of major pathogens isolated from patients in ICUs were studied by three Italian microbiological laboratories. Consecutive aerobic strains were collected over two different time periods from protected brushing bronchoscopy, broncho-alveolar lavage and blood cultures. A total of 420 strains were isolated during the first period (47.3% gram-negative and 52.7% gram-positive) and 412 over the second period (50.5% gram-negative and 49.5% gram-positive). Pseudomonas aeruginosa was the most frequently isolated organism from the respiratory tract followed by Staphylococcus aureus. Methicillin resistance was 47.9 and 44.5% in S. aureus and 63.0 and 65.1% in coagulase-negative staphylococci over the two periods. No glycopeptide-resistance was found in gram-positive organisms. Ceftazidime-resistance in Klebsiella pneumoniae was very high.

Molecular analysis of population structure and antibiotic resistance of Klebsiella isolates from a three-year surveillance program in Florence hospitals, Italy

We report the results of a three-year surveillance program of Klebsiella spp. in six hospitals in Florence (Italy). A total of 172 Klebsiella isolates were identified and typed by AFLP: 122 were K. pneumoniae and 50 were K. oxytoca. Most K. pneumoniae (80%) and K. oxytoca (93%) showed unrelated AFLP profiles. Beside this heterogeneous population structure, we found five small epidemic clonal groups of K. pneumoniae. Four of these groups were involved in outbreak events, three of which occurred in neonatal ICUs. The fifth clonal group spread in three different wards of two hospitals. Only one non-epidemic clonal group of K. oxytoca was detected. The frequencies of isolates with multiple antibiotic resistances increased with time; at the end of the study period, most K. pneumoniae were resistant to all the antibiotics tested. A PCR analysis of seven ertapenem resistant isolates was unable to detect any of the major genes known to underlie carbapenem resistance in K. pneumoniae.

Reinterpreting a community outbreak of Salmonella enterica serotype Enteritidis in the light of molecular typing

BackgroundIn November 2005, a large outbreak due to Salmonella enterica serotype Enteritidis (S. Enteritidis) was observed within children who had eaten their meals at 53 school cafeterias in Florence and the surrounding area. A total of 154 isolates of S. Enteritidis were recovered from human cases between November 2005 and January 2006. All strains were assigned phage type 8 (PT8) and a common XbaI pulsotype.This paper reports the findings of a molecular epidemiological investigation performed on 124 strains of S. Enteritidis isolated in the years 2005 and 2006 in Florence and the surrounding area, including the epidemic isolates.MethodsOne hundred twenty-four human isolates of S. Enteritidis identified in the period January 2005 – December 2006 were submitted to molecular typing by single enzyme – amplified fragment length polymorphism (SE-AFLP).ResultsMolecular subtyping by SE-AFLP yielded five different profiles. In the pre-epidemic phase, type A included 78.4% of isolates, whereas only three (8.1%) belonged to type C. All isolates, but one, of the epidemic phase were indistinguishable and attributed to type C. In the post-epidemic period, a polymorphic pattern of SE-AFLP types was again recognized but type C accounted for 73.3% of the isolates during the first six months of 2006, whereas during the remaining six months type A regained the first place, including 52.0% of the isolates.ConclusionThe epidemic event was attributed to the emergence and clonal expansion of a strain of S. Enteritidis PT8-SE-AFLP type C. Circulation of the epidemic clone was much more extensive than the surveillance and traditional laboratory data demonstrated.

Cluster of cases of Salmonella enterica Serotype Rissen infection in a General Hospital, Italy, 2007.

In 2007, three strains of Salmonella enterica serotype Rissen (S. Rissen) were isolated in the laboratory of diagnostic microbiology of the General Hospital of Prato, Tuscany, Italy, over a 1 month and half interval of time. The first isolate was recovered on January 26 from an outpatient with enteritis. Then, two strains were isolated on February 16 and March 11 respectively, from central venous catheters of patients who were being hospitalized in two departments of the Hospital. An epidemiologically linked cluster of cases of salmonellosis was suspected. The three strains were submitted to single enzyme‐amplified fragment length polymorphism (SE‐AFLP) and XbaI macrorestriction and pulsed‐field gel electrophoresis (PFGE) that yielded undistinguishable profiles. Epidemiological investigations failed to identify a common source of infection within the Hospital. Moreover, the third patient had been exclusively total parenteral nutrition fed since his admission with a stomach cancer diagnosis. The first patient had a community‐acquired infection, but the source of her illness was uncertain. Twenty‐five further isolates identified in the years 2004–2007 in the same geographical area showed distinctly different PFGE and SE‐AFLP patterns. The three patients seemed to represent a cluster of epidemiologically unrelated cases caused by a previously never recognized S. Rissen strain. Rapid subtyping of isolates is essential in the early investigation of potential outbreaks, but synthesis of conventional and molecular epidemiological investigation and availability of surveillance data is often critical to prevent the initiation of time‐consuming, expensive and ineffective further investigations and control interventions.

Molecular Typing Reveals Frequent Clustering among Human Isolates of Listeria monocytogenes in Italy

In Italy, the annual incidence of reported cases of listeriosis amounts in recent years (2004 to 2006) to 0.8 case per million inhabitants. Our study is a subtyping analysis by serotyping, ribotyping, and pulsed-field gel electrophoresis analysis of 44 human isolates from apparently sporadic cases of infection in the Lombardy region and in the Province of Florence, Italy, in the years 1996 to 2007. Based on the results of the different subtyping methods, 10 occasions were detected when strains of L. monocytogenes with the same subtype were isolated from more than one listeriosis case. A total of 28 (66.7%) of 44 isolates were attributed to molecular subtype clusters. Our data support the use of sensitive molecular approaches to identify and trace L. monocytogenes isolates responsible for foodborne outbreaks of human listeriosis.

Molecular Surveillance and Population Structure Analysis of Methicillin-Susceptible and Methicillin-Resistant Staphylococcus aureus in High-Risk Wards

ABSTRACT In this study we report the results of analysis of 253 isolates of Staphylococcus aureus (132 methicillin [meticillin]-resistant S. aureus [MRSA] isolates and 121 methicillin-susceptible S. aureus [MSSA] isolates) from 209 patients admitted to 18 high-risk wards of six hospitals located in Florence, Italy, over an 8-month period during which a program of epidemiological surveillance of hospital-acquired infections was conducted. The majority (69%) of the 87 reported S. aureus infections were caused by MRSA. No outbreak events have been reported. All the isolates were typed by amplified fragment length polymorphism (AFLP), and AFLP profiles were analyzed in order to define similarity groups. The discriminatory power of AFLP is very high with MSSA (Simpson index of diversity [D], 95.9%), whereas its resolution capability with MRSA (D, 44.7%) is hampered by the well-known high clonality of these populations (the main MRSA group accounted for 74% of the MRSA isolates). Combining AFLP, improved by visual inspection of polymorphisms, with multiplex PCR greatly increases MRSA resolution (D, 85.5%), resolving the MRSA population to a level that is one of the highest reported in the literature. Widespread and sporadic clones of MSSA and MRSA were identified, and their diffusion in the different hospitals and wards over the surveillance period was studied. The understanding of MSSA and MRSA population structures should be the starting point for the design of a more rational surveillance program for S. aureus species, maximizing benefits and reducing the cost of infection control strategies.