Patrizia Pecile

Update on the antibiotic resistance crisis

Antibiotics tend to lose their efficacy over time due to the emergence and dissemination of resistance among bacterial pathogens. Strains with resistance to multiple antibiotic classes have emerged among major Gram-positive and Gram-negative species including Staphylococcus aureus, Enterococcus spp., Pseudomonas aeruginosa, Acinetobacter spp. Enterobacteriaceae, and Neisseria gonorrhoeae. With some Gram-negatives, resistance may involve most or even all the available antimicrobial options, resulting in extremely drug-resistant or totally drug-resistant phenotypes. This so-called antibiotic resistance crisis has been compounded by the lagging in antibiotic discovery and development programs occurred in recent years, and is jeopardizing the essential role played by antibiotics in current medical practices.

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.

Large Nosocomial Outbreak of Colistin-Resistant, Carbapenemase-Producing Klebsiella pneumoniae Traced to Clonal Expansion of an mgrB Deletion Mutant

ABSTRACT We describe a large hospital outbreak (93 bloodstream infections) of colistin-resistant Klebsiella pneumoniae carbapenemase (KPC)-producing K. pneumoniae isolates which was mirrored by increased colistin consumption. The outbreak was mostly traced to the clonal expansion of an mgrB deletion mutant of an ST512 strain that produced KPC-3.

FIM-1, a New Acquired Metallo-β-Lactamase from a Pseudomonas aeruginosa Clinical Isolate from Italy

ABSTRACT Acquired metallo-β-lactamases (MBLs) are resistance determinants of increasing clinical importance in Gram-negative bacterial pathogens, which confer a broad-spectrum β-lactam resistance, including carbapenems. Several such enzymes have been described since the 1990s. In the present study, a novel acquired MBL, named FIM-1, was identified and characterized. The blaFIM-1 gene was cloned from a multidrug-resistant Pseudomonas aeruginosa clinical isolate (FI-14/157) cultured from a patient with a vascular graft infection in Florence, Italy. The isolate belonged in the sequence type 235 epidemic clonal lineage. The FIM-1 enzyme is a member of subclass B1 and, among acquired MBLs, exhibited the highest similarity (ca. 40% amino acid identity) with NDM-type enzymes. In P. aeruginosa FI-14/157, the blaFIM-1 gene was apparently inserted into the chromosome and associated with ISCR19-like elements that were likely involved in the capture and mobilization of this MBL gene. Transfer experiments of the blaFIM-1 gene to an Escherichia coli strain or another P. aeruginosa strain by conjugation or electrotransformation were not successful. The FIM-1 protein was produced in E. coli and purified by two chromatography steps. Analysis of the kinetic parameters, carried out with the purified enzyme, revealed that FIM-1 has a broad substrate specificity, with a preference for penicillins (except the 6α-methoxy derivative temocillin) and carbapenems. Aztreonam was not hydrolyzed. Detection of this novel type of acquired MBL in a P. aeruginosa clinical isolate underscores the increasing diversity of such enzymes that can be encountered in the clinical setting.

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.

Results of a 5-year prospective surveillance study of antibiotic resistance among Salmonella enterica isolates and ceftriaxone therapy among children hospitalized for acute diarrhea.

BACKGROUNDnThe spread of resistant Salmonella strains continues to increase worldwide. It is necessary to establish epidemiologic information to determine an appropriate empiric antibiotic regimen (when indicated) in infants and children with suspected Salmonella infections for whom the results of susceptibility tests are not yet available.nnnOBJECTIVESnThe aim of the present study was to investigate resistance rates and their modifications among Salmonella enterica strains isolated from Italian children hospitalized for acute diarrhea over 5 years. In addition, when antibiotic treatment was indicated, we assessed the in vivo success of parenteral ceftriaxone therapy.nnnMETHODSnThis study included children admitted consecutively for acute diarrhea to the Division of Pediatrics and Infectious Diseases, Department of Pediatrics, University of Florence, Italy, from January 1, 1997, to December 31, 2001. S enterica strains were isolated from stool cultures, biochemically identified, and serotyped. These isolates were tested by disk-diffusion assay, using the Kirby-Bauer method, for susceptibilities to ampicillin, ceftriaxone, ciprofloxacin, chloramphenicol, neomycin, tetracycline, and trimethoprim/sulfamethoxazole. The limits used for definition of resistance were those established by the guidelines of the National Committee for Clinical Laboratory Standards.nnnRESULTSnA total of 2003 children (1051 boys, 952 girls; median age, 10.3 years; age range, 1 month-16.8 years) with acute diarrhea were admitted to the study. S enterica strains were isolated using stool cultures from 218 (10.9%) children (108 boys, 110 girls; median age, 3.3 years; age range, 2 months-15.8 years). A total of 148 (67.9%) isolates were resistant to at least 1 antibiotic and 57 (26.1%) were multiresistant. The highest rates of resistance were those to tetracycline (132/218 [60.6%]), ampicillin (102/218 [46.8%]), and chloramphenicol (47/218 [21.6%]). The lowest rate of resistance was to ceftriaxone (4/218 [1.8%]). Overall, the rate of resistance to ciprofloxacin (19/218 [8.7%]) was significantly higher than that for ceftriaxone (P = 0.003). Salmonella typhimurium (119/218 [54.6%]) and Salmonella enteritidis (62/218 [28.4%]) were the most frequently identified serotypes. Ceftriaxone was effective in vivo in all 56 children who required antibiotic therapy.nnnCONCLUSIONSnThere was a high prevalence of resistant S enterica strains. Ceftriaxone was used effectively in the treatment of S enterica infection in the population studied.

Molecular Characterization of Acinetobacter Isolates Collected in Intensive Care Units of Six Hospitals in Florence, Italy, during a 3-Year Surveillance Program: a Population Structure Analysis

ABSTRACT The strain diversity and the population structure of nosocomial Acinetobacter isolated from patients admitted to different hospitals in Florence, Italy, during a 3-year surveillance program, were investigated by amplified fragment length polymorphism (AFLP). The majority of isolates (84.5%) were identified as A. baumannii, confirming this species as the most common hospital Acinetobacter. Three very distinct A. baumannii clonal groups (A1, A2, and A3) were defined. The A1 isolates appeared to be genetically related to the well-characterized European EU II clone. A2 was responsible for three outbreaks which occurred in two intensive care units. Space/time population dynamic analysis showed that A1 and A2 were successful nosocomial clones. Most of the A. baumannnii isolates were imipenem resistant. The genetic determinants of carbapenem resistance were investigated by multiplex PCR, showing that resistance, independently of hospital origin, period of isolation, or clonal group, was associated with the presence of a bla OXA-58-like gene and with ISAba2 and ISAba3 elements flanking this gene. bla OXA-58 appeared to be horizontally transferred. This study showed that the high discriminatory power of AFLP is useful for identification and typing of nosocomial Acinetobacter isolates. Moreover the use of AFLP in a real-time surveillance program allowed us the recognition of clinically relevant and widespread clones and their monitoring in hospital settings. The correlation between clone diffusion, imipenem resistance, and the presence of the bla OXA-58-like gene is discussed.

Intestinal carriage of Shewanella xiamenensis simulating carriage of OXA-48–producing Enterobacteriaceae

Positivity for bla(OXA-48)-like carbapenemase genes was revealed by molecular testing of a surveillance rectal swab from a patient who had previously been colonized and infected by an OXA-48-producing Klebsiella pneumoniae. Positivity was due to a coincidental carriage of Shewanella xiamenensis harboring a new bla(OXA-48)-like gene, while the K. pneumoniae was no longer present.

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.