Evolution of macrolide resistance in Streptococcus pyogenes over 14 years in an area of central Italy.

We evaluated temporal fluctuations in macrolide resistance rates, analysing genetic determinants of resistance and clonal evolution in a population of 2744 S. pyogenes isolates collected in the period 2000-2013. The total resistance rate to erythromycin of the isolates was 17.9 %. A maximum of erythromycin resistance emerged in 2000 (38.6 %), followed by a significant decrease to 5.2 % in 2012 (P < 0.0001). Molecular analysis revealed the presence and co-presence of known genetic resistance determinants mefA, mefE, ermTR and ermB, in line with phenotypes. PFGE analysis identified genetically related groups in 2000 and 2007-2008, mainly the MLS and M phenotypes, respectively. The most prevalent emm types among a representative subset of resistant isolates were emm2, emm75 and emm77. All emm2 and 88.2 % of the strains harbouring the emm75 gene were only recorded in M-phenotype strains, whilst all emm77-positive strains had the inducible MLS phenotype. The analysed susceptible isolates showed several emm types partially shared with resistant ones. Our results suggest that changes in bacterial population clonality, rather than horizontal transfer of resistance determinants, plays a major epidemiological role in S. pyogenes. Continuous monitoring of microbiological epidemiology seems to be crucial for correct and effective management of streptococcal infections.

Large oligoclonal outbreak due to Klebsiella pneumoniae ST14 and ST26 producing the FOX-7 AmpC ß-lactamase in a neonatal intensive care unit.

A large outbreak caused by expanded-spectrum cephalosporin-resistant Klebsiella pneumoniae (ESCRKP) was observed in a neonatal intensive care unit (NICU) in central Italy. The outbreak involved 127 neonates (99 colonizations and 28 infections, with seven cases of sepsis and two deaths) over a period of more than 2 years (February 2008 to April 2010). Characterization of the 92 nonredundant isolates that were available for further investigation revealed that all of them except one produced the FOX-7 AmpC-type ß-lactamase and belonged to either sequence type 14 (ST14) or ST26. All of the FOX-7-positive isolates were resistant to cefotaxime, ceftazidime, and piperacillin-tazobactam, while 76% were susceptible to cefepime, 98% to ertapenem, 99% to meropenem, and 100% to imipenem. The two carbapenem-nonsusceptible isolates had alterations in the genes encoding outer membrane proteins K35 and K36, which resulted in truncated and likely nonfunctional proteins. The outbreak was eventually controlled by the reinforcement of infection control measures based on a multitiered interventional approach. This is the first report of a large NICU outbreak caused by ESCRKP producing an AmpC-type enzyme. This study demonstrates that AmpC-type enzyme-producing strains can cause large outbreaks with significant morbidity and mortality effects (the mortality rate at 14 days was 28.5% for episodes of sepsis), and it underscores the role of laboratory-based surveillance and infection control measures to contain similar episodes.

Phacoemulsificator and sterile drapes contamination during cataract surgery: a microbiological study.

PURPOSE: To determine the microbial contamination of the irrigating fluids at the time of phacoemulsification after the use of topical povidone-iodine and antibiotics prophylaxis. METHODS: A total of 119 patients undergoing cataract surgery were enrolled in this prospective study. All patients received 5 mg/mL levofloxacin starting from the day prior to surgery and topical and 5% povidone-iodine drops starting from 30 minutes before the surgery. At the end of each surgery, 2 samples of drainage liquids were sterilely collected from the drainage bags (DBL) and from the peristaltic pump single-cassettes (PCL) of the phacoemulsification machine. Search for aerobic and anaerobic bacteria and fungi was performed. RESULTS: Seventy-five patients (31.5%) revealed a growth of at least one microbial species (53 DBL and 22 PCL, 44.5% vs 18.5%; p<0.001). Sixty-six patients (55.5%) had at least one positive intraoperative solution. Overall, 111 microbial strains were collected: 82 (74%) Gram-positive bacteria, 20 (18%) fungi, and 9 (8%) Gram-negative bacteria. Thirteen staphylococcal isolates from PCL, compared with 52 out of DBL (11% vs 43.7%, p<0.001), fungi were essentially isolated from PCL. No significant correlation was found between microbial isolation and risk factors. No postsurgical infective complication occurred in the follow-up. CONCLUSIONS: Evaluation of intraoperative fluids can provide evidence on sources or vehicles of postsurgical infections. Antibiotic prophylaxis and topical povidone-iodine can significantly contribute to minimize the risk of endophthalmitis.

Microbiological features of acute bacterial conjunctivitis in a central Italian area.

The study aims to identify bacteria causing conjunctivitis in a central Italian area and to analyze chemosusceptibility. From 2005 to 2006, 91 conjunctival swabs were collected from acute conjunctivitis cases and screened for common bacteria and fungi. Susceptibility tests were performed on isolates. Staphylococcus aureus, Streptococcus pneumoniae and Haemophilus influenzae amounted to 86.2%. Overall, 100% of strains were susceptible to chloramphenicol and 96.6% to quinolones. Conversely, 20.7% of isolates were tetracycline-resistant and, even if all Gram negative isolates were susceptible to gentamicin, the most frequently isolated pneumococci are constitutively resistant. The study provides support for a rational choice of empiric therapy.

Pneumococcal disease in a paediatric population in a hospital of central Italy: a clinical and microbiological case series from 1992 to 2006.

OBJECTIVES: Streptococcus pneumoniae is frequently isolated from carrier children, but it also causes localized and invasive diseases. Increasing incidence of chemoresistance can affect the efficacy of empiric therapy and it motivates interest in primary prophylaxis. The study aims to investigate clinical and microbiological features of paediatric pneumococcal infections in an Italian province. METHODS: Retrospective clinical analysis of 640 children, hospitalized from 1992 to 2006 with one culture positive for S. pneumoniae, was performed. Chemosusceptibility tests and serotyping were carried out on isolates; statistical analysis was applied to compare variables. RESULTS: Overall, 47.8% were carriers, 49% and 3.2% had, respectively, a localized or invasive disease; S. pneumoniae aetiology accounted for 25% of meningitis and 16% of sepsis. On the total isolates, 10.2% were penicillin non-susceptible, 35.15% were erythromycin resistant, with increasing rates over years. Prevalent invasive serotypes were 1 (38.1%) and 7F (9.5%). CONCLUSIONS: The study sustains pneumococcal disease relevance in children, on the strength of a 15 year observation. Long time period can represent a limit due to population characteristics changing; a selection bias could also be present due to hospitalized only patient analysis. However, we documented variable evolution of chemoresistance and a peculiar serotype spreading, offering microbiological basis for an appropriate clinical approach.

Resistance determinants and clonal diversity in group A streptococci collected during a period of increasing macrolide resistance.

Susceptibility to macrolides and lincosamides was investigated with 299 consecutive nonduplicate Streptococcus pyogenes clinical isolates collected over a 6-year period (1992 to 1997) from an area of central Italy. During this period, macrolide resistance rates steadily increased (from 9% in 1992 to 53% in 1997; P < 0.001). The increase was caused by isolates with a macrolide-lincosamide-streptogramin B resistance phenotype, carrying mostly erm(B) but also erm(TR) genes, that were not detected in the first 2 years and were detected with increasing prevalence (8, 5, 26, and 37%, respectively) during the following 4 years. During the same period, the prevalence of isolates with a macrolide resistance phenotype, carrying mef(A) determinants, did not vary significantly; on average it was 13%, with modest rate fluctuations in different years and no definite trend. Molecular typing revealed a remarkable clonal diversity among susceptible and resistant isolates and a notable heterogeneity of the genetic environment of the resistance genes. The analysis of clonal diversity in relation with resistance phenotypes and genotypes revealed that increased macrolide resistance rates were due to a complex interplay of different mechanisms, with a relevant contribution played by an "epidemic" spread of genetic elements carrying the erm(B) gene among the circulating streptococcal population.

Identification of Aeromonas strains of clinical origin with atypical phenotypical profiles

A total of 47 strains of Aereomonas isolated from patients with gastroenteritis was analyzed for 40 phenotypical characters and for evaluating the numeric taxonomy based on 27 discriminatory tests. It was proved that the clinical isolates showed a relative phenotypical distance and the groups of strains that had atypical profiles were compared with the type species by the present identification schemes.

Susceptibilidad antimicrobiana en cepas italianas de Aeromonas / Antimicrobial susceptibility in Italian Aeromonas strains

Treinta y una cepas de Aeromonas spp. aisladas de heces humanas fueron sometidas al estudio de susceptibilidad antimicrobiana por el método de Kirby-Bauer. Todas las Aeromonas fueron suceptibles al mezlocilin, cefalosporina de segunda y tercera generación, aztrionan y aminoglucósidos (excepto para streptomycin) trimetropin-sulfametoxazol, ácido nalidíxico, rifampicina, norfloxaxin y colistin. Todas las cepas fueron resistentes a la ampicillina, carbanecillin y lincomicina. Todas menos 1 Aeromonas sobria fueron susceptibles al cefalotin. En conclusión, estos resultados mostraron que muchos aislamientos fueron sensibles a un amplio rango de agentes antimicrobianos

Susceptibilidad antimicrobiana en cepas italianas de Aeromonas / Antimicrobial susceptibility in Italian Aeromonas strains

Treinta y una cepas de Aeromonas spp. aisladas de heces humanas fueron sometidas al estudio de susceptibilidad antimicrobiana por el método de Kirby-Bauer. Todas las Aeromonas fueron suceptibles al mezlocilin, cefalosporina de segunda y tercera generación, aztrionan y aminoglucósidos (excepto para streptomycin) trimetropin-sulfametoxazol, ácido nalidíxico, rifampicina, norfloxaxin y colistin. Todas las cepas fueron resistentes a la ampicillina, carbanecillin y lincomicina. Todas menos 1 Aeromonas sobria fueron susceptibles al cefalotin. En conclusión, estos resultados mostraron que muchos aislamientos fueron sensibles a un amplio rango de agentes antimicrobianos.