MICs Of Penicillin Research Articles

Ocular Propionibacterium Acnes: A Study On Antibiotic Susceptibility Profiling And Their Epidemiological Pattern

Purpose: To identify the antibiotic pattern of commonly used P. acnes isolates and to analyse the epidemiological patterns using Random Amplification of Polymorphic DNA (RAPD) technique. Methods: One hundred P. acnes isolates (90 % extraocular and 10% intraocular) recovered from ocular clinical specimens identified by conventional method were studied. MIC of ciprofloxacin, norfloxacin, nalidixic acid, clindamycin, penicillin G, vancomycin and metronidazole, cefotaxime and imepenum were carried out for 100 P. acnes ophthalmic isolates by spot inoculation technique. Results: Six distinct RAPD patterns were observed among these isolates of which the 4 pattern was the most predominant one (41%), which was isolated mostly from conjunctival swabs. Of the 100 clinical anaerobic P. acnes isolates, highest resistant antibiotic pattern was seen among conjunctival swabs isolates for metronidazole (100%). Following it was the clindamycin (79%) and penicillin G (64%). Conclusion: This study has proven that RAPD is a reproducible, powerful technique for P. acnes genomic typing and may definitely play a vital role in identifying epidemiology of P. acnes. There was no correlation between the antibiotic pattern and the corresponding RAPD fingerprinting results in our study. Resistance to Vancomycin, the most commonly used intravitreal antibiotic is emerging among P. acnes is being reported for the first time. Studies at molecular level with vancomycin resistant isolates will help to understand the mechanism of resistance.

Gentamicin-Resistant Enterococcus faecalis Sequence Type 6 with Reduced Penicillin Susceptibility: Diagnostic and Therapeutic Implications

In 2007, 20 Enterococcus faecalis isolates from bloodstream infections diagnosed at seven hospitals in the North Denmark region were recorded by the regional clinical microbiology laboratory as being penicillin resistant (MICs ≥ 16 μg/ml) and ampicillin susceptible (MICs ≤ 4 μg/ml) using Etest (AB bioMerieux, Solna, Sweden). Seventeen and two isolates were additionally resistant to gentamicin (MICs ≥ 1,024 μg/ml) and imipenem (MIC = 32 μg/ml), respectively (Table ​(Table11). TABLE 1. Origin, MICs determined by Etest, and genotypes based on partial (gdh gene) or full multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE) of 33 E. faecalis isolates from bloodstream infections in the North Denmark region in 2007 ... Due to the unusual susceptibility pattern obtained by Etest, the penicillin MICs were measured by broth microdilution (BMD) according to the Clinical and Laboratory Standards Institute (CLSI) (1). Twofold dilutions of penicillin G sodium salt (Sigma-Aldrich Denmark A/S, Copenhagen, Denmark) in the range between 0.5 and 32 μg/ml were prepared using Mueller-Hinton broth (MHB, Oxoid A/S, Greve, Denmark). Thirteen E. faecalis blood culture isolates from hospitalized patients obtained during the same year were randomly selected for comparative purposes based on their susceptibility to penicillin determined by Etest (MICs ≤ 12 μg/ml) (Table ​(Table1).1). All 20 isolates were reported as being penicillin resistant according to Etest and the 13 control isolates were found to be penicillin susceptible by BMD based on the CLSI interpretive MIC breakpoint (S ≤ 8 μg/ml) and fell into the wild-type E. faecalis MIC distribution (1 to 16 μg/ml), provided by the European Committee on Antimicrobial Susceptibility Testing (EUCAST). However, using BMD according to CLSI standards, the penicillin MICs for the isolates that were reported to be penicillin resistant according to Etest were two- to eightfold higher (4 to 8 μg/ml) than those for the control isolates reported to be susceptible by Etest (1 to 2 μg/ml), with the exception of a single isolate displaying a MIC of 2 μg/ml. Gentamicin resistance (MIC ≥ 1,024 μg/ml) was confirmed in 17 of the 20 isolates displaying reduced susceptibility to penicillin, whereas the two isolates displaying imipenem resistance were susceptible to this agent (MICs ≤ 2 μg/ml). Multilocus sequence typing (MLST) (2) showed that most (17/20) E. faecalis isolates with reduced penicillin susceptibility belonged to sequence type 6 (ST6), whereas none of the control isolates belonged to ST6, as shown by partial (gdh gene) MLST typing. Pulsed-field gel electrophoresis (PFGE) (3) demonstrated closely related patterns (≤5-band difference) among the 17 ST6 isolates with reduced penicillin susceptibility (data not shown). Eight PFGE profiles (A1 to A8) were designated on the basis of minor band differences, and the most common profile (A1) was found in six isolates originating from four hospitals (Table ​(Table11). We report the occurrence in several Danish hospitals of a distinctive penicillin susceptibility phenotype in E. faecalis consisting of reduced penicillin susceptibility and full ampicillin susceptibility. Most isolates displaying this phenotype were additionally resistant to gentamicin, belonged to type ST6, and had indistinguishable or closely related PFGE patterns, indicating the occurrence of a clonal outbreak. Despite the increased MICs of penicillin and imipenem obtained by Etest, the ST6 isolates were susceptible according to CLSI standards. The results draw attention to the ambiguity of penicillin and imipenem MICs determined by concentration gradient diffusion assays such as Etest. In laboratories where these assays are routinely employed for susceptibility testing of E. faecalis, resistant isolates should be confirmed by broth dilution. As long as the mechanism leading to in vitro-reduced penicillin susceptibility in E. faecalis ST6 remains unknown, the use of penicillin should be considered with caution for treatment of infections caused by strains displaying this atypical phenotype.

Trends in Antimicrobial Susceptibility of Neisseria gonorrhoeae in Israel, 2002 to 2007, With Special Reference to Fluoroquinolone Resistance

MICs for penicillin, tetracycline, ceftriaxone, ciprofloxacin, spectinomycin, and azithromycin were determined by the Etest method for 406 gonococcal strains obtained in 2002-2007 from an STI clinic and a general microbiology laboratory in Central Israel. A total of 27.1% were resistant to ciprofloxacin, with increasing resistance over the years All isolates remain susceptible to ceftriaxone and spectinomycin.

Antimicrobial Resistance among Respiratory Pathogens in Spain: Latest Data and Changes over 11 Years (1996-1997 to 2006-2007)

A nationwide multicenter susceptibility surveillance study (Susceptibility to the Antimicrobials Used in the Community in España [SAUCE] project), SAUCE-4, including 2,559 Streptococcus pneumoniae, 2,287 Streptococcus pyogenes, and 2,736 Haemophilus influenzae isolates was carried out from May 2006 to June 2007 in 34 Spanish hospitals. Then, the results from SAUCE-4 were compared to those from all three previous SAUCE studies carried out in 1996-1997, 1998-1999, and 2001-2002 to assess the temporal trends in resistance and the phenotypes of resistance over the 11-year period. In SAUCE-4, on the basis of the CLSI breakpoints, penicillin (parenteral, nonmeningitis breakpoint) and cefotaxime were the antimicrobials that were the most active against S. pneumoniae (99.8% and 99.6%, respectively). Only 0.9% of isolates had a penicillin MIC of > or = 2 microg/ml. In S. pyogenes, nonsusceptibility to erythromycin was observed in 19.4% of isolates. Among the H. influenzae isolates, a beta-lactamase-positive prevalence of 15.7% was found. A statistically significant temporal decreasing trend over the 11-year period was observed for nonsusceptibility (from 60.0% to 22.9%) and resistance (from 36.5% to 0.9%) to penicillin and for the proportion of erythromycin-resistant isolates of S. pneumoniae of the macrolide-lincosamide-streptogramin B (MLS(B)) phenotype (from 98.4% to 81.3%). A similar trend was observed for the prevalence of ampicillin resistance (from 37.6% to 16.1%), beta-lactamase production (from 25.7% to 15.7%), and beta-lactamase-negative ampicillin resistance (BLNAR) in H. influenzae (from 13.5% to 0.7%). Among erythromycin-resistant isolates of S. pyogenes, a significant increasing trend in the prevalence of MLS(B) was observed (from 7.0% to 35.5%). SAUCE-4 confirms a generalized decline in the resistance of the main respiratory pathogens to the antimicrobials as well as a shift in their resistance phenotypes.

Neisseria lactamica Arthritis and Septicemia Complicating Myeloma

Neisseria lactamica is a common and normally harmless commensal of the upper respiratory tract found especially in young children. In the July 2006 edition of this journal, Zavascki and colleagues reported the first case of N. lactamica causing cavitatory lung disease in an adult organ transplant recipient (3). The same year, Wang et al. reported a case of N. lactamica bacteremic pneumonia in an adult with liver cirrhosis (2). Apart from a 1991 report of N. lactamica meningitis following skull trauma (1), there are no other published reports of invasive N. lactamica infection in adults or cases listed in selected bacteremia databases from New Zealand, Australia, or North America. We present a case of N. lactamica arthritis and septicemia in a patient immune suppressed by myeloma and corticosteroids. This 60-year-old male from a small mining city in the West Australian outback presented with 1 day of rigors, hypotension, and acute knee pain and swelling. He had been prescribed prednisolone at 50 mg daily, reduced to 15 mg daily, for an infective exacerbation of chronic obstructive airways disease during the 17 days before admission. The myeloma was associated with an IgG kappa-type paraprotein, mild suppression of serum IgA and IgM, and lytic bony lesions. HIV serology was negative. The cloudy knee fluid aspirate had neutrophilic pleocytosis (100 white cells/mm3) and Gram-negative cocci by microscopy. Culture of both joint fluid and blood yielded a Neisseria species, provisionally identified as Neisseria gonorrhoeae. This caused distress for the patient and his wife, who denied sexual activity for 5 years. The isolate was oxidase and catalase positive but Superoxol and Phadebact Monoclonal GC test (Bactus AB, Huddinge, Sweden) negative. API NH (bioMerieux, La Balme-les-Grottes, France) identified N. lactamica (99.9%, profile 5041). BLAST analysis (http://www.ncbi.nlm.nih.gov/blast/) of an amplified 2,098-nucleotide 16S rRNA sequence (GenBank accession no. {type:entrez-nucleotide,attrs:{text:GU980596,term_id:294874967,term_text:GU980596}}GU980596) showed 98% homology with both N. lactamica (GenBank accession no. {type:entrez-nucleotide,attrs:{text:AJ239305.1,term_id:5327203,term_text:AJ239305.1}}AJ239305.1) and Neisseria polysaccharea (GenBank accession no. {type:entrez-nucleotide,attrs:{text:AJ239314.1,term_id:5327212,term_text:AJ239314.1}}AJ239314.1). The isolate was o-nitrophenyl-β-d-galactopyranoside (ONPG) positive and generated acid from sucrose, excluding N. polysaccharea. Our isolate was thus identified biochemically and genetically as N. lactamica but may represent a new virulent strain. The penicillin MIC was 3 mg/liter, and the ceftriaxone MIC was 0.006 mg/liter, both determined by Etest. An echocardiogram showed no endocarditis, and the neisserial infection was cured with 11 days of ceftriaxone therapy. It should not be a surprise that N. lactamica causes septic arthritis, as there are case reports of septic arthritis, discitis, or bursitis caused by other commensal Neisseria spp., including N. sicca, N. subflava, and N. mucosa. Neisseria meningitidis (especially serogroup W-135) and N. gonorrhoeae also cause septic arthritis. Commensal neisserial infections have often been reported in compromised patients, including those who are neutropenic, have invasive devices, or have undergone procedures. Meningococcal infections (especially nonpathogenic strains) have also been reported in compromised patients, including those with complement deficiency, prior corticosteroid use, myeloma, Waldenstrom's disease, and hypogammaglobulinemia. Like the case presented by Zavascki et al. (3), our patient represents a rare example of invasive adult N. lactamica infection and highlights the propensity for commensal neisserial species to cause bloodstream and joint infections and to be of special concern to patients with immune compromises. We encourage others isolating clinically significant N. lactamica strains to deposit the sequences in GenBank to enable further study of this emerging pathogen in compromised patients.

Antimicrobial Resistance of Listeria monocytogenes Strains Isolated from Humans in France

Susceptibility to antibiotics of 4,816 clinical L. monocytogenes strains isolated since 1926 was studied, and the temporal evolution of susceptibility to antibiotics was analyzed through several decades. The mechanisms of resistance in each resistant strain were studied. The prevalence of resistant strains was estimated at 1.27% among isolates from humans. Resistance to tetracyclines+ and fluoroquinolones was more common and has recently emerged. Although acquired resistance in clinical L. monocytogenes did not implicate clinically relevant antibiotics, the possibility of resistance gene transfers, the description of the first clinical isolate with high-level resistance to trimethoprim, and the recent increase in penicillin MICs up to 2 microg/ml reinforce the need for microbiological surveillance.

Epidemiology of invasive meningococcal disease with decreased susceptibility to penicillin in Ontario, Canada, 2000 to 2006.

Neisseria meningitidis has been relatively slow to acquire resistance to penicillin. We previously reported an increase in the incidence of invasive meningococcal disease (IMD) strains with decreased susceptibility to penicillin (DSP) in Ontario. Our objectives were to evaluate trends in IMD with DSP, to identify case-level predictors of IMD with DSP, and to evaluate the relationship among DSP, bacterial phenotype, and the likelihood of a fatal outcome. All IMD isolates received in Ontario between 2000 and 2006 were submitted to the Public Health Laboratories, Toronto, for confirmation of the species, serogroup determination, and susceptibility testing. Isolates were considered to be IMD strains with DSP if the penicillin MIC was > or =0.125 microg/ml. Temporal trends were evaluated using multivariable Poisson regression models. Correlates of diminished susceptibility and fatal outcome were evaluated with multivariable logistic regression models. The overall rate of IMD caused by strains with DSP in Ontario was approximately 1.20 cases per million population annually (95% confidence interval [95% CI], 0.99 to 1.46). Seventy-nine strains (21.7%) were IMD strains with DSP. There was no year-to-year trend in the incidence of IMD with DSP. IMD with DSP was strongly associated with strains of serogroups Y (odds ratio [OR], 6.3; 95% CI, 3.6 to 11.1) and W-135 (OR, 8.2; 95% CI, 4.0 to 16.7). Infection with serogroup B or C strains was associated with a marked increase in the risk of mortality (OR, 3.07; 95% CI, 1.39 to 6.75); however, no association between IMD with DSP and mortality was observed. In contrast to trends of the 1990s, the incidence of IMD with DSP was stable in Ontario between 2000 and 2006. In Ontario, the serogroup rather than the penicillin MIC is the microbiological parameter most predictive of mortality.

Neisseria meningitidis with reduced susceptibility to quinolones in Singapore

Sir, Ciprofloxacin is commonly prescribed as a single-dose chemoprophylactic agent for close contacts of patients with meningococcal infection. Neisseria meningitidis with reduced susceptibility to fluoroquinolones has recently emerged, with sporadic cases reported in France, Australia, Argentina, Spain, Hong Kong and Israel. Recently an outbreak of serogroup A emerged in India, and a cluster of three cases of serogroup B in the USA. To our knowledge, failure of ciprofloxacin prophylaxis due to quinolone resistance has not been reported To date, reduced susceptibility to fluoroquinolones in meningococci has remained rare, with 10 unrelated strains found in an analysis of 5300 isolates in Spain, and only 3 from .5000 isolates in France. Most mutations have arisen in GyrA. However, mutations have also been detected in GyrB and ParE, although their significance remains uncertain. In addition, in vitro changes have been induced in ParC and resistance to quinolones has also been reported through an efflux mechanism. – 4 Following the isolation of N. meningitidis with reduced susceptibility to ciprofloxacin from a 36-year-old man with meningitis in 2008, all stored viable clinical isolates from Singapore’s three largest hospitals (Tan Tock Seng, Singapore General and National University hospitals) were screened for reduced susceptibility to nalidixic acid and rifampicin by disc diffusion, using the CLSI guidelines. Ciprofloxacin MICs were determined by agar plate dilution for isolates with reduced susceptibility to nalidixic acid, using the Australian Gonococcal Surveillance Programme (AGSP) guidelines. MICs obtained with this method give identical results for identical GyrA changes in Neisseria gonorrhoeae and N. meningitidis. All isolates for which the MIC is .0.03 mg/L either have changes in the quinolone resistance determining region (QRDR) or an increased efflux of quinolones, while those for which the MIC is ,0.03 mg/L do not. In the absence of clinical correlation data, an MIC of .0.03 mg/L is taken to indicate reduced susceptibility by both the AGSP and CLSI methods. Multilocus sequence typing (MLST) was carried out using protocols available on the Neisseria MLST website. To characterize the mechanisms of resistance to ciprofloxacin, we sequenced the QRDRs of GyrA, GyrB, ParC and ParE of isolates with a ciprofloxacin MIC of .0.03 mg/L. Penicillin MICs were determined with Etests (AB BIODISK, Solna, Sweden) for all isolates, using Mueller–Hinton agar with 5% sheep blood and interpreted according to CLSI criteria for agar dilution. Of 75 isolates collected between 2000 and 2008, two (3%) were resistant to nalidixic acid, a Group C isolate from 2008 and a Group B isolate from 2002. Both isolates had a raised ciprofloxacin MIC of 0.25 mg/L. All 75 isolates were susceptible to rifampicin. There were 13 isolates (17%) intermediate and 2 (3%) resistant to penicillin (MICs of 0.38 and 0.47 mg/L). MLST confirmed that the two isolates with reduced quinolone susceptibility were unrelated. The 2008 isolate was identified as sequence type (ST)-4821. The 2002 isolate was a new ST with alleles 4, 10, 76, 71, 13, 2, 75 although the aroE allele had one nucleotide different from allele 76 (C to T at position 39). The 2008 ST-4821 isolate had the most common GyrA substitution of threonine to isoleucine at position 91. The 2002 isolate had three mutations detected in GyrA: Thr91!Val; Asn103!Asp; and Ala105!Ser. To our knowledge, the Thr91!Val substitution has not been previously described in N. meningitidis. Neither of the isolates had changes in GyrB, ParC or ParE. Similarities in the mechanism of quinolone resistance in meningococci and gonococci, have prompted concerns that resistance will climb to mirror that of gonococci. Resistance to quinolones among N. gonorrhoeae is now so common that use of ciprofloxacin for the treatment of gonorrhoea is no longer recommended by the US Centers for Disease Control and Prevention. In Singapore, ciprofloxacin resistance among gonococci reached an alarming 61.8% in 2006 (74% in 2008; A. L. Tan, unpublished data). Ciprofloxacin is a prescription-only medicine in Singapore, but is in widespread use. An outbreak of meningococcal meningitis with reduced susceptibility to quinolones has already been seen in India in 2005, a country with liberal use of ciprofloxacin. Although our data are from small numbers, as meningococcal infections are uncommon in Singapore (usually ,10 cases per year), the 3% rate of quinolone resistance in this study is remarkably high when compared with other reports. Surveillance for reduced susceptibility and judicious quinolone use is forever increasing in importance but our local resistance data for the related N. gonorrhoeae may suggest the future is already written.

Observatoire régional du pneumocoque en région Pays de la Loire : résistance de Streptococcus pneumoniae aux antibiotiques en 2007

Objectives Between 1st January and 31st December 2007, 331 Streptococcus pneumoniae strains were collected from 20 participating laboratories in the Pneumococcus Network Pays de la Loire county to assess their susceptibility to antibiotics and to evaluate serogroups of strains. Method The coordinating centre performed MICs of penicillin G, amoxicillin and cefotaxime by the reference agar dilution method. Results were interpreted according to CA-SFM breakpoints. Sensitivity to other antibiotics were studied and serotyping of each strain performed. Results Three hundred and thirty one strains were isolated in 2007. They were collected from 30 cerebrospinal fluids, 239 blood samples, 53 middle ear fluids and nine pleural fluids. The percentage of pneumococci with decreased susceptibility to penicillin G (PDSP) was 39% and was higher in children (51%) than in adults (35%). The PDSP were often multidrug resistants especially with a high percentage of resistance to erythromycin (87.6% versus 8.4% for pneumococci sensitive to penicillin G). Finally, the most prevalent serogroup was the serogroup 19 (29.6% of isolates). Conclusion A decrease of PDSP was observed since 2001 and high-level resistant strains to β-lactams remain low. The rate of PDSP in Pays de la Loire is in the national average.

Imported Ciprofloxacin-ResistantNeisseria meningitidis

Imported Ciprofloxacin-Resistant<i>Neisseria meningitidis</i>

Genetics of Chromosomally Mediated Intermediate Resistance to Ceftriaxone and Cefixime in Neisseria gonorrhoeae

All strains of Neisseria gonorrhoeae with reduced susceptibility to ceftriaxone and cefixime (cephalosporin-intermediate-resistant [Ceph(i)] strains) contain a mosaic penA allele encoding penicillin-binding protein 2 (PBP 2) with nearly 60 amino acid differences compared to the sequence of wild-type PBP 2, together with a set of resistance determinants (i.e., mtrR, penB, and/or ponA1) that are required for high-level penicillin resistance. To define the individual contributions of these determinants to reduced susceptibility to ceftriaxone and cefixime, we created isogenic strains containing the mosaic penA allele from the Ceph(i) strain 35/02 (penA35) together with one or more of the other resistance determinants and determined the MICs of penicillin G, ceftriaxone, and cefixime. The majority of cefixime resistance is conferred by the penA35 allele, with only a small contribution coming from mtrR and penB, whereas ceftriaxone resistance is nearly equally dependent upon mtrR and penB. Unlike high-level penicillin resistance, the ponA1 allele does not appear to be important for Ceph(i). A strain containing all four determinants has increased resistance to ceftriaxone and cefixime but not to the levels that the donor Ceph(i) strain does, suggesting that Ceph(i) strains, similar to high-level-penicillin-resistant strains, contain an additional unknown determinant that is required to reach donor levels of resistance. Our data also suggest that the original Ceph(i) strains arose from the transformation of penA genes from commensal Neisseria species into a penicillin-resistant strain already harboring mtrR, penB, ponA1, and the unknown gene(s) involved in high-level penicillin resistance.

Antimicrobial susceptibility of Streptococcus pneumoniae at a university hospital in Taiwan, 2000-07: impact of modified non-meningeal penicillin breakpoints in CLSI M100-S18

In 2008, a new set of penicillin breakpoints was published in the CLSI revised guideline, M100-S18, to define the susceptibility of non-meningeal isolates of Streptococcus pneumoniae. The impact of the change is studied and discussed. Laboratory data on pneumococcal isolates collected from Chang Gung Memorial Hospital during 2000-07 were analysed using the original and modified penicillin CLSI breakpoints. A total of 3729 non-duplicate isolates were identifed, including 43 (1.2%) meningeal isolates showing high rates of penicillin (79.1%) and ceftriaxone (34.9%) resistance. For non-meningeal isolates, penicillin non-susceptibility was reduced significantly from 75.1% (72.4% in 2000-03 increasing to 77.4% in 2004-07) to 16% (28.6% in 2000 decreasing to 2.4% in 2007) if the modified breakpoints were applied. However, isolates for which penicillin MICs were 1-2 mg/L increased significantly from 34.2% in 2000 to 59.8% in 2007. Ceftriaxone non-susceptibility also increased significantly from 2.8% before 2005 to 18.4% thereafter. A quarter (25.7%) of the pneumococcal isolates were recovered from patients <10 years old. Higher resistance to penicillin (89.8% versus 70.4%; or 19.1% versus 13.2% by the modified breakpoints) or ceftriaxone (11.1% versus 5.8%) was found among these isolates, compared with those from older patients. With the implementation of the new breakpoints, clinicians may continue to use penicillin for the treatment of non-meningeal pneumococcal infections in preference to other drug classes. However, as isolates with borderline penicillin MICs are increasing, continued surveillance of pneumococcal susceptibility to penicillin will be needed.

Comparative Antipneumococcal Activities of Sulopenem and Other Drugs

For 297 penicillin-susceptible, -intermediate, and -resistant pneumococcal strains, the sulopenem MIC(50)s were 0.008, 0.06, and 0.25, respectively, and the sulopenem MIC(90)s were 0.016, 0.25, and 0.5 microg/ml, respectively. The MIC(50)s of amoxicillin for the corresponding strains were 0.03, 0.25, and 2.0 microg/ml, respectively, and the MIC(90)s were 0.03, 1.0, and 8.0 microg/ml, respectively. The combination of amoxicillin and clavulanate gave MICs similar to those obtained with amoxicillin alone. The sulopenem MICs were similar to those of imipenem and meropenem. The MICs of ss-lactams increased with those of penicillin G, and among the quinolones tested, moxifloxacin had the lowest MICs. Additionally, 45 strains of drug-resistant type 19A pneumococci were tested by agar dilution and gave sulopenem MIC(50)s and MIC(90)s of 1.0 and 2.0 microg/ml, respectively. Both sulopenem and amoxicillin (with and without clavulanate) were bactericidal against all 12 strains tested at 2x MIC after 24 h. Thirty-one strains from 10 countries with various penicillin, amoxicillin, and carbapenems MICs, including those with the highest sulopenem MICs, were selected for sequencing analysis of the pbp1a, pbp2x, and pbp2b regions encoding the transpeptidase active site and MurM. We did not find any correlations between specific penicillin-binding protein-MurM patterns and changes in the MICs.

Sensibilité aux antibiotiques et distribution des sérotypes des souches de Streptococcus pneumoniae isolées chez l’enfant à Tunis

Streptococcus pneumoniae is a major causative agent of severe infectious diseases. More than 90 pneumococcal serotypes are known, although most invasive and noninvasive diseases are associated with a much smaller number of serotypes. The aim of this study was to determine the antimicrobial susceptibility of S. pneumoniae isolates in children, the distribution of serogroups and serotypes, and the coverage by the serotypes included in the seven-valent pneumococcal conjugate vaccine toward pneumococcal disease. This study investigated 210 nonrepetitive isolates of S. pneumoniae isolated between 1998 and 2004. Antimicrobial susceptibility was tested using the disk diffusion method as determined by the CA-SFM guidelines. Penicillin susceptibility was determined using the oxacillin 5-microg disk screening test. The MICs of penicillin G, amoxicillin, and cefotaxime were determined using the E-test (ABBIODISK). Serotype was determined using rapid latex agglutination (Pneumotest Latex) and the capsular reaction test used antisera from the Staten Serum Institute. The evaluation of susceptibility to ss-lactamins showed that 52.8% of the strains were penicillin non susceptible strains (PNSs), 16.6% had decreased susceptibility to amoxicillin, and 8.5% to cefotaxime. Among noninvasive isolates, 55.2% were PNSs and 50.4% were invasive PNSs. The PNS strains were more frequently resistant to other antibiotics, with 68.4% resistance to erythromycin, 44.1% to trimethoprim-sulfamethoxazole, and 9.9% to chloramphenicol versus 32.3, 11.1, and 1%, respectively, in penicillin-susceptible strains. The predominant serogroups/serotypes of our study were 14 (22%), 23 (14.3%), 19 (11.9%), and 4 (8.5%). The study of the vaccine serotype distribution showed that the theoretical vaccinal coverage of the seven valent vaccines was 62.8% for all the isolates, 55.2% for the invasive isolates, and 67.9% for the PNSs.

Host and microbiologic factors associated with mortality in Taiwanese children with invasive pneumococcal diseases, 2001 to 2006

We concurrently evaluated host- and organism-related factors in determining the outcomes of 160 invasive pneumococcal diseases episodes in 158 Taiwanese children during 2001 and 2006. Most (138/160, 86.2%) episodes occurred at age less than 60 months, and an underlying condition was present in 35 (22.2%) cases. Common disease syndromes included complicated pneumonia (29.4%), uncomplicated pneumonia (29.4%), occult bacteremia (17.5%), and meningitis (14.4%). Mortality (13/160, 8.1%) was associated with age less than 24 months, underlying conditions, meningitis, cytopenia, intensive care, and penicillin MIC ≥2 μg/mL in univariate analysis. Pneumococcal serotypes, genotypes, origin of infections, and discordant therapy did not influence the outcome. Multivariate analysis determined the presence of underlying conditions (adjusted odds ratio [OR], 30.5; 95% confidence interval [CI], 4.8–193.1) and penicillin MIC ≥2 μg/mL (adjusted OR, 8.1; 95% CI, 1.4–47.3), which are the independent predictors for fatality. This finding highlighted the importance of immunization of disadvantaged children, targeting drug-resistant pneumococci.

Genetic heterogeneity in pbp genes among clinically isolated group B Streptococci with reduced penicillin susceptibility.

The recent emergence of group B streptococcal isolates exhibiting increased penicillin MICs at the Funabashi Municipal Medical Center and other hospitals in Japan prompted a comparative analysis of the penicillin-binding proteins (PBPs) from those strains with the PBPs from penicillin-susceptible strains comprising four neonatal invasive strains isolated from 1976 to 1988 and two recent isolates. The PBP sequences of the penicillin-susceptible strains were highly conserved, irrespective of their isolation date. Of six strains with reduced susceptibility to penicillin (penicillin MICs, 0.25 to 0.5 mug/ml), strains R1, R2, R5, and R6 shared a unique set of five amino acid substitutions, including V405A adjacent to the (402)SSN(404) motif in PBP 2X and one in PBP 2B. The remaining two strains, R3 and R4, shared several substitutions, including Q557E adjacent to the (552)KSG(554) motif in PBP 2X, in addition to the substitutions in PBP 2B, which are commonly found among penicillin-insusceptible strains. Strains R7 and R8, which had a penicillin MIC of 1 mug/ml, shared a unique set of eight amino acid substitutions (two in PBP 2X; two in PBP 2B, including G613R adjacent to the (614)KTG(616) motif; three in PBP 1A; and one in PBP 2A), and the Q557E substitution in PBP 2X was common to R3 and R4. The binding of Bocillin FL was reduced or not detected in some PBPs, including PBP 2X of penicillin-insusceptible strains, but no significant reduction in the level of pbp2x transcription was found in such strains. The results of phylogenetic comparative analyses imply the absence of epidemic penicillin-insusceptible strains, and several genetic lineages of penicillin-insusceptible strains have been independently emerging through the accumulation of mutations in their pbp genes, especially in pbp2x.

Breakthrough in penicillin resistance? Streptococcus pneumoniae isolates with penicillin/cefotaxime MICs of 16 mg/L and their genotypic and geographical relatedness

To phenotypically and genotypically characterize 11 strains (isolated in four different centres) exhibiting penicillin MIC of 8-32 mg/L among isolates of the SPICE project. Nine isolates were from Romania (9/162; 5.56%) and two from Poland (2/305; 0.66%). In vitro susceptibility was determined in triplicate by microdilution (CLSI guidelines), and additionally, MICs of penicillin, cefotaxime and amoxicillin were confirmed in triplicate by agar dilution. Multilocus sequence typing (MLST), PFGE and gene amplification and sequencing were performed. For the nine Romanian isolates, MICs were >/=16 mg/L for penicillin, cefotaxime and amoxicillin, >/=32 mg/L for cefuroxime and cefpodoxime, 4-8 mg/L for cefditoren and >/=128 mg/L for erythromycin and gentamicin. All isolates were non-susceptible to imipenem (MIC = 0.5-1 mg/L) and susceptible to levofloxacin (MIC = 0.5-1 mg/L) and vancomycin (MIC = 0.25-0.5 mg/L). These Romanian strains presented a new cluster in the 595-600 region of PBP2X (YSGIQL-->LSTPWF) conferring 98% homology with Streptococcus mitis PBP2X, with a new MurM allele (seven strains) with eight amino acid changes versus R6. PBP nucleotide sequences were highly conserved suggesting a common origin. Allelic profiles of two strains gave sequence type 321, three strains exhibited a single- and four a double-locus variance. MLST-predicted serotype was 23F in all but one strain (19F), but three strains were 19A by Quellung. The multidrug high resistance (precluding adequate oral therapy in children), its origin, the prevalence found in Romania and the presence of non-vaccine (7-valent) serotypes should worry the medical community because of a possible clonal diffusion that would limit therapeutic alternatives.

Cell surface hydrophobicity and adherence of a strain of group B streptococci during the post-antibiotic effect of penicillin

The minimum inhibitory concentration and post-antibiotic effects of an antimicrobial agent are parameters to be taken into consideration when determining its dosage schedules. The in vitro post-antibiotic effects on cell surface hydrophobicity and bacterial adherence were examined in one strain of group B streptococci. Exposure of the microorganism for 2 h at 37 degrees C to 1 x MIC of penicillin induced a PAE of 1.1 h. The cell surface charge of the Streptococcus was altered significantly during the post-antibiotic phase as shown by its ability to bind to xylene: hydrophobicity was decreased. Bacterial adherence to human buccal epithelial cells was also reduced. The results of the present investigation indicate that studies designed to determine therapeutic regimens should evaluate the clinical significance of aspects of bacterial physiology during the post-antibiotic period.

In vitro activity of tigecycline against Gram-positive cocci: a multicentre study in Greece

than imipenem, meropenem and ceftriaxone. Our findings suggest that against these multidrug-resistant pneumococcal isolates, the ranking of in vitro activity based on MIC90 for the b-lactams would be ME1036 (0.12 mg/L) (most active).imipenem (0.5 mg/L). meropenem (1 mg/L).ceftriaxone (1 mg/L).cefotaxime (2 mg/L).penicillin1⁄4cefepime (4 mg/L).amoxicillin (8–16 mg/L).cefuroxime (16 mg/L).ampicillin ( 16 mg/L) (least active). A previous study that employed agar dilution testing against a smaller number of non-selected penicillin-resistant S. pneumoniae isolates reported an MIC90 value of 0.03 mg/L for ME1036, 4 a value two dilutions lower than the MIC90 value determined in this study against multidrug-resistant strains belonging to troublesome serotypes exhibiting higher amoxicillin than penicillin MIC. MIC90 values determined for ME1036 by broth microdilution against a small number (11 strains) of penicillin-resistant S. pneumoniae isolates in a previous study showed values similar to those in the present study. In conclusion, ME1036 exhibited excellent intrinsic activity against penicillin-resistant S. pneumoniae belonging to serotypes 9V, 14, 6B and 19A, exhibiting higher amoxicillin than penicillin MIC. The spread of multidrug resistance that includes b-lactams (including penicillins, secondand third-generation cephalosporins and previous carbapenems) may challenge empirical hospital treatment of lower respiratory tract infections. The high intrinsic activity of ME1036 against resistant strains of S. pneumoniae may represent an advantage when broadspectrum activity is required.

In vitro activity of ME1036 versus other -lactams against penicillin-resistant Streptococcus pneumoniae serotypes exhibiting higher amoxicillin than penicillin MIC

In vitro activity of ME1036 versus other -lactams against penicillin-resistant Streptococcus pneumoniae serotypes exhibiting higher amoxicillin than penicillin MIC