Penicillin Minimum Inhibitory Concentration Research Articles

Evolving pneumococcal serotypes and sequence types in relation to high antibiotic stress and conditional pneumococcal immunization

In Taiwan, beginning in 2013, the 13-valent pneumococcal conjugate vaccine (PCV13) was provided free of charge to children 2–5 years of age. In 2014, this was extended to children 1–5 years old. During 2012–2014, 953 cases of culture-confirmed pneumococcal disease (CCPD), including 104 invasive pneumococcal disease (IPD), were prospectively identified and analyzed at a 3,700-bed hospital in Taiwan. From 2012 to 2014, the incidence per 10,000 admissions decreased from 26.7 to 20.4 for CCPD (P < 0.001) and from 3.2 to 1.9 for IPD (P < 0.05). Significant reduction of PCV13 serotypes was firstly noted in children in 2013 and extended to both paediatric and adult populations in 2014. Simultaneously, the incidence per 10,000 admissions of non-PCV13 serotypes increased from 6.1 in 2012 to 9.3 in 2014 (P < 0.005). The most prevalent non-PCV13 serotypes were 15A, 15B, and 23A, each containing a predominant clone, ST6315A, ST8315B, and ST33823A. From 2012 to 2014, isolates with penicillin minimum inhibitory concentrations >2 mg/L decreased from 27.8% to 8.1% (P < 0.001) among all isolates. PCV13 immunization in young children demonstrated an early protective effect in all ages. However, in the elderly, the effect was compromised by an emergence of non-PCV13 serotypes.

The prevalence and epidemiology of plasmid-mediated penicillin and tetracycline resistance among Neisseria gonorrhoeae isolates in Guangzhou, China, 2002-2012.

BackgroundGonococcal antimicrobial resistance is a global problem. Different resistance plasmids have emerged and spread among the isolates of Neisseria gonorrhoeae worldwide and in China. We conducted this study to monitor the plasmid-mediated penicillin and tetracycline resistance among N. gonorrhoeae isolates in Guangzhou from 2002 to 2012.MethodsConsecutive isolates of N. gonorrhoeae were collected from outpatients with gonorrhea attending the STD clinic in Guangdong Provincial Centre for Skin Diseases and STIs Control and Prevention. Penicillinase-producing N. gonorrhoeae (PPNG) isolates were analyzed by the paper acidometric method. Plasmid-mediated resistance to tetracycline in N. gonorrhoeae (TRNG) isolates was screened by the agar plate dilution method. Plasmid types were determined for TRNG and PPNG isolates using polymerase chain reaction (PCR). Minimum inhibitory concentrations (MICs) to penicillin and tetracycline were detected by the agar plate dilution.ResultsOf 1378 consecutive N. gonorrhoeae isolates, 429 PPNG and 639 TRNG isolates were identified. The prevalence of PPNG, TRNG, and PPNG/TRNG increased from 18.3 to 47.1 % (χ2 = 31.57, p < 0.001), from 29.4 to 52.1 % (χ2 = 16.28, p < 0.001) and from 10.0 to 26.2 % (χ2 = 10.46, p < 0.001) between 2002 and 2012, respectively. Genotyping of plasmids among PPNGs showed that the majority (93.7 %) of the isolates were the Asian type plasmids, while the African type plasmid emerged in 2008 and rapidly increased to 14.0 % in 2012 (χ2 = 25.03, p < 0.001). For TRNGs, all 639 isolates carried the Dutch type plasmid. MICs of penicillin G and tetracycline persisted at high levels and the MIC90s were 32-fold higher than the resistant cutoff point over 11 years. The prevalence rates of penicillin- and tetracycline-resistant N. gonorrhoeae varied from 90.9 to 91.1 % and from 88.3 to 89.3 % during 2002 to 2012, respectively.ConclusionsResistance to penicillin and tetracycline among N. gonorrhoeae isolates remained at high levels in Guangzhou. The Asian type PPNG continued to spread and Dutch type TRNG was still the dominant strain. The African type PPNG has emerged and is spreading rapidly.

In vitro susceptibility of a penicillin-resistant and tolerable isolate of Streptococcus pneumoniae to combination therapy.

Preference for combination therapy to treat infection due to multidrug-resistant S. pneumoniae (MDRSP) has not been well elucidated in previous studies. In the present study, 19 antibiotics in combinations were tested against an MDRSP isolate. In vitro susceptibility studies including minimum inhibitory concentration (MIC), minimal bactericidal concentrations (MBC) and disk agar diffusion (DAD), tolerance to resistant antibiotics, checkerboard assay, time-kill curve, hemolytic assay, and autolysis assay were performed on the test strain to study its in vitro susceptibility to combination therapy. From the checkerboard assay and time-kill curve, it was observed that a combination of levofloxacin (MIC, 16 µg/mL) and ceftriaxone (MIC, 2 µg/mL), at sub-MIC concentration was synergistic and most effective against the MDRSP isolate (penicillin MIC, > 64 µg/mL). Hemolytic activities also increased significantly with combination therapy compared to monotherapy (p < 0.05). Moreover, the hemolytic activity of levofloxacin in combination with ceftriaxone was better than ciprofloxacin plus ceftriaxone or cefepime. The autolysis rate was also found to increase rapidly within one hour of exposure to levofloxacin plus ceftriaxone, and this was found to be significantly different from the other combinations at the fifth and sixth hour post incubation (p < 0.05). This data suggests that this combination is bactericidal in vitro, and requires further studies in in vivo models for treatment against MDRSP infections.

Activation of persistent Streptococcus equi subspecies zooepidemicus in mares with subclinical endometritis

Endometritis in horses caused by Streptococcus equi subspecies zooepidemicus (S. zooepidemicus) may be underdiagnosed due to traditional diagnostic methods lacking sensitivity and specificity. We serendipitously identified a bacterial growth medium (bActivate) that appeared capable of inducing growth of dormant S. zooepidemicus, which subsequently allowed detection by standard diagnostics. To assess the effect of bActivate we compared its ability to activate dormant S. zooepidemicus in a group of potentially infected subfertile mares with phosphate-buffered saline (PBS). All mares had to test negative for S. zooepidemicus on a low-volume uterine lavage, be negative on endometrial cytology and without clinical signs of endometritis to be included in the investigation. The mares were instilled with bActivate or PBS in the uterus. Growth of S. zooepidemicus was induced by bActivate in 64% (16/25) and PBS in 8% (1/12) of the mares, respectively (p<0.002).In vitro studies supported that some strains of S. zooepidemicus were able to form persister cells tolerating 32-times of the minimal inhibitory concentration of penicillin compared to normal growing cells. Persister cells had not acquired penicillin resistance, but seemed to tolerate the antimicrobial due to dormancy.This is, to our knowledge, the first description of controlled growth induction of dormant bacteria from a subclinical infection. Moreover we demonstrated how endometritis can origin from a reservoir of dormant bacteria residing within the endometrium, and not only as an ascending infection. Further studies should aim at determining the prevalence of dormant S. zooepidemicus, impact of activation on diagnostic and treatment efficacy, uterine health and mare fertility.

Predominant β-lactamase genotypes of Escherichia coli isolates and induction and inhibition mechanisms of β-lactamase gene expression

To understand the predominant β-lactamase genotypes and their carrying modes of Escherichia coli isolates in Zhejiang province, and the effects of β-lactam antibiotics on inducing or histidine kinase inhibitor closantel (CLO) on inhibiting the expression of β-lactamase genes. Micro-dilution method and E-test were applied to measure the resistant rate and minimal inhibitory concentration (MIC) in E. coli isolates against β-lactam antibiotics. PCR and sequence analysis of PCR products were conducted to detect the β-lactamase genotypes and their carrying modes. Real-time fluorescent quantitative RT-PCR and β-lactamase confirmation test were performed to determine the influence of 1/4 MIC penicillin and cefotaxime, and CLO on the transcription and expression of β-lactamase genes in the resistant E. coli isolates. Among the 462 E. coli strains isolated in Zhejiang, 285 (61.7%) were resistant to penicillin, ampicillin, cefoxitin, cefotaxim and ceftazidime. In the 285 resistant isolates, the detection rate of TEM or CTX-M β-lactamase gene (83.2% or 75.1%) was significantly higher than that of KPC, SHV or OXA β-lactamase gene (1.4%-10.2%) (P<0.01) and the carrying rate of two or more β-lactamase genes (68.8%) was also significantly higher than that of single β-lactamase gene (31.2%) (P<0.01), and 61.4% of the resistant isolates carried TEM+CTX-M genes (P<0.01). Except KPC gene, 1/4 MIC of cefotaxim and penicillin induced a rapid increase of TEM-mRNA, CTX-M-mRNA, SHV-mRNA or OXA-mRNA levels (P<0.01), but 50-500 µg/ml CLO inhibited these levels (P<0.01). After pre-treatment with 100 µg/ml CLO, 82.8%-85.6% of the resistant isolates became sensitive to β-lactam antibiotics (P<0.01), while the detection rate of β-lactamases was also decreased from 95.1% to 16.1% (P<0.01). TEM and CTX-M are the predominant β-lactamase genotypes in E. coli isolates in Zhejiang and TEM+CTX-M is the predominant carrying mode of β-lactamase genes. Low concentrations of β-lactam antibiotics can up-regulate the expression levels of β-lactamase genes in E. coli through bacterial two-component signaling systems, but this effect can be inhibited by CLO, a histidine kinase inhibitor.

Prevalence of penicillin-non-susceptible Streptococcus pneumoniae in children in day-care centres subjected to an intervention to prevent dispersion

Background: The aim of this study was to evaluate the day-care interventions implemented in southern Sweden to restrict the dispersion of penicillin-non-susceptible pneumococci with a minimum inhibitory concentration of penicillin G of at least 0.5 mg/l (PNSP0.5). Methods: A retrospective epidemiological study was performed and data from 109 day-care centre interventions from 2000 to 2010 were analysed, including screening results from 7157 individuals. Results: It was found that 42% of the children were carriers of pneumococci and 5% of the screened children were PNSP0.5 carriers. Very few personnel were PNSP0.5 carriers and they were carriers for only a short time. Significantly more contact cases with the same serogroup as the index case were found in the first screening and in the same department as the index case, but a substantial number of contact cases were found in adjacent departments. Conclusions: Screening of personnel is not worth the effort. Based on our results, procedures to restrict dispersion of PNSP0.5 in day-care centres could be improved. To find the majority of contact cases with PNSP0.5 an early screening including adjacent departments seems to be the best approach.

The association of serotype and pulsed-field gel electrophoresis genotype in isolates of Streptococcus pneumoniae isolated in Israel

The relationship between Streptococcus pneumoniae isolates causing invasive infections in children admitted to a single center in central Israel was examined by pulsed-field gel electrophoresis (PFGE) and serotyping. Although there was a close correlation between serotype and PFGE clone, the genetic diversity varied by serotype, with some genotypes comprising multiple serotypes. Additionally, clones C and D were associated with higher penicillin minimum inhibitory concentrations. Serotyping alone may be insufficient for epidemiological mapping of pneumococcal isolates in the era of pneumococcal conjugate polysaccharide vaccines.

Multicenter surveillance of Streptococcus pneumoniae isolates from middle ear and mastoid cultures in the 13-valent pneumococcal conjugate vaccine era.

Streptococcus pneumoniae is a common cause of otitis media (OM) in children; mastoiditis remains an important complication of OM. Limited data are available on the impact of the 13-valent pneumococcal conjugate vaccine (PCV13) on pneumococcal otitis. Investigators from 8 children's hospitals in the United States prospectively collected pneumococcal isolates from middle ear or mastoid cultures from children from 2011 to 2013. Serotype and antibiotic susceptibilities were determined and PCV13 doses for children documented. Over the 3-year period, the proportion of isolates included in PCV13 (plus a related serotype) decreased significantly (P = .0006) among the middle ear/mastoid isolates (2011, 50% [74/149]; 2012, 40.5% [47/116]; 2013, 29% [34/118]). The number of serotype 19A isolates in 2013 (n = 12, 10.2% of total) decreased 76% compared with the number of 19A isolates in 2011 (n = 50, 33.6% of total). Of the children from whom serotype 19A was isolated (n = 93), 55% had previously received <3 doses of PCV13. The most common non-PCV13 serotypes for the combined years were 35B (n = 37), 21 (n = 20), 23B (n = 20), 15B (n = 18), 11 (n = 17), 23A (n = 14), 15A (n = 14), and 15C (n = 14). The proportion of isolates with a penicillin minimal inhibitory concentration >2 µg/mL decreased significantly over the 3 years (2011, 22% [35/154]; 2012, 20% [24/118]; 2013, 10% [12/120]; P < .02). The number of pneumococcal isolates and the percentage of isolates with high-level penicillin resistance from cultures taken from children with OM or mastoiditis for clinical indications have decreased following PCV13 use, largely related to decreases in serotype 19A isolates.

Nasopharyngeal carriage of Streptococcus pneumoniae in Romanian children before the introduction of the pneumococcal conjugated vaccination into the national immunization programme: a national, multi-centre, cross-sectional observational study

We analysed the distribution of vaccine and non-vaccine Streptococcus pneumoniae serotypes and the antimicrobial susceptibility of pneumococcal strains isolated from healthy Romanian children. A multi-centre cross-sectional study was performed in four counties to evaluate carried strains of S. pneumoniae isolated from 2000 children aged 0-5 years. S. pneumoniae carriage was detected in 25.25% of the tested children. Carriage increased from 16.7% among infants to 29.4% in 3-5-year-old children (p<0.0001). The proportions of the serotypes included in pneumococcal conjugate vaccines PCV7, PCV10, and PCV13 among our isolates were 39.9%, 40.1%, and 58.7%, respectively. Erythromycin resistance was 72.5%, and it was significantly lower in non-vaccine serotypes compared with PCV13 serotypes: 57.3% versus 83.6% (p<10(-7)). Penicillin minimum inhibitory concentrations (MICs) >0.064mg/l were recorded in 71.6%, but the penicillin MIC was >2mg/l for only 8.4% of tested isolates. In Romanian children, the majority of carried S. pneumoniae isolates are vaccine serotypes. The isolates with MICs defining macrolide resistance were very frequent, as well as the isolates with MICs defining penicillin resistance in the case of meningitis or penicillin dose-dependent susceptibility for other infections, mainly for the strains belonging to PCV13 serotypes. The implementation of PCV13 within the Romanian national immunization programme could reduce the circulation of these strains with higher macrolide and/or penicillin MICs.

Resistant mechanism of β-lactam antibiotic of invasive @(xt)Streptococcus pneumoniae

Objective To understand the drug resistance and antibiotic resistance mechanism of β-lactam antibiotics of invasive Streptococcus pneumoniae isolated from Shanghai Children′s Hospital, provides the reference for the rational use of antimicrobial agents. Methods This study is based on the research of the mechanism of drug resistance. 62 isolates of invasive Streptococcus pneumoniae were collected from Shanghai Children′s Hospital from January 2005 to December 2011. Minimum inhibitory concentrations (MIC) of strains to 9 antimicrobial agents were determined by E-test method. The penicillin binding protein coding genes pbp2x, pbp2b, and pbp1a of Streptococcus pneumoniae were amplified by PCR. Then, the correlation between the gene mutation and β-lactam antibiotics resistant level were analyzed. The murM gene of Streptococcus pneumoniae was amplified by PCR and the correlation of mutation and β-lactam antibiotics resistant level was analyzed. Results Out of 62 strains of invasive Streptococcus pneumoniae from children, the detection rate of penicillin resistant Streptococcus pneumoniae was 43.6% (27/62). Between penicillin intermediate Streptococcus pneumoniae (PISP) (100%, 25/25) and penicillin sensitive Streptococcus pneumoniae (PSSP) (3/10), the difference of gene mutation rate near the pbp2b conserved sequence was statistically significant (χ2=21.875, P＜0.01). The same situation occurred between penicillin resistant Streptococcus pneumoniae (PRSP)(100%, 27/27)and PSSP (3/10) (χ2=23.310, P＜0.01). Also the difference of gene mutation rate of PISP (84%, 21/25) vs PSSP (0) and PSSP (0) vs PRSP (85.2%, 23/27) near or in the pbp2x conserved sequence were statistically significant (χ2=21.000，P＜0.01；χ2=22.513，P＜0.01). The difference of gene mutation rate near the pbp1a conserved sequence and Insertion sequence, which were statistically significant, occurred between PISP and PSSP (χ2=13.22，P＜0.01), between PRSP and PSSP (χ2=37.000，P＜0.01), between PISP and PRSP (χ2=10.211，P=0.001). MurM gene mutation rate was statistically significant different between the 2 group penicillin MIC≥8 mg/L or ceftriaxone MIC≥2 mg/L group (95.8%, 23/24) and penicillin MIC<8 mg/L or ceftriaxone MIC<2 mg/L group (0) (χ2=56.2，P=0.002 6). Conclusions The resistance phenomenon of invasive Streptococcus pneumoniae in Shanghai Children′s Hospital is serious. The gene mutations of pbps and murM play a role in amide in the beta of antibiotic resistance, and there is a certain correlation with the antibiotic resistance level. （Chin J Lab Med,2014,37:748-752） Key words: Streptococcus pneumoniae; Beta-Lactam resistance; Genotype; Penicillin-binding proteins; Bacterial proteins

Impact of the 13-valent pneumococcal conjugate vaccine on chronic sinusitis associated with Streptococcus pneumoniae in children.

The widespread use of the 7-valent pneumococcal conjugate vaccine has been associated with epidemiologic changes of mucosal and invasive pneumococcal disease. No study describes the impact of 13-valent pneumococcal conjugate vaccine (PCV13) on chronic sinusitis in children. We describe changes in epidemiology of Streptococcus pneumoniae chronic sinusitis after the introduction of PCV13 at Texas Children's Hospital. We identified patients <18 years with positive sinus culture for S. pneumoniae who underwent endoscopic sinus surgery because of chronic sinusitis from August 2008 to December 2013 at Texas Children's Hospital. Isolates were serotyped by the capsular swelling method. Demographic and clinical information was collected retrospectively. The χ test and Fisher's exact test were used to analyze dichotomous variables. We identified 91 cases of chronic sinusitis with positive sinus culture for S. pneumoniae. Sixty-one (67%) isolates were non-PCV13 serotypes. PCV13 cases decreased 31% in the post-PCV13 period (P = 0.003). Serotype 19A decreased 27% in the post-PCV13 period (P = 0.007), but accounted for all the isolates with penicillin minimal inhibitory concentration ≥ 4 μg/mL and ceftriaxone minimal inhibitory concentration ≥ 2 μg/mL. Serotypes 19A (38%) and 15C (17%) were the most common in the pre- and post-PCV13 periods, respectively. The most common organism co-isolated was Haemophilus influenzae (52%). Isolation of Prevotella spp. increased in the post-PCV13 period (P = 0.02). S. pneumoniae continues to represent an important pathogen in chronic sinusitis in children <5 years of age. After the introduction of PCV13, S. pneumoniae isolation declined in children with chronic sinusitis at Texas Children's Hospital. We also observed a substantial reduction of PCV13 serotypes, predominantly serotype 19A.

Evaluation of Enterococcus faecalis clinical isolates with ‘penicillin-resistant, ampicillin-susceptible’ phenotype as reported by Vitek-2 Compact system

It has been recently reported that ampicillin susceptibility cannot accurately predict piperacillin and imipenem susceptibilities in penicillin-resistant, ampicillin-susceptible (Pen-R, Amp-S) Enterococcus faecalis isolates, contrary to the current Clinical and Laboratory Standards Institute (CLSI) recommendations. This has important therapeutic implications. Such isolates were noted after the use of Vitek-2 Compact system AST-GP67 susceptibility cards in a Singapore general hospital and they were increasing in numbers. The primary aim of this study was to evaluate these clinical isolates against microbroth dilution (MBD) technique and other commonly used antimicrobial susceptibility test (AST) methods for penicillin and ampicillin. The secondary aim was to evaluate whether ampicillin susceptibility could indeed be a reliable surrogate marker for piperacillin and imipenem susceptibilities in E. faecalis isolates that were confirmed Pen-R, Amp-S.From 2009 to 2013, a total of 49 isolates (5%) of 983 non-duplicate E. faecalis tested by Vitek-2 displayed the 'Pen-R, Amp-S' phenotype in a general hospital in Singapore. These were tested against MBD which was the reference method, Etest and disc diffusion for penicillin and ampicillin. Susceptibilities to piperacillin and imipenem were also tested using MBD. In addition, β-lactamase production test was performed. Forty E. faecalis isolates with penicillin-susceptible, ampicillin-susceptible (Pen-S, Amp-S) phenotype were included for comparative purposes.The categorical agreement rate was 100% for all AST methods in ampicillin reporting for the 'Pen-R, Amp-S' group of E. faecalis isolates. However, a large number of isolates (46 isolates, 93.9%) fell into the major error category for penicillin testing by the Vitek-2 system. Penicillin minimum inhibitory concentrations (MICs) generated by the Vitek-2 system for the majority of these isolates were two doubling dilutions higher compared to those obtained by the reference test. The Etest method correlated well with the MBD method. Thirty-two isolates (65.3%) were in categorical agreement with the MBD method when tested by the disc diffusion method for penicillin. Only three E. faecalis isolates (6.1%) were confirmed to have the uncommon penicillin resistance phenotype, with two of them showing resistance to piperacillin and intermediate to imipenem. β-lactamase production test was negative for all isolates. Among the Pen-S, Amp-S E. faecalis isolates, the categorical agreement was 100% for penicillin and ampicillin in all the tested methods.Enterococcus faecalis with 'Pen-R, Amp-S' phenotype reported by the Vitek-2 system using AST-GP67 susceptibility cards must be confirmed with a reference test, the Etest method being a good alternative. The Vitek-2 system generated higher penicillin MIC readings compared to MBD in this study. The actual prevalence of this uncommon penicillin resistance phenotype in E. faecalis was found to be low in this institution. More studies are required to confirm the reliability of ampicillin as a surrogate marker for piperacillin and imipenem susceptibilities in these isolates.

High levels of Staphylococcus aureus contamination in Chinese-style roast pork.

Chinese roasted pork has been implicated as a major source of food poisoning caused by Staphylococcus aureus. Establishing the source, either as contaminants from raw meat or from food handlers, could facilitate drafting more appropriate guidelines for better prevention of food poisoning. To determine the rate and source of staphylococcal contamination, roasted pork purchased from 50 sui-mei shops in Hong Kong was sampled for presence of S. aureus by enrichment and subsequent culture. Isolates were characterized for methicillin sensitivity, spa type, and presence of Panton-Valentine leukocidin (PVL) and staphylococcal enterotoxins (SEs). Methicillin-resistant isolates were confirmed by presence of mecA and SCCmec type and sensitivity to vancomycin investigated. S. aureus was isolated from 25 (50%) samples, with 3 yielding two colony types. Of the 28 isolates, 3 were resistant to cefoxitin, but only 2 were mecA positive and belonged to SCCmec type V. The mecA negative isolate also lacked mecC, but had a penicillin minimum inhibitory concentration of 10 mg/L. A livestock-associated spa type (t034) was only observed in one methicillin-sensitive strain, all other isolates appearing to be of human origin, with 30% belonging to t189. One isolate was PVL positive and five carried genes for classical SEs. The high rate of staphylococcal contamination observed was probably associated with food handlers, as the strains belonged to spa types previously reported in clinical and nasal carriage isolates. The presence of enterotoxins in 18% of isolates confirms the risk of food poisoning associated with this product and emphasizes the need for improved guidelines for handling after preparation. Use of refrigerated display areas should be considered.

Antimicrobial Resistance and Serotype Distribution of Nasopharyngeal Pneumococcal Isolates From Healthy Toddlers of Evros, Greece

Background: Streptococcus pneumoniae (SP) strains carried in the nasopharynx of healthy children reflect the circulating strains implicated in respiratory and invasive infections. Methods: We prospectively analyzed the serotype distribution of SP nasopharyngeal isolates in healthy toddlers aged 21 to 78 months (median age, 63 months) attending day care centers during the winters of 2010Y2012. All children were sampled once during the study period. Serotyping was performed by the Quellung reaction using the 12 pooled antisera Pneumotest panel and specific factor sera. We also studied the in vitro antimicrobial susceptibilities of the isolated pneumococci to several antibiotics by E-test, and for macrolide-resistant isolates of 2010 only, the resistance genes mef(A) and erm(B). Results: Among the 543 toddlers studied, 98.8% had received 1 or more doses of 7-valent pneumococcal conjugate vaccine (PCV7), whereas none was immunized with PCV10 or PCV13. Overall, 27.4% of the children tested were colonized with SP, whereas 22.8% and 52.3% of the isolates belonged to PCV7 and PCV13 serotypes, respectively. Overall, 25.5% of the isolates had intermediate resistance to penicillin (minimal inhibitory concentration, 0.12Y1 Kg/mL) and 3.4% were resistant to penicillin (minimal inhibitory concentration, 2 Kg/mL). All isolates were susceptible to amoxicillin, whereas 28.2% were resistant to macrolides, with the mef(A) geneYmediated M phenotype being the most common in 2010, the year that macrolide resistance genes were studied (93.4% of macrolideresistant isolates). Conclusions: Implementation of PCV13 will increase the coverage of children in our area for invasive pneumococcal serotypes by approximately 30%. Postlicensure serotyping and antimicrobial susceptibility surveillance are essential for designing rational immunization strategies.

Development and validation of a clinical model to predict the presence of β-lactam resistance in viridans group streptococci causing bacteremia in neutropenic cancer patients.

Concern for serious infection due to β-lactam-resistant viridans group streptococci (VGS) is a major factor driving empiric use of an anti-gram-positive antimicrobial in patients with febrile neutropenia. We sought to develop and validate a prediction model for the presence of β-lactam resistance in VGS causing bloodstream infection (BSI) in neutropenic patients. Data from 569 unique cases of VGS BSI in neutropenic patients from 2000 to 2010 at the MD Anderson Cancer Center were used to develop the clinical prediction model. Validation was done using 163 cases from 2011 to 2013. In vitro activity of β-lactam agents was determined for 2011-2013 VGS bloodstream isolates. In vitro resistance to β-lactam agents commonly used in the empiric treatment of febrile neutropenia was observed only for VGS isolates with a penicillin minimum inhibitory concentration (MIC) of ≥ 2 µg/mL. One hundred twenty-nine of 732 patients (17%) were infected with VGS strains with a penicillin MIC ≥ 2 µg/mL. For the derivation and validation cohorts, 98% of patients infected by VGS with a penicillin MIC of ≥ 2 µg/mL had at least 1 of the following risk factors: current use of a β-lactam as antimicrobial prophylaxis, receipt of a β-lactam antimicrobial in the previous 30 days, or nosocomial VGS BSI onset. Limiting empiric anti-gram-positive therapy to neutropenic patients having at least 1 of these 3 risk factors would have reduced such use by 42%. Simple clinical criteria can assist with targeting of anti-gram-positive therapy to febrile neutropenic patients at risk of serious β-lactam-resistant VGS infection.

Serotype distribution and antimicrobial susceptibility of group B streptococci in pregnant women: results from a Swiss tertiary centre

To evaluate the rates of penicillin, clindamycin and erythromycin resistance and the serotype distribution among isolates of group B streptococcus (GBS) obtained from pregnant women at the University Hospital of Bern in Switzerland. We prospectively collected screening samples for GBS colonisation at the University Women's Hospital Bern, Switzerland, between March 2009 and August 2010. We included 364 GBS isolates collected from vaginal, cervical or vaginal-perianal swabs at any gestation time. The minimal inhibitory concentrations for penicillin, clindamycin and erythromycin were established using Etest with 24 hours of incubation, and inducible clindamycin resistance was tested with double disk diffusion tests. Serotyping was done with a rapid latex agglutination test or, if not conclusive, with polymerase chain-reaction (PCR) testing. We looked for significant associations between resistance patterns, age groups, serotype and ethnicity. All isolates were susceptible to penicillin. Resistance rates were 14.5% for erythromycin and 8.2% for clindamycin. Of 364 isolates, 5.8% were susceptible to clindamycin but not to erythromycin, although demonstrating inducible clindamycin resistance. Hence, the final reported clindamycin resistance rate was 14%. Serotype III was the most frequent serotype (29%), followed by V (25%) and Ia (19%). Serotype V was associated with erythromycin resistance (p = 0.0007). In comparison with all other ethnicities, patients from Asia showed a higher proportion of erythromycin and clindamycin resistance (p = 0.018). No significant association between resistance patterns and age groups was found. In pregnant women with GBS colonisation, penicillin is the antibiotic of choice for intrapartum prophylaxis to prevent neonatal early-onset GBS sepsis. In women with penicillin allergy and at high risk for anaphylactic reaction, clindamycin may be an alternative. The resistance rate for clindamycin at our institution was 14%; therefore, susceptibility must be tested before administration.

Bacteremia with Aerococcus sanguinicola: Case Series with Characterization of Virulence Properties.

Since Aerococcus sanguinicola was designated as a species in 2001, only a few cases of bacteremia have been reported. The aim with this study was to describe the clinical presentation of A sanguinicola bacteremia and to determine the antibiotic susceptibility and the capacity of the bacteria to form biofilm and to induce platelet aggregation. Isolates of A sanguinicola from blood cultures were retrospectively identified from 2 clinical microbiology laboratories for 2006 to 2012. Species identity was confirmed through sequencing of the 16S rRNA gene. The medical charts of patients were reviewed. The minimum inhibitory concentration (MIC) for relevant antibiotics was determined. Biofilm formation was measured as the amount of crystal violet absorbed. Platelet aggregation was determined by aggregometry. Eleven cases of A sanguinicola bacteremia were identified. All patients were male and the median age was 82 years (range 67-93). Nine patients fulfilled criteria for severe sepsis, and 2 patients died at hospital. Two patients were diagnosed with infective endocarditis. Most patients had underlying urinary tract diseases or an indwelling urinary tract catheter. Five patients suffered from dementia. None of the patients was treated with immunosuppressive medications. The MIC values of the isolates were in line with previous reports, with low MICs for penicillin, cefotaxime, and vancomycin. All 11 isolates produced biofilms but not all could induce platelet aggregation. A sanguinicola can cause severe infections in elderly men with urinary tract abnormalities and the bacteria possess potential virulence mechanisms.

Antimicrobial susceptibility of Streptococcus pneumoniae in adult patients with pneumococcal pneumonia in an urban hospital in Mozambique

BackgroundStreptococcus pneumoniae is the leading cause of community–acquired pneumonia in Africa. Antimicrobial resistance of S. pneumoniae to penicillin and other commonly used antibiotics has increased worldwide. However, prevalence data from the African region are sparse, especially with regard to adults.FindingsIn this study, adult patients presenting at an urban referral hospital in central Mozambique were screened for pneumococcal pneumonia during an 8-week period in 2010: Patients with a respiratory syndrome underwent chest radiography and a sputum sample was collected for pneumococcal culture and antimicrobial susceptibility testing. A urine sample was tested for the presence of pneumococcal antigen.177 patients with a respiratory syndrome were included. Overall, 41/177 (23%) patients fulfilled criteria for definite or probable pneumococcal pneumonia and in the group of patients with a positive chest x-ray this concerned 35/86 (41%) patients. 166 sputum cultures yielded 16 pneumococcal strains. One mg oxacillin disc testing identified potential penicillin resistance in 7/16 (44%) strains. Penicillin minimal inhibitory concentrations (MICs) were measured for 15 of these strains and ranged from <0.016-0.75 mg/L. No MICs >2 mg/L were found, but 3/15 (20%) pneumococcal strains had MICs >0.5 mg/L. All pneumococci were sensitive to erythromycin as measured by disc diffusion testing, whereas 44% was resistant to trimethoprim-sulfametoxazole.ConclusionsThe proportion of pneumonia cases attributable to pneumococcus appeared to be high. Whilst none of the S. pneumoniae strains tested were penicillin resistant, standard penicillin dosing for pneumonia may be insufficient given the observed range of pneumococcal penicillin MICs.

P5.100 Trends in the Antimicrobial Susceptibility of Neisseria Gonorrhoeae Isolates in Belgium (2006–2011)

BackgroundIncreased resistance of Neisseria gonorrhoeae to antimicrobials has been reported worldwide, jeopardising the treatment of gonorrhoea. In order to provide guidance in treatment guidelines a national gonococcal antimicrobial surveillance programme...

Pneumococcal Serotypes Causing Acute Otitis Media Among Children in Barcelona (1992–2011)

There is scarce information about changes in serotypes and clonal types of Streptococcus pneumoniae causing acute otitis media (AOM) in recent years, particularly in European countries. Pneumococcal serotypes and clones from S. pneumoniae strains isolated from children with AOM who were attended at Hospital Sant Joan de Déu, Barcelona (1992 to 2011), were studied. Heptavalent pneumococcal conjugate vaccine (PCV7) was introduced in June 2001. We defined 3 periods: prevaccine period 1992 to 2001, early vaccine period 2002 to 2006 and late vaccine period 2007 to 2011. There were 376 pneumococcal strains causing AOM, and 373 (99.2%) of them were serotyped. AOM caused by PCV7 serotypes declined significantly: 161 of 245 (65.7%) episodes in 1992 to 2001 versus 22 of 67 (32.8%) in 2002 to 2006 versus 8 of 61 (13.1%) in 2007 to 2011 P < 0.001. In the last period (2007 to 2011), the potential serotype coverage for the PCV10 was 16.4% and for the PCV13 was 68.9% (P < 0.001). Serotype 19A increased from 5.7% in 1992 to 2001 to 42.6% in 2007 to 2011 (P < 0.001). Among strains with penicillin minimal inhibitory concentration ≥0.12 μg/mL (n = 241), serotype 19A rose from 2.3% in the first period to 57.9 % in the last period (P < 0.001). The clonal-type ST320 was initially detected in 2005, and in the period 2007 to 2011, the ST320 was found in 72.7% of nonsusceptible serotype 19A isolates. Among children with AOM, a rapid expansion of the multiresistant clone ST320 expressing serotype 19A has been observed in Barcelona. The implementation of PCV13, which includes this serotype, may decrease the prevalence of AOM and reduce antimicrobial resistance.