Penicillin Susceptibility Research Articles

Increased photoinactivation stress tolerance of Streptococcus agalactiae upon consecutive sublethal phototreatments

Streptococcus agalactiae (Group B Streptococcus, GBS) is a common commensal bacterium in adults but remains a leading source of invasive infections in newborns, pregnant women, and the elderly, and more recently, causes an increased incidence of invasive disease in nonpregnant adults. Reduced penicillin susceptibility and emerging resistance to non-β-lactams pose challenges for the development and implementation of novel, nonantimicrobial strategies to reduce the burden of GBS infections. Antimicrobial photodynamic inactivation (aPDI) via the production of singlet oxygen or other reactive oxygen species leads to the successful eradication of pathogenic bacteria, affecting numerous cellular targets of microbial pathogens and indicating a low risk of resistance development. Nevertheless, we have previously reported possible aPDI tolerance development upon repeated sublethal aPDI applications; thus, the current work was aimed at investigating whether aPDI tolerance could be observed for GBS and what mechanisms could cause it. To address this problem, 10 cycles of sublethal aPDI treatments employing rose bengal as a photosensitizer, were applied to the S. agalactiae ATCC 27956 reference strain and two clinical isolates (2306/02 and 2974/07, serotypes III and V, respectively). We demonstrated aPDI tolerance development and stability after 5 cycles of subculturing with no aPDI exposure. Though the treatment resulted in a stable phenotype, no increases in mutation rate or accumulated genetic alterations were observed (employing a RIF-, CIP-, STR-resistant mutant selection assay and cyl sequencing, respectively). qRT-PCR analysis demonstrated that 10 sublethal aPDI exposures led to increased expression of all tested major oxidative stress response elements; changes in sodA, ahpC, npx, cylE, tpx and recA expression indicate possible mechanisms of developed tolerance. Increased expression upon sublethal aPDI treatment was reported for all but two genes, namely, ahpC and cylE. aPDI targeting cylE was further supported by colony morphology changes induced with 10 cycles of aPDI (increased SCV population, increased hemolysis, increased numbers of dark- and unpigmented colonies). In oxidant killing assays, aPDI-tolerant strains demonstrated no increased tolerance to hypochlorite, superoxide (paraquat), singlet oxygen (new methylene blue) or oxidative stress induced by aPDI employing a structurally different photosensitizer, i.e., zinc phthalocyanine, indicating a lack of cross resistance. The results indicate that S. agalactiae may develop stable aPDI tolerance but not resistance when subjected to multiple sublethal phototreatments, and this risk should be considered significant when defining efficient anti-S. agalactiae aPDI protocols.

Antimicrobial susceptibility patterns of uropathogens isolated from pregnant women in KwaZulu-Natal Province: 2011 - 2016.

Urinary tract infection (UTI) is one of the most common infections during pregnancy, which can lead to significant maternal and perinatal morbidity and mortality if left untreated. Challenges when treating UTIs in pregnancy include fetal protection and resistance development of uropathogens. Currently, the Essential Medicines List recommends nitrofurantoin to treat cystitis and ceftriaxone to treat pyelonephritis in pregnant women. To determine common pathogens causing UTI in pregnancy and their antibiotic susceptibility patterns. A retrospective analysis was performed of laboratory data for positive urine specimens from obstetric departments of 6 KwaZulu- Natal Province hospitals during 2011 - 2016. Identification and susceptibility testing were performed using the VITEK 2 system. Results were interpreted according to the breakpoints of the Clinical and Laboratory Standards Institute, USA. From 5 971 positive urine specimens, the most common isolate was Escherichia coli (n=3 236; 54.2%), followed by Klebsiella pneumoniae (n=770; 12.9%). Group B streptococcus (GBS) (n=239; 4.0%) and Enterococcus faecalis (n=251; 4.2%) were the most common Gram-positive pathogens. E. coli displayed significant resistance to trimethoprim-sulfamethoxazole (65.1%), cephalothin (38.3%), cefuroxime (27.3%), ciprofloxacin (16.9%) and amoxicillin-clavulanic acid (17.1%). Resistance to ceftriaxone and nitrofurantoin remained low ‒ 9.1% and 7.7%, respectively. Among Gram-positive pathogens, GBS displayed 100% penicillin susceptibility and E. faecalis showed 92.9% susceptibility to ampicillin. E. coli is unsurprisingly the most common cause of UTI in pregnancy in KwaZulu-Natal. Susceptibility to ceftriaxone and nitrofurantoin remains good. Among Gram positives, GBS is prevalent and susceptible to penicillin, while E. faecalis is susceptible to ampicillin. As antimicrobial resistance evolves, routine surveillance is necessary to modify recommended empirical antibiotic use.

Virulence-Associated Characteristics of Serotype 14 and Serogroup 9 Streptococcus pneumoniae Clones Circulating in Brazil: Association of Penicillin Non-susceptibility With Transparent Colony Phenotype Variants.

Streptococcus pneumoniae remains a major agent of invasive diseases, especially in children and the elderly. The presence of pneumococcal capsule, pneumococcal surface protein A (PspA), and pilus type 1 (PI-1) and the ability of colony phase variation are assumed to play important roles in the virulence potential of this microorganism. Differences in the capsular polysaccharide allow the characterization of more than 90 pneumococcal serotypes; among them, serotype 14 and serogroup 9 stand out due to their prevalence in the pre- pneumococcal conjugate vaccine era and frequent association with penicillin non-susceptibility. Here we investigated the distribution of PI-1 and pspA genes and colony phase variants among 315 S. pneumoniae isolates belonging to serotype 14 and serogroup 9, recovered over 20 years in Brazil, and correlated these characteristics with penicillin susceptibility and genotype as determined by multilocus sequence typing. All strains were shown to carry pspA genes, with those of family 2 (pspA2) being the most common, and nearly half of the strains harbored P1-1 genes. The pspA gene family and the presence of PI-1 genes were conserved features among strains belonging to a given clone. A trend for increasing the occurrence of pspA2 and PI-1 genes over the period of investigation was observed, and it coincided with the dissemination of CC156 (Spain9V-3) clone in Brazil, suggesting a role for these virulence attributes in the establishment and the persistence of this successful clone. Opaque variant was the colony phenotype most frequently observed, regardless of clonal type. On the other hand, the transparent variant was more commonly associated with penicillin-non-susceptible pneumococci and with strains presenting evidence of recombination events involving the genes coding for polysaccharide capsule and PspA, suggesting that pneumococcal transparent variants may present a higher ability to acquire exogenous DNA. The results bring to light new information about the virulence potentials of serotype 14 and serogroup 9 S. pneumoniae isolates representing the major clones that have been associated with the emergence and the dissemination of antimicrobial resistance in our setting since the late 1980s.

Penicillin-susceptible Staphylococcus aureus bacteremia: Epidemiological and clinical relevance. Possible therapeutic implications

IntroductionThe increase in penicillin susceptibility among Staphylococcus aureus (SA-PenS) might have therapeutic relevance. We aimed to study the current situation in our environment. Material and methodsOver a 2.5 years period, all SA isolates from bacteraemia were analysed. For all isolates, antimicrobial susceptibility profile, beta-lactam resistance genes (blaZ, mecA) and Panton-Valentine leucocidine encoding-genes were studied. For SA-PenS-blaZnegative isolates, spa-type, MLST and the presence of other resistance genes were studied. ResultsAmong 84 patients with SA bacteraemia (35.7% MRSA and 64.3% MSSA), 77 were analysed; 22.2% of MSSA isolates were PenS and blaZnegative (Pen-MIC ≤0.03 µg/mL) corresponding to 14.3% of the total SA. In MSSA-PenS-blaZnegative isolates, eight spa-types corresponding to seven clonal complexes were detected. ConclusionA high prevalence of MRSA/SA and MSSA-PenS-blaZnegative/MSSA was detected in blood cultures. Pen-MIC ≤0,3 µg/mL corresponded to MSSA-PenS-blaZnegative. This situation raises therapeutic options which should be further evaluated in larger studies and clinical trials.

沖縄県内で分離されたStreptococcus agalactiae（GBS）の薬剤感受性とペニシリン低感受性株の検出状況

沖縄県内で分離されたStreptococcus agalactiae（GBS）の薬剤感受性とペニシリン低感受性株の検出状況

Antibiotic Sensitivity of Streptococcus Pneumoniae that Isolated from Different Pneumococcal Infections

During the period from June of 2018 to February 2019 (150) isolates of Streptococcus pneumoniae were isolated from 600 patients with clinical symptoms of Lower respiratory tract infections (LRTI) (pneumonia), otitis media and meningitis obtained from Baqubah Hospitals. The results showed that not only S. pneumoniae causes pneumonia and it can causes diseases other than pneumonia such as otitis media and meningitis but with less frequency. S. pneumoniae showed different susceptibilities towards antibiotics used in this study. The total susceptibility was (65.8%) and the total resistance was (34.2%). The highest pneumococcal susceptibility was showed to the cell wall inhibitors (44.4%) followed by protein synthesis inhibitors (28%) and quinolones (17.3%), and the lowest susceptibility was to folate antagonists with 0%. The highest rates of susceptibility was to penicillin (100%), chloramphenicol (86%), vancomycin (80%) and moderate rates of susceptibility to levofloxacin (90) 60%, linezolid (42.7) %, cefotaxime (40%), ofloxacin (40%) whereas there was a relatively lower susceptibility rate towards other antibiotics such as ampicillin, imipenem, amoxicillin, trimethoprim/sulfamethoxazole. Therefore, it should be avoided in the treatment in addition to tazobactam, amikacin, gentamicin, which had lowest rates susceptibility against S. pneumoniae. As a result, it required more research to identify new antibiotic or vaccine to reduce the risk of pneumococcal infection.

Genomic Insight into the Spread of Meropenem-Resistant Streptococcus pneumoniae Spain23F-ST81, Taiwan.

Incidence of invasive pneumococcal disease caused by antimicrobial-resistant Streptococcus pneumoniae types not included in pneumococcal conjugate vaccines has increased, including a penicillin- and meropenem-resistant serotype 15A-ST63 clone in Japan. During 2013–2017, we collected 206 invasive pneumococcal isolates in Taiwan for penicillin and meropenem susceptibility testing. We found serotypes 15B/C-ST83 and 15A-ST63 were the most prevalent penicillin- and meropenem-resistant clones. A transformation study confirmed that penicillin-binding protein (PBP) 2b was the primary meropenem resistance determinant, and PBP1a was essential for high-level resistance. The rate of serotype 15B/C-ST83 increased during the study. All 15B/C-ST83 isolates showed an ermB macrolide resistance genotype. Prediction analysis of recombination sites revealed 12 recombination regions in 15B/C-ST83 compared with the S. pneumoniae Spain23F-ST81 genome. Pneumococcal clones rapidly recombine to acquire survival advantages and undergo local expansion under the selective pressure exerted by vaccines and antimicrobial drugs. The spread of 15B/C-ST83 is alarming for countries with high antimicrobial pressure.

Results from the Survey of Antibiotic Resistance (SOAR) 2015–17 in Latin America (Argentina, Chile and Costa Rica): data based on CLSI, EUCAST (dose-specific) and pharmacokinetic/pharmacodynamic (PK/PD) breakpoints

To determine antibiotic susceptibility of Streptococcus pneumoniae and Haemophilus influenzae isolates from community-acquired respiratory tract infections (CA-RTIs) collected in 2015-17 from Argentina, Chile and Costa Rica. MICs were determined by CLSI broth microdilution and susceptibility was assessed using CLSI, EUCAST (dose-specific) and pharmacokinetic/pharmacodynamic (PK/PD) breakpoints. A total of 170 S. pneumoniae and 218 H. influenzae isolates were collected at five centres in Argentina, Chile and Costa Rica in 2015-17. Small S. pneumoniae isolate numbers from Costa Rica (n = 2) meant that these could only be included in the penicillin susceptibility analysis; they were excluded from further country analyses. Around one-third of pneumococcal isolates from Argentina and two-thirds from Chile were non-susceptible to penicillin by CLSI oral or EUCAST low-dose IV breakpoints, but most (≥89%) were susceptible by CLSI IV or EUCAST high-dose breakpoints. Amongst pneumococci from Argentina, about 80% or more were susceptible to most other antibiotics except cefaclor (all breakpoints), cefixime (PK/PD breakpoints), cefuroxime (EUCAST breakpoints) and trimethoprim/sulfamethoxazole (CLSI and PK/PD breakpoints). S. pneumoniae isolates from Chile showed significantly lower susceptibility (P < 0.05) using CLSI breakpoints compared with those from Argentina for many of the antibiotics tested. Among isolates of H. influenzae from Latin America, more than 90% were susceptible to amoxicillin/clavulanic acid (high dose), cefixime, cefpodoxime, ceftriaxone and fluoroquinolones, irrespective of the breakpoints used. The application of different EUCAST breakpoints for low and higher doses for some of the antibiotics (amoxicillin, amoxicillin/clavulanic acid, ampicillin, penicillin, ceftriaxone, clarithromycin, erythromycin, levofloxacin and trimethoprim/sulfamethoxazole) allowed, for the first time in a SOAR study, the effect of raising the dosage on susceptibility to be quantified. Antibiotic susceptibility of H. influenzae isolates was generally high in the Latin American countries studied; however, susceptibility profiles varied for S. pneumoniae by country and depending on the breakpoints used, especially for cefaclor. These factors are important in decision making for empirical therapy of bacterial infections.

Expanded sequential quadriplex real-time polymerase chain reaction (PCR) for identifying pneumococcal serotypes, penicillin susceptibility, and resistance markers

We expanded our current Centers for Disease Control and Prevention triplexed real-time polymerase chain reaction scheme identifying 11 individual serotypes and 10 serogroups to a quadriplex format identifying 34 individual serotypes and 13 small serogroups, 4 antibiotic resistance determinants, pilus targets, and penicillin susceptibility. Newly developed assays are specific for serotypes/serogroups, are sensitive (10 copies/reaction), and further discriminate larger serogroups into individual serotypes or smaller serogroups.

Evaluation of penicillin G susceptibility testing methods for Staphylococcus lugdunensis.

Background Staphylococcus lugdunensis belongs to the CoNS group, but is regarded to be more virulent than most other CoNS. It is also remarkably susceptible to antibiotics, including penicillin G.ObjectivesTo evaluate different methods for penicillin susceptibility testing, to assess penicillin susceptibility rates among S. lugdunensis and to describe the clinical presentation including antibiotic treatment.MethodsClinical isolates of S. lugdunensis were tested for penicillin susceptibility using disc diffusion according to CLSI (10 U disc) and EUCAST (1 U disc), assessment of zone-edge appearance, nitrocefin test and Etest for MIC determination. PCR of the blaZ gene was used as a reference method.ResultsOf the 112 isolates included in the study, 67% were susceptible to penicillin G according to blaZ PCR. The EUCAST disc diffusion test had 100% sensitivity, whereas the CLSI method had one very major error with a false-susceptible isolate. When zone-edge appearance was included in the assessment, the false-susceptible isolate was correctly classified as resistant. Foreign-body infection was the most common focus of infection, affecting 49% of the participants. Only 4% of the patients were treated with penicillin G.ConclusionsPenicillin susceptibility is common in S. lugdunensis and the disc diffusion method according to EUCAST had a higher sensitivity than that of CLSI. Assessment of zone-edge appearance could increase the sensitivity of the disc diffusion test. Penicillin susceptibility testing and treatment should be considered in S. lugdunensis infections.

Bacteriemia por Staphylococcus aureus sensible a penicilina. Importancia epidemiológica, clínica y posibles implicaciones terapéuticas

IntroductionThe increase in penicillin susceptibility among Staphylococcus aureus (SA-PenS) might have therapeutic relevance. We aimed to study the current situation in our environment. Material and methodsOver a 2.5 years period, all SA isolates from bacteraemia in one hospital were analysed. For all isolates, antimicrobial susceptibility profile, beta-lactam resistance genes (blaZ, mecA) and Panton-Valentine leucocidine encoding-genes were studied. For SA-PenS-blaZnegative isolates, spa-type, MLST and the presence of other resistance genes were studied. ResultsAmong 84 patients with SA bacteraemia (35.7% MRSA and 64.3% MSSA), 77 were analysed; 22.2% of MSSA isolates were PenS and blaZnegative (Pen-MIC≤0.03μg/ml) corresponding to 14.3% of the total SA. In MSSA-PenS-blaZnegative isolates, eight spa-types and 7 clonal-complexes were detected. ConclusionA high prevalence of MRSA/SA and MSSA-PenS-blaZnegative/MSSA was detected in blood cultures. Pen-MIC≤0,3μg/ml corresponded to MSSA-PenS-blaZnegative. This situation raises therapeutic options which should be further evaluated in larger studies and clinical trials.

Phenotypic and Genotypic Correlates of Penicillin Susceptibility in Nontoxigenic Corynebacterium diphtheriae, British Columbia, Canada, 2015-2018.

In 2015, the Clinical and Laboratory Standards Institute (CLSI) updated its breakpoints for penicillin susceptibility in Corynebacterium species from <1 mg/L to <0.12 mg/L. We assessed the effect of this change on C. diphtheriae susceptibility reported at an inner city, tertiary care center in Vancouver, British Columbia, Canada, during 2015–2018 and performed whole-genome sequencing to investigate phenotypic and genotypic resistance to penicillin. We identified 44/45 isolates that were intermediately susceptible to penicillin by the 2015 breakpoint, despite meeting previous CLSI criteria for susceptibility. Sequencing did not reveal β-lactam resistance genes. Multilocus sequence typing revealed a notable predominance of sequence type 76. Overall, we saw no evidence of penicillin nonsusceptibility at the phenotypic or genotypic level in C. diphtheriae isolates from our institution. The 2015 CLSI breakpoint change could cause misclassification of penicillin susceptibility in C. diphtheriae isolates, potentially leading to suboptimal antimicrobial treatment selection.

The Association between Antimicrobial Resistance and HIV Infection: A Systematic Review and Meta-Analysis

Background: Increasing antimicrobial resistance (AMR) is threatening our ability to effectively treat infections. People living with HIV (PLWH) may be at increased risk of infections with resistant organisms due to more frequent healthcare utilisation and antimicrobial prescriptions. This systematic review investigated the association between HIV and AMR. Methods: Studies reporting on AMR for colonisation or infection with bacterial pathogens excluding mycobacteria and bacteria causing sexual transmitted infections stratified by HIV status, species and antimicrobial tested were included. Pooled odds ratios were used to evaluate the association between HIV and resistance. The completeness of reporting was evaluated using the STROBE checklist. Findings: A total of 92 studies from 23 countries published between 1995 and 2020 were identified. The studies included the following organisms: Staphylococcus (n=47), Streptococcus pneumoniae (n=28), Escherichia coli (n=6) and other Gram-negative bacteria. PLWH had a 2·12 (95% CI 1·36-3·30) higher odds for colonization and 1·90 (95%CI 1·45-2·48) higher odds for infection with methicillin-resistant S. aureus; a 2·28 (95%CI 1·75-2·97) higher odds of infections with S. pneumoniae with decreased penicillin susceptibility and a 1·59 (95%CI 0·83-3·05) higher odds of resistance to third-generation cephalosporins in E. coli and Klebsiella pneumoniae. Overall, there was a high heterogeneity between studies. Interpretation: This review shows an increased risk of AMR in PLWH across a range of bacterial pathogens and multiple drug classes, which has important clinical implications for treatment. The lack of laboratory capacity for identifying AMR and limited access to alternative treatment options in countries with the highest burden of HIV highlights the need for more research on AMR in PLWH. This knowledge should translate into treatment guideline changes especially in settings where diagnostics are limited. Funding: IDO received funding though the Wellcome Trust Clinical PhD Programme awarded to the London School of Hygiene & Tropical Medicine (grant number 203905/Z/16/Z). Declaration of Interests: None of the authors have any competing interests.

Nasopharyngeal cultures in children; when, what and why?

IntroductionNasopharyngeal cultures are commonly used to determine the causative bacteria in upper airway infections. However, several bacteria can occupy the nasopharynx simultaneously and most healthy children are asymptomatic carriers of presumptive pathogens. This makes the interpretation of nasopharyngeal cultures difficult. Knowledge about which bacteria reside in the nasopharynx can assist the physician in the choice of antibiotic treatment and might also predict the risk of complications. Today, little is known about how nasopharyngeal cultures are being used in clinical practice. ObjectivesThe aim of this study was to explore how nasopharyngeal cultures are used in clinical practice, when and why they are performed, what they show, and what impact they have on the treatment of the patient. MethodsThe results of all nasopharyngeal cultures taken from children aged 0–12 years in the county of Skåne, Sweden, during 2018 were obtained. Medical charts from hospitals and primary care centres were used to determine why the cultures were taken and whether they resulted in a change of treatment. ResultsDuring 2018, 2200 nasopharyngeal cultures were taken, most of them during the winter season. Forty-one percent of children had on-going antibiotic treatment or had been treated with antibiotics in the previous two months. Acute otitis media (AOM) was the most common reason for taking a culture. The most frequently identified bacteria were Moraxella catarrhalis and Haemophilus influenzae. There was a positive correlation between M. catarrhalis on one hand and Streptococcus pneumoniae and H. influenzae on the other. Overall, bacterial resistance was rare. The presence of beta-lactamase negative ampicillin resistant H. influenzae was associated with recent or on-going antibiotics, whereas S. pneumoniae with decreased penicillin susceptibility were found less frequently in the same group of children. A positive culture resulted in a change of treatment in 29% of the cases. ConclusionApart from playing a confirmatory role and monitoring the incidence of resistant bacteria, almost a third of the nasopharyngeal cultures analysed in this study contributed to decision-making. It therefore appears that bacterial sampling have a role in clinical practice. It would be valuable to study more closely why nasopharyngeal cultures are taken in during AOM and how the result affects the treatment.

Heterogeneity of penicillin-non-susceptible group B streptococci isolated from a single patient in Germany.

Objectives Streptococcus agalactiae [group B streptococci (GBS)] have been considered uniformly susceptible to penicillin. However, increasing reports from Asia and North America are documenting penicillin-non-susceptible GBS (PRGBS) with mutations in pbp genes. Here we report, to the best of our knowledge, the first two PRGBS isolates recovered in Europe (AC-13238-1 and AC-13238-2), isolated from the same patient. MethodsTwo different colony morphologies of GBS were noted from a surgical abscess drainage sample. Both were serotyped and antimicrobial susceptibility testing was performed by different methodologies. High-throughput sequencing was done to compare the isolates at the genomic level, to identify their capsular type and ST, to evaluate mutations in the pbp genes and to compare the isolates with the genomes of other PRGBS isolates sharing the same serotype and ST.ResultsIsolates AC-13238-1 and AC-13238-2 presented MICs above the EUCAST and CLSI breakpoints for penicillin susceptibility. Both shared the capsular type Ia operon and ST23. Genomic analysis uncovered differences between the two isolates in seven genes, including altered pbp genes. Deduced amino acid sequences revealed critical substitutions in PBP2X in both isolates. Comparison with serotype Ia clonal complex 23 PRGBS from the USA reinforced the similarity between AC-13238-1 and AC-13238-2, and their divergence from the US strains.ConclusionsOur results support the in-host evolution of β-lactam-resistant GBS, with two PRGBS variants being isolated from one patient.

2478. Surveillance of antibacterial resistance among clinical isolates from hospitals in Shanghai: results of 2018

BackgroundTo investigate the current state of antibacterial resistance of clinical isolates from hospitals in Shanghai, China.MethodsAntimicrobial susceptibility testing (AST) was carried out for the clinical isolates from 50 hospitals (including 30 grade A tertiary hospitals and 20 grade B tertiary hospitals/grade A secondary hospitals, and there were 3 children hospitals among them) according to a unified protocol using Kirby–Bauer(KB) method or automated AST systems. Results were analyzed according to CLSI 2018 breakpoints.ResultsOf the 144373 clinical isolates, Gram-positive cocci and Gram-negative bacilli accounted for 29.6% and 70.4%, respectively. The overall prevalence of MRSA in Staphylococcus aureus was 45.9% and 78.4% for MRCNS in coagulase-negative Staphylococcus. No strains were found resistant to vancomycin in Staphylococcus spp. 84.1% of the 1204 strains of non-meningitis S. pneumoniae isolated from children were penicillin-susceptible (PSSP), 15.9% were penicillin-nonsusceptible, including penicillin-intermediate (PISP, 10.5%) and penicillin-resistant (PRSP, 5.4%) strains. Of the 361 strains isolated from adults, 94.5%, 3.0% and 2.5% were PSSP, PISP, and PRSP, respectively. Vacomycin-resistance E. feacium was 0.7% and no vacomycin-resistant E. feacalis were identified. According to PCR results, most of these resistant strains were vanA genotype. The prevalence linezolid-nonsusceptible E. faecalis was about 1.6%, few E. feacium was resistant to Linezolid. The overall prevalence of ESBL-producing strains was 54.0% in E. coli, 35.0% in Klebsiella pneumoniae and 47.1% in Proteus mirabilis. Enterobacteriaceae isolates were still mainly susceptible to carbapenems. Overall, 11.7% and 11.2% of the Enterobacteriaceae isolates were resistant to imipenem and meropenem, respectively. The predominant organism of CRE isolates was K. pneumoniae. The prevalence of CRAB and CRPA were 62.5% and 28.7%, respectively.ConclusionAntimicrobial resistance remains to be a problematic issue in healthcare settings, especially in Gram-negative bacilli, effective infection-control measures should be promoted to tackle this critical threat.Disclosures All authors: No reported disclosures.

184. Channeling Alexander Fleming: Efficacy of Penicillin (PCN) to Treat Staphylococcus aureus (SA) Bacteremia

BackgroundUp to 20% of SA isolates in the United States are penicillin-susceptible (PSSA); however, treatment with penicillin has been discouraged because of concern that routine testing may miss strains that have the capacity to produce clinically significant ß-lactamase in vivo. We performed a retrospective analysis to determine whether PCN therapy for the treatment of PSSA bacteremia was of comparable efficacy and safety to standard therapies.MethodsWe identified all episodes of SA bacteremia (March 18, 2010–July 23, 2018). SA penicillin susceptibility testing in our lab was performed by broth microdilution followed by nitrocefin ß-lactamase testing per CLSI guidelines on these isolates. A retrospective chart review was performed and our primary outcome was a composite endpoint of clinical success (no change in PSSA therapy due to persistent or worsening signs and symptoms, no PSSA bacteremia recurrence or persistence, and no infection‐related mortality). Microbiologic failure was defined as either failure to clear bacteremia/infection or recurrence after completion of therapy. Patients were followed until last contact with our medical system, the only tertiary center in the region. We compared our rates of success, mortality, and adverse drug reaction to historical SA bacteremia controls from the literature.ResultsPSSA accounted for 13% (130/971) of SA bloodstream episodes. Nineteen patients with PSSA (15%) were treated with PCN and 79% (15/19) achieved the primary endpoint of clinical success. Of the 4 patients who did not achieve the endpoint, 2 developed rash and were switched to a different antibiotic and 2 died from complications of sepsis. One of the patients died after clearing blood cultures but had DIC and a catastrophic intracranial hemorrhage, the other died of overwhelming sepsis after 4 days (2 days nafcillin, 2 days PCN) with continued bacteremia. Thus, our only microbiologic failure was due to early death from sepsis. Rates of success, mortality and drug reaction were similar to prior reports of alternative standard therapies (Table 1).ConclusionPCN is a viable treatment option for PSSA bacteremia as identified by routine laboratory testing. Further study will include characterizing the presence of ß-lactamase in these patient’s isolates. Disclosures All authors: No reported disclosures.

Streptococcus pneumoniae carriage among febrile children at the time of PCV-10 immunization in pediatric emergencies at Mohammed VI University Hospital Centre in Marrakesh (Morocco)

ObjectivesIn Morocco, 13-valent pneumococcal conjugated vaccine (PCV) was introduced in the childhood immunization program in October 2010 and changed to PCV-10 in July 2012. The purpose of this study was firstly to determine the prevalence of pneumococcus carriage in a population of febrile infants in Marrakesh and secondly, to investigate the risk factors for carriage and the distribution of circulating serotypes. Material and methodsThis prospective study was conducted from February to June 2017, in the pediatric emergency department of the Mother and Child Hospital of Mohammed VI University Hospital Centre (UHC) in Marrakesh. At total of 183febrile infants, aged 2–18months, were enrolled in this study and were swabbed for nasopharyngeal carriage. Pneumococci were cultured, identified, serotyped, and tested for penicillin susceptibility. Demographic data and risk factors for carriage were collected. The statistical analyses performed were the following: the analysis of the risk factors using logistic regression, the estimation of serotype diversity with the Simpson index, and the Chi2 test to compare serotype distribution in the prevaccination (a cohort of 660 healthy children, less than 2years old, in the Marrakesh region, in 2008–2009) and postvaccination periods. ResultsThe prevalence of Streptococcus pneumoniae carriage was 68.3%. Of the 183infants enrolled in this study, 111 had received at least one dose of PCV-10. Colonization by vaccine serotype among febrile children was related to incomplete vaccination status. In total, vaccine serotypes accounted for 6.4% (n=8): 19F (n=2), 1 (n=2) and one strain for each of the following serotypes: 14, 23F, 6B, and 9V. Non-vaccine and nontypeable strains presented 63.2% and 23.2%, respectively, with dominance of serotypes 6A (6.4%), 15A/15F (5.6%), 20, 22F/22A, 23B, and 11A/11D with a prevalence of 3.2%. The rate of pneumococcus strains with reduced susceptibility to penicillin was 33.6%, of which 90.2% were non-vaccine serotypes and nontypeable strains. Serotype diversity increased in the postvaccination period and the effectiveness of PCV-10 against vaccine serotypes was estimated at 89.6%. ConclusionAn important change in the distribution of vaccine and non-vaccine serotypes was observed after the introduction of the PCVs. In fact, the prevalence of vaccine serotypes decreased significantly while non-vaccine serotypes emerged. These results underscore the importance of maintaining close and prolonged surveillance of serotype distribution to monitor the dynamics of nasopharyngeal pneumococcal carriage.

Fibronectin and laminin induce biofilm formation by Streptococcus uberis and decrease its penicillin susceptibility

The aim of this study was to determine the effect of fibronectin and laminin on the in vitro biofilm formation by Streptococcus uberis and the susceptibility to penicillin under planktonic and biofilm growth conditions. We observed that a high percentage (76.5%) of the S. uberis isolates was weak biofilm producers in Todd Hewitt Broth (THB). A high percentage of moderate (38.2%) or strong (53%) biofilm producers was observed in THB supplemented with laminin or fibronectin, respectively. All S. uberis isolates growing as planktonic cells were sensitive to penicillin. Minimum biofilm inhibitory concentrations (MBICs) were ranging between 0.25 and 2 μg/ml, whereas minimum biofilm eradication concentrations (MBECs) ranging from 8 to 256 μg/ml. These results show that biofilm-growing S. uberis cells required higher concentrations of the antibiotic than those needed to inhibit planktonic cells. Similar MBICs of penicillin were obtained when S. uberis cells growing in THB supplemented or not with laminin or fibronectin, whereas the MBECs markedly increased when one of two proteins were added to culture medium compared with the medium without proteins. To the best of our knowledge, this is the first report of decreased susceptibility to penicillin likely related to a higher production of biofilms stimulated by laminin or fibronectin. Therapeutic failures of penicillin to treat S. uberis infections may be due to biofilm formation.

Pneumococcal susceptibility to antibiotics in carriage: a 17 year time series analysis of the adaptive evolution of non-vaccine emerging serotypes to a new selective pressure environment.

Pneumococcal conjugate vaccine (PCV) implementations led to major changes in serotype distribution and antibiotic resistance in carriage, accompanied by changes in antibiotic consumption. To assess the dynamic patterns of antimicrobial non-susceptibility across non-PCV13 serotypes following PCV implementations. We conducted a quasi-experimental interrupted time series analysis based on a 17 year French nationwide prospective cohort. From 2001 to 2018, 121 paediatricians obtained nasopharyngeal swabs from children with acute otitis media who were aged 6 months to 2 years. The main outcome was the rate of penicillin-non-susceptible pneumococci (PNSP), analysed by segmented regression. We enrolled 10 204 children. After PCV13 implementation, the PNSP rate decreased (-0.5% per month; 95% CI -0.9 to -0.1), then, after 2014, the rate slightly increased (+0.7% per month; 95% CI +0.2 to +1.2). Global antibiotic use within the previous 3 months decreased over the study period (-22.2%; 95% CI -33.0 to -11.3), but aminopenicillin use remained high. Among the main non-PCV13 serotypes, four dynamic patterns of penicillin susceptibility evolution were observed, including unexpected patterns of serotypes emerging while remaining or even becoming penicillin susceptible. In contrast to PNSP strains, for these latter patterns, the rate of co-colonization with Haemophilus influenzae increased concomitant with their emergence. In a context of continuing high antibiotic selective pressure, a progressive increase in PNSP rate was observed after 2014. However, we highlighted an unexpected variability in dynamic patterns of penicillin susceptibility among emerging non-PCV13 serotypes. Antibiotic resistance may not be the only adaptive mechanism to antimicrobial selective pressure, and co-colonization with H. influenzae may be involved.