Sensitive and Specific Loop-Mediated Isothermal Amplification Assays for Detection of Salmonella, CTX-M-1 Group Genes, mph(A), and ermB in Stool and Blood Samples Based on Orange to Green Visible Dye

Salmonella is a globally prevalent foodborne bacterium, and ceftriaxone and azithromycin have been regarded as drugs of choice for treating Salmonella infections, particularly in children. With the growing incidence of ceftriaxone and azithromycin resistance in Salmonella, there is an urgent requirement for a rapid and dependable gene testing approach to enhance the efficacy of treating Salmonella infections. Utilizing the orange to green visible dye approach, this study developed loop-mediated isothermal amplification (LAMP) assays for the sensitive and specific detection of Salmonella, ceftriaxone and azithromycin resistance genes (including CTX-M-1 group, mph(A), and ermB genes) in stool and blood samples. The specificity and sensitivity of primers during the LAMP assays for detection of Salmonella, CTX-M-1 group, mph(A), and ermB genes were determined in this study. The detection threshold for Salmonella was found to be 1.5 × 103 colony-forming units (CFU)/mL, while it was 1.5 × 102 CFU/mL for CTX-M-1 group genes (including blaCTX-M-3, blaCTX-M-15, and blaCTX-M-55), 1.5 × 102 CFU/mL for mph(A), and 1.5 × 102 CFU/mL for ermB, showing 10-103-fold, 103-fold, and 105-fold increased sensitivity compared with the polymerase chain reaction assay, respectively. Results indicated that the LAMP primers designed for Salmonella, CTX-M-1 group, mph(A), and ermB genes possess high specificity (100%) and sensitivity (over 94%). This novel approach advocates its application in detecting Salmonella, CTX-M-1 group, mph(A), and ermB genes.

Antibiotic Susceptibility, Resistance Gene Determinants and Corresponding Genomic Regions in Lactobacillus amylovorus Isolates Derived from Wild Boars and Domestic Pigs

Restrictions on the use of antibiotics in pigs lead to the continuous search for new probiotics serving as an alternative to antibiotics. One of the key parameters for probiotic bacteria selection is the absence of horizontally transmissible resistance genes. The aim of our study was to determine antibiotic susceptibility profiles in 28 Lactobacillus amylovorus isolates derived from the digestive tract of wild boars and farm pigs by means of the broth microdilution method and whole genome sequencing (WGS). We revealed genetic resistance determinants and examined sequences flanking resistance genes in these strains. Our findings indicate that L. amylovorus strains from domestic pigs are predominantly resistant to tetracycline, erythromycin and ampicillin. WGS analysis of horizontally transmissible genes revealed only three genetic determinants (tetW, ermB and aadE) of which all tetW and ermB genes were present only in strains derived from domestic pigs. Sequence analysis of coding sequences (CDS) in the neighborhood of the tetW gene revealed the presence of site-specific recombinase (xerC/D), site-specific DNA recombinase (spoIVCA) or DNA-binding transcriptional regulator (xre), usually directly downstream of the tetW gene. In the case of ermB, CDS for omega transcriptional repressor or mobilization protein were detected upstream of the ermB gene.

Development of Two Loop-Mediated Isothermal Amplification Assays for Rapid Detection of ermB and mefA Genes in Streptococcus suis

Streptococcus suis is an important zoonotic pathogen that poses a serious threat to the pig industry and human health. The massive use of macrolides has led to the emergence of resistance in S. suis, and S. suis is suspected to be a reservoir of antimicrobial resistance genes. The mechanism to macrolide resistance in S. suis is mainly due to ermB and mefA. In this study, loop-mediated isothermal amplification (LAMP) methods were developed to detect ermB and mefA genes in S. suis through turbidimetry detection. The sensitivity and specificity of the LAMP reactions were determined. All results of LAMP and polymerase chain reaction (PCR) assay were compared to determine whether LAMP method was accurate and reliable. The results showed that all 100 nonstreptococcus clinical isolates tested negative, indicating the high specificity of LAMP assays. The detection limit of LAMP assay was 1 fg per reaction, and 10²-10⁴-fold lower than those of conventional PCR methods. Evaluation of the performance of the LAMP assay in S. suis clinical strains revealed a good consistency between LAMP and PCR assays. In conclusion, LAMP assays are specific, sensitive, and rapid methods to detect ermB and mefA in S. suis.

Characterization of Streptococcus pneumoniae Macrolide Resistance and Its Mechanism in Northeast China over a 20-Year Period

Due to the resistance of Streptococcus pneumoniae to β-lactams, macrolides, and tetracyclines, treatment alternatives have become increasingly limited worldwide. We aim to describe the characterization of erythromycin-resistant S. pneumoniae (ERSP) strains in northeastern China over a period of 20 years. A total of 1,240 ERSP strains were collected and classified into five groups based on the ages of the patients. Etest strips and Kirby-Bauer disk diffusion were performed for drug susceptibility testing. The capsule swelling test was used for capsule typing. The phenotype of drug resistance was detected by the erythromycin and clindamycin double-disk method. The ermB, ermTR, mefA, and tetM genes were detected by PCR. Among the 1,240 ERSP strains, 510 were invasive isolates, and 730 were noninvasive isolates. The results of drug susceptibility testing showed that the rates of resistance to penicillin, amoxicillin, cefotaxime, ceftriaxone, meropenem, tetracycline, trimethoprim-sulfamethoxazole, and chloramphenicol varied among the different age groups. 19F, 19A, 23F, 14, and 6B were the serotypes that were commonly found among ERSP strains. Among all strains, 99.03% (1,228/1,240) exhibited an MLSB (macrolide-lincosamide-streptogramin B) resistance phenotype, of which 1,221 strains displayed a constitutive MLSB (cMLSB) phenotype and 7 strains showed an inducible MLSB (iMLSB) phenotype. All of these strains carried the ermB gene. In contrast, only 0.97% of strains of M phenotypes were found to carry the mefA gene. Both the ermB and mefA genes were detected in 704 strains that exhibited multidrug resistance, whereas the ermTR gene was not detected. Furthermore, 1,185 tetracycline-resistant strains were found to carry the tetM gene. Macrolide antimicrobial drugs should be used cautiously for the empirical treatment of S. pneumoniae infections. IMPORTANCE This study presents a retrospective analysis using 1,240 clinical erythromycin-resistant Streptococcus pneumoniae (ERSP) isolates collected in northeastern China between January 2000 and December 2019. The serotype distribution, corresponding vaccine coverage, as well as resistance phenotypes, genes, and mechanisms to macrolide and tetracycline of these isolates were systematically described, analyzed, and discussed. We hope that this study will inform clinicians in their respective regions when selecting antimicrobial agents. We also hope that this study is useful for researchers in related fields. Finally, we emphasize in this study that vaccination is the best preventive measure for S. pneumoniae infection considering its resistance to commonly used antibiotics. The determination of the S. pneumoniae serotype distribution also provides valuable empirical evidence for local health authorities when introducing appropriate vaccines in a specific area.

Detection of macrolide resistance genes, ermC and ermB, in Japanese honey using real-time PCR assays

American foulbrood (AFB) is a honeybee disease caused by Paenibacillus larvae, and tylosin is used as the prophylactic in Japan. Honey contains macrolide-resistant bacteria that are a potential source of genes that may confer tylosin resistance to P. larvae. To investigate the potential risk of such genes in Japanese honey, we developed real-time PCR assays for the detection of important macrolide resistance genes, ermC and ermB, and analyzed 116 Japanese honey samples with known contamination status of P. larvae. Consequently, 91.38% of samples contained ermC and/or ermB, and 71.55% of samples contained both ermC and P. larvae, suggesting the possible emergence of tylosin-resistant P. larvae in Japan. Therefore, judicious use of the prophylactic is essential in maintaining its effectiveness.

Hybrid genome assembly of Shigella sonnei reveals the novel finding of chromosomal integration of an IncFII plasmid carrying a mphA gene

Azithromycin is increasingly being used for the treatment of shigellosis despite a lack of interpretative guidelines and with limited clinical evidence. The present study determined azithromycin susceptibility and correlated this with macrolide-resistance genes in Shigella spp. isolated from stool specimens in Vellore, India. The susceptibility of 332 Shigella isolates to azithromycin was determined using the disc diffusion method. Of these, 31 isolates were found to be azithromycin resistant. The azithromycin minimum inhibitory concentration (MIC) was determined using the broth microdilution method. In addition, isolates were screened for mphA and ermB genes using conventional PCR. Furthermore, an isolate that was positive for resistance genes was subjected to complete genome analysis, and was analysed for mobile genetic elements. The azithromycin MIC for the 31 resistant Shigella isolates ranged between 2 and 16 mg l^-1. PCR results showed that a single isolate of Shigella sonnei carried a mphA gene. Complete genome analysis revealed integration of an IncFII plasmid into the chromosome of S. sonnei , which was also found to carry the following resistance genes: sul1, bla _DHA1, qnrB4, mphA, tetR. Mutations in the quinolone-resistance-determining region (QRDR) were also observed. Additionally, prophages, insertion sequences and integrons were identified. The novel finding of IncFII plasmid integration into the chromosome of S. sonnei highlights the potential risk of Shigella spp. becoming resistance to azithromycin in the future. These suggests that it is imperative to monitor Shigella susceptibility and to study the resistance mechanism of Shigella to azithromycin considering the limited treatment choices for shigellosis.

Erythromycin-Susceptible but Clindamycin-Resistant Phenotype of Clinical ermB-PCR-Positive Group B Streptococci Isolates with IS1216E-Inserted ermB

Streptococcus agalactiae (Group B Streptococcus, GBS) is a pathogen which causes neo natal sepsis, meningitis, and invasive infections in the elderly and people with medical conditions. Macrolide and lincosamide resistance rates of GBS strains have been increasing worldwide. A macrolide resistance gene, erythromycin ribosomal methylase (erm), typically confers macrolides, lincosamides, streptogramin B resistance phenotype. However, in the current study, we recovered and characterized 3 clinical ermB-PCR-positive isolates of GBS with L phenotype. The presence of ermB and lnuB (lincosamide nucleotidyltransferase) genes in all 3 clinical isolates was confirmed using PCR. The ermB gene of the clinical isolates harbored C222T (N74N), T224C (I75T), and A299G (N100S) nucleotide (amino acid) substitutions, and insertion of an IS1216E element at nucleotide position 643, resulted in the deletion of a segment spanning nucleotides 643-738 of ermB gene, which suggested the loss-of-function of ErmB protein in the 3 clinical isolates. Since these clinical isolates show positive PCR result for a drug resistance gene despite its partial deletion, these results contradict their drug resistance phenotype. These factors must be considered while performing PCR-based detection of antimicrobial drug resistance genes.

Predominance of emm4 and antibiotic resistance of Streptococcus pyogenes in acute pharyngitis in a southern region of Korea

BACKGROUND

Streptococcus pyogenes is the most common cause of bacterial pharyngitis. Genotyping of emm is useful for molecular epidemiological survey of S. pyogenes. Antibiotic resistance data are needed for empirical treatments.

METHODS

In total, 358 children in Changwon, Korea who had pharyngitis symptoms were subjected to throat cultures to isolate S. pyogenes in 2017. emm genotyping was performed by direct sequencing. An antibiotic susceptibility test was performed using the disk diffusion method for erythromycin (ERY), clindamycin (CLI), tetracycline (TET) and ofloxacin (OFX). Screening for macrolide resistance phenotype and its determinants was performed for the ERY-resistant strains.

RESULTS

A total of 190 strains (53.1 %) of S. pyogenes were isolated from 358 children. The most frequent emm genotype was emm4 (53.2 %), followed by emm89 (12.6 %), emm28 (11.6 %) and emm1 (10 %). Antibiotic resistance rates to ERY, CLI, TET and OFX were 3.2 %, 2.6 %, 1.1 % and 2.6%, respectively. There were five isolates of the cMLSB phenotype having the ermB gene and one M phenotype harbouring the mefA gene.

CONCLUSIONS

The distribution of emm genotypes was quite different from those previously reported in Korea. emm4 accounted for more than 50  % of the genotypes. Macrolide resistance rates remained very low, but five of six ERY-resistant strains displayed the cMLSB phenotype.

Phenotypic and genotypic characterization of glycopeptide, aminoglycoside and macrolide resistance among clinical isolates of Enterococcus faecalis: a multicenter based study

Objectives

Enterococcus faecalis as part of the normal floras of human gastrointestinal and genitourinary tracts are an important cause of nosocomial infections. The present study aimed to investigate the prevalence of genes encoding antimicrobial resistance and genetic relatedness of clinical isolates of E. faecalis among Iranian hospitalized patients.

Results

Antibiotic susceptibility testing results indicated that 53 (22.8%) out of 232 E. faecalis isolates were vancomycin resistant (MIC ≥ 256 μg/ml). All of the 53 vancomycin-resistant E. faecalis isolates carried the vanA and ermB genes; whereas aac (6′)-Ie aph (2″), msrA, and ermA gene were found in 96.2%, 30.2% and 3.8% of vancomycin-resistant isolates, respectively. ERIC-PCR typing revealed that 53 vancomycin-resistant isolates were classified into 14 ERIC types. In our results, the high level of resistance to gentamicin, erythromycin and vancomycin in enterococci isolates were mainly related to the presence of aac (6′)-Ie aph (2″), ermB and vanA genes, respectively. Meanwhile, ERIC-PCR analysis demonstrated that most of the evaluated isolates have a close genetic relatedness.

High Frequency of Macrolide-Resistant Streptococcus pneumoniae Colonization in Respiratory Tract of Healthy Children in Ardabil, Iran

BACKGROUND

Streptococcus pneumoniae (S. pneumoniae) is one of the most common causes of human diseases in young children. Macrolides are commonly antibiotics used for empirical treatment of community-acquired respiratory infections. The purpose of this study was to determine antibiotic resistance pattern as well as the relationship between macrolide resistance and the major mechanisms of resistance in pneumococci isolated from healthy children.

MATERIALS AND METHODS

In this cross-sectional study, 43 isolates of S. pneumoniae were collected from healthy children in Ardabil. Resistance pattern against tested antibiotics was determined using the disk diffusion method. The Minimum Inhibitory Concentration (MIC) of erythromycin was determined using the E-test strips. The mefA/E and ermB gene were detected in erythromycin-resistant isolates using the specific primers and Polymerase Chain Reaction (PCR) technique.

RESULTS

According to antimicrobial susceptibility testing, 74.4 % of the isolates were resistant to erythromycin, 95.3 % to penicillin, 81.3 % to co-trimoxazole, 72 % to azithromycin, 41.8 % to tetracycline, 27.9 % to clindamycin, and 16.2 % to chloramphenicol. All isolates were susceptible to levofloxacin and vancomycin. In the case of rifampin, 95.3% of the isolates were sensitive and 4.6% semi-sensitive. The MIC of erythromycin for resistant isolates was between 1.5 and ≥ 256 μg/ml. PCR results revealed that 100% of erythromycin-resistant isolates contained mefA/E gene and 81.25 % contained both the ermB and mefA/E genes.

CONCLUSION

The prevalence of antibiotic-resistant strains of S. pneumoniae, especially resistance to macrolides, was high among healthy children in Ardabil. According to the results of this study, we suggest using levofloxacin, rifampin and vancomycin antibiotics as an appropriate prophylactic regimen in pneumococcal infections.

Metabolomic profiling of Campylobacter jejuni with resistance gene ermB by ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry and tandem quadrupole mass spectrometry

The metabolome changes of Campylobacter jejuni with resistant gene ermB remain unclear. Here, we described an untargeted metabolomic workflow based on ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry to investigate the metabolites perturbations mediated by ermB in C. jejuni. After optimization of extractants and chromatographic conditions, the combination of 100% methanol extraction with a 12 min gradient by C18 column was adopted for untargeted metabolomic profiling in reversed phase separation. Meanwhile, 60% methanol extraction followed by a 14 min separation using hydrophilic interaction chromatography column was suitable to complementally expand the metabolite coverage of C. jejuni. Multivariate statistical analysis was performed by means of orthogonal projection to latent structures-discriminant analysis to select metabolic features. The selected features were further confirmed by ultra-high performance liquid chromatography-tandem quadrupole mass spectrometry. A total of thirty-six differential metabolites between the susceptible strain (C. jejuni NCTC 11168) and resistant stain (C. jejuni NCTC 11168 with ermB) were identified. These pivotal metabolites were primarily participated in biological processes as cell signaling, membrane integrity/stability, fuel and energy source/storage and nutrient. The biofilm formation capability of resistant strain was inferior to that of susceptible strain, confirming the influence of ermB on membrane integrity/stability of C. jejuni. Our findings revealed important metabolic regulatory pathways associated with resistant C. jejuni with ermB.

First Description in Greece of mphC-Positive Staphylococci Causing Subclinical Mastitis in Ewes

The aim of the present study was to describe the first mphC-positive staphylococci, including two Staphylococcus lentus (Sle-087lar and Sle-091lar) and one Staphylococcus xylosus (Sxy-228lar), isolated from samples of animal origin, in Greece. Isolates Sle-087lar and Sxy-228lar were resistant to erythromycin, whereas Sle-091lar was resistant to erythromycin and lincomycin. All three isolates were susceptible to the remaining antibiotics. PCR screening showed that isolate Sle-091lar carried also ermB. For Sxy-228lar, whole-genome sequencing (WGS) and de novo assembly obtained an mphC-positive contig of 57.3-kb exhibiting high similarity with the genome of mphC-negative S. xylosus S170. However, mphC of Sxy-228lar was 91% similar to that found in plasmid pJW2311 from S. xylosus JW2311. Additionally, WGS data showed that Sle-087lar and Sle-091lar harbored mphC-carrying sequences being highly similar to the recently announced genome of the mphC-carrying S. lentus isolate 050AP from Tanzania. However, differences were observed in the mphC environment, suggesting the independent acquisition of the gene by each isolate. Sle-091lar also harbored transposon Tn917, which carries ermB resistance gene, integrated into S. lentus chromosome. These findings indicated that acquisition of resistance genes can lead to the emergence of multiresistant staphylococci, causing animal infections with economic burden.

Phenotypic and Genotypic Analysis of Antimicrobial Resistance among Listeria monocytogenes Isolated from Australian Food Production Chains

The current global crisis of antimicrobial resistance (AMR) among important human bacterial pathogens has been amplified by an increased resistance prevalence. In recent years, a number of studies have reported higher resistance levels among Listeria monocytogenes isolates, which may have implications for treatment of listeriosis infection where resistance to key treatment antimicrobials is noted. This study examined the genotypic and phenotypic AMR patterns of 100 L. monocytogenes isolates originating from food production supplies in Australia and examined this in the context of global population trends. Low levels of resistance were noted to ciprofloxacin (2%) and erythromycin (1%); however, no resistance was observed to penicillin G or tetracycline. Resistance to ciprofloxacin was associated with a mutation in the fepR gene in one isolate; however, no genetic basis for resistance in the other isolate was identified. Resistance to erythromycin was correlated with the presence of the ermB resistance gene. Both resistant isolates belonged to clonal complex 1 (CC1), and analysis of these in the context of global CC1 isolates suggested that they were more similar to isolates from India rather than the other CC1 isolates included in this study. This study provides baseline AMR data for L. monocytogenes isolated in Australia, identifies key genetic markers underlying this resistance, and highlights the need for global molecular surveillance of resistance patterns to maintain control over the potential dissemination of AMR isolates.

Antibiotic Resistance-Susceptibility Profiles of Streptococcus thermophilus Isolated from Raw Milk and Genome Analysis of the Genetic Basis of Acquired Resistances

The food chain is thought to play an important role in the transmission of antibiotic resistances from commensal and beneficial bacteria to pathogens. Streptococcus thermophilus is a lactic acid bacterium of major importance as a starter for the dairy industry. This study reports the minimum inhibitory concentration (MIC) of 16 representative antimicrobial agents to 41 isolates of S. thermophilus derived from raw milk. Strains showing resistance to tetracycline (seven), erythromycin and clindamycin (two), and streptomycin and neomycin (one) were found. PCR amplification identified tet(S) in all the tetracycline-resistant strains, and ermB in the two erythromycin/clindamycin-resistant strains. Hybridisation experiments suggested each resistance gene to be located in the chromosome with a similar genetic organization. Five antibiotic-resistant strains -two resistant to tetracycline (St-2 and St-9), two resistant to erythromycin/clindamycin (St-5 and St-6), and one resistant to streptomycin/neomycin (St-10)- were subjected to genome sequencing and analysis. The tet(S) gene was identified in small contigs of 3.2 and 3.7 kbp in St-2 and St-9, respectively, flanked by truncated copies of insertion sequence (IS) elements. Similarly, ermB in St-6 and St-5 was found in contigs of 1.6 and 28.1 kbp, respectively. Sequence analysis and comparison of the largest contig showed it to contain three segments (21.9, 3.7, and 1.4 kbp long) highly homologous to non-collinear sequences of pRE25 from Enterococcus faecalis. These segments contained the ermB gene, a transference module with an origin of transfer (oriT) plus 15 open reading frames encoding proteins involved in conjugation, and modules for plasmid replication and segregation. Homologous stretches were separated by short, IS-related sequences, resembling the genetic organization of the integrative and conjugative elements (ICEs) found in Streptococcus species. No gene known to provide aminoglycoside resistance was seen in St-10. Four strain-specific amino acid substitutions in the RsmG methyltransferase were scored in this strain; these might be associated to its streptomycin/neomycin resistance. Under yogurt manufacturing and storage conditions, no transfer of either tet(S) or ermB from S. thermophilus to L. delbrueckii was detected. The present results contribute toward characterisation of the antibiotic resistance profiles in S. thermophilus, provide evidence for the genetic basis of acquired resistances and deepen on their transference capability.

Inducible Expression of both ermB and ermT Conferred High Macrolide Resistance in Streptococcus gallolyticus subsp. pasteurianus Isolates in China

Streptococcus gallolyticus subsp. pasteurianus is an under-recognized pathogen and zoonotic agent causing opportunistic infections in humans. Despite increasing recognition of this subspecies as a cause for human infectious diseases, limited information is known about its antibiotic resistance mechanism. In this study, we aim to identify the molecular mechanism underlying the high macrolide resistance of six S. gallolyticus subsp. pasteurianus isolates from dead ducklings collected in several natural outbreaks in China during 2010–2013. All isolates exhibited multi-drug resistance including high macrolide resistance (MIC ≥ 1024 mg/L for erythromycin, and 512 mg/L for clarithromycin). Efflux-encoding mefA and mefE genes were not detectable in these isolates. The presence of 23S rRNA mutations in specific isolates did not significantly change macrolide MICs. No nucleotide substitutions were found in genes encoding ribosomal proteins L4 or L22. The ermB and ermT genes were found in the genomes of all isolates. These two genes were acquired independently in one highly virulent isolate AL101002, and clustered with Tn916 and IS1216, respectively. The expression of both ermB and ermT in all isolates was erythromycin inducible and yielded comparable macrolide MICs in all six isolates. Taken together, inducible expression of both ermB and ermT conferred high macrolide resistance in these S. gallolyticus subsp. pasterianus isolates. Our findings reveal new macrolide resistance features in S. gallolyticus subsp. pasteurianus by both ermB and ermT.

Molecular subtyping and erythromycin resistance of Campylobacter in China

AIMS

To investigate the erythromycin resistance patterns and mechanism for Campylobacter isolates in China.

METHODS AND RESULTS

The minimum inhibitory concentrations of erythromycin on 858 Chinese Campylobacter isolates were analysed. PCR and DNA sequencing were used to identify mutations in the 23S rRNA and the presence of the ermB gene in the 158 erythromycin resistance isolates (18·4%). About 83% (131/158) had A2075G mutation in their 23S rRNA; no A2074C/G mutants were found. The ermB gene was identified in 30 Campylobacter coli isolates (19%). Four types of multidrug-resistant gene islands (MDRGIs) were found. Fifty-three types were identified by multilocus sequence typing among the resistant isolates. All isolates of STs 6322 and 1145 had the ermB gene.

CONCLUSIONS

The erythromycin resistance rate of Camp. coli (58·56%) was much higher than Campylobacter jejuni (0·67%). The insertion sites between cadF and CCO1582 and between nfsB and cinA on the chromosome might be hot spots for MDRGI transformation.

SIGNIFICANCE AND IMPACT OF THE STUDY

Point mutation in domain V of the 23S rRNA and the ermB gene accounted for 100% of the erythromycin resistance of Campylobacter in China.

Phenotypic and genotypic characterization of Streptococcus pneumoniae resistant to macrolide in Casablanca, Morocco

In Morocco, the 13-valent pneumococcal conjugate vaccine (PCV-13) was introduced in the national immunization program (NIP) in October 2010 and replaced by the PCV-10 in July 2012. The present study aimed to determine the prevalence of erythromycin-resistant Streptococcus pneumoniae (ERSP) and to analyze the phenotypic and genotypic characteristics of these isolates in Casablanca, Morocco from January 2007 to December 2014. Isolates were obtained from the Microbiology Laboratory of Ibn Rochd University Hospital Centre of Casablanca. Serogrouping was done using Pneumotest Kit and serotyping by the Quellung capsular swelling. Antibiotic susceptibility pattern was determined by disk diffusion and Etest methods. A total of 655S. pneumoniae isolates were collected from 2007 to 2014 from pediatric and adult patients. Fifty-five percent of these isolates were from invasive pneumococcal diseases. Of the 655 isolates, 92 (14%) were ERSP. Globally, the proportion of ERSP from 2007 to 2010 (before vaccination) and from 2011 to 2014 (after vaccination) were 11.6% and 17.2% (p=0.04), respectively. Of the 92 ERSP, 89%, 4% and 7% displayed constitutive MLSB (resistance to macrolide, lincosamide and streptogramin B), inducible MLSB, and M phenotype (resistance to macrolide only), respectively. ERSP genotypic analysis showed that 90.2% carried the ermB gene, 6.5% the mefE gene, and 3.3% both the genes (ermB+mefE). The most prevalent ERSP serotypes were 6B, 19F and 23F before vaccination and 19F, 6B, 6A and 23F after vaccination. Erythromycin resistance among S. pneumoniae is relatively high in Casablanca. The contribution of PCVs to the reduction in antibiotic use is encouraging but this should be accompanied by a rational use of antibiotic.

Improving the reproducibility of the NAP1/B1/027 epidemic strain R20291 in the hamster model of infection

Comparative analysis of the Clostridium difficile BI/NAP1/027 strain R20291 and ClosTron-derived ermB mutants in the hamster infection model are compromised by the clindamycin susceptibility of the parent. Mutants can appear more virulent. We have rectified this anomaly by genome engineering. The variant created (CRG20291) represents an ideal control strain for virulence assays of ClosTron mutants.