Antimicrobial resistance in colonizing group B Streptococci before the implementation of a Swedish intrapartum antibiotic prophylaxis program

The prevalence of antibiotic resistance and their genetic determinants in colonizing group B streptococci (GBS) sampled in a Swedish nationwide survey was examined. In five GBS isolates (1.3%), kanamycin/amikacin resistance and the presence of the aphA-3 gene was identified. Three of these isolates carried the aad-6 gene and were streptomycin-resistant. Screening with kanamycin and streptomycin 1,000-μg disks enabled a rapid and easy detection of these isolates. In all, 312/396 (79%) GBS were tetracycline-resistant and 95% of the examined isolates harbored the tetM gene. Among the 22 (5.5%) GBS resistant to erythromycin and/or clindamycin, the ermB gene was detected in nine isolates (41%) and erm(A/TR) in ten isolates (45%). A high level of erythromycin and clindamycin resistance with minimum inhibitory concentrations (MICs) >256 mg/L was found in four serotype V isolates that harbored ermB. The erythromycin/clindamycin resistance was distributed among all of the common serotypes Ia, Ib, II, III, IV, and V, but was not present in any of the 44 serotype III isolates associated to clonal complex 17. Screening for penicillin resistance with 1-μg oxacillin disks showed a homogenous population with a mean inhibition zone of 20 mm. A change in the present oxacillin breakpoints for GBS is suggested.     

Prevalence of inducible clindamycin resistance among community-associated staphylococcal isolates in central Serbia

The emergence of resistance to most antimicrobial agents in staphylococci indicates the need for new effective agents in the treatment of staphylococcal infections. Clindamycin is considered to be one safe, effective and less costly agent. We analysed 482 staphylococcal isolates. Detection of inducible clindamycin resistance was performed by the D-test, while the presence of methylases genes: erm (A), erm (B) and erm (C), as well as, macrolide efflux gene mef was determined by polymerase chain reaction. Inducible clindamycin resistance phenotype was significantly higher in Staphylococcus aureus (S. aureus) strains then in coagulase-negative staphylococci (CNS). Among analysed S. aureus isolates, the predominance of the erm (C) gene, followed by the erm (A) gene were detected. These results indicate that the D-test should be routinely performed on each staphylococcal isolates.     

Identification of ribosomal RNA methyltransferase gene ermF in Riemerella anatipestifer

Riemerella anatipestifer is a major bacterial pathogen of waterfowl, globally responsible for avian septicaemic disease. As chemotherapy is the predominant method for the prevention and treatment of R. anatipestifer infection in poultry, the widespread use of antibiotics has favoured the emergence of antibiotic-resistant strains. However, little is known about R. anatipestifer susceptibility to macrolide antibiotics and its resistance mechanism. We report for the first time the identification of a macrolide resistance mechanism in R. anatipestifer that is mediated by the ribosomal RNA methyltransferase ermF. We identified the presence of the ermF gene in 64/206 (31%) R. anatipestifer isolates from different regions in China. An ermF deletion strain was constructed to investigate the function of the ermF gene on the resistance to high levels of macrolides. The ermF mutant strain showed significantly decreased resistance to macrolide and lincosamide, exhibiting 1024-, 1024-, 4- and >2048-fold reduction in the minimum inhibitory concentrations for erythromycin, azithromycin, tylosin and lincomycin, respectively. Furthermore, functional analysis of ermF expression in E. coli XL1-blue showed that the R. anatipestifer ermF gene was functional in E. coli XL1-blue and conferred resistance to high levels of erythromycin (100 µg/ml), supporting the hypothesis that the ermF gene is associated with high-level macrolide resistance. Our work suggests that ribosomal RNA modification mediated by the ermF methyltransferase is the predominant mechanism of resistance to erythromycin in R. anatipestifer isolates.     

Utility of Sequencing the erm(41) Gene in Isolates of Mycobacterium abscessus subsp. abscessus with Low and Intermediate Clarithromycin MICs

The erm(41) gene confers inducible macrolide resistance in Mycobacterium abscessus subsp. abscessus, calling into question the usefulness of macrolides for treating M. abscessus subsp. abscessus infections. With an extended incubation (14 days), isolates with MICs of ≥8 μg/ml are considered macrolide resistant by current CLSI guidelines. Our goals were to determine the incidence of macrolide susceptibility in U.S. isolates, the validity of currently accepted MIC breakpoints, and the erm(41) sequences associated with susceptibility. Of 349 isolates (excluding those with 23S rRNA gene mutations), 85 (24%) had clarithromycin MICs of ≤8 μg/ml. Sequencing of the erm(41) genes from these isolates, as well as from isolates with MICs of ≥16 μg/ml, including ATCC 19977^T, revealed 10 sequevars. The sequence in ATCC 19977^T was designated sequevar (type) 1; most macrolide-resistant isolates were of this type. Seven sequevars contained isolates with MICs of >16 μg/ml. The T28C substitution in erm(41), previously associated with macrolide susceptibility, was identified in 62 isolates (18%) comprising three sequevars, with MICs of ≤2 (80%), 4 (10%), and 8 (10%) μg/ml. No other nucleotide substitution was associated with macrolide susceptibility. We recommend that clarithromycin susceptibility breakpoints for M. abscessus subsp. abscessus be changed from ≤2 to ≤4 μg/ml and that isolates with an MIC of 8 μg/ml have repeat MIC testing or erm sequencing performed. Our studies suggest that macrolides are useful for treating approximately 20% of U.S. isolates of M. abscessus subsp. abscessus. Sequencing of the erm gene of M. abscessus subsp. abscessus will predict inducible macrolide susceptibility.     

Differences in potential for selection of clindamycin-resistant mutants between inducible erm(A) and erm(C) Staphylococcus aureus genes

In staphylococci, inducible macrolide-lincosamide-streptogramin B (MLS_B) resistance is conferred by the erm(C) or erm(A) gene. This phenotype is characterized by the erythromycin-clindamycin “D-zone” test. Although clindamycin appears active in vitro, exposure of MLS_B-inducible Staphylococcus aureus to this antibiotic may result in the selection of clindamycin-resistant mutants, either in vitro or in vivo. We have compared the frequencies of mutation to clindamycin resistance for 28 isolates of S. aureus inducibly resistant to erythromycin and bearing the erm(C) (n = 18) or erm(A) (n = 10) gene. Seven isolates susceptible to erythromycin or bearing the msr(A) gene (efflux) were used as controls. The frequencies of mutation to clindamycin resistance for the erm(A) isolates (mean ± standard deviation, 3.4 × 10⁻⁸ ± 2.4 × 10⁻⁸) were only slightly higher than those for the controls (1.1 × 10⁻⁸ ± 6.4 × 10⁻⁹). By contrast, erm(C) isolates displayed a mean frequency of mutation to clindamycin resistance (4.7 × 10⁻⁷ ± 5.5 × 10⁻⁷) 14-fold higher than that of the S. aureus isolates with erm(A). The difference was also observed, although to a lower extent, when erm(C) and erm(A) were cloned into S. aureus RN4220. We conclude that erm(C) and erm(A) have different genetic potentials for selection of clindamycin-resistant mutants. By the disk diffusion method, erm(C) and erm(A) isolates could be distinguished on the basis of high- and low-level resistance to oleandomycin, respectively.     

Genomic epidemiology and antimicrobial resistance determinants of Neisseria gonorrhoeae isolates from Ukraine, 2013–2018

Antimicrobial resistance (AMR) in Neisseria gonorrhoeae is a major health threat compromising the gonorrhoea treatment globally. AMR surveillance including whole genome sequencing (WGS)-based epidemiology provides ideal resolution to identify and describe AMR gonococcal clones, AMR determinants and populations, which can inform management guidelines and antimicrobial stewardship policies. Our aims were to, for the first time, elucidate the WGS-based epidemiology and characterize AMR determinants of gonococcal strains spreading in Ukraine, 2013–2018. Gonococcal isolates (n = 150) from Ternopil and Dnipro, Ukraine (2013–2018), were subjected to AMR testing (Etest) for eight antimicrobials and WGS. Overall, 11.3% of isolates were resistant to ciprofloxacin, 6.0% to tetracycline, and 0.7% to benzylpenicillin. No isolates were resistant to azithromycin, spectinomycin, ceftriaxone, or cefixime, but one isolate was bordering resistance to both cephalosporins. Twenty-five MLST STs, 50 NG-MAST STs, and 34 NG-STAR types were identified. The phylogenomic analysis revealed six main clusters, mostly associated with the internationally described multidrug-susceptible gonococcal lineage. Resistance to ciprofloxacin was associated with GyrA S91F and ParC S87R mutations; tetracyclines with rpsJ V57M and tetM; penicillins with mosaic penA-34.001 and β-lactamase; mtrR; PorB1b G101D, and PBP1 L421P mutations. One isolate of the multidrug-resistant NG-MAST ST1407, MLST ST1901 was found, which was bordering resistance to ceftriaxone and cefixime. The antimicrobial susceptibility of gonococcal strains spreading in Ternopil and Dnipro, Ukraine, in 2013–2018 was surprisingly high. Continued and expanded gonococcal AMR surveillance, ideally including WGS, in Ukraine is essential. This could inform action plans and public health policies to control the spread of AMR gonococcal strains in Ukraine.     

Molecular basis of antimicrobial drug resistance in Staphylococcus aureus isolates recovered from young healthy carriers in Spain

The frequency and genetic bases of antimicrobial drug resistance was determined for 111 Staphylococcus aureus recovered from young healthy carriers in a Spanish region. Resistances to ampicillin (84.7%), kanamycin (27%), erythromycin (25.2%), clindamycin (22.5%), tetracycline (11.7%), amikacin and tobramycin (6.3% each), gentamicin (5.4%), chloramphenicol (2.7%), ciprofloxacin (0.9%; MIC 4 μg/ml), moxifloxacin (0.9%) and mupirocin (0.9%; MIC 60 μg/ml) were found, and all were susceptible to methicillin (MSSA). Nearly 50% of the isolates were resistant to one antibiotic, 30% to two, 15.3% to three and 1.8% to four, while only 6.3% remained fully susceptible. A total of 31 profiles were found. For each phenotypic resistance, at least one gene accounting for it was identified. The detected genes were blaZ; erm(A)-erm(B)-erm(C)-msr(A)-msr(B)-lnu(A), aphA-aadE-sat4-aacA + aphD-aadD, tet(K), cat, and qacA/B, for resistance to ampicillin, macrolides and/or lincosamides, aminoglycosides, tetracycline, chloramphenicol, and quaternary ammonium compounds, respectively. In all isolates carrying cat genes, in all except one of the isolates positive for tet(K), and in most isolates with blaZ, erm(C), msr(A), or msr(B), the gene(s) mapped on resistance plasmids, which were detected in 69.2% of the resistant isolates (65% of the total). The S. aureus from young healthy carriers analysed in the present study do not constitute a reservoir of MRSA, but they represent a repository of multiple determinants conferring resistance to “old” antimicrobials. Some of these have still clinical applications and, considering the increasing resistance to recently introduced antimicrobials, none of them can be disregarded.     

Invasive neonatal GBS infections from an area-based surveillance study in Italy

During an area-based study, 75 group B streptococcus (GBS) strains isolated both from early-onset disease (EOD, 37 strains) and from late-onset disease (LOD, 38 strains) were analysed for serotype, pulsed field gel electrophoresis (PFGE) and multilocus sequence typing profiles, protein markers and antibiotic resistance. Serotype III, possessing the rib gene, was the most frequent (54 strains, 72%) and responsible for 89.5% and 54% of LOD and EOD, respectively. Forty-six serotype III strains belonged to the same PFGE type and clonal complex 17, already described as an over-represented clone in neonatal invasive GBS infections. Other serotypes were Ia (9.3%), II (6.7%), Ib (5.3%), V (5.3%) and IV (1.3%). Seventeen PFGE groups were identified comprising strains with related sequence types; conversely, strains displaying the same sequence type could belong to different PFGE groups. When both neonate and maternal strains from vaginorectal swabs and/or milk were available (eight cases), they were indistinguishable. Resistance to erythromycin (12%) was associated with a constitutive resistance to clindamycin in five cases (four carrying the erm(B) gene and one both the erm(B) and mef(E) genes) and with an inducible clindamycin resistance in two cases (one possessing the erm(A) gene, the other the erm(T) gene). Two isolates displayed the M phenotype (mef(E) gene). All strains but five were resistant to tetracycline, mostly mediated by the tet(M) gene (97.1%). The study underlined the importance of an active surveillance system for the elucidation of a GBS population structure causing neonatal infections and allowed the detection of rare antibiotic resistance determinants [erm(T)].     

Absence of a Functional erm Gene in Isolates of Mycobacterium immunogenum and the Mycobacterium mucogenicum Group,Based on In Vitro Clarithromycin Susceptibility

Macrolide resistance has been linked to the presence of a functional erythromycin ribosomal methylase (erm) gene in most species of pathogenic rapidly growing mycobacteria (RGM). For these Mycobacterium isolates, extended incubation in clarithromycin is necessary to determine macrolide susceptibility. In contrast, the absence of a detectable erm gene in isolates of M. chelonae, M. senegalense, and M. peregrinum and a nonfunctional erm gene in M. abscessus subsp. massiliense and 15% to 20% of M. abscessus subsp. abscessus isolates renders these species intrinsically macrolide susceptible. Not all RGM species have been screened for the presence of an erm gene, including the Mycobacterium mucogenicum group (M. mucogenicum, M. phocaicum, and M. aubagnense) and Mycobacterium immunogenum. A total of 356 isolates of these two pathogenic RGM taxa from two reference laboratories (A.R.U.P. Reference Laboratories and the Mycobacteria/Nocardia Laboratory at the University of Texas Health Science Center at Tyler) underwent clarithromycin susceptibility testing with readings at 3 to 5 days and 14 days. Only 13 of the 356 isolates had resistant clarithromycin MICs at initial extended MIC readings, and repeat values on all available isolates were ≤2 μg/ml. These studies suggest that these two additional RGM groups do not harbor functional erm genes and, like M. chelonae, do not require extended clarithromycin susceptibility testing. We propose to the Clinical Laboratory and Standards Institute that isolates belonging to these above-mentioned six rapidly growing mycobacterial groups based on molecular identification with no known functional erm genes undergo only 3 to 5 days of susceptibility testing (to exclude mutational resistance).     

Antimicrobial susceptibility of Neisseria gonorrhoeae isolates and treatment of gonorrhoea patients in Ternopil and Dnipropetrovsk regions of Ukraine, 2013–2018

Antimicrobial resistance (AMR) in Neisseria gonorrhoeae is a major public health concern globally. However, recent gonococcal AMR data from Eastern Europe are extremely limited and no AMR data for strains spreading in Ukraine have ever been internationally published. We investigated the AMR of N. gonorrhoeae isolates in two regions of Ukraine (Ternopil 2013–2018, Dnipropetrovsk 2013–2014), and, where information was available, the treatment administered to the corresponding gonorrhoea patients. Determination of minimum inhibitory concentration (MIC) of eight antimicrobials was performed using Etest and resistance breakpoints from the European Committee on Antimicrobial Susceptibility Testing (EUCAST) were applied. Overall, 9.3% of the examined 150 isolates were resistant to ciprofloxacin, 6.0% to tetracycline, 2.0% to azithromycin, and 0.7% to benzylpenicillin. No isolates were resistant to ceftriaxone, cefixime, spectinomycin, or gentamicin. However, one (0.7%) isolate showed a MIC value of 0.125 mg/L for both ceftriaxone and cefixime, i.e., bordering resistance. Eighty‐eight (67.2%) of 131 patients were administered dual therapy (ceftriaxone 1 g plus doxycycline/clarithromycin/azithromycin/ofloxacin) and 22 (16.8%) ceftriaxone 1 g monotherapy. Worryingly, 21 (16.0%) patients received monotherapy with clarithromycin/doxycycline/azithromycin/ofloxacin/benzylpenicillin. In conclusion, the antimicrobial susceptibility of gonococcal strains spreading in Ternopil and Dnipropetrovsk, Ukraine during 2013–2018 was high. Low levels of resistance to ciprofloxacin, tetracycline, azithromycin, and benzylpenicillin were found, but no resistance to the internationally recommended ceftriaxone, cefixime, or spectinomycin. Ceftriaxone 1 g should remain as empiric first‐line treatment, in dual therapy with azithromycin or doxycycline or in monotherapy. Continued and expanded gonococcal AMR surveillance in Ukraine is essential to monitor the susceptibility to particularly extended‐spectrum cephalosporins, azithromycin and doxycycline.     

Rationale of azithromycin prescribing practices for enteric fever in India

Purpose: The present study was performed to assess the current susceptibility pattern of blood isolates of Salmonella spp from a super specialty hospital in North India against nalidixic acid, ciprofloxacin and azithromycin and compare the in vitro and in vivo response against azithromycin. Materials and Methods: We evaluated the minimum inhibitory concentration’s (MIC’s) of 107 blood isolates of Salmonella spp against nalidixic acid, azithromycin and ciprofloxacin and correlated in vitro and in vivo response of azithromycin from the treatment and discharge summaries from the Hospital Information System (HIS) software. Results: Among the 107 isolates evaluated, 94 (87.8%) were nalidixic acid-resistant (NAR) Salmonella and 36 were resistant to azithromycin by MIC testing. The MIC₉₀ value for azithromycin was 24 μg/mL. Among the 57 treatment histories evaluated using the HIS software, 19 (33%) patients had documented clinical non-response to azithromycin which required change of therapy. Conclusions: The present study observed a higher MIC₉₀ values for azithromycin compared to Salmonella isolates from Western studies. There was also a documented clinical non-response against azithromycin. The in vitro and in vivo findings in this study suggest a guarded use of azithromycin for cases of enteric fever in India. The study also augments the reversal of resistance pattern in favour of chloramphenicol, ampicillin and trimethoprim – sulfamethoxazole.     

Antimicrobial resistance trends in blood culture positive Salmonella Typhi isolates from Pondicherry,India, 2005–2009

Typhoid fever is caused by Salmonella enterica serovar Typhi, a major public health concern in developing countries. Recently, there has been an upsurge in the occurrence of bacterial isolates that are resistant to ciprofloxacin, and the emergence of broad spectrum β-lactamases in typhoidal salmonellae constitutes a new challenge for the clinician. A total of 337 blood culture isolates of S. Typhi, isolated from Pondicherry, India, between January 2005 and December 2009, were investigated using phenotypic, molecular and serological methods. Of the 337 isolates, 74 (22%) were found to be multidrug resistant (MDR) and 264 (78%) nalidixic acid resistant (NAR). Isolates with reduced susceptibility to ciprofloxacin possessed single mutations in the gyrA gene. A high rate of resistance (8%) was found to ciprofloxacin. All isolates with a ciprofloxacin MIC ≥ 4 mg/L possessed both double mutations in the QRDR of the gyrA gene and a single mutation in the parC gene. Active efflux pump mechanisms were also found to be involved in ciprofloxacin resistance. Finally, a large number of PFGE patterns (non-clonal genotypes) were observed among the S. Typhi isolates. In conclusion, a high rate of ciprofloxacin resistance was observed in comparison to other endemic areas in blood culture isolates of S. Typhi from Pondicherry, India, with steadily increasing NAR but decreasing MDR isolations over the study period. This is most likely to be due to an increased use of ciprofloxacin as a first-line drug of choice over more traditional antimicrobial agents for the treatment of typhoid fever.     

Decline in macrolide-resistant Streptococcus pyogenes isolates from French children

We studied the macrolide resistance and serotypes of 585 group A streptococcus (GAS) isolates collected from French children with pharyngitis. Nineteen isolates (3.2%) were erythromycin-resistant and harbored the following resistance genes: 31.6% mef(A), 15.8% erm(A), and 52.6% erm(B). The 19 isolates included 7 different emm types (4, 1, 11, 2, 28, 12, and 77) and 7 corresponding multilocus sequence types. The current fall in macrolide consumption has led to a very low rate of GAS macrolide resistance.     

Clinical and microbiological aspects of linezolid resistance mediated by the cfr gene encoding a 23S rRNA methyltransferase

The cfr (chloramphenicol-florfenicol resistance) gene encodes a 23S rRNA methyltransferase that confers resistance to linezolid. Detection of linezolid resistance was evaluated in the first cfr-carrying human hospital isolate of linezolid and methicillin-resistant Staphylococcus aureus (designated MRSA CM-05) by dilution and diffusion methods (including Etest). The presence of cfr was investigated in isolates of staphylococci colonizing the patient's household contacts and clinical isolates recovered from patients in the same unit where MRSA CM-05 was isolated. Additionally, 68 chloramphenicol-resistant Colombian MRSA isolates recovered from hospitals between 2001 and 2004 were screened for the presence of the cfr gene. In addition to erm(B), the erm(A) gene was also detected in CM-05. The isolate belonged to sequence type 5 and carried staphylococcal chromosomal cassette mec type I. We were unable to detect the cfr gene in any of the human staphylococci screened (either clinical or colonizing isolates). Agar and broth dilution methods detected linezolid resistance in CM-05. However, the Etest and disk diffusion methods failed to detect resistance after 24 h of incubation. Oxazolidinone resistance mediated by the cfr gene is rare, and acquisition by a human isolate appears to be a recent event in Colombia. The detection of cfr-mediated linezolid resistance might be compromised by the use of the disk diffusion or Etest method.     

Rapid Molecular Detection of Inducible Macrolide Resistance in Mycobacterium chelonae and M. abscessus Strains: a Replacement for 14-Day Susceptibility Testing?

The erm(41) gene causes inducible macrolide resistance in Mycobacterium abscessus but not Mycobacterium chelonae. erm(41) sequencing of 285 M. abscessus and 45 M. chelonae isolates was compared to 14-day susceptibility; agreement percentages were 98.9% and 100%, respectively. Extended incubation may not be necessary for M. chelonae, and the erm(41) genotype is a useful adjunct for M. abscessus.     

Changing Molecular Epidemiology of Group B Streptococcus in Korea

The prevalence of group B streptococcus (GBS) among pregnant women and disease burdens in neonates and adults are increasing in Korea. Colonizing isolates, collected by screening pregnant women (n=196), and clinical isolates collected from clinical patients throughout Korea (n=234), were serotyped and screened for antibiotic resistance. Serotype III (29.8%) and V (27.7%) predominated, followed by Ia (17.0%). Antibiotic resistance was higher among clinical than colonizing isolates for erythromycin (35.1% and 26.9%; P=0.10) and for clindamycin (49.4% and 42.1%; P=0.17). erm(B) occurred in 91.9% of erythromycin resistant isolates, and 84.0% of isolates resistant to clindamycin. Only five isolates (4.2%) resistant to erythromycin were susceptible to clindamycin; by contrast, and unique to Korea, 34% of isolates resistant to clindamycin were erythromycin susceptible. Among these 60 erythromycin-susceptible & clindamycin-resistant isolates, 88% was serotype III, and lnu(B) was found in 89% of strains. Four fifths of the serotype V isolates were resistant to both erythromycin and clindamycin. Further characterization of the genetic assembly of these resistance conferring genes, erm(B) and lnu(B), will be useful to establish the clonal lineages of multiple resistance genes carrying strains.     

Allele-specific duplex polymerase chain reaction to differentiate Mycobacterium abscessus subspecies and to detect highly clarithromycin-resistant isolates

On the basis of the structural differences of erm, we used a duplex polymerase chain reaction (PCR) to differentiate Mycobacterium abscessus subsp. abscessus and subsp. massiliense isolates and to detect the point mutations of 23S rRNA gene that confer a high level of resistance to clarithromycin. Subsp. massiliense strains occupying almost half of the clinical isolates can be simply identified, and their clarithromycin susceptibility can be rapidly determined.     

Macrolide and fluoroquinolone resistance in Mycoplasma genitalium in two Swedish counties, 2011–2015

Mycoplasma genitalium, causing non‐gonococcal non‐chlamydial urethritis and associated with cervicitis, has developed antimicrobial resistance (AMR) to both the macrolide azithromycin (first‐line treatment) and the fluoroquinolone moxifloxacin (second‐line treatment). Our aim was to estimate the prevalence of resistance, based on genetic AMR determinants, to these antimicrobials in the M. genitalium population in two Swedish counties, Örebro and Halland, 2011–2015. In total, 672 M. genitalium positive urogenital samples were sequenced for 23S rRNA and parC gene mutations associated with macrolide and fluoroquinolone resistance, respectively. Of the samples, 18.6% and 3.2% in Örebro and 15.2% and 2.7% in Halland contained mutations associated with macrolide and fluoroquinolone resistance, respectively. The predominating resistance‐associated mutations in the 23S rRNA gene was A2059G (n = 39) in Örebro and A2058G (n = 13) and A2059G (n = 13) in Halland. The most prevalent possible resistance‐associated ParC amino acid alterations were S83I (n = 4) in Örebro and S83N (n = 2) in Halland. Resistance‐associated mutations to both macrolides and fluoroquinolones were found in 0.7% of samples. Our findings emphasize the need for routine AMR testing, at a minimum for macrolide resistance, of all M. genitalium‐positive samples and regular national and international surveillance of AMR in M. genitalium, to ensure effective patient management and rational antimicrobial use.     

Antimicrobial resistance and molecular epidemiology using whole-genome sequencing of <Emphasis Type="Italic">Neisseria gonorrhoeae</Emphasis> in Ireland, 2014–2016: focus on extended-spectrum cephalosporins and azithromycin

High-level resistance and treatment failures with ceftriaxone and azithromycin, the first-line agents for gonorrhoea treatment are reported and antimicrobial-resistant Neisseria gonorrhoeae is an urgent public health threat. Our aims were to determine antimicrobial resistance rates, resistance determinants and phylogeny of N. gonorrhoeae in Ireland, 2014–2016. Overall, 609 isolates from four University Hospitals were tested for susceptibility to extended-spectrum cephalosporins (ESCs) and azithromycin by the MIC Test Strips. Forty-three isolates were whole-genome sequenced based on elevated MICs. The resistance rate to ceftriaxone, cefixime, cefotaxime and azithromycin was 0, 1, 2.1 and 19%, respectively. Seven high-level azithromycin-resistant (HLAzi-R) isolates were identified, all susceptible to ceftriaxone. Mosaic penA alleles XXXIV, X and non-mosaic XIII, and G120K plus A121N/D/G (PorB1b), H105Y (MtrR) and A deletion (mtrR promoter) mutations, were associated with elevated ESC MICs. A2059G and C2611T mutations in 23S rRNA were associated with HLAzi-R and azithromycin MICs of 4–32 mg/L, respectively. The 43 whole-genome sequenced isolates belonged to 31 NG-MAST STs. All HLAzi-R isolates belonged to MLST ST1580 and some clonal clustering was observed; however, the isolates differed significantly from the published HLAzi-R isolates from the ongoing UK outbreak. There is good correlation between previously described genetic antimicrobial resistance determinants and phenotypic susceptibility categories for ESCs and azithromycin in N. gonorrhoeae. This work highlights the advantages and potential of whole-genome sequencing to be applied at scale in the surveillance of antibiotic resistant strains of N. gonorrhoeae, both locally and internationally.     

Diversity in the antimicrobial susceptibility patterns of methicillin-resistant Staphylococcus aureus clones

Methicillin-resistant Staphylococcus aureus (MRSA) is well known for its epidemicity, with the emergence of new clones on a daily basis. Diversity in the clonal types of MRSA challenges the success of treatment, as different clones respond to different sets of antibiotics. However, the antibiotic susceptibility among the isolates within the same clones is largely unexplored. In a previous study on MRSA epidemiology in Malaysia, we identified six major clonal complexes (ST-239-CC8, ST-1-CC1, ST-188-CC1, ST-22-CC22, ST-7-CC7 and ST-1283-CC8). In the present study, we investigated the antibiotic susceptibility patterns of isolates of different clones. Three hundred and eighty-nine MRSA isolates were subjected to the disc diffusion test, oxacillin minimum inhibitory concentration (MIC) determination and assessment of the distribution of macrolide, lincosamide and streptogramin B (MLS_B) resistance genes. Thirty-six different antibiotic profiles were observed: 30 (83.3?%) among ST-239, 2 (5.6?%) among ST-1283 and 1 (2.8?%) each for ST-1, ST-7, ST-22 and ST-188. All ST-239 (362, 9?%) isolates were multiple drug-resistant (MDR; resistant to more than three classes of antibiotics) and had oxacillin MICs >256?mg/l. Among the 385 clindamycin-resistant isolates, 375 (96.4?%) illustrated inducible resistance (D-zone-positive), while 10 (2.6?%) showed constitutive resistance. The vast majority of the macrolide-resistant isolates carried the ermA gene (95.1?%), followed by ermC (12.9?%). Diversity in the antibiotic susceptibilities of isolates within the clones emphasises the need for continuous surveillance of MDR strains to prescribe the correct antibiotic rather than empirical treatment. This will likely reduce the emergence of new endemic or epidemic resistant MRSA clones.