Macrolide-resistant Strains Research Articles

Clonal Expansion of Macrolide-Resistant Sequence Type 3 Mycoplasma pneumoniae, South Korea.

To investigate the genetic background for the emergence of macrolide resistance, we characterized the genetic features of Mycoplasma pneumoniae using multilocus sequence typing. Of the 146 M. pneumoniae strains collected during the 5 consecutive outbreaks of M. pneumoniae pneumonia during 2000–2016 in South Korea, macrolide resistance increased from 0% in the first outbreak to 84.4% in the fifth. Among the 8 sequence types (STs) identified, ST3 (74.7%) was the most prevalent, followed by ST14 (15.1%). Macrolide-susceptible strains comprised 8 different STs, and all macrolide-resistant strains were ST3 (98.3%) except 1 with ST14. The proportion of macrolide-resistant strains in ST3 remained 2.2% (1/46) until the 2006–2007 outbreak and then markedly increased to 82.6% (19/23) during the 2010–2012 outbreak and 95.0% (38/40) during the 2014–2016 outbreak. The findings demonstrated that clonal expansion of ST3 M. pneumoniae was associated with the increase in macrolide resistance in South Korea.

Community outbreak of invasive group A streptococcus infection in Ontario, Canada.

Outbreaks of invasive group A streptococcal infection (iGAS) have historically occurred in institutional settings. Increasingly, community-based outbreaks have been reported, often among marginalized populations, yet few guidelines exist for managing iGAS outbreaks in such settings. To describe the ongoing outbreak of iGAS in Middlesex-London, Ontario, and the challenges that arose while applying current guidelines to a marginalized population in a community setting. The outbreak investigation included all iGAS cases in Middlesex-London with an onset date from April 1, 2016 to February 28, 2018. Clinical specimens were submitted to provincial and federal laboratories for typing. Public health management of the outbreak involved environmental health inspections, contact tracing, chemoprophylaxis of close contacts, swabbing to determine colonization rates of Streptococcus pyogenes, and communicating with stakeholders and the public. A total of 156 confirmed cases of iGAS corresponding to 147 individuals were reported in less than two years. More than 60% of cases occurred in men (n=91) and almost half (n=71) of the total number of cases were persons who used drugs (PWUD) and/or were under-housed. Of the PWUD cases, 58 of 65 (89%) used injection drugs. Key challenges in controlling this outbreak included reaching PWUD and under-housed people; completing a case history and contact list; facilitating completion of treatment; dealing with concurrent infections such as human immunodeficiency virus (HIV) and hepatitis C virus (HCV); and optimizing environmental health conditions. Guidelines were adapted so contacts who shared drugs or injection drug equipment with a known iGAS case would be offered chemoprophylaxis regardless of the clinical severity of the case. To optimize treatment completion, a single-dose of azithromycin for individuals in close contact with PWUD and/or under-housed cases was given. Cases with macrolide-resistant strain emm9 have recently emerged. The application of institution-based guidelines for iGAS outbreaks has been ineffective in controlling this particular community outbreak. There is a need for guidelines on managing outbreaks of iGAS in the community especially when an outbreak involves marginalized populations.

Antibacterial activities of a series of novel 5-O-(4′, 6′-O-dimodified)-mycaminose 14-membered ketolides

A series of novel 5-O-(4′,6′-O-dimodified)-mycaminose 14-membered ketolides were assessed for their in vitro antibacterial activities against a panel of sensitive and resistant pathogens. Compound 1 and compound 2, two ester analogs, showed the best antibacterial activities against several macrolide-sensitive and macrolide-resistant strains. These results indicated that introducing ester to 6-OH and a small volume ether substituent to the 4-OH of mycaminose could improve the antibacterial activities of ketolides.

FEATURES OF THE OUTBREAK OF THE COMMUNITY-ACQUIRED PNEUMONIA CAUSED BY MYCOPLASMA PNEUMOINIAE AT CHILDREN IN KHABAROVSK REGION

Aim. To study the features of outbreak of community-acquired pneumonia caused by M. pneumoniae in children in the Khabarovsk region during the autumn-winter period 2016 - 2017. Materials and methods. A study was conducted of 30 clinical samples - smears from the posterior pharyngeal wall and sputum samples obtained from patients with community-acquired pneumonia due to M. pneumoniae. Samples were examined for the presence of mutations in the 23S rRNA gene of M. pneumoniae. Results. The age ofthe patients was from 2 to 16 years. In two cases, family foci of the incidence of community-acquired pneumonia occurred. In 19 samples, a mutation was detected in 23S rRNA of M. pneumoniae. Conclusion. The data obtained indicate that in the development of the outbreak of community-acquired pneumonia caused by M. pneumoniae in children in the Khabarovsk region in the autumn-winter period 2016 - 2017, macrolide-resistant strains of the pathogen were involved.

In vitro activity of zoliflodacin (ETX0914) against macrolide-resistant, fluoroquinolone-resistant and antimicrobial-susceptible Mycoplasma genitalium strains.

Mycoplasma genitalium is estimated to be the second most common cause of bacterial sexually transmitted infection in Europe. It is of increasing public health concern due to the rapid development of resistance to different antimicrobial classes, including the preferred first- and second-line treatments azithromycin and moxifloxacin. Thus, new antimicrobial agents are urgently needed, especially for the treatment of MDR strains. The in vitro activity of the new spiropyrimidinetrione zoliflodacin against 47 M. genitalium strains was assessed by growing M. genitalium in Vero cell culture and measuring growth by quantitative PCR. The collection included 34 moxifloxacin-susceptible (MIC <1 mg/L) and 13 moxifloxacin-resistant (MIC ≥1 mg/L) strains. Twenty-three of the strains were azithromycin resistant (MIC ≥16 mg/L) and 12 of these strains were MDR. Only one (2.1%) strain with substantially increased MIC (4 mg/L) and potential resistance to zoliflodacin was found. Zoliflodacin was overall more potent than moxifloxacin (P = 0.009) and no cross-resistance was observed between the two drug classes of topoisomerase II inhibitors. Differences in the MICs of zoliflodacin and azithromycin were not statistically significant; however, 23 (48.9%) compared with potentially 1 (2.1%) of the strains were resistant to azithromycin and zoliflodacin, respectively. Zoliflodacin is a promising candidate for the treatment of M. genitalium and it is important to further develop and evaluate this drug.

Molecular characterisation of multidrug-resistant pneumococcal clones colonising healthy children in Mérida, Venezuela.

Genetic mechanisms of resistance, clonal composition and the occurrence of pili were analysed in 48 multidrug-resistant (MDR) pneumococci isolated from healthy children in Mérida, Venezuela. Intermediate resistance to penicillin was related to variations in pbp2b and pbp2x. High-level resistance to penicillin as well as low susceptibility to cephalosporins and carbapenems were associated with alterations in pbp1a, pbp2b and pbp2x. Non-β-lactam resistance was associated with Tn3872, Tn5253, Tn6002 and Tn2010 transposons. Macrolide-resistant strains carried ermB or mefE, but not mefA. Tetracycline- and chloramphenicol-resistant pneumococci carried tetM and cat, respectively. MDR pneumococci were related to six clonal complexes (CCs), largely CC156 or CC15. Limited diversity in pbp2a,2b,2x-RFLP profiles within each clone was observed. Conversely, detection of non-β-lactam resistance and transposons revealed clear genetic diversity within clones. A group of non-typeable/cpsA-negative pneumococci related to the null capsule clade 1 (NCC1) carrying a Tn2009 element was found. Each NCC1-related strain showed a novel MLST allelic combination and a different pbp2a,2b,2x-RFLP profile. PI-1 (pilus type 1 rrgC gene) was present in most of the MDR pneumococci and its occurrence was commonly homogeneous within each clone. PI-1 was present in all CC242 and CC320 pneumococci, whereas it was absent in all CC37, CC81 and NCC1 isolates. CC156 and CC15 isolates showed variations in the occurrence of PI-1. Both PI-1 and the islet for pilus type 2 were present in CC320 isolates. We provide useful data to follow the evolution of clonal composition, mechanisms of antibiotic resistance and the occurrence of pili among pneumococci circulating in Mérida.

Recent trends in practice patterns and impact of corticosteroid use on pediatric Mycoplasma pneumoniae-related respiratory infections.

Mycoplasma pneumoniae is a major pathogen causing community-acquired pneumonia/bronchitis in children, and macrolide-resistant strains are increasing in East Asian countries. Recent practice patterns, especially for antibiotic selection, and benefits of corticosteroid treatment in pediatric Mycoplasma pneumoniae infections remain unclear. Using the Japanese Diagnosis Procedure Combination inpatient database, we analyzed recent trends in antibiotic selection and corticosteroid use for pediatric Mycoplasma pneumoniae-related respiratory infections, using multivariable mixed effects logistic regressions. In addition, we compared hospital utilization and readmission between children who received corticosteroids and those who did not, using propensity-score matching and instrumental variable analyses. Overall, 51,633 inpatients were identified. From 2010 to 2014, the use of macrolides and lincosamides decreased from 62.8% to 50.6% and from 25.6% to 13.7% respectively (Ptrend < 0.001), whereas fluoroquinolone use increased from 4.6% to 22.6% (Ptrend < 0.001). Tetracycline use did not demonstrate a significant change in trend. Propensity score matching analysis showed that hospital stay in the steroid group was 0.90 days longer than in the non-steroid group (95% confidence interval, 0.84-0.96). Total hospitalization cost was higher in the steroid compared to the non-steroid group (57.6 US dollars; 95% CI, 48.8-66.8). A significant difference in 30-day readmission risk was observed between the steroid (1.6%) and non-steroid (1.2%) groups (risk difference 0.4%; 95% CI, 0.1-0.7%). Similar results were observed on instrumental variable analyses. Increasing trends in fluoroquinolone use and decreasing trends in macrolide use were observed. Our study did not prove the benefits of corticosteroid use. Further studies are required to confirm the clinical benefits of corticosteroid treatment.

Pathogenicity of Mycoplasma genitalium and treatment of its infection

Mycoplasma genitalium is an important sexually transmitted pathogen which infects the reproductive tract and rectum of males and females. It can cause local inflammation by adhering to epithelial cells and activating the host immune response. In recent years, with the wide spread of macrolide-resistant strains, the efficacy of early use of azithromycin for the treatment of Mycoplasma genitalium infection has been obviously decreased. Quinolones such as moxifloxacin can increase the cure rate of Mycoplasma genitalium infection. However, with the emergence of quinolones-resistant strains, treatment failure cases have been reported. More seriously, there have been reports on multidrug-resistant strains which are resistant to both macrolides and quinolones. Doxycycline and pristinamycin can also be used for the treatment of Mycoplasma genitalium infection, but there are some disadvantages of low bacterial clearance rate and multiple daily administration. Therefore, new drugs and better treatment approaches for Mycoplasma genitalium infection are needed. Key words: Mycoplasma genitalium; Microbiological phenomena; Therapeutic uses; Anti-bacterial agents; Drug resistance

The macrolide antibiotic renaissance

Macrolides represent a large family of protein synthesis inhibitors of great clinical interest due to their applicability to human medicine. Macrolides are composed of a macrocyclic lactone of different ring sizes, to which one or more deoxy-sugar or amino sugar residues are attached. Macrolides act as antibiotics by binding to bacterial 50S ribosomal subunit and interfering with protein synthesis. The high affinity of macrolides for bacterial ribosomes, together with the highly conserved structure of ribosomes across virtually all of the bacterial species, is consistent with their broad-spectrum activity. Since the discovery of the progenitor macrolide, erythromycin, in 1950, many derivatives have been synthesised, leading to compounds with better bioavailability and acid stability and improved pharmacokinetics. These efforts led to the second generation of macrolides, including well-known members such as azithromycin and clarithromycin. Subsequently, in order to address increasing antibiotic resistance, a third generation of macrolides displaying improved activity against many macrolide resistant strains was developed. However, these improvements were accompanied with serious side effects, leading to disappointment and causing many researchers to stop working on macrolide derivatives, assuming that this procedure had reached the end. In contrast, a recent published breakthrough introduced a new chemical platform for synthesis and discovery of a wide range of diverse macrolide antibiotics. This chemical synthesis revolution, in combination with reduction in the side effects, namely, 'Ketek effects', has led to a macrolide renaissance, increasing the hope for novel and safe therapeutic agents to combat serious human infectious diseases.

Distribution of macrolide resistance mechanisms in Bulgarian clinical isolates of Streptococcus pyogenes during the years of 2013-2016.

Objectives of the present study was to determine and evaluate the distribution of genetic mechanisms associated with certain phenotypes of macrolide resistance in Bulgarian GAS isolated during the years of 2013-2016. All GAS strains were screened for the macrolide resistance genes erm(A), erm(B) and mef(A), using multiplex polymerase chain reaction (PCR). The minimal inhibitory concentrations (MICs) of erythromycin, azithromycin, clarithromycin, clindamycin were determined by E-tests. Almost 23% of GAS isolates obtained in 2013-2014 and near 40% of them in 2015-2016 contained various elements of resistance. The predominant gene was mef(A), which encodes an efflux pump (M-phenotype), identified in 57.84% of the macrolide-resistant strains. The next frequently prevalent mechanism was a combination of mef(A) and erm(B) in 22.55%, which determined high-level inducible or constitutive resistance to macrolides, lincosamides and streptogramins (iMLSB or cMLSB). The highest MIC value (>256mg/L) was detected in association with erm(B) (p<0.05). The MIC range was observed to be much higher in the isolates with combinations of resistance genes vs. those with mef genes alone (p<0.05). The data about the distribution and prevalence of macrolide resistance mechanisms obtained in this study can help in the treatment of persistent and recurrent GAS infections and in the correct choice of empiric therapy.

New Horizons in Mycoplasma genitalium Treatment.

Mycoplasmagenitalium is an important sexually transmitted pathogen responsible for both male and female genital tract disease. Appreciation of its significance in human disease has been hampered by its slow growth in culture, difficulty in isolating it, and lack of commercial molecular-based tests for rapid detection. Comparatively few in vitro data on antimicrobial susceptibility are available due to the scarcity of clinical isolates and difficulty in performing susceptibility tests to determine minimum inhibitory concentrations for M. genitalium. Antimicrobial agents that inhibit protein synthesis such as macrolides, along with fluoroquinolones that inhibit DNA replication, have been the treatments of choice for M. genitalium infections. Even though international guidelines recommend azithromycin as first-line treatment, rapid spread of macrolide resistance as well as emergence of quinolone resistance has occurred. Increasing rates of treatment failure have resulted in an urgent need for new therapies and renewed interest in other classes such as aminocyclitols, phenicols, and streptogramins as treatment alternatives. Limited data for new investigational antimicrobials such as the ketolide solithromycin suggest that this drug may eventually prove useful in management of some resistant M. genitalium infections, although it is not likely to achieve cure rates >80% in macrolide-resistant strains, in a similar range as recently reported for pristinamycin. However, agents with completely new targets and/or mechanisms that would be less likely to show cross-resistance with currently available drugs may hold the greatest promise. Lefamulin, a pleuromutilin, and new nonquinolone topoisomerase inhibitors are attractive possibilities that require further investigation.

Macrolide Hybrid Compounds: Drug Discovery Opportunities in Anti- Infective and Anti-inflammatory Area.

Macrolides, polyketide natural products, and their 15-membered semi-synthetic derivatives are composed of substituted macrocyclic lactone ring and used primarily as potent antibiotics. Recently their usefulness was extended to antimalarial and anti-inflammatory area. Hybrid macrolides presented in this article are the next generation semi-synthetic compounds that combine pharmacophores from antibacterial, antimalarial and anti-inflammatory area with 14- and 15-membered azalide scaffolds. Antibacterial azalide hybrids with sulphonamides showed improved activity against resistant streptococci while quinolone conjugates demonstrated full coverage of respiratory pathogens including macrolide resistant strains and their efficacy was confirmed in mouse pneumonia model. Antimalarial macrolide hybrids, mainly involving (chloro)quinoline pharmacophores, showed outstanding activity against chloroquine resistant strains, favourable pharmacokinetics, promising in vivo efficacy as well as encouraging developmental potential. Anti-inflammatory hybrids were obtained by combining macrolides with corticosteroid and non-steroidal anti-inflammatory drugs. They were found active in in vivo animal models of locally induced inflammation, asthma, inflammatory bowel disease and rheumatoid arthritis and demonstrated improved safety over parent steroid drugs. Overall, macrolide hybrids possess significant potential to be developed as potent novel medicines in therapeutic areas of utmost pharmaceutical interest.

In Vitro Activities of Lefamulin and Other Antimicrobial Agents against Macrolide-Susceptible and Macrolide-Resistant Mycoplasma pneumoniae from the United States, Europe, and China.

Lefamulin, an investigational pleuromutilin, was tested against a collection of 18 macrolide-susceptible and 42 macrolide-resistant Mycoplasma pneumoniae strains, and the results were compared with those of azithromycin, erythromycin, tetracycline, doxycycline, and moxifloxacin testing. Lefamulin was highly active against all strains tested, with all MICs at ≤0.008 μg/ml. The lefamulin MIC90 (0.002 μg/ml) for macrolide-resistant strains was the lowest among all drugs tested. Minimum bactericidal concentrations were within 2 dilutions of the MIC values, indicating a bactericidal effect.

In vitro antibacterial activity of α-methoxyimino acylide derivatives against macrolide-resistant pathogens and mutation analysis in 23S rRNA.

We characterized in vitro activities of α-methoxyimino acylides against macrolide-resistant clinical isolates of Streptococcus pneumoniae, Streptococcus pyogenes and Mycoplasma pneumoniae with ribosome modification or substitution and selected acylide-resistant mutants to clarify the binding point of the acylides. The acylides had low MICs against erm(B) gene-containing S. pneumoniae and S. pyogenes (MIC90s, 1-4 μg ml-1). For M. pneumoniae, although they had poor potencies against macrolide-resistant strains with the A2058G (Escherichia coli numbering) mutation in 23S rRNA (MICs, >32 μg ml-1), one of them showed in vitro activities against macrolide-resistant strains with the A2058U or A2059G mutations (MICs, 0.5-1 μg ml-1). These A2058U and A2059G mutant strains were used for the selection of acylide-resistant mutants. A genetic analysis showed that new point mutations in acylide-resistant mutants were found at G2576 in domain V of 23S rRNA and at Lys90 in L22 ribosomal protein. Furthermore, a molecular modeling study revealed that G2505/C2610, which enables stacking with G2576, might interact with a pyridyl moiety or an α-methoxyimino group at the 3-position of acylides. The α-methoxyimino acylides were shown to possess a tertiary binding point at G2505/C2610 in 23S rRNA. Our results suggest that α-methoxyimino acylides represent significant progress in macrolide antimicrobials.

A Novel SimpleProbe PCR Assay for Detection of Mutations in the 23S rRNA Gene Associated with Macrolide Resistance in Mycoplasma genitalium in Clinical Samples

Macrolide-resistant strains of Mycoplasma genitalium are an increasing problem throughout the world, and the implementation of a rapid and sensitive assay for mutation detection to guide treatment is needed. Macrolide-resistant strains have been shown to contain base substitutions in positions 2058 and 2059 (Escherichia coli numbering) in region V of the 23S rRNA gene. In this study, we present a SimpleProbe PCR followed by melting curve analysis to differentiate between macrolide-resistant mutants and wild types. The assay was performed on 159 Mycoplasma genitalium-positive samples, and the results were compared with DNA sequencing. We also looked at the prevalence of macrolide-resistant strains in a Norwegian population. Of 139 samples characterized successfully by sequencing, 54 (39%) were wild types and 85 (61%) were mutants, consisting of 59 (42%) A2059G, 24 (17%) A2058G, 1 (1%) A2058T, and 1 (1%) A2059C mutation. The melting curve analysis correctly differentiated between wild-type and mutant strains in all cases, but it could not identify the different mutant types. The SimpleProbe PCR proved to be a simple, rapid, and reliable method for the detection of macrolide-resistant isolates of Mycoplasma genitalium in a clinical setting.

Dinamica antibiorezistenţei celor mai frecvent izolate bacterii cu potenţial patogen, în Spitalul de Boli Infecţioase şi Tropicale „Dr. V. Babeş“, în perioada 2000-2015

Objective. Analyzing the dynamycs of global antibiotic resistance of some bacterial species isolated from patients admitted to the „Dr. V. Babes” Hospital for Infectious and Tropical Diseases, between the years 2000 to 2015. Material and methods. Antibiotic resistance profiles of bacteria isolated from inpatients, were identified by the standard diffusion method and MIC values by VITEK2C and E-test methods. (CLSI and EUCAST standards). Screening of carbapenemases – producing isolates were performed by phenotipic methods, and the confirmation by RealTimePCR: “MasterPure™ Complete DNA and RNA Purification Kit” (Epicentre), „Primer Design™ Kit” (blaOXA48; blaKPC, blaNDM, blaVIM)/ LightScanner 32 Instrument/LS32 (Idaho Technology), and GeneXpert. Internal quality control: Staphylococcus aureus ATCC29213, Streptococcus pneumoniae ATCC49619, E. coli ATCC25922, Pseudomonas aeruginosa ATCC27853. Results. The incidence of St. aureus meticilino-rezistent (MRSA) highlights an increase from 12.2% (2002) to 40.4% (2015). In the past 3 years SVB microbiology lab found a sharp increase in the incidence of erytromycin resistant strains of Streptococcus pyogenes. In 2015 we registered 20.3% of macrolide resistant strains. Global resistance to penicillin G for Str. pneumoniae (non-meningeal infections) was 45.3%- 54.5% until 2009, and 2.7% in 2013. Enterococcus faecium strains showed 0% resistance to vancomycin between 2000 and 2012. A significant growth was recorded in 2015 of 11%. Isolation rate of Klebsiella pneumoniae ESBL producing strains has increasewd progressively from 17.6 in 2000 to 57% in 2015. Carbapenems – resistant K. pneumoniae isolated strains were 18,8% in 2015. Carbapenemases types identified by phenotypic and genetic methods where: 35/ Oxa48, 8 KPC and 21/MBL (NDM-1). Resistance to carbapenems recorded an upward trend: 23.9% in 2004 to 37.9% in 2015, and for Acinetobacter baumannii 69%. Conclusions. Antibiotic resistance of bacteria is a major challenge for public healts. Therapeutic solutions are extremely limited.

Interferon-γ Autoantibodies as Predisposing Factor for Nontuberculous Mycobacterial Infection

Interferon-γ Autoantibodies as Predisposing Factor for Nontuberculous Mycobacterial Infection

Long-term effects of azithromycin in patients with cystic fibrosis

BackgroundLow-dose azithromycin has beneficial effects on severity of the lung disease in cystic fibrosis (CF) patients for a period of 6–12 months after initiation of the treatment. Although its impact in the longer term is uncertain, this treatment is frequently used chronically. The aim of this retrospective study was to investigate the effects of low-dose azithromycin treatment on the progression of CF lung disease in patients treated for more than 12 months. MethodsAll of the CF patients followed in our pediatric center and who had been on low-dose azithromycin for more than 12 sequential months were included. The clinical data were collected for one year before and three years after the initiation of the azithromycin treatment. These data comprised lung function analyses, rates of exacerbations and of antibiotic courses, and changes in the airways’ bacterial colonization. ResultsA total of 68 patients were included (mean age: 9.95 yrs (3.61)). After 12 months, significant reductions in the numbers of pulmonary exacerbations and antibiotic courses were present. However, this effect was not maintained in the subsequent periods, during which increased rates of both pulmonary exacerbations and antibiotic courses were observed. The lung function decline was not modified during the treatment, and a decreasing time-dependent trend typical of CF was observed for the various parameters. No differences in the airway colonization by pathogens such as Pseudomonas aeruginosa and methicillin-sensitive and/or -resistant Staphyloccocus aureus were observed during the treatment. However, isolated Staphyloccocus aureus strains became resistant to macrolides after 6 months of azithromycin and remained resistant thereafter. ConclusionsNo clinical benefits of low-doses azithromycin were present after one year of treatment in young CF patients. Selection for macrolide-resistant strains of bacteria occurred, which should lead to a reconsideration of the duration of azithromycin treatment in CF.

The sensitivity to antibiotics of strains of group B streptococcus isolates from pregnant women in Belgrade

Introduction: Group B streptococcus (GBS) is a significant human pathogen. GBS colonizes the vagina and it is one of the most important causes of early neonatal sepsis and meningitis. In many countries, screening of pregnant women and intrapartal use of antibiotics are common practice. Macrolide and lincosamide resistant strains of GBS are a significant problem, because these antibiotics are the second line therapy in case of penicillin allergy. Aim: Our aim was to investigate the frequency of antibiotic resistant strains of GBS and to detect macrolide resistance phenotypes in GBS strains obtained from pregnant women in Belgrade. Material and Methods: 105 GBS isolates were obtained from vaginal swabs of pregnant women attending two Gynecology and Obstetrics Centers in Belgrade. The isolates were tested for antimicrobial susceptibility pattern and D test were performed on Mueller Hinton agar. Results: Macrolide and lincosamide resistance was found in 30.4 %, and 23.8 % of isolates, respectively. There was a high frequency of tetracycline resistant strains (88.6 %). Most frequent macrolide resistant phenotype was iMLSb (macrolide and inducibile lincosamide resistance) (62.4%). Conclusion: The results of our study indicate that there is a high level of macrolide resistance among GBS isolates in Serbia and the active surveillance is needed.

Bacterial Load in Daily Urine Samples of Patients Infected with Mycoplasma genitalium, Mutation Analysis, and Response to Treatment.

Objective. Increasing macrolide resistant strains of Mycoplasma genitalium is a challenge, and to differentiate between treatment failure and reinfection a timely test of cure (TOC) is warranted. The aim of this study was to evaluate the best time for TOC after five days' treatment of Mycoplasma genitalium infection with azithromycin. Methods. Nineteen patients with positive PCR for Mycoplasma genitalium in urine provided urine samples daily for 2 weeks and on days 21, 28, and 35. Samples were tested by a commercial qPCR and by sequencing of the 23S rRNA gene. Results. Eight patients with a wild type of Mycoplasma genitalium responded successfully within four days after treatment initiation. Eleven patients had a mutation in the 23S rRNA gene. These samples exhibited high variations in bacterial load, and some patients tested negative at several time points during the observation period. Conclusions. Day-to-day fluctuations in the mutation samples allow for false negative TOC during the first 5 weeks after start of treatment. Due to increasing macrolide resistance of Mycoplasma genitalium, pretreatment mutation analysis is recommended. When a wild type is verified, TOC performed one week after initiation of treatment is suggested.