Latest Advances in Laboratory Detection of Mycoplasma genitalium

Mycoplasma genitalium is an important sexually transmitted pathogen affecting both men and women. Its extremely slow growth in vitro and very demanding culture requirements necessitate the use of molecular-based diagnostic tests for its detection in clinical specimens. The recent availability of U.S. Food and Drug Administration (FDA)-cleared commercial molecular-based assays has enabled diagnostic testing to become more widely available in the United States and no longer limited to specialized reference laboratories. Advances in the knowledge of the epidemiology and clinical significance of M. genitalium as a human pathogen made possible by the availability of molecular-based testing have led to updated guidelines for diagnostic testing and treatment that have been published in various countries. This review summarizes the importance of M. genitalium as an agent of human disease, explains the necessity of obtaining a microbiological diagnosis, describes currently available diagnostic methods, and discusses how the emergence of antimicrobial resistance has complicated treatment alternatives and influenced the development of diagnostic tests for resistance detection, with an emphasis on developments over the past few years.

Omadacycline Is Highly Active In Vitro against Mycoplasma genitalium

Here, we performed in vitro susceptibility testing on 10 Mycoplasma genitalium isolates against omadacycline, minocycline, tetracycline, doxycycline, moxifloxacin, levofloxacin, and azithromycin. Omadacycline was the most potent agent, with all MICs of ≤0.5 μg/mL. MICs were not affected by resistance to other agents, including resistance to other tetracycline class drugs. Omadacycline may be a potential treatment option for M. genitalium infection. IMPORTANCE There are very few clinical isolates of Mycoplasma genitalium available for in vitro susceptibility testing. We studied 10 isolates and determined that the new semisynthetic aminomethylcycline omadacycline is active against isolates that are resistant to tetracyclines, macrolides, and quinolones. These data suggest that clinical studies should be performed in order to see if omadacycline may be useful to treat urogenital infections caused by M. genitalium.

Antimicrobial susceptibilities and mechanisms of resistance of commensal and invasive Mycoplasma salivarium isolates

Mycoplasma salivarium, an oral commensal organism, can cause severe invasive infections in immunocompromised individuals. Currently there is no treatment guidance for such infections. We performed antimicrobial susceptibility tests on 39 commensal and invasive M. salivarium isolates and investigated the mechanisms of antimicrobial resistance. Clindamycin was the most active agent [minimum inhibition concentration (MIC) range: 0.004–128 mg/L, MIC₅₀ = 0.031 mg/L, MIC₉₀ = 0.125 mg/ml], followed by tetracycline and levofloxacin. All isolates were resistant to erythromycin (MIC ≥4 mg/L) due to the presence of 2057A (Escherichia coli numbering) in 23S rRNA. Three isolates with elevated clindamycin MICs (≥8 mg/L) harbored A2058T/G mutations in 23S rRNA gene; four sequential isolates from one patient developed C2611T and A2059G mutations accompanying the increase of clindamycin MICs. Five isolates with elevated tetracycline MICs (≥4 mg/L) had mutations in 16S rRNA gene (A965G/T, G966T, or A967C/T) and one of them harbored TetM. Nine isolates with elevated levofloxacin MICs (≥4 mg/L) had one or more mutations in gyrA, gyrB, parC, or parE. Susceptibility breakpoints for clindamycin, tetracycline and levofloxacin were suggested to be ≤0.125, ≤2, and ≤2 mg/L, respectively. Antimicrobial resistance to any of the three agents (clindamycin, tetracycline, or levofloxacin) was documented in 12 (34.3%) non-duplicate isolates, of which 10 were invasive. Levofloxacin resistance was most frequent (25.7%). Multi-drug resistance was also observed (14.3%). This study demonstrates the frequent occurrence of antimicrobial resistance in M. salivarium, emphasizing the need for culture and susceptibility testing to guide antimicrobial therapy.

Septic polyarthritis with Mycoplasma salivarium in a patient with common variable immunodeficiency: case report and review of the literature

Mycoplasma salivarium is a common mycoplasma usually isolated from human oropharynx, particularly from individuals with periodontal disease. It is also among the more common mycoplasmal contaminants of eukaryotic cell cultures. Although M. salivarium has been isolated occasionally from abscesses and other sterile sites, to our knowledge, only three cases of septic arthritis have been documented in the past due to this organism, all in patients with humoral immunodeficiency. We now report a fourth case of septic polyarthritis in a patient with profound hypoimmunoglobulinemia who had experienced dental abscesses within the preceding 2 years. Our case highlights the importance of considering invasive mycoplasmal infection in hypogammaglobulinemic patients. It is likely of significance that the patient had suffered recurrent dental abscesses as a source of infection with M. salivarium .

Macrolide-resistant Mycoplasma pneumoniae pneumonia in transplantation: Increasingly typical?

Mycoplasma pneumoniae is one of the most common bacterial causes of pneumonia. Macrolide-resistant M pneumoniae (MRMP) was documented in 7.5% of isolates in the United States. Resistance portends poor outcomes to macrolide therapy, yet patients respond well to fluoroquinolones or tetracyclines such as minocycline. However, MRMP may be under-appreciated because M pneumoniae generally causes relatively mild infections in non-immunosuppressed adults that may resolve without effective therapy and because microbiological confirmation and susceptibility are not routinely performed. We report two cases of pneumonia due to MRMP in kidney transplant recipients. Both patients required hospital admission, worsened on macrolide therapy, and rapidly defervesced on doxycycline or levofloxacin. In one case, M pneumoniae was only identified by multiplex respiratory pathogen panel analysis of BAL fluid. Macrolide resistance was confirmed in both cases by real-time PCR and point mutations associated with macrolide resistance were identified. M pneumoniae was isolated from both cases, and molecular genotyping revealed the same genotype. In conclusion, clinicians should be aware of the potential for macrolide resistance in M pneumoniae, and may consider non-macrolide-based therapy for confirmed or non-responding infections in patients who are immunocompromised or hospitalized.

Mycoplasma hominis Infections Transmitted Through Amniotic Tissue Product

Background

Mycoplasma hominis is a commensal genitourinary tract organism that can cause infections outside the genitourinary tract. We investigated a cluster of M. hominis surgical site infections in patients who underwent spine surgery, all associated with amniotic tissue linked to a common donor.

Methods

Laboratory tests of tissue product from the donor, including culture, quantitative real-time polymerase chain reaction (qPCR), and whole-genome sequencing were performed. Use of this amniotic tissue product was reviewed. A multistate investigation to identify additional cases and locate any unused products was conducted.

Results

Twenty-seven tissue product vials from a donor were distributed to facilities in 7 states; at least 20 vials from this donor were used in 14 patients. Of these, 4 of 14 (29%) developed surgical site infections, including 2 M. hominis infections. Mycoplasma hominis was detected by culture and qPCR in 2 unused vials from the donor. Sequencing indicated >99% similarity between patient and unopened vial isolates. For 5 of 27 (19%) vials, the final disposition could not be confirmed.

Conclusions

Mycoplasma hominis was transmitted through amniotic tissue from a single donor to 2 recipients. Current routine donor screening and product testing does not detect all potential pathogens. Clinicians should be aware that M. hominis can cause surgical site infections, and may not be detected by routine clinical cultures. The lack of a standardized system to track tissue products in healthcare facilities limits the ability of public health agencies to respond to outbreaks and investigate other adverse events associated with these products.

Allergic airway sensitization impairs antibacterial IgG antibody responses during bacterial respiratory tract infections

BACKGROUND

Mycoplasma pneumoniae, an atypical human pathogen, has been associated with asthma initiation and exacerbation. Asthmatic patients have been reported to have higher carriage rates of M pneumoniae compared with nonasthmatic subjects and are at greater risk for invasive respiratory infections.

OBJECTIVE

We sought to study whether prior allergen sensitization affects the host response to chronic bacterial infection.

METHODS

BALB/cJ and IL-4 receptor α^-/- mice were sensitized with ovalbumin (OVA) and then infected with M pneumoniae or Streptococcus pneumoniae. Immune parameters were analyzed at 30 days postinfection and included cellular profiles in bronchoalveolar lavage fluid (BALF) and serum IgG and IgE antibody levels to whole bacterial lysate, recombinant P1 adhesin, and OVA. Total lung RNA was examined for transcript levels, and BALF was examined for cytokine protein profiles.

RESULTS

Anti-M pneumoniae antibody responses were decreased in allergen-sensitized, M pneumoniae-infected animals compared with control animals, but OVA-specific IgG responses were unaffected. Similar decreases in anti-S pneumoniae antibody levels were found in OVA-sensitized animals. However, M pneumoniae, but not S pneumoniae, infection augmented anti-OVA IgE antibody responses. Loss of IL-4 receptor signaling partially restored anti-M pneumoniae antibody responses in IgG_2a and IgG_2b subclasses. Inflammatory cytokine levels in BALF from OVA-sensitized, M pneumoniae-infected or S pneumoniae-infected animals were reduced compared with those in uninfected OVA-sensitized control animals. Unexpectedly, airway hyperreactivity to methacholine was essentially ablated in M pneumoniae-infected, OVA-sensitized animals.

CONCLUSIONS

An established type 2-biased host immune response impairs the host immune response to respiratory bacterial infection in a largely pathogen-independent manner. Some pathogens, such as M pneumoniae, can augment ongoing allergic responses and inhibit pulmonary type 2 cytokine responses and allergic airway hyperreactivity.

Analysis of the tonsillar microbiome in young adults with sore throat reveals a high relative abundance of Fusobacterium necrophorum with low diversity

Fusobacterium necrophorum (Fn), a gram-negative anaerobe, is increasingly implicated as an etiologic agent in older adolescents and young adults with sore throat. Inadequately treated Fn pharyngitis may result in suppurative complications such as peritonsillar abscess and Lemierre’s syndrome. Data from the literature suggest that the incidence of life-threating complications in these age groups from Fn pharyngitis (Lemierre’s syndrome) in the United States exceeds those associated with group A beta-hemolytic streptococcal (GAS) pharyngitis (acute rheumatic fever). Using real-time PCR, we previously reported about a 10% prevalence of Fn in asymptomatic medical students and about 20% in students complaining of sore throat at a university student health clinic (p = 0.009). In this study, a comprehensive microbiome analysis of the same study samples confirms that Fn pharyngitis was more common than GAS pharyngitis. Eighteen patients were found to have Fn OTU values exceeding an arbitrary cutoff value of 0.1, i.e. greater than 10% of total sequences, with five subjects reaching values above 0.7. By contrast only 9 patients had GAS OTU values greater than 0.1 and none exceeded 0.6. When the data were analyzed using five separate assessments of alpha diversity, in each case for Fn there were statistically significant differences between Fn positive_high (OTU abundance > 0.1) vs control, Fn positive_high vs Fn negative (OTU abundance = 0), Fn positive_high vs Fn positive_low (OTU abundance > 0 and < 0.1). When the data were analyzed using three beta diversity indexes (Bray-Curtis, weighted unifrac, and unweighted unifrac), there were statistically significant differences between Fn positive_high (OTU abundance ≥ 0.1) vs control for all three. Statistically significant differences remained if we chose somewhat different OTU abundance cutoffs of 0.05 or 0.15. We conclude that Fn appears to play a dominant role in bacterial pharyngitis in the older adolescent and young adult age groups and that the development of a productive mucosal infection with Fn is linked to a significant decrease in the diversity of the associated tonsillar microbiome.

Loss of IL-4Rα signaling is partially able to restore anti-Mycoplasma pneumoniae IgG titers during allergic airway disease

Rationale

Mycoplasma pneumoniae (Mpn) is the leading bacterial agent of pediatric community acquired pneumonia. Epidemiologic evidence has suggested increased susceptibility to Mpn infection among asthmatics. We hypothesized that allergic airway sensitization would impair host immune responses to Mpn infection, but that loss of Th2 cytokine signals (IL-4, IL-13) would overcome this impairment in a murine model.

Methods

Wild type (Wt) and IL-4Rα−/− BALB/cJ mice were sensitized and challenged with ovalbumin (OVA) to induce allergic airway inflammation, and then infected with Mpn. Immune parameters were studied by analysis of cellular profiles in bronchoalveolar lavage fluid (BALF), serum IgG and IgE antibody levels to a whole bacterial antigen preparation, recombinant Mpn P1 adhesin (rP1), and OVA. Total lung RNA was used to examine cytokine transcript levels for Th1, Th2 and Th17 biasing transcripts.

Results

Anti-Mpn and P1-specific total IgG responses were decreased in allergen-sensitized animals compared to unsensitized controls (p &lt; 0.01). Decreased titers of IgG1, IgG2a, IgG2b and IgG3 were present in rP1-specific, but not OVA-specific IgG subclass levels. Loss of IL-4Rα signaling partially restores total and subclass-specific responses. Th2 cytokine mRNA levels were increased in Wt, but not IL-4Rα−/− OVA sensitized groups compared to controls. IL-4Rα−/− animals had increased Interferon-γ(IFN-γ) and IL-17A mRNA levels compared to Wt animals.

Conclusions

Anti-Mpn IgG antibody titers were decreased in Wt allergic animals compared to unsensitized controls and the impairment in immune response to the pathogen was partially restored by inhibition of Th2 signaling in IL-4Rα−/− animals.

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.

Macrolide-Resistant Mycoplasma pneumoniae, United States

Macrolide-resistant Mycoplasma pneumoniae (MRMP) is highly prevalent in Asia and is now being reported from Europe. Few data on MRMP are available in the United States. Using genotypic and phenotypic methods, we detected high-level MRMP in 13.2% of 91 M. pneumoniae­–positive specimens from 6 US locations.

Comparative genome analysis of Mycoplasma pneumoniae

Background

Mycoplasma pneumoniae is a common pathogen that causes upper and lower respiratory tract infections in people of all ages, responsible for up to 40 % of community-acquired pneumonias. It also causes a wide array of extrapulmonary infections and autoimmune phenomena. Phylogenetic studies of the organism have been generally restricted to specific genes or regions of the genome, because whole genome sequencing has been completed for only 4 strains. To better understand the physiology and pathogenicity of this important human pathogen, we performed comparative genomic analysis of 15 strains of M. pneumoniae that were isolated between the 1940s to 2009 from respiratory specimens and cerebrospinal fluid originating from the USA, China and England.

Results

Illumina MiSeq whole genome sequencing was performed on the 15 strains and all genome sequences were completed. Results from the comparative genomic analysis indicate that although about 1500 SNP and indel variants exist between type1 and type 2 strains, there is an overall high degree of sequence similarity among the strains (>99 % identical to each other). Within the two subtypes, conservation of most genes, including the CARDS toxin gene and arginine deiminase genes, was observed. The major variation occurs in the P1 and ORF6 genes associated with the adhesin complex. Multiple hsdS genes (encodes S subunit of type I restriction enzyme) with variable tandem repeat copy numbers were found in all 15 genomes.

Conclusions

These data indicate that despite conclusions drawn from 16S rRNA sequences suggesting rapid evolution, the M. pneumoniae genome is extraordinarily stable over time and geographic distance across the globe with a striking lack of evidence of horizontal gene transfer.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1801-0) contains supplementary material, which is available to authorized users.

The clinical presentation of Fusobacterium-positive and streptococcal-positive pharyngitis in a university health clinic: a cross-sectional study

BACKGROUND

Pharyngitis guidelines focus solely on group A β-hemolytic streptococcal infection. European data suggest that in patients aged 15 to 30 years, Fusobacterium necrophorum causes at least 10% of cases of pharyngitis; however, few U.S. data exist.

OBJECTIVE

To estimate the prevalence of F. necrophorum; Mycoplasma pneumoniae; and group A and C/G β-hemolytic streptococcal pharyngitis and to determine whether F. necrophorum pharyngitis clinically resembles group A β-hemolytic streptococcal pharyngitis.

DESIGN

Cross-sectional.

SETTING

University student health clinic.

PATIENTS

312 students aged 15 to 30 years presenting to a student health clinic with an acute sore throat and 180 asymptomatic students.

MEASUREMENTS

Polymerase chain reaction testing from throat swabs to detect 4 species of bacteria and signs and symptoms used to calculate the Centor score.

RESULTS

Fusobacterium necrophorum was detected in 20.5% of patients and 9.4% of asymptomatic students. Group A β-hemolytic streptococcus was detected in 10.3% of patients and 1.1% of asymptomatic students. Group C/G β-hemolytic streptococcus was detected in 9.0% of patients and 3.9% of asymptomatic students. Mycoplasma pneumoniae was detected in 1.9% of patients and 0 asymptomatic students. Infection rates with F. necrophorum, group A streptococcus, and group C/G streptococcus increased with higher Centor scores (P < 0.001).

LIMITATIONS

The study focused on a limited age group and took place at a single institution. Asymptomatic students-rather than seasonal control participants-and a convenience sample were used.

CONCLUSION

Fusobacterium necrophorum-positive pharyngitis occurs more frequently than group A β-hemolytic streptococcal-positive pharyngitis in a student population, and F. necrophorum-positive pharyngitis clinically resembles streptococcal pharyngitis.

PRIMARY FUNDING SOURCE

University of Alabama at Birmingham and the Justin E. Rodgers Foundation.

Comparative genome analysis of 19 Ureaplasma urealyticum and Ureaplasma parvum strains

Background

Ureaplasma urealyticum (UUR) and Ureaplasma parvum (UPA) are sexually transmitted bacteria among humans implicated in a variety of disease states including but not limited to: nongonococcal urethritis, infertility, adverse pregnancy outcomes, chorioamnionitis, and bronchopulmonary dysplasia in neonates. There are 10 distinct serotypes of UUR and 4 of UPA. Efforts to determine whether difference in pathogenic potential exists at the ureaplasma serovar level have been hampered by limitations of antibody-based typing methods, multiple cross-reactions and poor discriminating capacity in clinical samples containing two or more serovars.

Results

We determined the genome sequences of the American Type Culture Collection (ATCC) type strains of all UUR and UPA serovars as well as four clinical isolates of UUR for which we were not able to determine serovar designation. UPA serovars had 0.75−0.78 Mbp genomes and UUR serovars were 0.84−0.95 Mbp. The original classification of ureaplasma isolates into distinct serovars was largely based on differences in the major ureaplasma surface antigen called the multiple banded antigen (MBA) and reactions of human and animal sera to the organisms. Whole genome analysis of the 14 serovars and the 4 clinical isolates showed the mba gene was part of a large superfamily, which is a phase variable gene system, and that some serovars have identical sets of mba genes. Most of the differences among serovars are hypothetical genes, and in general the two species and 14 serovars are extremely similar at the genome level.

Conclusions

Comparative genome analysis suggests UUR is more capable of acquiring genes horizontally, which may contribute to its greater virulence for some conditions. The overwhelming evidence of extensive horizontal gene transfer among these organisms from our previous studies combined with our comparative analysis indicates that ureaplasmas exist as quasi-species rather than as stable serovars in their native environment. Therefore, differential pathogenicity and clinical outcome of a ureaplasmal infection is most likely not on the serovar level, but rather may be due to the presence or absence of potential pathogenicity factors in an individual ureaplasma clinical isolate and/or patient to patient differences in terms of autoimmunity and microbiome.

Mutations in ribosomal proteins and ribosomal RNA confer macrolide resistance in human Ureaplasma spp

Genetic mechanisms of macrolide resistance were investigated in six isolates of Ureaplasma spp. with erythromycin minimum inhibitory concentrations (MICs)≥ 8 μg/mL that were derived from 370 cultures obtained over a several year period. Point mutations in domain V of 23S rRNA and/or mutations in ribosomal protein L4 genes are likely to be responsible for this drug resistance. Overall, macrolide resistance was uncommon, in contrast to tetracycline resistance that was documented in 121 unique isolates (33%).

Comparative in vitro susceptibilities of human mycoplasmas and ureaplasmas to a new investigational ketolide, CEM-101

MICs were determined for an investigational ketolide, CEM-101, and azithromycin, telithromycin, doxycycline, levofloxacin, clindamycin, and linezolid against 36 Mycoplasma pneumoniae, 5 Mycoplasma genitalium, 13 Mycoplasma hominis, 15 Mycoplasma fermentans, and 20 Ureaplasma isolates. All isolates, including two macrolide-resistant M. pneumoniae isolates, were inhibited by CEM-101 at < or = 0.5 microg/ml, making CEM-101 the most potent compound tested.

Comparative in vitro activities of investigational peptide deformylase inhibitor NVP LBM-415 and other agents against human mycoplasmas and ureaplasmas

Peptide deformylase inhibitor LBM-415 and seven other drugs were tested against Mycoplasma pneumoniae (100 isolates), Mycoplasma hominis (20 isolates), Mycoplasma fermentans (10 isolates), and Ureaplasma species (50 isolates). LBM-415 was active against M. pneumoniae (MICs, <or=0.008 microg/ml). It showed no activity against M. hominis and M. fermentans and modest activity against Ureaplasma spp.

In vitro comparison of agar and microbroth dilution methods for determination of MICs for Mycoplasma hominis

Ten replicates of three Mycoplasma hominis strains were tested by microbroth and agar dilution against levofloxacin, moxifloxacin, gatifloxacin, erythromycin, tetracycline, and clindamycin. Both methods provide reproducible results. Agar dilution tends to yield higher MIC values for some drugs.

Comparative in vitro susceptibilities and bactericidal activities of investigational fluoroquinolone ABT-492 and other antimicrobial agents against human mycoplasmas and ureaplasmas

We determined in vitro susceptibilities for ABT-492 and other antimicrobials against Mycoplasma pneumoniae, Mycoplasma fermentans, Mycoplasma hominis, and Ureaplasma species. ABT-492 MICs were < or =1 microg/ml, and the agent was bactericidal against selected isolates of M. pneumoniae and M. hominis. ABT-492 has potential for treatment of infections due to these microorganisms.

Inhibitory and bactericidal activities of gemifloxacin and other antimicrobials against Mycoplasma pneumoniae

The MIC of gemifloxacin was compared with that of sparfloxacin, levofloxacin, moxifloxacin, gatifloxacin, ciprofloxacin, doxycycline, erythromycin, azithromycin and clarithromycin using 97 clinical isolates of Mycoplasma pneumoniae. MBCs of fluoroquinolones were determined for a subgroup of 12 isolates. Macrolides were the most potent agents with MIC(90)s for all drugs <or=0.001 mg/l. The doxycycline MIC(90) was 0.5 mg/l. Gemifloxacin MICs ranged from <or=0.001 to 0.25 mg/l. The gemifloxacin MIC(90) (0.125 mg/l) was equivalent to moxifloxacin and gatifloxacin, was 2-fold lower than sparfloxacin, 8-fold lower than levofloxacin and 32-fold lower than ciprofloxacin. MBCs for gemifloxacin were predominantly within 2-4 times the corresponding MIC values, indicating a bactericidal effect.

In vitro susceptibilities to and bactericidal activities of garenoxacin (BMS-284756) and other antimicrobial agents against human mycoplasmas and ureaplasmas

The in vitro susceptibilities to garenoxacin (BMS-284756), an investigational des-fluoroquinolone, and eight other agents were determined for 63 Mycoplasma pneumoniae, 45 Mycoplasma hominis, 15 Mycoplasma fermentans, and 68 Ureaplasma sp. isolates. Garenoxacin was the most active quinolone, inhibiting all isolates at <or=1 microg/ml. The garenoxacin MIC at which 90% of isolates are inhibited (MIC(90)s; <or=0.008 microg/ml) was at least 4-fold less than those of moxifloxacin and clindamycin, 8-fold less than that of sparfloxacin, and 64-fold less than those of levofloxacin and ciprofloxacin for M. pneumoniae. For M. hominis, the garenoxacin MIC(90) (<or=0.008 microg/ml) was 4-fold less than those of clindamycin and moxifloxacin, 8-fold less than that of sparfloxacin, and 64-fold less than those of levofloxacin and ciprofloxacin. All 15 M. fermentans isolates were inhibited by garenoxacin at concentrations <or=0.008 microg/ml, making it the most active drug tested against this organism. For Ureaplasma spp., the garenoxacin MIC(90) (0.25 microg/ml) was equivalent to those of moxifloxacin and doxycycline, 4-fold less than those of levofloxacin and sparfloxacin, 8-fold less than that of azithromycin, and 32-fold less than that of ciprofloxacin. Garenoxacin and the other fluoroquinolones tested were demonstrated to have bactericidal activities against M. pneumoniae and M. hominis by measurement of minimal bactericidal activities and by time-kill studies. Further study of garenoxacin is required, as it has great potential for use in the treatment of infections due to mycoplasmas and ureaplasmas.

In vitro activities of ABT-773 and other antimicrobials against human mycoplasmas

The in vitro susceptibilities of 103 Mycoplasma pneumoniae isolates, 14 Mycoplasma hominis isolates, 12 Mycoplasma fermentans isolates, and 24 Ureaplasma species to ABT-773, an investigational ketolide, and seven other agents were determined. For M. pneumoniae, the ABT-773 MIC at which 90% of isolates are inhibited (MIC(90); <or=0.001 microg/ml) was comparable to those of azithromycin, clarithromycin, and erythromycin and at least 128-fold lower than those of levofloxacin, gatifloxacin, moxifloxacin, and doxycycline. For M. fermentans, the ABT-773 MIC(90) (<or=0.008 microg/ml) was 2- to 128-fold lower than those of all other agents tested. For M. hominis, the ABT-773 MIC(90) (0.031 microg/ml) was equivalent to that of moxifloxacin, 2-fold lower than those of gatifloxacin and clindamycin, and 16-fold lower than that of levofloxacin. ABT-773 was equally active against doxycycline-susceptible and doxycycline-resistant organisms. The ABT-773 MICs (0.016 microg/ml) for Ureaplasma species were the lowest of those of any drug tested. The MIC(90) was 4- to 64-fold lower than those of clarithromycin, azithromycin, and erythromycin and >or=16-fold lower than those of all three fluoroquinolones. Minimal bactericidal concentrations determined for a subgroup of organisms were <or=0.063 micro g/ml for M. pneumoniae and 0.25 microg/ml for M. fermentans, but they were several dilutions higher for M. hominis and Ureaplasma spp. ABT-773 has great potential for further study for the treatment of infections due to mycoplasmas and ureaplasmas.

Evaluation of the Etest for detection of tetracycline resistance in Mycoplasma hominis

The Etest was compared with microbroth dilution for performing in vitro susceptibility tests in 38 isolates of Mycoplasma hominis chosen to represent a wide range of MIC values. MIC50s were 4 micrograms/ml for both methods; whereas, MIC90s were 64 and > 256 micrograms/ml for broth and Etest, respectively. Etest MICs determined on SP 4 agar were usually two or more dilutions greater than microbroth MICs in SP 4 broth, and values were prone to change by one to two dilutions when different inoculum densities were used. Inocula of 10(5) to 10(6) color-changing units/ml gave the most consistently readable MICs, with discrete colony formation surrounding the ellipse. Etest MICs for 5 isolates tested a second time at the same inoculum on SP 4 agar agreed with the original value within 1 dilution. For 12 isolates tested on A 8 agar simultaneously with SP 4 agar, MICs for 10/12 agreed within one dilution; whereas, in the other 2 isolates, MICs varied by two dilutions. These findings suggest that the Etest, when properly controlled, can be used to determine tetracycline MICs for M. hominis.

Rapid detection of tetM in Mycoplasma hominis and Ureaplasma urealyticum by PCR: tetM confers resistance to tetracycline but not necessarily to doxycycline

Tetracycline resistance in Mycoplasma hominis and Ureaplasma urealyticum has been associated with the tetM determinant and has recently been increasing in incidence. We report here a rapid method for detection of the tetM determinant based on the use of the polymerase chain reaction (PCR) to amplify a 397-bp DNA fragment from the tetM gene and verification of specificity using the restriction enzyme TaqI. Analysis of 42 U. urealyticum and 49 M. hominis isolates indicates that the PCR method may be clinically useful for determination of tetracycline sensitivity, as tetM is presently the only known determinant associated with tetracycline resistance in these two organisms. All of the tetM-positive M. hominis isolates were sensitive to doxycycline, indicating that tetM does not necessarily confer resistance to this antibiotic.

Comparison of agar versus broth dilution techniques for determining antibiotic susceptibilities of Ureaplasma urealyticum

We determined minimal inhibitory concentrations (MIC) for tetracycline and erythromycin for 72 clinical isolates using broth and agar dilution methods. Erythromycin MIC ranges were less than 0.125-8 micrograms/ml and 1-64 micrograms/ml in broth and agar, respectively. The erythromycin MIC50 and MIC90 as determined by broth were two dilutions (fourfold) lower than those for agar. Tetracycline MIC ranges in broth and agar were less than 0.125-greater than 64 and 0.25-greater than 64 micrograms/ml, respectively. The tetracycline broth MIC50 was one dilution lower than that for agar. The tetracycline broth MIC90 was 64 micrograms/ml and that for agar was greater than 64 micrograms/ml. Of the strains tested, 98.6% using broth were susceptible or moderately susceptible to erythromycin as compared with 75% using agar, representing a significant difference (p less than 0.001). For tetracycline, 80.6% of strains were susceptible or moderately susceptible using broth and 73.6% using agar. MICs were determined by agar dilution after 72 and 96 hr of incubation in 32 strains. There was an increase in the erythromycin MIC by one dilution in 16 strains and two dilutions in one strain with the longer incubation. The tetracycline MIC increased by one dilution in nine strains between readings. Broth MICs were reproducible with one dilution for both drugs in 10 of 12 strains tested twice. Agar MICs were reproducible within a maximum of two dilutions (fourfold). Different interpretations of susceptibility versus resistance may be made depending on which assay is utilized, thus influencing conclusions regarding spectrum of activity of investigational drugs as well as treatment options. The technique employed should always be considered whenever apparently differing drug susceptibility patterns are reported.

The instep of the foot as a fasciocutaneous island and as a free flap for heel defects

The instep flap needs neither muscle nor a transposition base for survival or innervation. It can be transposed as an island fasciocutaneous flap either on the medial or lateral plantar neurovascular bundles or both, and it can be transferred also as a free flap from the opposite foot. Four cases demonstrating the use of the flap as an island and free flap are presented with follow-up ranging from 1 to 2 years. The absence of muscle in the flap provides greater stability of the heel reconstruction and results in a lesser secondary defect. Sensation in the flaps is diminished but adequate for long-term function, but hyperkeratotic reaction remains an unpredictable problem. The ability to transfer the flap as a free transfer widens the scope of the flap to reconstruct both heel and forefoot defects where local instep tissue or vascularity are inadequate for local reconstruction. The secondary defect, particularly when no muscle is included in the flap, has been minimal.