Antimicrobial agents and gonorrhoea: therapeutic choice, resistance and susceptibility testing

Sonodynamic inactivation of Gram-positive and Gram-negative bacteria using a Rose Bengal-antimicrobial peptide conjugate

Combating antimicrobial resistance is one of the most serious public health challenges facing society today. The development of new antibiotics or alternative techniques that can help combat antimicrobial resistance is being prioritised by many governments and stakeholders across the globe. Antimicrobial photodynamic therapy is one such technique that has received considerable attention but is limited by the inability of light to penetrate through human tissue, reducing its effectiveness when used to treat deep-seated infections. The related technique sonodynamic therapy (SDT) has the potential to overcome this limitation given the ability of low-intensity ultrasound to penetrate human tissue. In this study, a Rose Bengal-antimicrobial peptide conjugate was prepared for use in antimicrobial SDT (ASDT). When Staphylococcus aureus and Pseudomonas aeruginosa planktonic cultures were treated with the conjugate and subsequently exposed to ultrasound, 5 log and 7 log reductions, respectively, in bacterial numbers were observed. The conjugate also displayed improved uptake by bacterial cells compared with a mammalian cell line (P ≤ 0.01), whilst pre-treatment of a P. aeruginosa biofilm with ultrasound resulted in a 2.6-fold improvement in sensitiser diffusion (P ≤ 0.01). A preliminary in vivo experiment involving ASDT treatment of P. aeruginosa-infected wounds in mice demonstrated that ultrasound irradiation of conjugate-treated wounds affects a substantial reduction in bacterial burden. Combined, the results obtained from this study highlight ASDT as a targeted broad-spectrum novel modality with potential for the treatment of deep-seated bacterial infections.

Recommendations for the laboratory-based detection of Chlamydia trachomatis and Neisseria gonorrhoeae--2014

This report updates CDC's 2002 recommendations regarding screening tests to detect Chlamydia trachomatis and Neisseria gonorrhoeae infections (CDC. Screening tests to detect Chlamydia trachomatis and Neisseria gonorrhoeae infections-2002. MMWR 2002;51[No. RR-15]) and provides new recommendations regarding optimal specimen types, the use of tests to detect rectal and oropharyngeal C. trachomatis and N. gonorrhoeae infections, and circumstances when supplemental testing is indicated. The recommendations in this report are intended for use by clinical laboratory directors, laboratory staff, clinicians, and disease control personnel who must choose among the multiple available tests, establish standard operating procedures for collecting and processing specimens, interpret test results for laboratory reporting, and counsel and treat patients. The performance of nucleic acid amplification tests (NAATs) with respect to overall sensitivity, specificity, and ease of specimen transport is better than that of any of the other tests available for the diagnosis of chlamydial and gonococcal infections. Laboratories should use NAATs to detect chlamydia and gonorrhea except in cases of child sexual assault involving boys and rectal and oropharyngeal infections in prepubescent girls and when evaluating a potential gonorrhea treatment failure, in which case culture and susceptibility testing might be required. NAATs that have been cleared by the Food and Drug Administration (FDA) for the detection of C. trachomatis and N. gonorrhoeae infections are recommended as screening or diagnostic tests because they have been evaluated in patients with and without symptoms. Maintaining the capability to culture for both N. gonorrhoeae and C. trachomatis in laboratories throughout the country is important because data are insufficient to recommend nonculture tests in cases of sexual assault in prepubescent boys and extragenital anatomic site exposure in prepubescent girls. N. gonorrhoeae culture is required to evaluate suspected cases of gonorrhea treatment failure and to monitor developing resistance to current treatment regimens. Chlamydia culture also should be maintained in some laboratories to monitor future changes in antibiotic susceptibility and to support surveillance and research activities such as detection of lymphogranuloma venereum or rare infections caused by variant or mutated C. trachomatis.

An insight into the drug resistance profile & mechanism of drug resistance in Neisseria gonorrhoeae

Among the aetiological agents of treatable sexually transmitted diseases (STDs), Neissseria gonorrhoeae is considered to be most important because of emerging antibiotic resistant strains that compromise the effectiveness of treatment of the disease - gonorrhoea. In most of the developing countries, treatment of gonorrhoea relies mainly on syndromic management rather than the aetiological based therapy. Gonococcal infections are usually treated with single-dose therapy with an agent found to cure > 95 per cent of cases. Unfortunately during the last few decades, N. gonorrhoeae has developed resistance not only to less expensive antimicrobials such as sulphonamides, penicillin and tetracyclines but also to fluoroquinolones. The resistance trend of N. gonorrhoeae towards these antimicrobials can be categorised into pre-quinolone, quinolone and post-quinolone era. Among the antimicrobials available so far, only the third-generation cephalosporins could be safely recommended as first-line therapy for gonorrhoea globally. However, resistance to oral third-generation cephalosporins has also started emerging in some countries. Therefore, it has become imperative to initiate sustained national and international efforts to reduce infection and misuse of antibiotics so as to prevent further emergence and spread of antimicrobial resistance. It is necessary not only to monitor drug resistance and optimise treatment regimens, but also to gain insight into how gonococcus develops drug resistance. Knowledge of mechanism of resistance would help us to devise methods to prevent the occurrence of drug resistance against existing and new drugs. Such studies could also help in finding out new drug targets in N. gonorrhoeae and also a possibility of identification of new drugs for treating gonorrhoea.

The use of cephalosporins for gonorrhea: the impending problem of resistance

Gonorrhea remains an important clinical and public health problem throughout the world. Gonococcal infections have historically been diagnosed by Gram stain and culture but are increasingly diagnosed through nucleic acid tests, thereby eliminating the opportunity for antimicrobial susceptibility testing. Gonococcal infections are typically treated with single-dose therapy with an agent found to cure > 95% of cases. Unfortunately, the gonococcus has repeatedly developed resistance to antimicrobials including sulfonamides, penicillin, tetracyclines and fluoroquinolones. This has now left third-generation cephalosporins as the lone class of antimicrobials recommended as first-line therapy for gonorrhea in some regions. However, resistance to oral third-generation cephalosporins has emerged and spread in Asia, Australia and elsewhere. The mechanism of this resistance seems to be associated with a mosaic penicillin binding protein (penA) in addition to other chromosomal mutations previously found to confer resistance to beta-lactam antimicrobials (ponA, mtrR, penB, pilQ). Few good options exist or are in development for treating cephalosporin-resistant isolates, as most have had multidrug resistance. Preventing the spread of resistant isolates will depend on ambitious antimicrobial management programs, strengthening and expanding surveillance networks, and through effective sexually transmitted disease control and prevention.

Multidrug-resistant strains of Neisseria gonorrhoeae in Greece

Eighty-seven out of 575 gonococci isolated in Greece from 1991 to 1998 belonged to serovar Bropyst and exhibited resistance to penicillin, tetracycline, erythromycin, and chloramphenicol. Conventional and molecular typing showed three clusters, A, B, and C, that were associated with networks of high- frequency transmitters (cluster A with homosexuals and clusters B and C with refugees from Eastern Europe). Study of one isolate revealed mutations in the penA, mtrR, and porB genes that may explain the multidrug-resistant phenotype.

In vitro susceptibilities of 400 Spanish isolates of Neisseria gonorrhoeae to gemifloxacin and 11 other antimicrobial agents

The in vitro activity of gemifloxacin versus those of 11 other antimicrobial agents against 400 strains of Neisseria gonorrhoeae was determined by microdilution with supplemented GC agar. A total of 37.5% of the strains were beta-lactamase positive. A total of 70 and 6.4% of the beta-lactamase-negative strains exhibited intermediate and high-level penicillin resistance, respectively. Ceftriaxone and gemifloxacin were the most active drugs (MICs at which 90% of isolates are inhibited, 0.01 versus 0.007 microg/ml, respectively), with 100% of strains inhibited by 0.12 microg/ml.

Susceptibility of gonococci isolated in London to therapeutic antibiotics: establishment of a London surveillance programme. London Gonococcal Working Group

OBJECTIVES

To establish the in vitro susceptibility of gonococci isolated in the London area to antibiotics in current therapeutic use and to establish a sentinel surveillance system for monitoring trends in antibiotic resistant gonorrhoea in London.

METHODS

Isolates of Neisseria gonorrhoeae from consecutive patients attending genitourinary medicine clinics at 10 hospitals in the London area were collected over a 3 month period, May to July 1997. The susceptibility to penicillin, ciprofloxacin, tetracycline, and spectinomycin was determined for each isolate. Isolates exhibiting either plasmid or chromosomally mediated resistance were additionally tested for susceptibility to agents used as alternative treatments including azithromycin, ceftriazone, and ofloxacin. The resistant isolates were also tested for plasmid profiles (penicillinase producing N gonorrhoeae, PPNG), type of tetM determinant (tetracycline resistant N gonorrhoeae, TRNG), and presence of gyrA and parC mutations (quinolone resistant N gonorrhoeae, QRNG).

RESULTS

A total of 1133 isolates were collected which represents > 95% of the total gonococci isolated in the 3 months. Plasmid mediated resistance was exhibited by 48 (4.2%) isolates; six (0.5%) were PPNG, 15 (1.3%) were PP/TRNG, and 27 (2.4%) were TRNG. The majority of PPNG (18 of 20 tested) carried the 3.2 MDa penicillinase plasmid whereas the two types of tetM determinant were more evenly distributed. High level resistance to ciprofloxacin was detected in four (0.4%) isolates and double mutations were found in the quinolone resistance determining region (QRDR) of the gyrA gene in three QRNG with MICs of 16 mg/l and a single mutation in one isolate with a MIC of 1 mg/l to ciprofloxacin. No parC mutations were found. Of the remaining 1081 isolates, 86 (8.0%) were chromosomally mediated resistant N gonorrhoeae (CMRNG).

CONCLUSIONS

A unique collection of gonococcal isolates has been established which can be used as a baseline for surveillance of susceptibility to antibiotics and for epidemiological purposes.

The laboratory investigation of vaginal discharge

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