Antimicrobial susceptibility testing and phenotyping of Neisseria gonorrhoeae isolated from patients with ophthalmia neonatorum in Nairobi, Kenya

Plasmid mediated penicillin and tetracycline resistance among Neisseria gonorrhoeae isolates from Kenya

BACKGROUND

Treatment of gonorrhea is complicated by the development of antimicrobial resistance in Neisseria gonorrhoeae (GC) to the antibiotics recommended for treatment. Knowledge on types of plasmids and the antibiotic resistance genes they harbor is useful in monitoring the emergence and spread of bacterial antibiotic resistance. In Kenya, studies on gonococcal antimicrobial resistance are few and data on plasmid mediated drug resistance is limited. The present study characterizes plasmid mediated resistance in N. gonorrhoeae isolates recovered from Kenya between 2013 and 2018.

METHODS

DNA was extracted from 36 sub-cultured GC isolates exhibiting varying drug resistance profiles. Whole genome sequencing was done on Illumina MiSeq platform and reads assembled de-novo using CLC Genomics Workbench. Genome annotation was performed using Rapid Annotation Subsystem Technology. Comparisons in identified antimicrobial resistance determinants were done using Bioedit sequence alignment editor.

RESULTS

Twenty-four (66.7%) isolates had both β-lactamase (TEM) and TetM encoding plasmids. 8.3% of the isolates lacked both TEM and TetM plasmids and had intermediate to susceptible penicillin and tetracycline MICs. Twenty-six (72%) isolates harbored TEM encoding plasmids. 25 of the TEM plasmids were of African type while one was an Asian type. Of the 36 isolates, 31 (86.1%) had TetM encoding plasmids, 30 of which harbored American TetM, whereas 1 carried a Dutch TetM. All analyzed isolates had non-mosaic penA alleles. All the isolates expressing TetM were tetracycline resistant (MIC> 1 mg/L) and had increased doxycycline MICs (up to 96 mg/L). All the isolates had S10 ribosomal protein V57M amino acid substitution associated with tetracycline resistance. No relation was observed between PenB and MtrR alterations and penicillin and tetracycline MICs.

CONCLUSION

High-level gonococcal penicillin and tetracycline resistance in the sampled Kenyan regions was found to be mediated by plasmid borne blaTEM and tetM genes. While the African TEM plasmid, TEM1 and American TetM are the dominant genotypes, Asian TEM plasmid, a new TEM239 and Dutch TetM have emerged in the regions.

gyrA and parC mutations in fluoroquinolone-resistant Neisseria gonorrhoeae isolates from Kenya

BACKGROUND

Phenotypic fluoroquinolone resistance was first reported in Western Kenya in 2009 and later in Coastal Kenya and Nairobi. Until recently gonococcal fluoroquinolone resistance mechanisms in Kenya had not been elucidated. The aim of this paper is to analyze mutations in both gyrA and parC responsible for elevated fluoroquinolone Minimum Inhibitory Concentrations (MICs) in Neisseria gonorrhoeae (GC) isolated from heterosexual individuals from different locations in Kenya between 2013 and 2017.

METHODS

Antimicrobial Susceptibility Tests were done on 84 GC in an ongoing Sexually Transmitted Infections (STI) surveillance program. Of the 84 isolates, 22 resistant to two or more classes of antimicrobials were chosen for analysis. Antimicrobial susceptibility tests were done using E-test (BioMerieux) and the results were interpreted with reference to European Committee on Antimicrobial Susceptibility Testing (EUCAST) standards. The isolates were sub-cultured, and whole genomes were sequenced using Illumina platform. Reads were assembled de novo using Velvet, and mutations in the GC Quinolone Resistant Determining Regions identified using Bioedit sequence alignment editor. Single Nucleotide Polymorphism based phylogeny was inferred using RaxML.

RESULTS

Double GyrA amino acid substitutions; S91F and D95G/D95A were identified in 20 isolates. Of these 20 isolates, 14 had an additional E91G ParC substitution and significantly higher ciprofloxacin MICs (p = 0.0044*). On the contrary, norfloxacin MICs of isolates expressing both GyrA and ParC QRDR amino acid changes were not significantly high (p = 0.82) compared to MICs of isolates expressing GyrA substitutions alone. No single GyrA substitution was found in the analyzed isolates, and no isolate contained a ParC substitution without the simultaneous presence of double GyrA substitutions. Maximum likelihood tree clustered the 22 isolates into 6 distinct clades.

CONCLUSION

Simultaneous presence of amino acid substitutions in ParC and GyrA has been reported to increase gonococcal fluoroquinolone resistance from different regions in the world. Our findings indicate that GyrA S91F, D95G/D95A and ParC E91G amino acid substitutions mediate high fluoroquinolone resistance in the analyzed Kenyan GC.

Emergence of fluoroquinolone resistance in Neisseria gonorrhoeae isolates from four clinics in three regions of Kenya

We have recently reported high levels of fluoroquinolone resistance in a single region of Kenya. In this article, we report high prevalence of fluoroquinolone resistance (53.2%) in Neisseria gonorrhoeae isolates from 4 clinics in 3 additional regions of Kenya. These findings highlight the need to change first-line treatment in these settings and the need to evaluate empirical management guidelines for treatment of gonococcal infection in Kenya.

Increasing resistance of Neisseria gonorrhoeae in west and central Africa. Consequence on therapy of gonococcal infection

BACKGROUND AND OBJECTIVES

Antimicrobial resistant strains of Neisseria gonorrhoeae have spread with remarkable rapidity in many African countries. Chromosomal resistance to penicillin, tetracycline, and thiamphenicol is frequent now, and reported prevalences of penicillinase-producing N. gonorrhoeae isolates vary between 15% and 80%. Plasmid-mediated tetracycline-resistant N. gonorrhoeae isolates have been observed in several African countries.

GOALS

To characterize gonococcal isolates from three sites in West and Central Africa, to determine antimicrobial susceptibility patterns, to document the spread of plasmid-mediated resistance to penicillin and tetracycline in these three sites, and to discuss the consequences of rising antimicrobial resistance on the management of gonococcal infection in Africa.

STUDY DESIGN

Over time, a total of 2,288 gonococcal isolates were obtained from Abidjan, Ivory Coast (1992-1993, n = 251), from Kigali, Rwanda (1988-1993, n = 952), and from Kinshasa, Zaire (1988-1990, n = 1,085). The isolates were characterized by auxotyping and serotyping. Plasmid-mediated resistance to penicillin and to tetracycline was determined. Antimicrobial susceptibility testing to ceftriaxone, ciprofloxacin, penicillin, spectinomycin, tetracycline, and thiamphenicol was performed with an agar dilution method.

RESULTS

The prevalence of penicillinase-producing N. gonorrhoeae increased significantly over time from 44% to 57% in Kigali and remained stable at a high level in Abidjan (73%) and in Kinshasa (67%). The frequency of tetracycline-resistant N. gonorrhoeae increased significantly during the observation periods in all three sites: from 20% to 65% in Abidjan, from 0% to 64% in Kigali, and from 14% to 41% in Kinshasa. Chromosomal resistance to penicillin was common in Kigali and Kinshasa, and chromosomal resistance to tetracycline and thiamphenicol was frequent in all three sites. All gonococcal isolates were susceptible to ceftriaxone, ciprofloxacin, and spectinomycin. Prototrophic and proline requiring strains were predominant, and IA-6 was the most common serovar in the three sites. IB-specific serovars were more common among penicillinase-producing N. gonorrhoeae and IA-specific serovars were more frequent among tetracycline-resistant N. gonorrhoeae, but there was no evidence for a clonal spread of resistant strains.

CONCLUSIONS

This study illustrates the high frequency of resistant gonococci in Africa and shows that tetracycline-resistant N. gonorrhoeae have become highly endemic in different geographic areas of the continent. The use of effective drugs is essential to reduce gonorrhea transmission. Surveillance of temporal changes in antimicrobial resistance in gonococcal strain populations should be part of sexually transmitted diseases control programs.

Neisseria meningitidis conjunctivitis in children

We examined two children from the same family who had purulent conjunctivitis. Isolates of Neisseria species were obtained from eye cultures and Gram stain of conjunctival scrapings disclosed many gram-negative intracellular diplococci. Colony structure and growth characteristics of the organism with subsequent carbohydrate fermentation tests and serotyping were consistent with Neisseria meningitidis Group B. The patients had no neurologic signs or symptoms. Results of laboratory investigations and blood cultures were normal. Early diagnosis is mandatory and aggressive systemic therapy with appropriate antibiotics may prevent ocular, neurologic, or systemic complications.

In vitro activity of ceftriaxone, cefetamet (Ro 15-8074), ceftetrame (Ro 19-5247; T-2588), and fleroxacin (Ro 23-6240; AM-833) versus Neisseria gonorrhoeae and Haemophilus ducreyi

We examined 300 strains of Neisseria gonorrhoeae and 100 strains of Haemophilus ducreyi to determine their in vitro susceptibility to two new cephalosporins, cefetamet (Ro 15-8074) and ceftetrame (Ro 19-5247; T-2588), and a new fluroquinolone, fleroxacin (Ro 23-6240; AM-833). Their activity was compared with that of ceftriaxone, penicillin, spectinomycin, tetracycline, and erythromycin. Cefetamet, ceftetrame, and fleroxacin had excellent in vitro activity against both groups of microorganisms. beta-Lactamase production did not significantly affect the MICs of these agents. The Mtr phenotype of N. gonorrhoeae raised the MICs two- to fourfold, but the MICs remained within the range of achievable levels in serum. These newer compounds have a distinct advantage over existing therapeutic agents in that they can be administered orally. Clinical trials are warranted to assess their usefulness in the therapy of gonorrhea and chancroid.

Single-dose therapy of gonococcal ophthalmia neonatorum with ceftriaxone

We conducted a randomized clinical trial comparing a single intramuscular dose of 125 mg of ceftriaxone with a single intramuscular dose of 75 mg of kanamycin followed by topical gentamicin for seven days, and with a single intramuscular dose of 75 mg of kanamycin followed by topical tetracycline for seven days, in the treatment of gonococcal ophthalmia neonatorum in Nairobi, Kenya. Of 122 newborns with culture-proved gonococcal ophthalmia neonatorum, 105 returned for follow-up. Sixty-one infants (54 percent) received ceftriaxone, 32 received kanamycin plus topical gentamicin, and 29 received kanamycin plus topical tetracycline. Sixty-six (54 percent) of the Neisseria gonorrhoeae isolates were penicillinase producing. All 55 newborns who received ceftriaxone and returned for follow-up were clinically and microbiologically cured. One of 26 returning newborns who received kanamycin plus tetracycline and 2 of 24 returning newborns who received kanamycin plus gentamicin had persistent or recurrent gonococcal conjunctivitis. Ceftriaxone also eradicated oropharyngeal gonococcal infection in 18 newborns, whereas oropharyngeal infection persisted in 2 of 8 newborns who had received kanamycin (P not significant). We conclude that 125 mg of ceftriaxone as a single intramuscular dose is very effective therapy for gonococcal ophthalmia neonatorum, with marked efficacy against extraocular infection and without the need for concomitant topical antimicrobial therapy.