T. Odugbemi

Antibacterial activity of some medicinal plants from Nigeria

Traditional herbalists in Nigeria use a variety of herbal preparations to treat different kinds of ailments, including many microbial infections, such as gonorrhoea, sore throat and diarrhoea. In most cases, the herbal practitioners are ignorant of the pharmacological and toxicological values of their medications. The uneven distribution of health personnel between rural and urban areas has left the rural dwellers with virtually no alternative other than to patronise the herbal practitioners. This has been the case even before the introduction of antibiotics and other modern drugs into Africa. As part of our investigation into the scientific basis of the use of Nigerian plants for medicinal purposes, ten medicinal plants used for the treatment of various microbial infections were studied for their antibacterial activity. It is hoped that this study might lead to the discovery of new compounds that could be used to formulate new and more potent antimicrobial drugs, that might overcome the problem of resistance to the currently available anti-microbial agents.

Extended-Spectrum β-Lactamase Enzymes in Clinical Isolates of Enterobacter Species from Lagos, Nigeria

ABSTRACT Over a 9-month period, 8 of 40 nonduplicate isolates of Enterobacter spp. producing extended-spectrum β-lactamase (ESBL) were detected for the first time from two hospitals in Lagos, Nigeria. Microbiologic and molecular analysis confirmed the presence of ESBL. Only four isolates transferred ESBL resistance as determined by the conjugation test, and pulsed-field gel electrophoresis showed genetically unrelated isolates.

Bacterial flora of burn wounds in Lagos, Nigeria: A prospective study

A prospective study of burn wound sepsis was carried out on 31 consecutive patients with fresh burns. Wound swab cultures were assessed at weekly intervals for 5 weeks. The study revealed that while 96.7 per cent of burn wounds were sterile on admission, bacterial colonization reached 80.6 per cent within the first week after admission. Although the Gram-negative organisms, as a group, were more predominant, Staph. aureus (38.2 per cent) was the most prevalent organism in the first week. It was however surpassed by Pseud. aeruginosa from the second week onwards. Anaerobes were conspicuous by their absence. Similarly, beta-haemolytic streptococcus was not isolated from any patient. Proteus mirabilis was unusually preponderant, forming 19.4 per cent of all isolates. The antibiotic sensitivity pattern showed resistance of most of the organisms to ampicillin. Only 15 per cent of staphylococci were sensitive to cloxacillin. Most of the organisms cultured (93.5 per cent) were sensitive to ceftazidime.

Occurrence of Aeromonas species and Plesiomonas shigelloides in patients with and without diarrhoea in Lagos, Nigeria.

The prevalence of Aeromonas spp. and Plesiomonas shigelloides was determined in patients attending the enteric laboratory of the Department of Medical Microbiology and Parasitology, Lagos University Teaching Hospital, Nigeria. During the 12-month study (October 1986-September 1987), Aeromonas spp. were isolated from 53 (2.26%) of 2350 patients with diarrhoea and only 2 (0.4%) of 500 patients without diarrhoea (p less than 0.01). Similarly, P. shigelloides was isolated from 16 (0.68%) patients with diarrhoea and none of the controls (p greater than 0.05). The seasonality, age and sex distribution of diarrhoea associated with Aeromonas spp. and P. shigelloides in this study were similar to those of diarrhoea associated with other recognised enteropathogens in Nigeria. Both species may play a role in the aetiology of acute diarrhoeal disease in that environment.

Isolation of species of Yersinia from patients with gastroenteritis in Nigeria.

From patients in Nigeria with acute gastroenteritis, strains of Yersinia were isolated from 14 (1.3%) of 1082 specimens of faeces examined specifically for yersiniae by direct plating and after cold enrichment. Clinical significance was ascribed to six isolates of Y. enterocolitica (serotypes 03, 05,27 and 09) but not to seven isolates of Y. intermedia or one isolate of Y. frederikseni.

Bacteriological study of cooked ogi (fermented cereal weaning food) and its potential safety in a rural Nigerian community

Thirty households with children receiving the fermented cereal food ogi were selected randomly from Ajara, a rural community in Lagos State, Nigeria. Eighty-one samples of ogi were collected from these households at the time of administration to the children. The degree of bacteriological contamination and pH values of the cooked ogi samples were determined. The mean pH was 3.6 +/- 0.2. Faecal coliform contamination levels of 3 to > or = 2400/ml were recorded in 26 (31.3%) of the 81 ogi samples. Levels of faecal coliforms increased significantly (P < 0.025) during storage of cooked samples for 9 h. The high contamination rate is unacceptable and is a potential health hazard. Although fermenting food like ogi, resulting in a low pH, may reduce bacterial contamination, hygienic practices during handling and preparation should be emphasized as adjuncts in intervention for control of diarrhoeal disease in developing countries.

Antimicrobial resistance patterns and plasmids of enteropathogenic Escherichia coli isolated in Nigeria

In an epidemiological study of enteropathogenic Escherichia coli, 102 strains were isolated from patients seen at the University Teaching Hospital in Lagos. The most common serotype encountered was 055 followed by 026. Antimicrobial susceptibility testing and plasmid profiling of the strains were done. All the strains were sensitive to colistin, nalidixic acid, nitrofurantoin, cefotaxime, amikacin, and augmentin. Of the 102 strains, 47 (46%) were resistant to one or more of the following antimicrobial agents: Co-trimoxazole, tetracycline, ampicillin, streptomycin, sulphonamide and a combination of ampicillin with sulbactam. All the strains that were resistant to any antimicrobial agents were also resistant to tetracycline. Seventy-two strains (70.6%) harbored plasmid whose molecular weights ranged from 0.8 to 120 × 106 daltons. The majority. of the plasmid were smaller than 6 × 106; 90% of strains carrying plasmid ranging in size from 2 to 6 × 106 daltons and 50 to 70 × 106 daltons were resistant to one or more antimicrobial agents. Trasformation and conjugation experiment showed that about 57% of the resistant strains carried R plasmid. Plasmld-determined resistance to tetracycline, ampicillin, streptomycin and sulphonamide was found.

Emergence of bla CTX-M-15, qnrB1 and aac(6′)-ib-cr resistance genes in Pantoea agglomerans and enterobacter cloacae from Nigeria (sub-Saharan Africa)

Resistance of Enterobacter species to extended-spectrum cephalosporins is known to be mediated by hyperproduction of chromosomal AmpC b-lactamases. However, the additional expression of plasmid-encoded extended-spectrum b-lactamases (ESBLs) has become more prevalent worldwide in recent years (Ko et al., 2008). In Nigeria, ESBL production in Enterobacter species has been associated with TEMand SHV-type ESBLs (Aibinu et al., 2003; Kasap et al., 2010). Other b-lactamase resistance determinants, conferring resistance to extendedspectrum cephalosporins, such as blaVEB, blaOXA and blaCMY, have recently been reported in Nigerian Providencia species strains (Aibinu et al., 2011). In addition, the worldwide spread of CTX-M-15 (Cantón & Coque, 2006) has reached Nigeria, having being identified in Klebsiella species and Escherichia coli (Soge et al., 2006; Olowe et al., 2010). There is no documented report yet on ESBL production mediated by blaCTX-M-15 or the association of the spread of PMQR determinants in Enterobacter species from Nigeria. This study reports the phenotypic and genotypic characteristics of ten clinical isolates of Enterobacter species and one isolate of Pantoea agglomerans with respect to the occurrence of blaCTX-M and other resistance genes. The Enterobacter species, which consisted of Enterobacter asburiae (n51), Enterobacter aerogenes (n51) and Enterobacter cloacae (n58), and the Pantoea agglomerans isolate represented 9.5 % of all members of the Enterobacteriaceae isolated within a period of 6 months from October 2008 to March 2009 at Lagos University Teaching Hospital (LUTH), a tertiary hospital, in Nigeria. Enterobacter agglomerans was previously renamed Pantoea agglomerans to reflect its genetic distance from the genus Enterobacter (Sanders & Sanders, 1997).

Emergence of β-lactamases OXA-10, VEB-1 and CMY in Providencia spp. from Nigeria

Sir, Resistance to cephalosporins of the third and fourth generations in Enterobacteriaceae is an increasing problem worldwide. This resistance is mainly attributed to the production of extended-spectrum b-lactamases (ESBLs). In Nigeria SHV-, TEMand CTX-M-type ESBLs have been reported in Enterobacter spp., Klebsiella spp. and Escherichia coli. Besides these classical ESBLs, there are various other plasmid-mediated b-lactamases that are less common but which are regarded as emerging and increasing in frequency among the b-lactamase family. Here we report the emergence of OXA-10, VEB-1 and CMYb-lactamases and mobile genetic elements in three clinical isolates of Providencia spp. isolated between October 2008 and April 2009 in two tertiary hospitals in Nigeria. Three strains of Providencia spp. were identified using the VITEK 2 GN card system following cultivation of clinical samples on MacConkey agar and blood agar base with 5% sheep blood (Oxoid, UK). Isolate Providencia rettgeri 58K was recovered in late 2008 from the catheter tip of a patient hospitalized at Lagos University Teaching Hospital (LUTH) in Lagos, Nigeria. The patient was notably hypertensive and was diagnosed with an exacerbation of chronic kidney disease, secondary to adult polycystic kidney disease. He had been catheterized for 19 days, with insertion of the catheter from the private hospital where he was hospitalized before his referral to LUTH. The patient was not febrile at any time and there was no infection documented. Isolate Providencia stuartii V1 was recovered from the gunshot wound of a patient admitted to the National Orthopaedic Hospital Igbobi (NOHI), Lagos, in early 2009, while isolate P. stuartii V2 was also recovered at NOHI from the wound swab of a patient who had had a motorcycle accident. The three patients had not received antibiotics prior to the isolation of the strains. The three clinical strains of Providencia spp. were multiply resistant to different b-lactams, fluoroquinolones and aminoglycosides but remained susceptible to carbapenems using the VITEK 2 GN card system (Table 1). ESBL and AmpC production was confirmed using the double disc synergy tests (ESbL/AmpC test D68C; Mast Diagnostica GmbH, Reinfeld, Germany) and ESBL-Etest strips (bioMerieux, Nurtingen, Germany). By PCR and sequence analysis, b-lactamase genes blaCMY-4, blaTEM-1, blaVEB-1 and blaOXA-10 were identified in isolate P. rettgeri 58K. Isolate P. stuartii V2 harboured blaCMY-41 and blaTEM-52, while ESBL genes blaVEB-1 and blaOXA-10 were found in isolate P. stuartii V1. The blaVEB-1 genes were located on sul-type class 1 integrons and ISCR2 mobile elements. The blaOXA-10 genes were also encoded on class 1 integrons. Furthermore, the plasmid-mediated quinolone resistance gene qnrA1 was found in all three clinical isolates (Table 1). Transfer of all b-lactamase genes and gene qnrA1 was successfully performed for the clinical isolates P. rettgeri 58K and P. stuartii V1 using broth mating assays with a sodium azide-resistant E. coli J53 recipient. In order to ascertain the potential transfer and acquisition of b-lactamase genes or resistant strains via the food chain, we investigated resistance determinants of Providencia spp. from faecal samples of apparently healthy farm animals. Farm animals serve as major sources of meat products for the population of Lagos. Between October 2008 and April 2009 we recovered 97 Enterobacteriaceae isolates from 115 faecal samples of different animals from three local farms. Using the VITEK 2 GN card system we identified seven Providencia spp. recovered from chickens (n1⁄46) and pigs (n1⁄41). Typing of human and animal Providencia spp. isolates by enterobacterial repetitive intergenic consensus PCR revealed different patterns, indicating no clonal relationship of these isolates. In contrast to the clinical strains, all animal isolates were susceptible to most of the antibiotics and none produced b-lactamases (Table 1). The variable regions of class 1 integrons in clinical and animal strains harboured the classic qacED-sul1 region and dfrA genes (dfrA1, dfrA14 and dfrA15). The class 2 integron was additionally found in two isolates from chickens. Furthermore, the sequence of one P. rettgeri isolate from a chicken (156K) showed 99% identity with the integrating conjugative element ICEPalban1 described in a Providencia alcalifaciens isolate from the USA (GenBank accession no. GQ463139). The absence of b-lactamase genes and quinolone resistance genes in the animal isolates suggested no correlation of horizontal transfer of these resistance genes between animal and human Providencia spp. strains. However, simultaneous occurrence of class 1 and 2 integrons in two isolates from chickens highlighted a possible variety of recombinatorial events among these genetic platforms according to Machado et al. This study presents the first report of Providencia spp. producing CMY-type and OXA-10 b-lactamases. To our knowledge, the only known documentation of a blaCMY gene in Providencia spp. is the submission of a blaCMY-16 gene sequence from a P. stuartii isolate from Tunisia (GenBank accession no. FJ855437.1). Horizontal gene transfer has played a major role in the global spread of b-lactamases and Qnr determinants into various Gram-negative species. Furthermore, this is the first report of ICEPalban1 in a P. rettgeri animal isolate. Though we only found a small number of Providencia spp. isolates, our data suggest that further population-based prevalence studies are needed in order to monitor the ability of clinical Providencia spp. to be a reservoir of different resistance genes. The nucleotide sequences of some of the resistance genes in this study have been deposited in the GenBank nucleotide sequence database under accession numbers GU056840, GU056841, GU056843 and GU056844. Research letters

The effects of iron chelators on the colonial morphology of Neisseria gonorrhoeae.

There has recently been considerable interest in the role of iron in microbial pathogenicity. Bullen, Rogers & Griffiths (1974) have reviewed the importance of iron compounds in enhancing the virulence of many bacteria. However, the gonococcus was not amongst those mentioned. Kellogg et al. (1963) showed that adding iron to medium improved the growth of gonococci. They also described four characteristic colonial types of gonococci which they were able to relate to infectivity for volunteers. Thus types I and 2 were virulent and types 3 and 4 non-virulent. Jephcott & Reyn (1971) confirmed these observations and added a further colonial type which they called type 5 and regarded as non-pathogenic. Payne & Finkelstein (1975) showed that iron compounds added to inocula of the relatively avirulent colonial types 3 and 4 increased their lethality for chick embryos on intravenous inoculation. They did not attribute the increased lethality in the presence of iron to a reversion to pathogenic colonial types but considered the effect to be host mediated. Hafiz, McEntegart & Jephcott (1977) found that a high concentration of iron, in the form of ferric citrate incorporated into liquid media, caused reversion of nonpathogenic type 4 colonies of gonococci (previously thought to be very stable and irreversible in vitro) to pathogenic type I. Iron, though an important component of the media in which the reversion was studied, could not be considered in isolation without looking at the possible effects of the other components, especially citrate which is known to chelate iron. Cole (1952) reported that metal chelators added to culture media suppressed colonial variation of smooth, pathogenic Brucella abortus to the rough non-pathogenic variant. The effects of iron chelators on the colonial morphology of the gonococcus have not to our knowledge been reported before. This study was undertaken to determine the role of iron and the possible effects of iron chelators on the colonial morphology of the gonococcus.