Bioactive Molecules from Sea Hares

Sea hares, belonging to the order Opisthobranchia, subclass Gastropoda, are mollusks that have attracted many researchers who are interested in the chemical defense mechanisms of these soft and "shell-less" snails. Numbers of small molecules of dietary origin have been isolated from sea hares and some have ecologically relevant activities, such as fish deterrent activity or toxicity. Recently, however, greater attention has been paid to biomedically interesting sea hare isolates such as dolastatins, a series of antitumor peptide/macrolides isolated from Dolabella auricularia. Another series of bioactive peptide/macrolides, as represented by aplyronines, have been isolated from sea hares in Japanese waters. Although earlier studies indicated the potent antitumor activity of aplyronines, their clinical development has never been conducted because of the minute amount of compound available from the natural source. Recent synthetic studies, however, have made it possible to prepare these compounds and analogs for a structure-activity relationship study, and started to uncover their unique action mechanism towards their putative targets, microfilaments. Here, recent findings of small antitumor molecules isolated from Japanese sea hares are reviewed. Sea hares are also known to produce cytotoxic and antimicrobial proteins. In contrast to the small molecules of dietary origin, proteins are the genetic products of sea hares and they are likely to have some primary physiological functions in addition to ecological roles in the sea hare. Based on the biochemical properties and phylogenetic analysis of these proteins, we propose that they belong to one family of molecule, the "Aplysianin A family," although their molecular weights are apparently divided into two groups. Interestingly, the active principles in Aplysia species and Dolabella auricularia were shown to be L-amino acid oxidase (LAAO), a flavin enzyme that oxidizes an alpha-amino group of the substrate with molecular oxygen and liberates hydrogen peroxide, with a sequence similar to other known LAAOs, including snake venom. Possible antibacterial activity and cytotoxic activity mechanisms of these proteins are also discussed.

Toxoplasma gondii Does Not Persist In Goldfish (Carassius auratus)

Recent reports of toxoplasmosis in marine mammals raise concern that cold-blooded marine animals are a potential source of Toxoplasma gondii infection. To examine the transmissibility of T. gondii to fish, we observed the development of T. gondii tachyzoites inoculated into oviduct epithelial cells of goldfish (Carassius auratus) microscopically in vitro. Further, the survival period of tachyzoites inoculated into goldfish muscle was bioassayed in mice and through PCR analysis. In cell cultures at 37 C, both RH and Beverley strains of T. gondii tachyzoites had penetrated into cells at 6 hr post inoculation, and were multiplying. In cell cultures at 33 C, many tachyzoites of both strains attached to the host cells, but no intracellular tachyzoites were observed at 24 hr post inoculation. In the T. gondii inoculated goldfish kept at 33 C, tachyzoite DNA was detected in the inoculated region on day 3, but not on day 7. When inoculated goldfish were kept at 37 C, live tachyzoites were seen at the inoculation site on day 3, but not on day 7. These results suggest that T. gondii does not persist in fish.

Human proinsulin C-peptide prevents proliferation of rat aortic smooth muscle cells cultured in high-glucose conditions

AIMS/HYPOTHESIS

Proinsulin C-peptide is involved in several biological activities. However, the role of C-peptide in vascular smooth muscle cells is unclear. We therefore investigated its effects, in vascular smooth muscle cells in high-glucose conditions.

METHODS

Rat aortic smooth muscle cells were cultured with 5.5 or 20 mmol/l glucose with or without C-peptide (1 to 100 nmol/l) for 3 weeks. Proliferation activities, the protein expression of platelet-derived growth factor (PDGF)-beta receptor, the phosphorylation of p42/p44 mitogen-activated protein (MAP) kinases, and glucose uptake were measured.

RESULTS

The proliferation activities increased approximately three-fold under high-glucose conditions (p<0.05). C-peptide suppressed hyperproliferation activities that were induced by high glucose. This happened in a dose-dependent manner from 1 to 100 nmol/l of C-peptide. C-peptide (10 and 100 nmol/l) inhibited the increased protein expression of PDGF-beta receptor and the phosphorylation of p42/p44 MAP kinases that had been induced by high glucose (p<0.05). Furthermore, 100 nmol/l of C-peptide augmented the impaired glucose uptake in the high-glucose conditions.

CONCLUSIONS/INTERPRETATION

These observations suggest that C-peptide could prevent diabetic macroangiopathy by inhibiting smooth muscle cell growth and ameliorating glucose utilisation in smooth muscle cells. C-peptide may thus be a novel agent for treating diabetic macroangiopathy in patients with type 1 and type 2 diabetes.

Morphological differences in cardiovascular anomalies induced by bis-diamine between Sprague-Dawley and Wistar rats

It is known that animals show different responses to the same teratogen between different strains. We examined cardiac malformations in Sprague-Dawley (SD) and Wistar rats induced by bis-diamine, which produced conotruncal anomalies and aortic arch malformations in embryos when administered to the dams, to elucidate the morphological differences and pathogenesis in the two strains. Two hundred milligrams of bis-diamine dissolved in 1% gum-tragacanth was administered to pregnant rats on embryonic day (ED) 9.5, 10.5 and 11.5 in each strain. The embryos were removed on ED 20.5. External appearances, cardiovascular morphology and associated anomalies were examined under a dissecting microscope. An immunohistological study with an anti-N-CAM antibody, an excellent marker for neural crest cells, was performed on ED 12.5 embryos. Isolated aortic arch anomalies were common features of malformations induced by bis-diamine in SD rats and intracardiac defects were found in a small number of the embryos. Wistar rats showed more serious cardiovascular anomalies, such as persistent truncus arteriosus and tetralogy of Fallot, especially when dams were treated on ED 10.5 and isolated arch anomalies were significantly less prevalent than in SD rats. Immunohistology demonstrated that there were fewer N-CAM positive cells in the conotruncal region in Wistar rats than in SD rats. Bis-diamine induced more critical cardiovascular malformations in Wistar rats because neural crest cells, which play an important role in conotruncal septation, were more extensively damaged. Different susceptibility to bis-diamine and/or different time of neural crest cell emigration from the hindbrain might explain those morphological differences.

Characterization of SSU and LSU rRNA genes of three Trypanosoma (Herpetosoma) grosi isolates maintained in Mongolian jirds

Trypanosoma (Herpetosoma) grosi, which naturally parasitizes Apodemus spp., can experimentally infect Mongolian jirds (Meriones unguiculatus). Three isolates from A. agrarius, A. peninsulae, and A. speciosus (named SESUJI, HANTO, and AKHA isolates, respectively) of different geographical origin (AKHA from Japan, and the others from Vladivostok), exhibited different durations of parasitaemia in laboratory jirds (2 weeks for HANTO, and 3 weeks for the others). To assess the genetic background of these T. grosi isolates, their small (SSU) and large subunit (LSU) ribosomal RNA genes (rDNA) were sequenced along with those of 2 other Herpetosoma species from squirrels. The SSU rDNA sequences of these 3 species along with available sequences of 3 other Herpetosoma trypanosomes (T. lewisi, T. musculi and T. microti) seemed to reflect well the phylogenetic relationship of their hosts. Three isolates of T. grosi exhibited base changes at 2-6 positions of 2019-base 18S rDNA, at 5-29 positions of 1817/1818-base 28Salpha rDNA, or 1-5 positions of 1557-1559-base 28Sbeta rDNA, and none was separated from the other 2 isolates by rDNA nucleotide sequences. Since base changes of Herpetosoma trypanosomes at the level of inter- and intra-species might occur frequently in specified rDNA regions, the molecular analysis on these regions of rodent trypanosomes could help species/strain differentiation and systematic revision of Herpetosoma trypanosome species, which must be more abundant than presently known.

T cell-dependent elimination of dividing Trypanosoma grosi from the bloodstream of Mongolian jirds

Mongolian jirds, Meriones unguiculatus, are susceptible to infection with Trypanosoma grosi, which naturally parasitizes Apodemus spp. The present study investigated T cell dependence of elimination of T. grosi from the bloodstream of jirds by in vivo T cell depletion using a monoclonal antibody (HUSM-M.g.15). In T cell-depleted jirds, elimination of T. grosi, particularly the dividing forms, from the bloodstream was significantly delayed, occurring at around week 3 p.i. The kinetics of serum levels of IgM and IgG specific to trypanosomes in T cell-depleted and control immunocompetent jirds were different; peak levels of IgM were noted on days 6-8 p.i. around the time of peak parasitaemia (day 6 p.i.) in immunocompetent jirds, whereas the serum levels began to increase abruptly after day 10 p.i., peaking at around day 18 p.i. in T cell-depleted jirds. Similarly, serum IgG increased after day 6 p.i. in immunocompetent jirds, in contrast to after day 12 p.i. in T cell-depleted jirds, and the level increased steadily even after disappearance of parasitaemia. Our findings indicate that T cells play a major role at least in the 'first crisis' during elimination of dividing T. grosi from the bloodstream.

Mechanism of improved gene transfer by the N-terminal stearylation of octaarginine: enhanced cellular association by hydrophobic core formation

The internalization mechanisms associated with octaarginine and stearyl-octaarginine were investigated using confocal laser microscopy and flow cytometric analysis. Octaarginine is able to translocate through cell membranes in a manner that does not exactly involve the classical endocytic pathways of internalization. However, when a stearyl moiety is attached to the N-terminus of octaarginine, the internalization shifts mainly to an endocytosis-dependent pathway. The transfection efficiency of stearyl-octaarginine was significantly higher than that of octaarginin. To understand the mechanism of the improved gene transfer by the N-terminal stearylation of octaarginine, the gene transfer processes mediated by octaarginine or stearyl-octaarginine were compared. Both octaarginine and stearyl-octaarginine are able to carry plasmid DNA into cells. The amount of plasmid DNA internalized as well as that delivered to the nucleus was higher in the case of stearyl-octaarginine. Even though the internalization mechanisms of octaarginine and stearyl-octaarginine were different, their complexes with plasmid DNA were internalized via the same pathway, presumably, the clathrin-mediated pathway of endocytosis. The results of the atomic force microscopy revealed that stearyl-octaarginine, but not octaarginine, can completely condense the DNA into stable complexes that can be highly adsorbed to the cell surface and subsequently highly internalized. Therefore, using stearylated-octaarginine provided higher internalization of plasmid DNA into cells, due to enhanced cellular association, as well as higher nuclear delivery. The results presented in this study provide a better understanding of the mechanisms of improved transfection using stearylated-octaarginine. The concept of using stearylated peptides may aid in the development of more efficient nonviral gene vectors.

Detection of nonmelanoma skin cancer micrometastases in lymph nodes by using reverse transcriptase-polymerase chain reaction for keratin 19 mRNA

BACKGROUND

A new sensitive method for the detection of skin cancer micrometastases in lymph nodes is based on amplification of keratin 19 (K19) mRNA by reverse transcriptase-polymerase chain reaction (RT-PCR).

OBJECTIVES

To compare results of RT-PCR with those of histological examination in terms of the detection rate of skin cancer micrometastases.

METHODS

Twenty-six lymph nodes obtained from 13 patients with squamous cell carcinoma (SCC), eccrine porocarcinoma and Paget's disease were investigated by histological examination (haematoxylin and eosin sections) and RT-PCR. RT-PCR was performed on extracted RNA by using K19 primer pairs. RT-PCR products were visualized by ethidium bromide staining and confirmed by non-radioactive hybridization with K19-specific probes.

RESULTS

All of 10 histologically positive lymph nodes yielded the expected 460-bp band. Of the 16 histologically negative lymph nodes, one (6%) was found by RT-PCR to express K19 mRNA, indicating the presence of micrometastases which could not be detected by histological examination. A serial dilution study using RNA extracted from SCC cells mixed with RNA extracted from normal lymph node cells showed a detection sensitivity of K19 RT-PCR of 10-5 micro g cancer cell RNA in 1 micro g lymph node RNA. Nested RT-PCR showed a detection sensitivity of one tumour cell in 106 lymphocytes.

CONCLUSIONS

These results demonstrate the usefulness of K19 RT-PCR for the detection of skin cancer micrometastases in lymph nodes.

Persistent infection of Mongolian jirds with a non-pathogenic trypanosome,Trypanosoma (Herpetosoma) grosi

Non-pathogenic trypanosomes of the subgenusHerpetosomaare normally host specific, and laboratory models includeTrypanosoma lewisiin rats andTrypanosoma musculiin mice. Two isolates ofTrypanosoma grosi, originating fromApodemus agrariusandApodemus peninsulae, grew well in Mongolian jirds,Meriones unguiculatus, after intraperitoneal inoculation of 2×105or a minimum 500 bloodstream forms. The course ofT. grosiinfection in jirds resembledT. musculiinfection in mice, rather thanT. lewisiinfection in rats. At week 2 to 3 p.i. trypanosomes disappeared from the bloodstream, and neither prednisolone treatment nor splenectomy prevented parasite elimination from the bloodstream. However, these treatments induced a marked increase in peak parasite counts. Regardless of prednisolone treatment or splenectomy, all jirds after day 21 p.i. became resistant to the reinfection. Although no trypanosomes were detected in the bloodstream of recovered jirds, dividing parasites persisted in the medullary capillaries of the kidney, likeT. musculiinfection in mice. We propose theT. grosiinfection in jirds as an additional laboratory model for the study of non-pathogenic trypanosomes.

Mutagenicity of 5-formyluracil in mammalian cells

5-Formyluracil, a major oxidized form of thymine, was incorporated into a predetermined site of one of the leading and lagging template strands of a double-stranded vector, and the DNA replication efficiency and the mutation frequency of 5-formyluracil in simian COS-7 cells were investigated. 5-Formyluracil did not block DNA replication and was weakly mutagenic in simian cells. 5-Formyluracil primarily elicited base substitutions at the modified positions.

Mutations induced by glyoxal and methylglyoxal in mammalian cells

To investigate the mutation spectra of glyoxal and methylglyoxal in mammalian cells, we analyzed mutations in a bacterial suppressor tRNA (supF) gene in the shuttle vector plasmid pMY189. The cytotoxicity and the mutation frequency increased according to the doses of glyoxal and methylglyoxal. The majority of glyoxal-induced mutations (65%) were base-pair substitutions, in which G:C-->C:G transversions were predominant. In the mutants induced by methylglyoxal, multi-base deletions were predominant (50%), followed by base-pair substitutions (35%), in which G:C-->C:G and G:C-->T:A transversions were predominant.

Monoclonal IgA antibody-mediated expulsion of Trichinella from the intestine of mice

To assess the potential role of IgA antibody in expulsion of the nematode of the genus Trichinella from the intestine, a panel of IgA monoclonal antibodies (mAbs) were produced from the mesenteric lymph node cells from BALB/c mice orally vaccinated with irradiated muscle larvae of Trichinella britovi. One IgA mAb, HUSM-Tb1, formed immunoprecipitates on the surface of live muscle larvae, and by immunohistochemistry reacted with their stichocytes and cuticular surface, but not with those tissues of the adult stage or newborn larvae. Intraperitoneal injection of BALB/c mice with this mAb 5 h before challenge conferred a high level of protection (more than 95%) against T. britovi infection, when 2.0 mg of specific IgA/20 g body weight was given to a mouse. The same treatment produced a similar effect in SCID mice lacking functional T- and B-cells, indicating no requirement of synergistc T-cell factors for the effect. Passive transfer of the mAb at the time of challenge or later showed less or no effect upon worm expulsion. It is concluded that the mucosal IgA response, when adequately induced, can impede the establishment of infective Trichinella parasites in the mouse intestine.

Size and topology of exogenous DNA as determinant factors of transgene transcription in mammalian cells

We prepared a series of linearized DNA duplexes of various lengths in order to examine the effects of topology and the size of exogenous, plasmid-derived DNAs on transgene expression. These linearized DNA duplexes were capped at each end with a highly stable loop (5'-GCGAAGC-3') to produce a dumbbell-shaped construct that is refractory to exonuclease digestion in comparison to the analogous uncapped DNA duplexes. Intranuclear microinjection of the DNA dumbbells into simian COS-7 cells allowed the expression of the green fluorescent protein (GFP) gene on the linearized molecules, which was expressed five- to 10-fold more than that on the circular DNA of the same size. In addition, the expression by the dumbbell DNA was higher than that by the circular plasmid for at least 14 days. Interestingly, the size of the dumbbell DNA affected the transgene expression upon their microinjection into cell nuclei. The GFP expression efficiency increased with decreasing DNA size below a DNA size of 5.7 kb. The effects of topology and size on the expression of DNAs transfected with cationic lipids are similar to those of DNAs microinjected into cell nuclei. In contrast, microinjection into the cytosol showed the inverse size dependency over a range of 2.3 to 9.4 kb. Thus, transcription of a transgene in the nucleus, but not endocytosis or nuclear entry, was influenced by the exogenous DNA structure, and this was the primary determinant of transgene expression upon transfection under our conditions. These results indicate that small, linearized DNA duplexes that are end-capped with a highly stable loop (dumbbell-shaped DNA) would be very useful for nonviral gene therapy.

Immunohistochemical localization of rhamnose-binding lectins in the steelhead trout (Oncorhynchus mykiss)

The localization of three -rhamnose-binding lectins named STL1, STL2, and STL3 from eggs of steelhead trout (Oncorhynchus mykiss) was analyzed by indirect immunohistochemical staining with specific antisera against individual lectins. In early previtellogenic oocyte, STL1 was localized not only in the cortical vesicles, but also in the plasma membrane and germinal vesicle. On the other hand, STL2 and STL3 were localized only in the cortical vesicles. In pre-fertilization mature egg, STLs were localized in a thin layer of cortical granules at the cytoplasmic side of the plasma membrane. STLs were accumulated on the surface of cytoplasm and inner membrane 30 min after fertilization. The strong staining with anti-STL1 antiserum was observed in several tissues and cells of the steelhead trout, such as spleen, thrombocytes, and blood leukocytes, but not erythrocytes. STL1 was also identified in exocrine cells, such as goblet cells of intestine and mucous cells of gill. These results indicate that the multiple lectins found in eggs of the steelhead trout play physiological roles not only in eggs, but also in various cells related to the innate immunity.

Airway epithelial cells promote transmigration of eosinophils in a new three-dimensional chemotaxis model

BACKGROUND

Prominent infiltration of eosinophils in airway mucosa is the pathognomonic sign of asthma. The role of airway epithelial cells in eosinophil infiltration, however, has not been fully elucidated.

OBJECTIVE

The aim of this study is to develop a new in vitro transmigration system composed of airway epithelial cells and extracellular matrix, and to investigate the role of airway epithelial cells in eosinophil infiltration.

METHODS

A layer of type I collagen gel was formed in Netwell, and BEAS-2B bronchial epithelial cells were cultured on the gel. Then the wells covered with epithelial monolayer were filled with medium, inverted, and new upper chambers were constructed on the gel side by applying a ring cap. After further incubation with or without exogenous cytokines for 48 h, eosinophils or neutrophils were loaded in upper chambers (the gel side) and cells transmigrated to lower chambers (the epithelial cell side) were counted. Immunohistochemical analyses were also performed.

RESULTS

While a simple collagen gel hardly promoted eosinophil migration even in the presence of eotaxin or RANTES, significant numbers of eosinophils migrated to lower chambers in the presence of the epithelial cells. Replacement of medium in the lower chamber (the epithelial cell side) with fresh medium, addition of exogenous eotaxin or RANTES in the upper chamber (the gel side), or pre-treatment of eosinophils with anti-CCR3 all inhibited transmigration. We found that the epithelial cells produced and deposited extracellular matrix proteins such as type IV collagen onto the type I collagen gel. Separately, we found that type IV collagen itself was capable of enhancing eotaxin-induced eosinophil migration in a standard chemotaxis assay. Neutrophils also efficiently migrated in the present transmigration system. Pre-treatment of epithelial cells with TNF-alpha and IL-4 enhanced eosinophil transmigration, while that of neutrophils was enhanced by TNF-alpha but suppressed by IL-4.

CONCLUSION

By utilizing a new in vitro transmigration system mimicking the airway mucosa, we have demonstrated that airway epithelial cells play an essential role in transmigration of eosinophils and that multiple factors such as chemokines, extracellular matrix proteins and exogenous inflammatory cytokines are involved in efficient transmigration.

A 12-year follow-up study of treated obese children in Japan

OBJECTIVE

To assess tracking for body weight from childhood to adulthood in obese Japanese children who were treated for obesity, investigate the relation between the changes in body weight status and morbidity, and identify correlates of the changes in body weight status.

STUDY DESIGN

Twelve-year retrospective cohort study.

SUBJECTS

A sample of 276 subjects (age 23.9+/-4.1, 176 males and 100 females) who responded to a questionnaire mailed in 1998 to 1047 children (age 10.6+/-2.2) treated for obesity at Mie National Hospital in Japan between 1976 and 1992.

MEASUREMENTS

Based on height and weight from medical records during childhood, the relative weight (RW; weight expressed as a percentage of the standard body weight for age, height, and sex) was calculated. Degrees of childhood obesity were based on RW: slight obesity (120% < or = RW<130%; n=17), moderate obesity (130% < or = RW <150%; n=131), and severe obesity (RW > or = 150%; n=128). Adult body mass index (BMI), which was obtained from the mailed questionnaires, was classified as normal, overweight and obese according to the WHO/NIH criteria. Body weight tracking by degree of obesity was evaluated. Subjects with severe obesity during childhood (n=128) were examined for their weight status in adulthood, prevalence of chronic diseases in adulthood, and factors such as parental obesity, dietary and exercise habits and obesity treatment during childhood.

RESULTS

Childhood obesity tracked into adulthood obesity or overweight in 54.7% of all cases. Severely obese children (36.7%) were more likely to be obese as an adult than moderately obese children (16.8%). The prevalence of adult obesity tended to be greater in boys with moderate childhood obesity than in girls (29.7% in boys vs 14.9% in girls, P=0.058). Among the severely obese children who became normal-weight adults, the prevalence of chronic diseases was about one-fifth of those who remained obese in adulthood (P=0.041). Four factors were associated with changes in body weight status: maternal BMI at entry (P=0.044), the changes in dietary and exercise habits after treatment (P=0.014, P=0.030, respectively), and satisfaction with obesity treatment in childhood (P=0.035).

CONCLUSIONS

Severely obese children have a higher risk of becoming obese adults even when they received obesity treatment in childhood. The risk of adulthood obesity was twice as high in moderately obese boys than in girls. On the other hand, many cases of childhood obesity can be corrected with obesity treatment, which in turn can decrease the risk for adult chronic diseases.

Schistosoma mansoni: kinetics of glomerulonephritis in Mongolian gerbils and its correlation with intensity and duration of infection

The frequent occurrence of glomerular lesions in schistosomiasis patients has been reported, although appropriate animal models for the study of schistosomal glomerulonephritis have not been developed. To analyze the relationship between glomerulonephritis and Schistosoma mansoni infection, gerbils, Meriones unguiculatus, were infected with different number of cercariae and sacrificed at different weeks of post infection. Fifty cercariae were the optimum dose to produce the disease, glomerulonephritis, without early death of the animal. Infected gerbils showed heterogeneous types of glomerular lesions with increased serum creatinine level. Immune complex deposition was not detected at glomeruli of infected gerbils even by means of immunuofluorescence and also by transmission electron microscopy. However, infiltration of mononuclear cells in and around some of the altered glomeruli was observed. Immunohistochemical staining, using monoclonal antibody (HUSM-M.g. 15) specific to gerbil's T-cells, revealed significant infiltration of T-cells. These findings suggest that T-cells might be involved in the development of glomerulonephritis. Gerbil could be a useful model to clarify the role of T-cells in the development of glomerulonephritis of schistosomiasis.

Mycoplasma pneumoniae in children with pneumonia at Mbagathi District Hospital, Nairobi

OBJECTIVE

To determine the prevalence of mycoplasma pneumoniae in nasopharyngeal aspirates of children under five years of age suffering from pneumonia.

DESIGN

Cross-sectional survey.

METHODS

Two primer sets targeting the genes coding for adhesion protein and 16S rRNA were used in PCR and M. pneumoniae specific antibodies were detected using commercial article agglutination kit. Microbiological investigations to isolate common acute respiratory infectious pathogens were also carried out.

RESULTS

M. pneumoniae was detected in nasopharyngeal aspirates of 33.7% of the cases by PCR while serology was positive in only 4.1%. M. pneumoniae alone (single detection) was detected in 25% of the cases while 75% occurred with other acute respiratory infectious (ARI) pathogens. However, the results did not correlate with clinical outcome or the severity of pneumonia. No significant aetiology was found in 28% of the cases investigated, however microbiological investigations by culture revealed the presence of other aetiological agents as follows: Streptococcus pneumoniae (26%), Klebsiella pneumoniae (1%), Staphylococcus aureus (3%), E. coli (2%), parainfluenza viruses (5%), Salmonella(1%), adenovirus (4%), RSV (22%) and Candida spp(13%), Mycoplasma pneumoniae was more prevalent in children aged between six months and three years. Cases of M. pneumoniae PCR positive and S. pneumoniae exhibited similar seasonal distribution with peaks in May and September. However, there was no relationship between M. pneumoniae PCR positive and the severity of pneumonia.

CONCLUSION

More investigation is required to establish the significance of atypical pathogens in respiratory infections in Kenya.