A Study of Respiratory Syncytial Virus Outbreak at Postpartum Care Center in Busan, Korea

Respiratory syncytial virus (RSV) is common cause of acute respiratory infection in infants and young children. Group life in postpartum care centers is easily exposed to infectious diseases in neonates and puerperds immediately after giving birth, and the harm caused by exposure to them is much greater. In particular, respiratory diseases are highly infectious and infections occur in a short period of time. among them, RSV infections are very serious in children under 5 years of age, leading to death. This paper studied an infection of RSV in outbreaks at postpartum care center in Busan. In 4 postpartum care centers, a total of 877 people (390 neonates, 386 puerperds, 106 others) were exposed to RSV outbreak. Of these, there were 73 RSV-positive patients; most of them had cough and runny nose and no fever. We were collected from neonates and puerperds with acute respiratory tract a total of 146 samples (throat swabs). In 51 samples, RSV (43 cases), human rhinovirus (6 cases), human coronavirus NL63 (1 case), and human coronavirus 229E (1 case) were found to be positive and the rest were negative. All 43 RSV positive samples were identified as RSV B. Sequence analysis of the detected strains was performed to confirm the molecular genetic information of RSV. Out of 43 RSV positive samples, 38 samples were successfully sequenced using the G gene, resulting in all of the same genotype BA9. This study provides a better understanding of RSV prevalence patterns and genetic characteristics. It also contributes to the accumulation of epidemiological data and the development of public health and hygiene.

Distribution and Characterization of Airborne Respiratory Pathogens in Public Facilities

Respiratory infections, which are caused by airborne pathogens, are the most common disease of all ages worldwide. This study was conducted to characterize the airborne respiratory pathogens in the public facilities in Busan, South Korea. A total of 260 public facilities were investigated in 2017, 52 seasonal indoor air from 2 hospitals and 208 indoor air samples from 208 randomly selected daycare centers. Among respiratory pathogen, 8 viral pathogens including human adenovirus (HAdV), human bocavirus (HBoV), human rhinovirus (HRV), human parainfluenza virus (HPIV), human respiratory syncytial virus (HRSV), human metapneumovirus (HMPV), human coronavirus (HCoV) and influenza virus (IFV), and 3 bacterial pathogens including Mycoplasma pneumoniae, Bordetella pertussis, and Chlamydophila pneumoniae, were investigated by multiplex real-time reverse transcription polymerase chain reaction. Pathogens were detected in 9 cases (3.4%). Among 9 positive samples, 6 (2.3%) cases were positive for HBoV and 3 (1.2%) cases were positive for IFV. All the positive cases were detected in daycare centers. Additionally, the concentration of HBoV was determined. In HBoV-positive samples, the cycle threshold (Ct) values of HBoV were 29.73~36.84, which are corresponding to the viral concentration of 4.91 × 10⁰ ~ 9.57 × 10² copies/ml. Serotype distribution of isolated HBoV was analyzed by sequencing of VP1/VP2 gene. All of the HBoV isolates were identified as HBoV type 1 with a high similarity among the isolates (>97%). No bacterial pathogen was identified in indoor air samples. Although virus concentration was not high in public facilities (daycare center), the presence of respiratory viral pathogens has been identified. Effective ventilation and air purification strategies are needed to reduce the indoor concentration of respiratory pathogens. A long-term and ongoing surveillance plan for respiratory pathogen management should be established.

Study on Causes of Respiratory Disease to the Middle East Respiratory Syndrome-negative Subjects

Middle East respiratory syndrome coronavirus (MERS-CoV) causes severe cases of human respiratory disease. The current outbreak of infection with this virus in South Korea, which began on May 20, 2015, has infected 186 patients and caused 36 deaths within 2 months. In this study, to investigate the viral pathogen causing acute respiratory infections, multiplex/RT-PCR was performed on were obtained from nucleic acid of the Middle East Respiratory Syndrome-negative subjects. Viruses and atypical bacteria were detected in 39 of 337 (11.6%). Frequent viruses were human rhinovirus (n=11, 3.3%), human metapneumovirus (n=9, 2.7%), parainfluenza (n=9, 2.7%) and adenovirus (n=4, 1.2%). Mycoplasma pneumonia (M. pneumonia) was detected in 1.8 % (n=6). Out of 9 human metapneumovirus (hMPV) positive samples, 6 samples were successfully sequenced using F gene. And M. pneumoniae was sequencing of a repetitive region of the P1 gene. Phylogenetic analysis revealed that hMPV clustered into A2b lineage (n=4), B2 lineage (n=2) and M. pneumoniae clustered into two genotypes: Type 1 (n=4), Type 2a (n=2).

Study on Causes of Respiratory Disease to the Middle East Respiratory Syndrome-negative Subjects

Middle East respiratory syndrome coronavirus (MERS-CoV) causes severe cases of human respiratory disease. The current outbreak of infection with this virus in South Korea, which began on May 20, 2015, has infected 186 patients and caused 36 deaths within 2 months. In this study, to investigate the viral pathogen causing acute respiratory infections, multiplex/RT-PCR was performed on were obtained from nucleic acid of the Middle East Respiratory Syndrome-negative subjects. Viruses and atypical bacteria were detected in 39 of 337 (11.6%). Frequent viruses were human rhinovirus (n=11, 3.3%), human metapneumovirus (n=9, 2.7%), parainfluenza (n=9, 2.7%) and adenovirus (n=4, 1.2%). Mycoplasma pneumonia (M. pneumonia) was detected in 1.8 % (n=6). Out of 9 human metapneumovirus (hMPV) positive samples, 6 samples were successfully sequenced using F gene. And M. pneumoniae was sequencing of a repetitive region of the P1 gene. Phylogenetic analysis revealed that hMPV clustered into A2b lineage (n=4), B2 lineage (n=2) and M. pneumoniae clustered into two genotypes: Type 1 (n=4), Type 2a (n=2).

Isolation and characterization of a cDNA encoding a mammalian cathepsin L-like cysteine proteinase from Acanthamoeba healyi

We have cloned a cDNA encoding a cysteine proteinase of the Acanthamoeba healyi OC-3A strain isolated from the brain of a granulomatous amoebic encephalitis patient. A DNA probe for an A. healyi cDNA library screening was amplified by PCR using degenerate oligonucleotide primers designed on the basis of conserved amino acids franking the active sites of cysteine and asparagine residues that are conserved in the eukaryotic cysteine proteinases. Cysteine proteinase gene of A. healyi (AhCP1) was composed of 330 amino acids with signal sequence, a proposed pro-domain and a predicted active site made up of the catalytic residues, Cys(25), His(159), and Asn(175). Deduced amino acid sequence analysis indicated that AhCP1 belongs to ERFNIN subfamily of C1 peptidases. By Northern blot analysis, no direct correlation was observed between AhCP1 mRNA expression and virulence of Acanthamoeba, but the gene was expressed at higher level in amoebae isolated from soil than those from clinical samples. These findings raise the possibility that Ahcp1 protein may play a role in protein metabolism and digestion of phagocytosed bacteria or host tissue debris rather than in invasion of amoebae into host tissue.

Subgenus classification of Acanthamoeba by riboprinting

Subgenus classification of Acanthamoeba remains uncertain. Twenty-three reference strains of Acanthamoeba including 18 (neo)type-strains were subjected for classification at the subgenus level by riboprinting. PCR/RFLP analysis of 18S rRNA gene (rDNA). On the dendrogram reconstructed on the basis of riboprint analyses, two type-strains (A. astronyxis and A. tubiashi) of morphological group 1 diverged early from the other strains and were quite distinct from each other. Four type-strains of morphological group 3, A. culbertsoni, A. palestinensis, A. healyi were considered taxonomically valid, but A. pustulosa was regarded as an invalid synonym of A. palestinensis. Strains of morphological group 2 were classified into 6 subgroups. Among them, A. griffini which has an intron in its 18S rDNA was the most divergent from the remaining strains. Acanthamoeba castellanii Castellani, A. quina Vil3, A. lugdunensis L3a, A. polyphaga Jones, A. triangularis SH621, and A. castellanii Ma strains belonged to a subgroup, A. castellanii complex. However, A. quina and A. lugdunensis were regarded as synonyms of A. castellanii. The Chang strain could be regarded as A. hatchetti. Acanthamoeba mauritaniensis, A. divionensis, A. paradivionensis could be considered as synonyms of A. rhysodes. Neff strain was regarded as A. polyphaga rather than as A. castellanii. It is likely that riboprinting can be applied for rapid identification of Acanthamoeba isolated from the clinical specimens and environments.

Bacterial endosymbiosis within the cytoplasm of Acanthamoeba lugdunensis isolated from a contact lens storage case

Transmission electron microscopy of an Acanthamoeba isolate (KA/L5) from a contact lens case revealed bacterial endosymbionts within cytoplasm of the amoebae. The Acanthamoeba isolate belonged to the morphological group II. Based on the polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) of 18S ribosomal RNA coding DNA (rDNA), the isolate was identified as A. lugdunensis. Strain typing by isoenzyme analysis using isoelectric focusing (IEF) and mitochondrial (Mt) DNA RFLP revealed that the isolate was closely related with KA/L1, the most predominant type of isolates from contact lens storage cases, KA/E2, a clinical isolate, KA/W4, previously reported to host endosymbionts, and L3a strains of A. lugdunensis. The endosymbionts were similar to those of KA/W4 in aspects that they were randomly distributed in both trophozoites and cysts, and were rod-shaped bacteria measuring approximately 1.38 x 0.50 microns. But the number of endosymbionts per amoeba was significantly lower than that of KA/W4. They were neither limited by phagosomal membranes nor included in lacunaelike structure.

Close relatedness of Acanthamoeba pustulosa with Acanthamoeba palestinensis based on isoenzyme profiles and rDNA PCR-RFLP patterns

The taxonomic validity of morphological group III Acanthamoeba spp. is uncertain. In the present study, six type strains of group III Acanthamoeba spp., Acanthamoeba culbertsoni, A. healyi, A. pustulosa, A. palestinensis, A. royreba and A. lenticulata were subjected for the evaluation of their taxonomic validity by comparison of the isoenzyme patterns by isoelectic focusing on polyacrylamide gels, mitochondrial DNA (Mt DNA) restriction fragment length polymorphism (RFLP), and small subunit ribosomal DNA (ssu rDNA) PCR-RFLP patterns. The Mt DNA RFLP patterns were heterogeneous between species. The type strains of A. palestinensis and A. pustulosa showed almost identical patterns of isoenzymes and rDNA PCR-RFLP with an estimated sequence divergence of 2.6%. The other species showed heterogeneous patterns of isoenzymes and rDNA PCR-RFLP. It is likely that A. pustulosa is closely related with A. palestinensis and that the former may be regarded as a junior synonym of the latter.