Indian Journal of Medical Microbiology Medknow Publications on behalf of Indian Association of Medical Microbiology ISSN: 0255-0857 EISSN: 1998-3646 Vol. 30, Num. 1, 2012, pp. 116-118

Indian Journal of Medical Microbiology, Vol. 30, No. 1, January-March, 2012, pp. 116-118

Research Snippets

Research snippets

P Desikan

Department of Microbiology, Bhopal Memorial Hospital and Research Centre, Raisen Bypass Road, Karond, Bhopal- 462 038, Madhya Pradesh, India

Correspondence Address:
P Desikan
Department of Microbiology, Bhopal Memorial Hospital and Research Centre, Raisen Bypass Road, Karond, Bhopal- 462 038, Madhya Pradesh
India
prabhadesikan@yahoo.com

Code Number: mb12029

Bacteria may eventually turn out to be the culprits responsible for human malaria. The African mosquito Anopheles gambiae sensu stricto is an important vector of this disease. A study found that the association of this mosquito with human beings was related to the odour of human skin (PLoS One 2011; 6(12):e28991. Epub 2011 Dec 28). Microbial communities on the skin play key roles in the production of human body odour. The study demonstrated that the composition of the skin microbiota affected the degree of attractiveness of human beings to this mosquito species. Bacterial plate counts and 16S rRNA sequencing revealed that individuals who were highly attractive to An. gambiaes.s. had a significantly higher abundance, but lower diversity of bacteria on their skin than individuals who were poorly attractive. Bacterial genera that correlated with the relative degree of attractiveness to mosquitoes were also identified.

Anopheles gambiae (Ag) seems to be particularly well equipped to sniff out attractive humans (and their bacteria). The first step in odorant recognition in antennal sensilla involves soluble odorant binding proteins (OBPs), which transfer odorous compounds to olfactory receptors (ORs) in the dendritic membrane of sensory neurons. A particular OBP subtype of the ′Plus-C′ class, called AgOBP48, is abundantly transcribed in female antennae and partially down-regulated after a blood meal, suggesting a possible role in host detection. The results of a recent study (Insect Mol Biol. 2011 Dec 29. doi: 10.1111/j.1365-2583.2011.01125.x. [Epub ahead of print]) indicate that cells that express either AgOBP48, AgOBP1, or AgOR1 are housed together in distinct olfactory sensilla and that an interplay of the proteins may contribute to the specific responsiveness of the sensillum to distinct odorants.

Although Rajasthan is known more for its hot, arid, desert climate, prolonged spells of rain in 2011 increased the number of malaria cases in the state compared to 2010. However, the cause for concern was the increase in the cases of fatal Plasmodium falciparum infections. The cases increased by almost 30% in 2011 as compared to the corresponding period in 2010 ( http://timesofindia.indiatimes.com/city/jaipur/30-increase-in-malaria-cases-in-2011/articleshow/11344727.cms ). A study examining the origin and spread of the chloroquine-resistant P. falciparum population in the Indian subcontinent found that the Indian P. falciparum population exhibited a selective valley of reduced genetic variation in the flanking microsatellites of the mutant pfcrt alleles (up to ±29 kb) as compared with the wild-type allele (J Antimicrob Chemother. 2011 Dec 29. [Epub ahead of print]). This valley is much narrower than the ±200 kb valley reported from African and South-East Asian countries. The majority of the isolates showed asymmetry in the selective valley, where upstream microsatellites showed less genetic variation than the downstream microsatellites. Regional variation in the width and symmetry of the selective valley was noticed, which seems to be related to the number of pfcrt alleles present in the parasite population of a region. Forty-six different microsatellite haplotypes were observed among the P. falciparum isolates containing mutant pfcrt alleles. Parasite populations from different regions of mainland India shared microsatellite haplotypes between them, but they shared none with the isolates from the Andaman and Nicobar Islands, and vice versa. Indian isolates shared microsatellite haplotypes with the isolates from Papua New Guinea and Thailand. The study concluded that, with regard to chloroquine, there is regional variation in the selection pressure on the P. falciparum population in India.

Mycobacterium tuberculosis Region-of-Difference-1 gene products present opportunities for specific diagnosis of M. tuberculosis infection, yet immune responses to only two gene products, early secretory antigenic target-6 (ESAT-6) and culture filtrate protein-10 (CFP-10), have been comprehensively investigated. In a recent study (PLoS One. 2011;6(12):e28754. Epub 2011 Dec 28), T-cell responses to Rv3873, Rv3878, and Rv3879c were quantified by IFN-γ-enzyme-linked-immunospot (ELISpot) in 846 children with recent household tuberculosis exposure and correlated with kinetics of tuberculin skin test (TST) and ESAT-6/CFP-10-ELISpot conversion over 6 months and clinical outcome over 2 years, The investigators concluded that these RD1-derived antigens are early targets of cellular immunity following tuberculosis exposure and that T-cells specific for these antigens predict progression to active tuberculosis suggesting diagnostic and prognostic utility.

Control of MDR TB is quite a challenge. A major challenge includes the diagnosis and treatment of MDR TB in animals, since they can also act as sources for human infection. In Florida, a female Asian elephant (Elephas maximus) developed vaginal and trunk discharge. Cultures were positive for pan-susceptible M. tuberculosis. Isoniazid and pyrazinamide were given rectally and monitored by serum levels. After being trained at 10 months to accept oral dosing, treatment was changed and rifampin was added. Oral medications were administered for another 10 months. A year after completion of therapy, the vaginal discharge increased and cultures yielded M. tuberculosis, resistant to isoniazid and rifampin. Treatment with oral ethambutol, pyrazinamide, and enrofloxacin and intramuscular amikacin was initiated. Although follow-up cultures became negative, adverse reactions to medications precluded treatment completion. Due to public health concerns related to multidrug-resistant M. tuberculosis (MDR-TB), the elephant was euthanized. Post-mortem smears from the lung, peribronchial, and abdominal lymph nodes yielded acid-fast bacteria although cultures were negative. While the need for euthanasia is questionable when cultures are negative, this case highlights important considerations in the treatment of M. tuberculosis in animals and the need for a consistent approach to diagnosis, treatment, and follow-up (J Zoo Wildl Med. 2011 Dec; 42(4):709-12).

A study using a sophisticated 'glass mouse' research model has found that MDR-TB is more likely caused in patients by speedy drug metabolism rather than inconsistent doses, as is widely believed ( http://www.medicalnewstoday.com/releases/239772.php ). This may have implications for tuberculosis control programmes. As recently as 10 years ago, few options for treatment and care were available to those affected by MDR-TB and extensively drug-resistant tuberculosis (XDR-TB). Later, accumulating evidence indicated that the programmatic management of M/XDR-TB was not only feasible but also cost effective. However, despite the significant progress that has been made, severe bottlenecks are seen limiting the response to the M/XDR-TB epidemic. Indeed, only 10% (24 511/250 000) of the estimated MDR-TB cases among notified TB cases in the high MDR-TB countries, and 11% (30 475/280 000) globally have been enrolled on treatment ( http://www.who.int/tb/publications/2011/mdr_report_2011/en/index.html ).

Managing drug-resistant M. tuberculosis (MTB) requires drug susceptibility testing. Conventional drug susceptibility testing has a long turnaround time molecular tests are not standardised for all antituberculous drugs. A study addressed these challenges by carrying out real-time PCR of mycobacteriophage D29 DNA to evaluate the drug resistance of clinical MTB isolates. Mycobacteriophages infect and replicate in viable bacterial cells faster than bacterial cells replicate. The primary protocol involved culturing MTB isolates for 48 hours with and without drugs at critical concentrations, followed by incubation with D29 mycobacteriophage for 24 hours, and then carrying out real-time PCR. The change in phage DNA real-time PCR cycle threshold (Ct) between control MTB and MTB treated with drugs was calculated and correlated with conventional agar proportion drug susceptibility results. This D29 qPCR assay was found to offer a rapid, accurate, 1-3 day phenotypic drug susceptibility test for first and second-line drugs and was also found to suggest an approximate MIC for the drugs (J Clin Microbiol. 2011 Dec 14. [Epub ahead of print]).

Keeping in perspective the need for an early diagnosis of invasive fungal infection, a real-time PCR assay for the detection and strain identification of Aspergillus species from culture strains was evaluated (Mycoses. 2011 Dec 11. doi: 10.1111/j.1439-0507.2011.02161.x. [Epub ahead of print]). A DNA preparation was evaluated in contaminated culture media, urine, and serum. The real-time PCR protocol was improved by generating plasmid standards, additional generation of melting curves for species identification and the correlation between the melting temperature and the nucleotide exchanges within the 18S rRNA gene region. The sensitivity of the test was <10 plasmid equivalents/assay. It was found to be a useful tool for the rapid identification of Aspergillus species and might be useful as an early diagnostic tool to detect an invasive fungal infection.

Fungi are not necessarily the villains of the piece in invasive fungal infections in immunocompromised patients. Outcomes of fungal infections in immunocompromised individuals depend on a complex interplay between host and pathogen factors, as well as treatment modalities. Problems occur when host responses to an infection are either too weak to effectively help eradicate the pathogen, or when they become too strong and are associated with host damage rather than protection. Immune reconstitution syndrome (IRS) can be generally defined as a restoration of host immunity in a previously immunosuppressed patient that becomes dysregulated and overly robust, resulting in host damage and sometimes death. IRS associated with opportunistic mycoses presents as new or worsening clinical symptoms or radiographic signs consistent with an inflammatory process that occur during receipt of an appropriate antifungal and that cannot be explained by a newly acquired infection. Because there are currently no established tests or biomarkers for IRS, it can be difficult to distinguish from progression of the original infection although culture and biomarkers for the fungal pathogen or infection are typically negative during diagnostic workup. (Am J Med. 2012 Jan; 125(1 Suppl):S39-51).

The New Year always seems to begin with a discussion of 'trends'. Where health is concerned, there seem to be mainly rising trends ( http://www.dentistryiq.com/index/display/article-display/7886039667/articles/dentisryiq/rdh-products/evillage-focus/2012/1/maria-intro_010612.html ). In most parts of the globe, life expectancy is rising, levels of medical knowledge and expertise are rising, and consumer expectations of healthcare are rising. However, on the down side, healthcare costs and obesity rates are also rising. In the near future, consumers and healthcare professionals will therefore need to be absorbed in maximizing the positive increases and minimizing the negative increases. I do hope this translates into better infection control, both in the community and in hospitals. On that note, I wish you a very happy 2012!

The top ten infection control trends envisaged

( http://www.healthcaredesignmagazine.com/blogs/jkovacs/ringing-new-year-infection-control ).

1. Increased availability of new disinfectants. The U.S. EPA is anticipated to approve new or existing disinfectants with a kill claim for Clostridium difficile in the next year. This will create further demand for improved disinfectant tools and technology.
2. Broader acceptance of disinfectant wipes. Non-sodium hypochlorite disinfectant wipes will gain a bigger share of the market due to convenience and efficacy against a wide spectrum of microorganisms.
3. Increased communication and education regarding emerging threats. Manufacturers will take a more active role in educating the public about threats associated with resistant microorganisms. This will help allay fears and hysteria associated with ′superbugs′.
4. Microfibre will continue to penetrate the market. Microfibre will gain a larger market share due to broader general acceptance. Outsourced microfibre programs will also generate increased attention in an effort to limit overhead costs and ensure proper laundering protocol is followed.
5. The threat of worldwide pandemics and flu-like viruses will persist. Resistance mechanisms like NDM-1 will continue to cause potential scares requiring facilities, manufacturers, and frontline healthcare personnel to stay prepared in the event of a potential outbreak.
6. New policies regarding patient curtains will emerge. Policies regarding changing cubicle or privacy curtains following isolation contact will gain momentum, forcing the development of disposable curtains or quick-change solutions that require minimal labour and/or expertise.
7. Greater attention will develop toward the disinfection practices for patient-use items. Mandates driven by the Joint Commission will generate a greater awareness for practices used to clean patient items such as wheelchairs, stretchers, IV poles, and other mobile objects. Infection preventionists and environmental service directors should be prepared for questions relating to who is responsible for cleaning these items, what is being used to clean or disinfect the surfaces, and the time allocated for cleaning to occur.
8. Increased budget cuts. New federal regulations will likely result in further budget deficits and cuts. This will have a potential impact on hospital housekeeping departments. Since 80 to 85% of a housekeeping department′s budget is spent on labour, it will be a challenge for department managers to maintain clean and sanitary facilities with less staff.
9. Renewed cooperation between all healthcare constituents. Infection preventionists, cleaning staff, patients, nursing staff, and doctors will increase coordination and efforts to reduce rates associated with hospital-acquired infections. New programs will help all healthcare personnel understand the significance of maintaining a clean and sanitary environment.
10. Increased use of cleanliness measurement tools. New innovations such as adenosine triphosphate meters and black light detection equipment will enable infection control personnel to get a better gauge of the quality of cleaning performed and provide essential benchmarking information.
11. New laundering regulations. Healthcare officials will face greater scrutiny regarding protocols used to launder patient use items and cleaning equipment, such as microfibre.