Abstract
Although coagulase-negative staphylococci (CONS) constitute normal flora of the human body, some species can produce human infections, particularly when the host defense is breached. There is little evidence of the pathogenicity of CONS in HIV-infected individuals. We present the case of a 14-year-old HIV-infected boy who presented with a right lower zone pneumonia and a cutaneous abscess, following which he developed pancytopaenia due to underlying CONS infection that responded to antibiotic treatment.
Keywords
Introduction
HIV-infected children have a higher risk of developing pneumonia and of more severe disease than immunocompetent children. 1 Skin and soft tissue infections (SSTIs) are most commonly reported 2 in patients and they are usually associated with risk factors such as low-serum CD4–T lymphocyte count, intravenous catheters, neutropaenia, Staphylococcus aureus colonization and underlying dermatological conditions. 2 Very few case reports in literature have reported coagulase-negative staphylococci (CONS) as an underlying cause for pneumonia and recurrent SSTIs in HIV-infected individuals.3,4 We present the case of a 14-year-old HIV-infected boy who had right lower zone pneumonia and a cutaneous abscess, following which he developed pancytopaenia due to underlying CONS infection that responded to treatment.
Case report
A 14½ year-old HIV-infected boy was started on antiretroviral therapy (ART) consisting of zidovudine (AZT), lamivudine (3TC) and nevirapine (NVP) in January 2011 in view of low CD4 count (237 cells/mm3). He subsequently developed right lower zone pneumonia in February 2011 and a right thigh abscess which was drained and a treated with amoxicillin–clavulanic acid for 10 days at a dose of 50 mg/kg/day of amoxicillin in two divided doses, to which he responded. But after 15 days, he was found to have severe pallor with congestive cardiac failure and bilateral crepitations without organomegaly and thus was hospitalized. His complete blood count showed haemoglobin of 3.1 mg/dl, WBC count of 2800 cells/mm3 (22% polymorphs and 76% lymphocytes) with platelets of 89,000/mm3. His renal and liver function tests were normal. He was given blood transfusions and zidovudine was decreased to half the dose but his haemoglobin did not improve. His chest X-ray still showed right lower zone haziness. A bone marrow examination was done on day 3 of hospitalization in view of pancytopaenia and fever that showed hypocellular marrow without abnormal cells. Bone marrow culture after five days grew CONS resistant to methicillin, clindamycin, erythromycin, cephalosporins and amoxicillin–clavulanic acid with susceptibility to cotrimoxazole, amikacin, ciprofloxacin, linezolid and vancomycin. He was started on oral ciprofloxacin and linezolid following which his blood count improved with haemoglobin 10.9 gm/dl, WBC count 4500 cells/mm3 (20% polymorphs, 66% lymphocytes, and 12% eosinophils) and platelets of 108,000/mm3. He was discharged on oral ciprofloxacin and oral linezolid.
Discussion
Staphylococcus infection has long been recognized as an important pathogen in human disease. CONS have been regarded as non-pathogenic but their important role as pathogens and their increasing incidence have been recognized and studied. 5 CONS are distinguishable from S. aureus by the lack of coagulase-encoding genes. They belong to the commensal flora of healthy human skin. CONS have been recognized as pathogens associated with medical devices. Staphylococcus epidermidis is referred to as a frequent cause of nosocomial infections. Staphylococcus saprophyticus is considered as a frequent pathogen responsible for uncomplicated urinary tract infections. 6 CONS are by far the most common cause of bacteraemia related to indwelling devices. 5 In a study from Nigeria, CONS and non-typhoidal Salmonellae are the most common aetiological agents of bacteraemia among HIV-infected adults. 7 Similarly from Zimbabwe, the commonest organisms causing bacteraemia in HIV-infected children were CONS, S. aureus, Streptococcus pneumoniae and gram-negative bacteria. 8 In Spain, the commonest organisms causing blood stream infections in HIV-infected patients were CONS and S. aureus. 9 CONS has also been implicated as cause of SSTI and pneumonia in HIV-infected patients.3,4 Bacterial infections in HIV-infected children are more invasive and more likely to disseminate, having worse outcomes, compared to HIV-negative children. 10 All organ systems can be involved; abscess formation of internal organs and skin can occur and concomitant bacteraemia is also common. 10 Our patient had bone marrow involvement due to CONS which may have spread from the cutaneous abscess on the thigh. Although CONS is considered as a contaminant in most culture-grown organisms, the response of the blood count and clinical improvement in the child with appropriate antibiotics was suggestive that it was the causative agent of pancytopaenia in this child. Other causes such as parvovirus infection, atypical mycobacteria, and fungal infections can also cause aplastic anaemia but they would not usually respond to antibiotics as were given in this child. HIV itself can cause bone marrow suppression but response would be expected with ART. This child was already on ART for a month before he developed the pancytopaenia.
Conclusion
Non-pathogenic organisms such as coagulase-negative staphylococci can cause serious infections in HIV-infected children. Bone marrow suppression on ART can also be due to infections and thus bone marrow aspiration is important to rule out infectious causes of pancytopaenia in patients on ART.
Footnotes
Conflict of interest
The authors declare no conflict of interest.
Funding
This research received no specific grant from any funding.