Fall 2014, Marine Corps Base Camp Pendleton experienced an
outbreak of ocular conjunctivitis among military recruits. This case study examines an
outbreak among recruits infected by a novel strain of untypable Streptococcus pneumoniae. This recent emergence of ocular bacterial
conjunctivitis shows remarkable resemblance to a 2003 outbreak among military trainees. The 2003 outbreak was preceded by two other similar
outbreaks on military bases in 1980 and 1996.
Conjunctival swabs were obtained from infected military recruits at Camp Pendleton and sent
to the Naval Health Research Center. Each sample underwent routine biochemical testing. Suspicious isolates were tested using the
BD Phoenix Automated Microbiology System. Isolates were tested by manual methods, including the optochin disk reaction test and the bile
solubility test. Isolates positive for Streptococcus pneumoniae were tested using the Pneumotest-Latex Agglutination Test and Quellung reaction for serotyping.
A total of 23 ocular samples were tested. Of those 23 samples, 15 tested positive
for Streptococcus pneumoniae. Six of the positively identified S.
pneumoniae samples were identified by the BD Phoenix System. Antibiotic
susceptibility results were also provided for all positively identified samples.
All positive BD Phoenix identified samples were resistant to the antibiotics,
trimethoprim/sulfamethoxazole and erythromycin. Nine of the positively identified S. pneumoniae
samples could only be tested by manual methods. Seven of the samples tested did not provide
growth after multiple attempts to grow the sample, and one sample provided an automated and
manual identification for a bacterial agent other than S. pneumoniae. All 15
of the S. pneumoniae isolates are suspected to be unencapsulated and from the same novel serotype. Each
positive isolate tested negative for all Latex Agglutination Pool Groups and Quellung reactions.
Additional research, focused on the development of a manual method for antibiotic
susceptibility testing, as well as sample identification validation through molecular laboratory sequencing,
should be performed. Our data suggest that the causative agent for ocular conjunctivitis among military
recruits is an unencapsulated, untypable novel strain of Streptococcus pneumoniae.